UPPER BELKHU KHOLA HYDROELECTRIC PROJECT DETAILED … Design Study- Report… · excavated by the...

UPPER BELKHU KHOLA HYDROELECTRICPROJECT

DETAILED DESIGN

Volume I (Main Report)

Dariyal Small Hydropower Company PrivateLimited

June 2015Jestha 2072

Dariyal Small Hydropower Company Upper Belkhu Khola HEP- Detail Design

UPPER BELKHU KHOLA HYDROELECTRICPROJECT

DETAILED DESIGN

Volume I: Main Report

Dariyal Small Hydropower Company PrivateLimited

June 2015Jestha 2072

Quality control Signature DatePrepared by Khem Pun

Shailesh ShakyaSatya Sunder ParjapatiIshwor Pokharel

Checked by: Uttam Dhakal

Approved by: Basanta Bagale


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TABLE OF CONTENTS.................................................................................................................. PAGE NO.

APPENDIX..........................................................................................................................................................IV

ANNEX- A – CONSTRUCTION SCHEDULE.............................................................................................IV

ANNEX- B – FINANCIAL ANALYSIS...........................................................................................................IV

LIST OF ABBREVIATIONS..............................................................................................................................V

Salient features ...........................................................................................................................................................................1

1. INTRODUCTION ..........................................................................................................................................5

1.1 General........................................................................................................................................................................51.2 Previous studies .......................................................................................................................................................51.3 Scope of services .....................................................................................................................................................51.4 Structure of the report .........................................................................................................................................51.5 Project descriptions ...............................................................................................................................................6

2. TOPOGRAPHIC SURVEY ...........................................................................................................................8

3. GENERAL DESIGN DATA AND CRITERIA............................................................................................9

3.1 Hydrology and Sediment Studies ......................................................................................................................93.1.1 Mean monthly flow ...................................................................................................................................93.1.2 Flow duration curve .................................................................................................................................93.1.3 Flood flow ................................................................................................................................................ 103.1.4 Diversion flood ....................................................................................................................................... 113.1.5 Sediment data.......................................................................................................................................... 11

3.2 Geology and Seismicity .......................................................................................................................................11

4. STANDARD CODES AND SOFTWARES............................................................................................. 13

4.1 Purpose .....................................................................................................................................................................134.2 Introduction.............................................................................................................................................................134.3 System of Units ......................................................................................................................................................134.4 Design Loads ...........................................................................................................................................................134.5 Code and standards..............................................................................................................................................13

4.5.1 Structural Load ....................................................................................................................................... 134.5.2 Civil Design.............................................................................................................................................. 134.5.3 Civil works ............................................................................................................................................... 144.5.4 Hydro-mechanical .................................................................................................................................. 144.5.5 Electromechanical .................................................................................................................................. 14

4.6 Software....................................................................................................................................................................144.6.1 Structural analysis of the Headwork and Powerhouse structures ............................................ 144.6.2 River Modelling ....................................................................................................................................... 144.6.3 Drawings................................................................................................................................................... 14

5. DETAILED ENGINEERING DESIGN .................................................................................................. 15

5.1 Hydraulic Design......................................................................................................................................................155.1.1 Diversion Weir ....................................................................................................................................... 155.1.2 Side Intake................................................................................................................................................ 155.1.3 Gravel Trap and Side Spillway............................................................................................................. 165.1.4 Approach Canal ...................................................................................................................................... 165.1.5 Settling Basin............................................................................................................................................ 165.1.6 Penstock Pipe and its support............................................................................................................. 175.1.7 Powerhouse............................................................................................................................................. 205.1.8 Switchyard area ...................................................................................................................................... 215.1.9 Tailrace ..................................................................................................................................................... 21

5.2 Structural Design .....................................................................................................................................................225.2.1 Headworks............................................................................................................................................... 225.2.2 Penstock Pipe .......................................................................................................................................... 255.2.3 Powerhouse............................................................................................................................................. 265.2.4 Machine foundation ............................................................................................................................... 285.2.5 Tailrace Culvert ...................................................................................................................................... 33

6. HYDROMECHANICAL WORKS.......................................................................................................... 34


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6.1 Introduction ..............................................................................................................................................................346.2 Gate Stoplog and Trashrack .................................................................................................................................346.3 Coarse Trashrack ....................................................................................................................................................346.4 Intake Gate................................................................................................................................................................346.5 Gravel Trap Flushing Gate ....................................................................................................................................346.6 Canal Inlet Gate .......................................................................................................................................................356.7 Fine Trashrack..........................................................................................................................................................356.8 Sand Flushing Gate ..................................................................................................................................................356.9 Tailrace Gate ............................................................................................................................................................366.10 Steel Penstock Pipes ...............................................................................................................................................36

7. TRANSMISSION LINE............................................................................................................................. 37

7.1 Energy Meter and Metering Equipment .............................................................................................................37

8. POWER FACILITIES-ELECTRICAL EQUIPMENT ............................................................................. 38

8.1 POWER HOUSE MECHANICAL EQUIPMENT.............................................................................................388.1.1 General ..................................................................................................................................................... 388.1.2 General design criteria.......................................................................................................................... 388.1.3 Turbine ..................................................................................................................................................... 388.1.4 Turbine Governor ................................................................................................................................. 418.1.5 Turbine Inlet Valve................................................................................................................................. 428.1.6 Cooling water supply system .............................................................................................................. 428.1.7 Drainage and Dewatering System...................................................................................................... 428.1.8 Mechanical Workshop .......................................................................................................................... 438.1.9 Grease lubricating system .................................................................................................................... 438.1.10 Oil handling system................................................................................................................................ 438.1.11 Ventilation and air conditioning system ........................................................................................... 438.1.12 Fire Protection System ......................................................................................................................... 438.1.13 Powerhouse Overhead Travelling Crane ........................................................................................ 44

8.2 POWER HOUSE ELECTRICAL EQUIPMENT ................................................................................................448.2.1 General ..................................................................................................................................................... 448.2.2 Generating Equipment .......................................................................................................................... 458.2.3 Excitation System ................................................................................................................................... 468.2.4 Power Transformer............................................................................................................................... 468.2.5 Station Supply Transformer................................................................................................................. 478.2.6 General Layout of Electrical Equipment ........................................................................................... 478.2.7 Auxiliary Systems ................................................................................................................................... 478.2.8 DC Auxiliaries......................................................................................................................................... 488.2.9 Control and Protection Systems........................................................................................................ 488.2.10 11 kV Switchgear.................................................................................................................................... 498.2.11 Battery and Battery Charger ............................................................................................................... 538.2.12 Communication System........................................................................................................................ 538.2.13 Grounding ................................................................................................................................................ 53

9. COMPUTATION OF PROJECT OUTPUT............................................................................................ 54

9.1 BASIC FOR COMPUTATION ............................................................................................................................549.2 ENERGY COMPUTATION..................................................................................................................................54

10.CONSTRUCTION PLANNING............................................................................................................... 56

10.1 GENERAL..................................................................................................................................................................5610.2 ACCESS .....................................................................................................................................................................5610.3 INFRASTRUCTURE FACILITIES.........................................................................................................................5610.4 CONSTRUCTION POWER................................................................................................................................5710.5 CONSTRUCTION MATERIALS.........................................................................................................................5710.6 CONTRACT PACKAGE ......................................................................................................................................5710.7 CONSTRUCTION SCHEDULE..........................................................................................................................58

11.COST ESTIMATE........................................................................................................................................ 59

11.1 CRITERIA AND ASSUMPTIONS .......................................................................................................................5911.2 ESTIMATING METHODOLOGY.......................................................................................................................5911.3 BASE COST AND TOTAL PROJECT COST..................................................................................................60


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12.FINANCIAL ANALYSIS AND PROJECT EVALUATION.................................................................. 63

12.1 ASSUMPTIONS........................................................................................................................................................6312.2 FINANCIAL PROJECTION..................................................................................................................................6312.3 CONCLUSIVE FINANCIAL INDICATOR.......................................................................................................64

13.CONCLUSIONS AND RECOMMENDATIONS................................................................................... 65

13.1 CONCLUSIONS .....................................................................................................................................................6513.2 RECOMMENDATIONS ........................................................................................................................................65

LIST OF FIGURES ...........................................................................................................................PAGE NO.

Figure 1-1 Project Area on Topo Map............................................................................................ 7

Figure 3-1 Flow Duration Curve .................................................................................................. 10

Figure 5-1 Weir at Rocky area..................................................................................................... 15

Figure 5-2 Penstock alignment of project ..................................................................................... 17

Figure 5-3 Penstock Diameter Optimization................................................................................. 18

Figure 5-4 Long side view of power house of project.................................................................... 21

Figure 5-5 Weir Stability tabulated form....................................................................................... 23

Figure 5-6 Typical weir Section.................................................................................................... 23

Figure 5-7 Settling Basin Stability Tabulated Form ......................................................................... 25

Figure 5-8 Typical Section of Settling Basin ................................................................................... 25

Figure 5-9-2D Finite Element Model of Truss ............................................................................... 27

Figure 5-10-3D Finite Element Model of main Powerhouse ........................................................... 27

Figure 8-1 Range of Gross Heads................................................................................................. 39

Figure 8-2 ALSTOM Turbine selection chart ................................................................................ 39

Figure 8-3 Application Zone in Selecting the Turbine Type ........................................................... 40

Figure 8-4 Efficiencies; Pelton vs Francis ....................................................................................... 41


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LIST OF TABLES PAGE NO.

Table 2-1 Coordinates of control points and permanent benchmarks 8

Table 3-1: Mean monthly flow at the proposed intake site, m3/s 9

Table 3-2: Flow duration curve data in m3/s 9

Table 3-3: Flood flow, m3/s 10

Table 5-1 Thickness of the pipe for different head 18

Table 5-2 : Stability Analysis 31

Table 5-3: Vibration Analysis 32

Table 9-1 Monthly Available Estimate of the Energy (MAE) 54

Table 11-1 Project Cost Summary 61

APPENDIX

ANNEX- A – CONSTRUCTION SCHEDULE

ANNEX- B – FINANCIAL ANALYSIS


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LIST OF ABBREVIATIONS

cm/s Centimetre per secondDHM Department of Hydrology and MeteorologyDoR Department of RoadsDoS Department of SurveyGWh Gigawatt hourP.A.C.T-Consult

Partnership for Architect and Civil Technology - Consult Pvt.Ltd

HMG/N His Majesty's Government of Nepalkm KilometrekV KilovoltkW KilowattkWh Kilowatt hourm Metrem2 Square metrem3/s Cubic metre per secondMCT Main Central ThrustMIP Medium Irrigation ProjectMW MegawattNEA Nepal Electricity AuthorityQ Rock quality indexRMR Rock Mass RatingUBKHP Upper Belkhu Khola Hydroelectric ProjectUSD United States DollarsVDC Village Development CommitteeYrs Yearsyr Year

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Salient featuresThe salient features of the project are presented below.

1 Project Location

Latitude : 27° 43’ 31” N to 27° 44’ 40” N

Longitude : 84° 56’ 36” E to 84° 57’ 30” E

Development Region : Central Development Region

Zone : Bagmati

District : Dhading

Intake Site : Kiranchowk VDC

Powerhouse Site : Kiranchowk VDC

2 General

Name of River : Belkhu Khola

Nearest Town : Aadhamghat Bazaar

Type of Scheme : Run-of-river

Gross Head : 151.0 m

Design Discharge : 0.81 m3/sec

Installed Capacity : 996 kW

Dry Season Energy : 1,164 MWh

Wet Season Energy : 4,768 MWh

Total Energy : 5,932 MWh

3 Hydrology

Catchment Area : 21 km2

Design Discharge : 0.81 m3/sec

Design Flood Discharge : 87.0 m3/s (1 in 100 yr. flood)

4 Diversion Weir

Type of Weir : Concrete Lined Slope weir

Length of Weir : 11 m


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Weir Crest Level : El. 905.00 masl

Height : 1 M above riverbed

5 Intake Structure

No. of Openings : 9 No. of 0.3 m (w) X 0.5 m (h)

Invert Level : El. 904.50 masl

6 Gravel Trap – Emergency Spillway

Type : Rectangular RCC

Gravel Trap Size : 2.25 m x 4.3 m

Particle size to be settled : 5 mm

Gravel Flushing Culvert (LxBxH) : 19.15 m x 1.0 m x 0.5 m

Crest Length of spillway : 5.93 m

Crest elevation : 908.0 masl

7 Approach Canal

No of canal : 1

Width : 0.75 m

Depth : 1.13 m

Length : 42.30m

8 Settling Basin

Type : Hopper

Nominal size of trapped particle : 0.2 mm

No of Chamber : 1

Trap efficiency : 90%

Length of Inlet transition : 8.32 m

Dimension (LxBxH) : 32.0 m x 4.0 m x 3.81 m

Flushing Culvert (LxBxH) : 24.50 m x 1.0m x 0.5 m

9 Penstock

Length of penstock pipe : 1887.60 m

Internal diameter : 750.00 mm

Thickness : 6 mm to 10 mm

10 Powerhouse


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Type : Surface

Dimension : 18.50 m x 10.73 m x 7.90 m

11 Turbine

Type : Pelton- Horizontal Axis

No of Unit : 2

Turbine Center Level : El 754.90 masl

Rated Output : 560kw

Rated Speed : 750 rpm

Rated Efficiency : 90%

No. of Poles : 8 nos

Runway Speed : 1425 rpm

12 Generator

Type : Synchronous -3 Phase - Horizontal Axis

No of Unit : 2

Rated Output : 625 kVA


Rated Frequency : 50 Hz

Rated Efficiency : 96%

No. of Poles : 8 nos

Excitation : Brushless

13 Power Transformer

No of Units : 1

Type : 3 Phase oil immersed

Rated Capacity : 1250 kVA

Efficiency : 99 %

Frequency : 50 Hz

14 Tailrace

Dimension : 36.63 m x 1.40 m x 1.92 m

15 Switch Yards

Length : 15 m

Breadth : 10 m

16 Transmission Line

Type : 11 kV

Length : 8.0 km


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Power Evacuation : Proposed Jahare substation, Dhading

17 Link Road

Length : 3 km

18 Total Project Cost : NRs. 185,013,103.00

19 Financial Indicator

IRR for Projects : 15.14 %

B/C Ration : 1.24

20 Construction Period : 18 Months


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1. INTRODUCTION

1.1 GeneralPartnership for Architect and Civil Technology (P.A.C.T) Pvt. Ltd has taken the responsibility ofdetail design and construction supervision with the Dariyal Small Hydropower Company Pvt.Ltd(DSHPC). The project is located in Dhading district of Bagmati zone in Central Development Regionof Nepal. Water will be diverted by constructing headworks at 18 km from Aadhamghat Bazzar onPritivi Highway and will be fed through a waterway, comprising of about 1865.0 m long waterway, toa powerhouse at the left bank of Belkhu Khola. This road has already been extended up to the550 m downstream of headwork’s site. The road up to the powerhouse site has already beenexcavated by the project. The road from Adamghat to the project site is needed to be upgraded forthe purpose of construction work of the project. This report is the outcome of the study and servesas the Detailed Design Report of UBKHP.

1.2 Previous studiesThe detailed project report was carried out by DSHPC in October 2013 by Himalayan PowerPartner Pvt. Ltd. Later, P.A.C.T- Consult carried out the detail design review along the data availablefrom Himalayan Power Partner and construction supervision. In this regards, P.A.C.T-Consultprepared the Detailed Project Report (DPR) for the plant capacity of 996 KW on the basis of samehydrology and geological study as well as drawing available from the previous consultant. There is noconcept of the surge tank and present consultant is encourage to the client to take the surge tank onappropriate position but present condition the surge is relish on forebay. Likewise, the penstockalignment may change after the detail site study. Moreover the other technical parameter on thewater way is same. On the same case the previous studies has been illustrated the francies turbinebut at present condition due to availability of discharge and head; it can be reached on the peltonturbines and same as other assocceries. The P.A.C.T –Consult is not the responsible for thehydrology, geology as well as data available from the previous studies.

1.3 Scope of servicesThe major task of the consultant is to conduct a detailed engineering design and constructionsupervision of the specified hydropower project. Detail Engineering Design consists of Hydraulic andStructural design of the following component of the project. It also includes the preparation ofconstruction drawing/reinforcement drawing and specification. The following works shall be carriedout in this stage of Detailed Engineering Design including the reinforcement details that can be issuedto the contractor for the construction:

Design of headworks with all components with detailed drawings Design of intake with detailed drawings Design of gravel Trap with detailed drawings Design of desander with detailed drawings Design of penstock with support piers and anchor blocks with detailed drawings Design and drawing of powerhouse civil works

1.4 Structure of the reportThe outcome of this study is presented in the report and the report is arranged in three volumes asmentioned below.

Volume 1 – Main Report


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This volume includes methodology of each and every studies conducted during the detail design levelof study of the project. Other tabular data, graphical data, necessary maps, and drawings arepresented in Volume II and III where appropriate.

Volume II - Drawings

This volume includes all drawings and maps which are outcomes of this study. Topographical surveymaps, geological maps, civil drawings and structural drawings are included in this volume.

Volume III –Design Calculations

This volume includes the spreadsheets of all the design calculations in details.

1.5 Project descriptionsUpper Belkhu Khola Hydroelectric project (UBKHP) is run-of-river (ROR) type hydropower projectwith an installed capacity of 996 KW located in Kiranchowk Village Development Committee (VDC)-2 in Dhading District of Bagmati zone in the Central Development Region of Nepal. Geographically,the project lies at 84 56' 36” E to 84 57' 30”E and 2741' 31” N to 2744' 40” N.

A diversion weir has been provided across the Belkhu Khola. Nine numbers of small intake orificeson the right bank feed the design discharge to the surface settling basin consisting single bays. The1845.551 m long penstock pipe excluding bifurcation length conveys water to the powerhouselocation at the left bank of Belkhu Khola. A surface powerhouse has been proposed on the cultivatedland. The gross head of the project is 150.10 m and the design discharge of the project is 0.81m3/s.

The proposed headworks site lies at an elevation of 905.5 m and the powerhouse is located at anelevation of 754.9 m in the same VDC. The project location is shown in Figure 1-1.The project areais about 55 km from Kathmandu to Aadhamgat bazzar on black toped road at prithivi highway and 18Km earthen road from Aadhamgat to the project area in Dhading district.

The proposed project site is located in Midland units of Lesser Himalaya zone in Central Nepal. TheLesser Himalayan Region in the Central Nepal consists mainly of Lesser Himalayan meta-sedimentary rocks such as phyllite, slate, quartzite, limestone, and to a minor extent of mica- schistand granitic gneiss. In the project area the Metasedimentary units are represented by Kunchhaformation comprising Grey to greenish grey phyllites, gritty phylites and quartzites with minorconglomeratic layers and granitic & basic intrusions.The geological trend of the rock formation is fair to good for the project structures. Majorstructure such as headworks will be founded on rock, gneiss, which is a known good rock. Theheadrace pipe alignment will be located mainly on rock outcrops, alluvium and colluvialdeposits. The powerhouse will be founded on the bed rock, phyllite with intercalated quartzite. Thethickness of the overburden deposits is expected to be not more than 5m in the powerhouse area.

Phyllites with quartzite and gneiss are the predominant rock types of the project area. The rockmass classification showed mainly fair to good quality rocks. Debris flows, small landslides and slopefailures are the major geological hazards observed in and around the project area which has directimpacts on the project structures. A surface landslide at the some parts of pipe alignment is foundactive. The adequate quantity and quality of construction materials is available within easy haulagedistance of the project site.


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Figure 1-1 Project Area on Topo Map

Belkhu Khola is one of the tributaries of the Trishuli River, which itself is one of the biggest riversystems of Nepal. Since there is no gauging station at the weir site and in the vicinity of theproject area, it is necessary to generate the discharge data by using data series of nearby gaugingstations. For the study purpose three nearest gauging stations viz gauging station at Sundarijal (GSno 505), at Lothar GS no. 470 and gauging station at Kulekhani GS570 are considered. Themonthly river discharge has also been generated by MIP method on the basis of direct dischargemeasurement at the intake site. It has been recommended that the average daily data series fromthe gauging stations 505 at Sundarijal and 470 at Lothar along with MIP method based onmeasured data will be appropriate for the analysis. Thus using the generated daily data series ofboth the gauging stations and data generated with MIP Method, averaging them, the long termmean monthly data for the proposed project has been generated. As per the generateddischarges at the intake site, the average flow is 1.42 m3/s. The adopted design discharge at the40% dependable flow is 0.81 m3/s. The 100 year flood discharge has been calculated at the intakesite and powerhouse site are 87 m3/s and 103 m3/s respectively.

The total annual suspended sediment yield is about 0.194 million tons which is equivalent to a meanannual daily concentration of about 3335 parts per million by weight (ppm) at the intake site usingthe mean annual discharge of 1.42 m3/s. The annual sediment concentration recommended forthe design purpose is 3335 ppm.As the project area falls on the Zone of Middle Mountains, the climate changes from humidtemperature in the south to cold towards the north. The climate of the project area, in general, isof a sub- tropical type. The area experiences a hot and humid climate during summer and cold anddry in winter. The mean monthly temperature varies from 14°C in January to 25°C in June. Theextreme maximum temperature reaches 38° C and the extreme minimum temperature falls below4°C. The relative humidity varies from 33% to 93% over the year. The average annual precipitationis 2000 mm.


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2. TOPOGRAPHIC SURVEYWith the reference of the established bench marks at old headworks site, the extended survey wascarried out. The headworks site has been shifted to about 350 m upstream and further survey andriver cross section survey was carried for this portion and topo map was generated merging with theprevious topo map. The topographical survey report below is copied from the previous DPR. Thetopographic survey and mapping was carried out for mapping of the project area, cross- section ofthe Belkhu Khola and fixing of ground control points. For this about 16.4 ha of the project area, i.e.headworks area, headrace canal, forebay, penstock and powerhouse area and tailrace site weresurveyed in scale 1:1000. All necessary ground control points in project area were established by theclose traverse. The proper survey works are necessary to design the components of the project, toprepare drawings and to calculate the quantities of the project components. The survey data greatlyinfluences the quantities of the design components affecting the cost of the project. Hence all thesurvey works were carried out precisely and correctly. To support for the geological and geo-technical investigations and studies, the hydrological and sedimentation studies, the layout andstructures optimization studies, topographic surveys are required to provide detailed mapping.Therefore, topographic survey for the major structure setting at the headwork site and tailrace sitewas carried out in a scale of 1:1000. The topographic map was prepared in 1:1000 scales forwaterways alignment. Similarly, a project layout map was prepared in 1:2000 scale. All the surveyworks were undertaken on the basis of the following information:

Topographic maps of the project area at a scale of 1:25000 prepared by Survey

Department GoN Sheet no. 2784 08B Baikuntha gaun.

Project layout map produced during feasibility phase for headworks, canal alignments, forebayand powerhouse sites.

The coordinates and levels of the control points and benchmarks are presented in Table 2-1.

Table 2-1 Coordinates of control points and permanent benchmarks

S.N. Point Name Northing Eastting Elevation Remarks

1 HW-1 3067514.999 593870.412 913.000 HW

2 HW-2 3067571.876 593837.865 913.308 HW

3 HW-3 3067582.761 593789.348 904.248 HW

4 HW-4 3067640.057 593718.790 895.498 HW

5 TBM-1 3067704.954 593704.874 894.812 PH

6 TBM-2 3068122.304 593339.000 862.331 PH

7 TBM-3 3068199.304 593380.292 868.149 PH

8 TBM-4 3068351.753 593456.418 850.854 PH

9 TBM-5 3068476.344 593471.330 841.802 PH

10 TBM-6 3068601.611 593444.517 829.017 PH

11 TBM-7 3068713.718 593386.881 809.649 PH

12 TBM-8 3068978.796 593180.901 761.021 Big Rock

13 TBM-9 3069095.421 593139.462 755.689 Big Boulder


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3. GENERAL DESIGN DATA AND CRITERIAThe purpose of this chapter is to describe the basic design data and criteria adopted for the design of the projectcomponents of UBKHP regarding the hydrology and sediment studies, and geology.

3.1 Hydrology and Sediment StudiesThe hydrology of Belkhu Khola presented in updated DPR is summarized in this section.

3.1.1 Mean monthly flowThe mean monthly flow at the intake site available for the power generation is employed for the estimation ofannual energy and therefore, presented in Table 3-1.

Table 3-1: Mean monthly flow at the proposed intake site, m3/s

Month DischargeJan 0.433Feb 0.327Mar 0.269Apr 0.235May 0.363Jun 0.809Jul 3.102Aug 4.667Sep 3.723Oct 1.736Nov 0.824Dec 0.579Annual Average 1.420

3.1.2 Flow duration curveThe numerical value of flow duration curve is presented in Table 3-2.

Table 3-2: Flow duration curve data in m3/s

Time Exceedence Days per YearDischarge Equaledor Exceeded (m3/s)

40 146 0.818

45 164 0.81

50 183 0.694

55 201 0.572

60 219 0.491

65 237 0.422

70 256 0.384

75 274 0.354

80 292 0.334

85 310 0.307

90 329 0.275


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95 347 0.254

100 365 0.235

Thus, according to the flow duration curve the 90%, 65% and 40% dependable flow are 0.275 m3/s, 0.422 m3/sand 0.81 m3/s respectively at the weir site. For the proposed project as the design discharge 40% dependabilityflow has been adopted and used for the design of the hydraulic structures.

Figure 3-1 Flow Duration Curve

3.1.3 Flood flowThe flood flows corresponding to the different return periods at the intake site and powerhouse site arepresented in Table 3-3.

Table 3-3: Flood flow, m3/s

Return Periods(Year) Adopted Peak Flows

Weir Site Powerhouse Site

2 9 11

5 15 17.75

10 25 29

20 38 43

50 61 71

100 87 103

200 122 148

500 190 239

1000 264 342


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95 347 0.254

100 365 0.235







2 9 11

5 15 17.75

10 25 29

20 38 43

50 61 71

100 87 103

200 122 148

500 190 239

1000 264 342


10

95 347 0.254

100 365 0.235







2 9 11

5 15 17.75

10 25 29

20 38 43

50 61 71

100 87 103

200 122 148

500 190 239

1000 264 342


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10000 766 1104

The flood of magnitude 87m3/s and 103 m3/s at the Intake site and powerhouse site corresponding to the 100-year return period have been taken for the design of the corresponding flood protection structures.

3.1.4 Diversion floodThe diversion flood is required from the construction point of view of the headworks. As it is recommended touse one or more dry seasons (November to May) for the construction of weir including the intake, settling basinand flood wall, the diversion flood corresponding to 1 in 10 year return period is taken as 25m3/s.

3.1.5 Sediment dataThe concentration of 3335 ppm has been taken for the design of settling basin. Similarly, particles size of 0.20 mmhas been considered to be settled with trap efficiency of 90% in the settling basin by using Vetter methods.

3.2 Geology and SeismicityThe purpose of this section is to give the background for general design data and criteria regarding to the geologyand seismicity of the project area.

The proposed project site is located in Midland units of Lesser Himalaya zone in Central Nepal. The LesserHimalayan Region in the Central Nepal consists mainly of Lesser Himalayan meta-sedimentary rocks such asphyllite, slate, quartzite, limestone, and to a minor extent of mica-schist and granitic gneiss. In the project area theMetasedimentary units are represented by Kunchha formation comprising Grey to greenish grey phyllites, grittyphylites and quartzites with minor conglomeratic layers and granitic & basic intrusions.

The geological trend of the rock formation is fair to good for the project structures. Major structure such asheadworks will be founded on rock, gneiss, which is a known good rock. The headrace pipe alignment will belocated mainly on rock outcrops, alluvium and colluvial deposits. The powerhouse will be founded on the bedrock, phyllite with intercalated quartzite. The thickness of the overburden deposits is expected to be not morethan 5m in the powerhouse area.

Phyllites with quartzite and gneiss are the predominant rock types of the project area. The rock mass classificationshowed mainly fair to good quality rocks. Debris flows, small landslides and slope failures are the major geologicalhazards observed in and around the project area which has direct impacts on the project structures. A surfaciallandslide at the some parts of pipe alignment is found active. The adequate quantity and quality of constructionmaterials is available within easy haulage distance of the project site.Nepal lies in a seismically active zone, at the interface between two of the world's major tectonic plates. All partsof Nepal are at risk from the effects of severe ground shaking and there have been many reminders of this withinliving memory. Kathmandu experienced catastrophic damage in 1934 and an earthquake in the East of Nepal in1988 severely damaged approximately 60000 residential buildings.

The design values of horizontal seismic coefficient αh, and vertical seismic coefficient αv, will be computed usingthe seismic coefficient method according to IS 1893-1984 Fourth Revision and IS 1893-2002. According to the ISstandard, these coefficients are calculated with consideration of seismic zone, location, importance of structure,ductility of the structure, natural period and foundation soil conditions.


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The following investigations are recommended for the detail design before starting the constructionof the project.

Necessary protection measures at critical locations on the pipe alignment are necessary.

Subsurface investigation such as Electrical Resistivity survey would be required to get information ongeotechnical properties of the subsurface material especially in the critical structure locations such inheadworks and powerhouse site.

Construction material survey and investigation is to be carried out before the project construction.


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4. STANDARD CODES AND SOFTWARES

4.1 PurposeThe purpose of this chapter is to define standards and codes applied for carrying out the detail design work andapplicable for all construction work of the project.

4.2 IntroductionIt has to be hereby, contended that the design, manufacture, materials and workmanship comply with the relevantStandards or Codes of Practices from one or more of the following organizations:

ASTM The American Society for Testing of Materials

BS The British Standards Institution

IS The Indian Standards Institution

NS The Nepal Bureau of Standards and Metrology

4.3 System of UnitsThe International System of Units (SI) applies to all aspects of the project.

4.4 Design LoadsDesign loads are specified in each individual section of the report where not specifically indicated in the relevantstandards or code of practice.

4.5 Code and standards4.5.1 Structural LoadFor civil structural design the following codes and standards are used for determining design loads:BS 6399: 1984 Loadings for BuildingsCP3: 1972 Code of Basic Data for the Design of BuildingsIS 875-1987 Code of practice for design loads (other than earthquake) for buildings and

structuresIS 1893-2002 Criteria for Earthquake Resistant Design of Structures Nepal Standard,

Seismic Design of Buildings in Nepal4.5.2 Civil DesignBS 8110: 1985 Structural use of concreteBS 8007: 1987 Design of concrete structures for retaining aqueous liquidsBS 4466: 1987 Specification for Bending Dimension and Scheduling of Reinforcement for

ConcreteBS 5628: 1978 Code of practice for use of MasonryBS 5268: 1984 Structural Use of TimberBS 6031: 1981 Code of Practice for EarthquakesIS 456: 2000 Plain and reinforce concrete – Code of practiceIS1893: 2002 Criteria for earthquake resistant design of structuresIS 13920:1993 Ductile detailing of reinforced concrete structures subjected to seismic forces

IS 4880 - 1971 (Part IV) Code of practice for design in tunnel conveying water(Structural design of concrete lining in rock)

IS 1161 – 1979 Specification for steel Tubes, Tubular and other Wrought Steel FittingsSP: 16 Design aids for reinforced concrete IS : 456-1978


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4.5.3 Civil worksBS 4449: 1978 Hot rolled steel bars for the reinforcement of concreteBS 4461: 1978 Cold worked steel bars for the reinforcement of concreteBS 4483 Steel mesh fabricBS 1377: 1975 Methods of test for soil for civil engineering purposesBS 1881: 1984 Method of testing concreteBS 812: 1984 Pt 101 Guide to sampling and testing aggregatesBS 882: 1983 Specification for aggregates from natural sources for concreteBS 3148: 1980 Testing for water for making concrete

4.5.4 Hydro-mechanicalIS 13623: 1993 Criteria for Choice of Gates and HoistIS 4622: 2003 Recommendation for Structural Design of Fixed - Wheel GatesIS 5820: 1985 Recommendations for Structural Design Criteria for Low Head Slide GatesIS 5820: 1985 Recommendations for Structural Design of Medium and High Head Slide

GatesIS 4623: 2000 Recommendation for Structural Design of Radial GatesIS 6938: 2005 Design of Rope Drum Hoists for Hydraulic Gates-Code of PracticeIS 11228: 1985 Recommendations for Design of Screw Hoists for Hydraulic GatesIS 11388: 1995 Recommendation for Design of Trash rack for IntakeIS 11639 (Part 2):1995 Structural Design of Penstock CriteriaIS 11639 (Part 3): 1996 Structural Design of Penstock CriteriaIS 12837:1989 Hydraulic Turbine for medium and large Power houses – Guidelines for

Selection4.5.5 ElectromechanicalIS 12800 (Part 1): 1993 Guidelines for selection of turbines, preliminary dimensioning and layout of

surface hydro-electric power housesIS 13118: 1991 Specification for high voltage alternating current circuit breaker

IS 2705 : Part 1 : 1992 Current transformers: Part 1 General requirements

4.6 Software4.6.1 Structural analysis of the Headwork and Powerhouse structures

SAP2000 Analysis and design of the structuresSAFE Mat foundation designTURBNPRO KC4 Design of powerhouse

4.6.2 River Modelling

HECRAS Hecras software was used to model the river forvarious flow patterns at the headwork and powerhouse.

Arc GIS 9.2 Hydrological AnalysisSEEPW Seepage Analysis of Barrage Section

4.6.3 Drawings

Final Drawings Autodesk Auto CAD, Land Development and CivilDesign

Profiles and Sections Land Development and Civil Design, SW_DTM


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5. DETAILED ENGINEERING DESIGN

5.1 Hydraulic Design5.1.1 Diversion Weir

Construction of the headworks structures requires temporary diversion of the Belkhu Khola. Based on the sizesof the structures to be constructed at the headworks and the duration of construction, the river diversionscheme during construction is designed for a return period of 1 in 10 year's dry season flood. For our case, due tounavailability of this data we have taken the maximum generated annual flood of 9 m3/sec for the design of cofferdam and diversion. The diversion is on the left bank of the river.

The diversion weir is a concrete lining slope of crest length 11 m. The crest level of the weir is fixed at 905.00 mand invert level of intake at 904.50 m to divert the design discharge of 0.89 m3/sec including flushing discharge forthe gravel trap and settling basin. As the river portion upstream of the weir is assumed to be filled up to the crestlevel with sediments, the weir will act as a Broad Crested Weir. The head over the weir during 1 in 100 yearflood, which is equivalent to 87.0 m3/s, is calculated to be about 1.0 m. Therefore; the top level of abutment of theweir is fixed at 908.00 m, which is 1.0 m above the 1 in 100 year flood level. The top level of operating platform isalso fixed as 908.00 m. The hydraulic jump is calculated on the basis of excess energy due to the head differencebetween u/s and d/s to be dissipated through the jump formation. The design of cut off wall is based on the scourdepth and seepage under the weir. The diameter of boulder is calculated based on the velocity of flow by usingthe formula developed by US Army Waterway Experimental Station, 1959.

Figure 5-1 Weir at Rocky area

The center portion of diversion weir consists of concrete cutoff wall as well as hard stone lining at the top anddownstream part having the slope of 1v:3h. The weir is in rocky area so the rock blot along with grouting iscarried out. As the same the base is prepared by plumb concrete and the concrete thickness is 0.5m atdownstream and 0.8 m at upstream part. The upstream and downstream part is carried by boulder lining worksalong with infill at the top. The excavation level at upstream and downstream level is 902.00masl.

The longitudinal section of the weir is shown in Volume II: Drawings.

5.1.2 Side Intake

The orifice type intake is proposed as the side intake, located immediately upstream and adjacent to the bed loadsluice to withdraw the design discharge of 0.89 m3/s including 15% flushing discharge for gravel trap and settlingbasin under normal operation condition. The invert level of the intake is fixed at 904.50 masl.


16

The intake will have 9 orifices separated by the GI pipe in filled with the concrete at the front of the intake havingopening of 0.3m width and 0.5m height. The approach velocity of about 1.1 m/s. The deck level as well as sidewalls are fixed at 908.00 m.

5.1.3 Gravel Trap and Side Spillway

A gravel trap of length 2.25 m and width 4.3 m is provided immediately after intake chamber to trap coarseparticles of size greater than 5 mm. The depth of the hopper portion provided for the deposition of gravel is 1.3m below orifice invert level and the water depth above hopper is 1.8 m. The proposed structure is designed witha single hopper bottom with longitudinal slope of 1 in 32. The areas in hopper and gravel flushing culvert areexposed to wear and tear due to high velocity and will be lined with dressed hard stone. The normal operatingwater level inside the hopper is 905.00 masl.

A side spillway of 1.0 m width is provided at the gravel trap to spill the excess discharge entered from the intakegate during high flood time and safely pass back to the river. The crest level of the spillway is fixed at 908.00 masl.The spillway canal is 5.92 m long upto the confluence and meets the gravel flushing culvert at elevation 905.00masl.

5.1.4 Approach Canal

Immediately after the gravel trap, a horizontal pressurized approach culvert is provided to cope with the existingtopographical and geological features of the site and to accelerate the flow towards the settling basin. The size ofthe culvert is 0.75 m wide by 1.13 m high with length 42.30 m. The invert level of the culvert is fixed at 904.00masl. The fine trashracks are provided at the beginning of the canal to prevent the chocking of the pressurizedapproach culvert. Approach canal is pressurized up to 4.2 m length and then gate control pressurized flow toopen channel flow which length is 37.1 m.

5.1.5 Settling Basin

A settling basin is required to trap the silt particles before entering into the turbines. The following design criteriaare applied in the design of settling basin of the project:

The settling basin shall have at least 90 % trapping efficiency for the particle size larger than 0.20 mm.

The critical velocity for the design particle size of 0.20 mm is 0.20 m/s, whereas the settling velocity is0.02 m/s at 10ºC.

The settled sediment particles shall be effectively flushed out back to the river.

Sizing of basin is based on the Vetter’s method.

A single chambered conventional type surface settling basin is proposed on the right bank of the Belkhu Khola. Itis designed with 10% extra discharge for flushing which will be used to flush out the deposited sediment duringflood. Chamber is 32 m long, 4 m wide and vertical depth of 3.80 m including free board and hopper. Taking intoaccount of effective area of the basin, flow velocity in the basin will be 0.11 m/s and the trapping efficiency of thebasin will be 90 % for particle size greater than 0.2 mm employing the Vetter’s Method. Inlet transition of 8.32 mis provided for the gradual reduction in flow velocity and to achieve designed velocity in smooth condition at theend of the transition. The bed slope of the basin is maintained at 1 in 50 for the easiness of flushing. The normalwater level inside the basin will be maintained at 904.80 masl, whereas the top levels of the side walls are fixed at905.00masl providing some allowance for free board.

There is a control structure with four identical orifice-type opening of dimension 1.0 m x 1.2 m at the end of thestraight portion of the settling basin. The invert of these opening is fixed at 903.13 masl. This structure helps tomaintain water level in the settling basin. The control structure is followed by a 1.85 m long head pond tomaintain adequate submergence and transition before entrance to the headrace pipe.


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The proposed settling basin is designed as an intermittent flushing type. The flushing channel is a rectangular typehaving 1.00 m width and 0.50 m height. There are one vertical lift flushing gates of 1.00 m x 0.50 m to control theflushing discharge. The settled silt particles will be flushed back to the Belkhu Khola through the flushing culvertof 24.50 m long followed by the cascade outlet

5.1.6 Penstock Pipe and its support

GeneralThe penstock pipe is used to convey water from forebay to the turbine. The penstock invert level center at anelevation of 902.00 masl, passes mild slope and terminate at the connection to the turbine at centre levelelevation of 754.90 masl. The penstock pipe arrangement consists of 1845.551 m long steel pipe of internaldiameter 750.0 mm. There is 42 nos of anchor blocks and the blocks is designed on the basis of deflection anglethe minimum size of block is 2.0m x2.5 mx1.5m and maximum size is 4.50m x 4.0 m x 1.5m.

Figure 5-2 Penstock alignment of project

The maximum pressure rise in the penstock pipe due to water hammer effect has been worked out as 13% of thestatic head when the both units are shutdown simultaneously. However it should be confirmed with theelectromechanical suppliers. In the design of the penstock pipe and supports, 15% of surge head has been taken.

Pipe materialThe raw material for penstock pipe could be in-accordance to the Indian Standards IS 2062: 1999 Grade B orequivalent national or international standards having minimum yield strength of 250.0 MPa and ultimate tensilestrength 410 MPa. The thickness of the pipe is calculated to withstand surge head plus hydrostatic head with anallowance of 2.0 mm for corrosion. The thickness of steel available in the market was also considered duringdesign. The pipe thickness varies from 6.0 mm at the start to 10.0 mm at the end. The minimum pipe thickness isselected based on buckling and handling thickness requirement criteria. Besides, the factor of safety for thicknessof pipe is taken as 2.0.

During this study, the pipe thickness has been varied in nine stretches as per the design criteria. Table 5-1 showsthe thickness of the pipe for different gross head. The optimization study of penstock pipe for differentarrangement and different operating modes are carried out.


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Table 5-1 Thickness of the pipe for different head

Section Section 1 Section 2 Section 3 Section 4 SectionBranch

Length of penstock ofsection, m 857.32 368.50 278.60 360.68 22.50

Static Head, m 62.13 63.41 98.11 150.00 150.00

Surge Head, m 9.32 9.51 14.72 22.50 22.50

Total Head, m 71.45 72.92 112.83 172.50 172.50

Wall thickness of penstockpipe, mm 6.00 6.00 8.00 10.00 10.00

The diameter of bifurcation is 500 mm having pipe thickness of 10 mm.

Figure 5-3 Penstock Diameter Optimization

Anchor blocks and support piersThe penstock, exposed above ground is supported on a series of anchor blocks and saddle supports with the rockanchorage. Because of topography and landmarks, the alignment requires 42 anchor blocks. All of them aredesigned for either vertical bends or horizontal bends or combined bends. The vertical bends along the alignmentminimize excavation and the height of the saddle supports.

The alignment along the pipe will require excavation and grading to prevent a frequent change in the slope of thepenstock.

The lower reach near the powerhouse requires more excavation to meet the turbine axis elevation.

Anchor blocks of grade C20 concrete with 40% plums and nominal reinforcement is provided to avoid unevensettlement & cracking. The block is designed on the core concrete as well as masonary of 1:4 for the loadsupport. The blocks have been designed to provide stability against sliding, overturning and bearing pressure. Thedetail design of penstock pipe anchor blocks is carried out based on the following assumptions:

Forces considered are enumerated as follows:

Weight of pipe and water enclosed

Frictional force of pipe on support piers

Hydrostatic pressure

-

0.60

0.65

0.70

0.75

0.80

0.85

0.90

0.95

1.00

1.05

1.10

1.15

1.20

1.35

1.40

Cos

t (i

n U

SD)

Diameter(m)

Penstock Diameter Optimisation

Series3


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Thermally induced stresses in the block

Hydrostatic force on exposed ends of pipe in expansion joints

Dynamic force at pipe bends

Soil pressure acting on the upstream face

Wind load

Snow load

Seismic load

Permissible stress in anchorage bars 0.42 fy

Design discharge 0.81 m3/s

Coefficient of friction between pipe and pier 0.25

Coefficient of friction between soil and concrete 0.5

Allowable bearing capacity at soil 180.0 KN/m2

Allowable bearing capacity at rock 250.0 KN/m2

Allowable eccentricity at base eallowable = Lbase/6 (Lbase = base Length)

Surge head 15% of gross head

Support piersSaddle type support piers are provided along the straight sections of exposed penstock pipe between anchorblocks to avoid overstressing in the pipe. The spacing of the piers is 8.0 m The piers will be constructed of C20grade concrete.

Saddle plates will be placed in the saddle along with 4 mm thick tarpaper to minimise the frictional effects andincrease the useful life of the pipe. Wear plate will be welded to the pipe at each support and the corners of thewear plate will be cut with a radius to avoid stress concentrations.

Three types of support piers have been designed based on the topography and steel pipe thickness. Support piersare designed considering earthquake force having seismic coefficient of 0.15.

Design Data and AssumptionsThe support pier design is based on the following assumptions:

Forces considered are

Weight of pipe and water enclosed

Frictional force of pipe on support piers

Soil pressure acting on the upstream face


Coefficient of friction between pipe and pier 0.25

Coefficient of friction between soil and concrete 0.5

Allowable bearing capacity at soil 180.0 KN/m2


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Allowable bearing capacity at rock 250.0 KN/m2

Allowable eccentricity at base eallowable = Lbase/6 (Lbase = Length of base)

Factor of safety on sliding 1.5

Design of the support piers has checked the structure in three criteria:

a) Safety against overturning

b) Safety against bearing

c) Safety against sliding

Concrete casing

At the penstock pipe, concrete casing is provided in the kholsi crossing between Sop16 to Sop17.Thelength of concrete casing is 15.0 m. The thickness of concrete casing is determined considering thediameter, thickness and total head at the section; i.e. 62.12m.

Design Data and AssumptionsThe Concrete casing design is based on the following assumptions:

Reinforcement Steel grade 500 MPaConcrete grade 20 MPa

Elastic Modulus of concrete Ec 25491.175 MPa

Elastic modulus of steel Es 2.00E+05 MPa

Sp. Wt of water Gamma 9810 N/m3

Allowable strain in steel εs 0.00075

Allowable Tensile stress in concrete Sigma c 3.130 MPa

Corresponding tensile strain in steel assumingtriangular strain diagram εs(c) 0.000128

Permissible shrinkage strain in concrete εsh 0.00030Allowance for surge Surge factor 1.15

5.1.7 Powerhouse

The proposed powerhouse is located at cultivated land on the left bank of the Belkhu Khola well above the highflood level of the 100 years return period The elevation of the powerhouse is fixed as such that it is free fromthe risk of flooding at the Belkhu Khola during the monsoon season. To ensure safety, flood protection wall nearthe powerhouse is also designed along the Belkhu Khola.

Considering the head and flow available, twin jets Pelton turbine with horizontal shaft alignment is selected. Theelevation of the turbine axis is set at 754.90 masl.

The hydraulic sizing and optimization of the turbine runner was done by using TURBNPRO KC4. Among severalalternatives, the one with best efficiency and the least weight for the turbine runner and shaft were selected.Some of the prominent characteristics of the selected option are listed below.


No. of jets : 2 per unit


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Peak Efficiency : 96.00%

Figure 5-4 Long side view of power house of project

The layout of powerhouse was carried out based on the IS 12800 (Part I): 1993 (reaffirmed 1998). Powerhouse isbasically designed as a house for the turbine and generator and other necessary electromechanical equipments.Also, it must have an area for service and maintenance and room for mounting control panel, transformer andhigh voltage panel in addition to an office room. Generally to lift the heavy installations in the powerhouse, anoverhead travelling crane or a suitable mechanism having chain pulley is equipped. The proposed powerhouseaccommodates two units of horizontal shaft Pelton turbine. The total length of powerhouse is 18.5m and width of10.73 m which includes the control building .Office area, control panel area, high voltage room, fire fightingsystems etc. are suitably arranged inside the control building and power house structure. The turbine axis is set at754.90 masl. Two units of main inlet valve, fitted in each of the distributor pipe, are located inside thepowerhouse. The roofing is done with the corrugated GI sheets, resting above the steel truss structure placedabove the top most beams.

5.1.8 Switchyard area

The area for switchyard is provisioned to be on the plain land near the powerhouse. The area required for thispurpose is approximately 15 m x 10 m. This area will be equipped with the various electrical installations, allrequired for the power evacuation to the Jahare. All the necessary equipment and fittings are supposed to be keptoutdoors in this area. Since there is a risk of fatal electric shock, this area is sensitive and is fenced well to protectfrom all kind of intruders. Power from the powerhouse is evacuated to Jahare sub-station through 33 kV singlecircuit transmission line of 8.0 km length, from where it is connected to the national grid.

5.1.9 Tailrace

The sizing of tailrace is based on the hydraulic design using manning’s formula. The input design parameters are:

Design discharge: 0.81 m3/sRoughness coefficient (n): 0.014Maximum allowable velocity for concrete: 1.51 m/sLength of tailrace culvert: 36.63 mFlood water level: El. 745.0 m (Water level corresponding to 100-year return period at the tailrace section in theRiver)


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The tailrace arrangement consists of a concrete box culvert of 1.40 m wide and 1.92 m deep that extends fromthe tailrace gate to the left bank of Belkhu Khola. The total length of rectangular shaped tailrace channel is 36.63m including all. Tailrace gate is equipped after combining the individual culverts.

5.2 Structural Design5.2.1 Headworks

Diversion weir cutoff

The main purpose of Weir is to divert water from river to intake and provide sufficient head to flush sediment ingravel flush.

The following loads and their combinations where applicable shall be taken and analyzed and structure shall bedesign based on the critical load combinations. The load conditions are:

Water pressure load from u/s and d/s at 1 in 100 year return period flood.

Boulder load from u/s.

Active soil pressure load from u/s.

Passive soil pressure load from d/s.

Earthquake load from u/s.

Dead load of structure itself.

All possible combinations of the above.

The analysis of force acting on the structure for ultimate conditions are carried out and the structure is designedto withstand the force calculated.

The bearing pressure of foundation of the structure will depend on type and general classification of soil. Forordinary soils with no reliable information, the permissible bearing pressure shall not be taken more than 180KN/m2. Suitable adjustment for depth of soil and overburden pressure will be made. For boulder mixed soil, thebearing capacity will be higher and a higher value will be taken from IS codes and other reliable literatures.However, the bearing pressure shall not exceed 250 KN/m2 at surface. In case of rocks, suitable values will betaken following codes and practices and depending on the geological investigation data, if any.

FOS against sliding > (greater than) 2.0 (without seismic consideration)

1.2 (seismic consideration)

FOS against overturning > (greater than) 1.5 (without seismic consideration)

1.1(seismic consideration)

Unit weight of dry soil = 18 KN/m3

Unit weight of saturated soil = 21 KN/m3

Unit weight of submerged soil = 11.19 KN/m3

Angle of repose for the soil (f) = 30◦ (for permanent structures and long term loading)


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35◦ (for short term loading and for temporarystructures)

The above mentioned soil parameters shall be used for computation of active and passive pressure due to soil forIntake, Settling basin ,Weir and other components of the head work. Additionally, the stability of the abovementioned structures shall be checked in Sliding, Overturning and Bearing failure using the same soil parameters.Factor of safety may change in the especial case during the design of the structures and which shall be relevantaccording to recent research and findings.

Remarks

Overturning Sliding

Allowable

bearing

stressOverturning Sliding Overturning Sliding

qmax qmin qmax qmin

1 Nwl 1.20 2.00 200 4.68 57.53 71.36 11.93 OK OK OK OK

2 Flood 1.20 2.00 200 3.12 61.20 72.51 9.07 OK OK OK OK

3 Nwl+Seismic 1.10 1.20 200 4.19 57.97 67.49 18.02 OK OK OK OK

4 Nwl-Seismic 1.10 1.20 200 4.90 57.97 79.00 6.52 OK OK OK OK

Stability of Weir

S.N. Condition

Safety factor From calculation Result

Bearing stress

(kn/m2)

Allowable bearing

stress

Figure 5-5 Weir Stability tabulated form

Figure 5-6 Typical weir Section

Settling Basin

A settling basin is required to trap the silt particles before entering into the turbines. The following design criteriaare applied in the design of settling basin of the project:

The settling basin shall have at least 90 % trapping efficiency for the particle size larger than 0.20 mm.

The critical velocity for the design particle size of 0.20 mm is 0.20 m/s, whereas the settling velocity is0.02 m/s at 10ºC.

According to Bouvard recommendation, the shear velocity shall be about 40 % of the settling velocityto avoid re-entrenchment of particles that has settled to the bottom of the basin.

The settled sediment particles shall be effectively flushed out back to the river.


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Sizing of basin is based on the Vetter’s method.

The following loads and their combinations where applicable shall be taken and analyzed and structure shall bedesign based on the critical load combinations. The load conditions are:

Water pressure load in side walls.

Soil pressure load from backfilling when there is no water inside the walls.

Earthquake load in side walls.

Silt Load.

All possible combinations of the above.

The same structures shall also be checked against uplift.

The analysis of force acting on the structure for ultimate conditions are carried out and the structure is designedto withstand the force calculated. The stability of the structure also shall be checked in the design calculations.

Allowable Bearing capacity of soil was selected based on the subsoil preliminary investigations taken as followsAllowable Bearing Capacity 200KN/m^2.

The bearing pressure of foundation of the structure will depend on type and general classification of soil. Forordinary soils with no reliable information, the permissible bearing pressure shall not be taken more than 180KN/m2. Suitable adjustment for depth of soil and overburden pressure will be made. For boulder mixed soil, thebearing capacity will be higher and a higher value will be taken from IS codes and other reliable literatures.However, the bearing pressure shall not exceed 250 KN/m2 at surface. In case of rocks, suitable values will betaken following codes and practices and depending on the geological investigation data, if any.

FOS against sliding > (greater than) 2.0 (without seismic consideration)

1.2 (seismic consideration)

FOS against overturning > (greater than) 1.5 (without seismic consideration)

1.1(seismic consideration)

Unit weight of dry soil = 18 KN/m3

Unit weight of saturated soil = 21 KN/m3

Unit weight of submerged soil = 11.19 KN/m3

Angle of repose for the soil (f) = 30◦ (for permanent structures and long term loading)

35◦ (for short term loading and for temporarystructures)

The above mentioned soil parameters shall be used for computation of active and passive pressure due to soil forIntake, Settling basin and Weir components of the head work. Additionally, the stability of the above mentionedstructures shall be checked in Sliding, Overturning and Bearing failure using the same soil parameters. Factor ofsafety may change in the especial case during the design of the structures and which shall be relevant according torecent research and findings.


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Remarks

Overturning Sliding

Allowable

bearing

stressOverturning Sliding Overturning Sliding

qmax qmin qmax qmin

1 Empty 2.00 1.50 200 14.40 13.43 44.15 38.29 OK OK OK OK

2 Full 2.00 1.50 200 4.40 18.32 68.29 44.15 OK OK OK OK

3 Empty+Eqx 1.50 1.10 200 15.30 6.29 46.36 38.29 OK OK OK OK

4 Empty-Eqx 1.50 1.10 200 7.60 3.25 52.23 36.08 OK OK OK OK

Stability of Structure

S.N. Condition

Safety factor From calculation Result

Bearing stress

(kn/m2)

Allowable bearing

stress

Figure 5-7 Settling Basin Stability Tabulated Form

Figure 5-8 Typical Section of Settling Basin

5.2.2 Penstock Pipe

5.2.2.1 Support design

Anchor block designFor detail design of the blocks, the final size from stability analysis has been considered. The wall thicknesses ofblocks are greater than 500mm; hence it has been designed for temperature reinforcement. To control crackspacing there must be sufficient reinforcement so that the reinforcement will not yield before the tensile strengthof the immature concrete is exceeded. For this the valued of tensile strength of immature concrete may be takenas 0.12*(characteristic strength of concrete) ^0.7 N/mm2. The area of effective concrete, Ac from which the valueof As (area of reinforcement in a given direction to prevent early thermal cracking) is determined is normally thegross cross sectional area. In sections thicker than 500mm, Ac is that area of concrete which lies within 250mm ofthe surface. This reinforcement should be distributed evenly around the perimeter of the section.

Support pier designFor detail design of the piers, the final size from stability analysis has been considered. Three types of supportpiers have been designed based on the topography, steel pipe thickness and shape of piers. The spacing of thepiers will be 8.0 m. The piers will be constructed of C20 grade concrete.


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In addition, the loads have been applied on the structures resembling the real loading condition. Member sizingand spacing of reinforcement has been performed by successive 3D-model analysis and corresponding design. TheRC design has been performed in spread sheet with the help of analysis result obtained from the softwareSAP2000.

The failure of structure was checked against the permissible limit of tensile, compressive, punching failure, bearingfailure and shear stresses. Successive iterations have been done in the sections of structure in order to bring thestresses within these limits.

The design has been done according with limit stress design method of IS456:2000 and other associatedliteratures whereas detailing has been done according to IS13920:1993and BS 4466.

5.2.3 Powerhouse

5.2.3.1 Introduction

The structural analysis of the powerhouse frame is carried out by means of a structural analysis and designsoftware, SAP2000 and some components by manual calculations. Seismic loads are applied according to theIS1893 (Part 1):2002. Analysis is performed for different load combinations as prescribed in the code. Thefundamental time period of the structural model is 0.46 sec. Both seismic coefficient method and responsespectrum method is carried out during the analysis. Importance factor of 2 is adopted with the responsereduction factor of 5 in the calculation of seismic coefficient for the sever zone having the zone factor of 0.36 andmedium soil type. While performing the analysis, moving load of the steel crane girder is considered in thepowerhouse. However, it has been assumed that the crane would not be operated during the occurrence of anEarthquake, and accordingly only 25% of the total load due to moving crane is considering in the seismic weightcalculation.

The structural analysis was followed by a RC design for the building frame and steel design for the Roof Truss.Member sizing and spacing has been performed by successive analysis and corresponding design. The RC designhas been performed with the help of the software SAP2000. The design is done according to IS456:2000 anddetailing is done according to IS13920:1993. British code has also been utilized during the detailing of the superand substructures. The design calculation according to the algorithm of SAP2000 has been followed again whichfollows the IS codes IS-456:2000 and IS13920:1993.

The Machine foundation has been analyzed by manual calculations as well. Depending on the various loadcombinations, a raft system is subjected to a system of forces that may change from time to time. The detailinghas extensively considered this issue. Therefore, it is highly recommended not to shift the location of lapping ofthe mat reinforcement as provided by the designer

The machine block has been designed considering its stability against bearing pressure, overturning, sliding andalso for an earthquake (IS 1893:2002).Seismic coefficient of 0.2 is adopted for the horizontal excitation duringseismic condition and 0.1 is considered for the vertical excitation. The machine block for two different blocks willbe casted monolithically to dampen the vibration from block to the powerhouse structure. The reinforcementdetailing of the machine raft and some portion of the block is accompanied with this report. The machine supplieris expected to provide detailing of the machine block, or supplier’s information can be processed to generate theone.

Vibration analysis of the machine foundation has been performed by the manual calculation (Bowels). For thisanalysis, information of machine regarding weight, unbalanced force and operating as well as peaking speed areneeded. Present analysis has been performed relying on the available machine specification. Wind loads are notconsidered in the design of RC structures where as wind loads are considered in the design of steel roof truss ofthe power house according to IS 875(part-3) 1987.

a) Geometry of Powerhouse


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Powerhouse has been analyzed using FEM software SAP2000. Beams and Columns have been modeled as frameelements and concrete walls have been modeled as shells.All frame elements adopted are simply 2 noded lineelements and all shell elements are 4 noded areas. Base of the structure have been restrained with fixed supports.

Model has been analyzed both statically as well as dynamically (Modal Analysis). Materials adopted are linear elasticwith the appropriate values of Modulus of Elasticity and Poisson ratio. The FEM model of the powerhouse hasboth the super as well as the substructure. The superstructure consists of the portal frame with beams andcolumns. The superstructure also includes the crane beam arrangement. The moving load due to the two-waymovement of the crane on the power house is carried out on the basis of machine weights required and theseloads are applied in the FEM model by assigning the vehicle load of moving nature (special tool in SAP2000). Inaddition to this, the vertical generator load as a point/joint load and torque load as a point/joint rotational loadwere also calculated. All these calculated loads are assigned in FEM model as input parameters.The following figure gives the overall picture of powerhouse.

Figure 5-9-2D Finite Element Model of Truss

Figure 5-10-3D Finite Element Model of main Powerhouse


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Material PropertiesConcreteThe following values are assumed for the properties of plain concrete and reinforced concrete:Concrete Grade : C25 for all frame and shell elementsUnit Weight of Concrete : 25 KN/m³Modulus of Elasticity (Mpa) : 5000 √fckPoisson’s Ratio : 0.2

ReinforcementCharacteristic strength of high yield steel is taken as 500 MPa for main rebar and for stirrups too. In the designfollowing properties of rebars are taken:Modulus of Elasticity : 2 х 105 N/mm²Poisson’s Ratio : 0.3

5.2.4 Machine foundation

5.2.4.1 Introduction

Design of machine foundations require a special consideration because they transmit dynamic loads to soil inaddition to static loads due to weight of foundation, machine and accessories. The dynamic load due to operationof the machine is generally small compared to the static weight of machine and the supporting foundation. In amachine foundation the dynamic load is applied repetitively over a very long period of time but its magnitude issmall and therefore the soil behavior is essentially elastic, or else deformation will increase with each cycle ofloading and may become unacceptable. The amplitude of vibration of a machine at its operating frequency is themost important parameter to be determined in designing a machine foundation, in addition to the naturalfrequency of a machine foundation soil system. There are many types of machines that generate different periodicforces. The most important categories are:

1. Reciprocating machines: The machines that produce periodic unbalanced forces (such as steam engines)belong to this category. The operating speeds of such machines are usually less than 600r/min. For analysisof their foundations, the unbalanced forces can be considered to vary in sinusoidal fashion.

2. Impact machines: These machines produce impact loads, for instance, forging hammers. Their speeds ofoperation usually vary from 60 to 150 blows per minute. Their dynamic loads attain a peak in a very shortinterval and then practically die out.

3. Rotary machines: High-speed machines like turbo generators or rotary compressors may have speeds ofmore than 3,000r/min and up to 12,000r/min.

For UBKHEP the type of machine is Rotary machines having frequency 500 rpm.

A suitable foundation is selected, depending upon the type of machine. A block foundation has a large mass and,therefore, a smaller natural frequency. However, if a relatively lighter foundation is desired, a box or a caissontype foundation may be provided. The mass of the foundation is reduced and its natural frequency increases. Butthe provided foundation is block foundation.

5.2.4.2 Dimensions Adopted and Input

Length 18.5m

Breadth 10.73 m

Net Pressure Head 150.10m


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Diameter of Penstock 0.50 m

Design Discharge 0.81 m3/sec

Rated Speed of rotor 750 rpm

Allowable Bearing Capacity 100KN/m2

5.2.4.3 Assumptions

The machine block has been designed considering its stability against bearing pressure, overturning, sliding and also

for the case when earthquake exist (both horizontal and vertical excitation. A very high head of water compels us

to go for a very large machine foundation block. The machine block for two different blocks will be casted

monolithically to dampen the vibration of the machine embedded.

The fundamental natural frequency shall be at least 20% away from the machine operating frequency. The machine

supplier is expected to provide machine detailing and orientation in the machine foundation block.

The reinforcement detailing of the machine raft and some portion of the block is accompanied with this report

having the quantity of more than 25kg/m3 as referred to IS 2974 (Part 3): 1992.

The structural design strength is derived from the characteristic strength multiplied by a coefficient 0.67 and

divided by the material partial safety factor. The partial factor for concrete in flexure and axial load is 1.5.

5.2.4.4 Criteria for design

A machine foundation should meet the following conditions for satisfactory performance

a) Static loads

1. It should be safe against crushing, bending and shear failure

2. It should not settle excessively.

b) Dynamic Loads

1. There should be no resonance; that is, the natural frequency of the machine-foundation-soil systemshould not coincide with the operating frequency of the machine. In fact, a zone of resonance is generallydefined and the natural frequency of the system must lie outside this zone. The foundation is high tunedwhen its fundamental frequency is greater than the operating speed or low tuned when its fundamentalfrequency is lower than the operating speed.

2. The amplitudes of motion at operating frequencies should not exceed the limiting amplitudes, which aregenerally specified by machine manufacturers. If the computed amplitude is within tolerable limits, but thecomputed natural frequency is close to the operating frequency, it is important that this situation beavoided.

3. The vibrations must not be annoying to the persons working in the shops or damaging to the otherprecision machines. The nature of vibrations that are perceptible, annoying, or harmful depends upon thefrequency of the vibrations and the amplitude of the motion.


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5.2.4.5 Degrees of freedom of a rigid block foundation

A typical concrete block is regarded as rigid as compared to the soil over which it rests. Therefore, it may beassumed that it undergoes only rigid-body displacements and rotations. Under the action of unbalanced forces,the rigid block may thus undergo displacements and oscillations as follows:

1. translation along Z axis2. translation along X axis3. translation along Y axis4. rotation about Z axis5. rotation about X axis6. rotation about Y axis

Any rigid-body displacement of the block can be resolved into these six independent displacements. Hence, therigid block has six degrees of freedom and six natural frequencies. Of six types of motion, translation along the Zaxis and rotation about the Z axis can occur independently of any other motion. However, translation about theX axis (or Y axis) and rotation about the Y axis (or X axis) are coupled motions. Therefore, in the analysis of ablock, four types of motions are being considered. Two motions are independent and two are coupled. Fordetermination of the natural frequencies, in coupled modes, the natural frequencies of the system in puretranslation and pure rocking need to be determined. Also, the states of stress below the block in all four modesof vibrations are quite different. Therefore, the corresponding soil-spring constants need to be defined before anyanalysis of the foundations can be undertaken.

For UBKHEP powerhouse the analysis was done for three modes of vibration namely,

1. vertical mode of vibration2. sliding mode of vibration3. Rocking mode of vibration.

There is another vibration mode namely ‘Torsional or Yawing mode of vibration’ which was not considered foranalysis as it is assumed that the machine foundation block of powerhouse is very heavy and is surrounded by thesoil in all four faces of the foundation block not allowing torsion.

5.2.4.6 Material Properties

ConcreteThe following values are assumed for the properties of plain concrete and reinforced concrete:

Concrete Grade : C25

Unit Weight of Concrete : 25 KN/m³

Modulus of Elasticity (Mpa) : 5000 √fck

Poission’s Ratio : 0.2

ReinforcementCharacteristic strength of high yield steel is taken as 500 MPa. In the design following properties of rebars aretaken:

Modulus of Elasticity : 2 х 105 N/mm²

Poission’s Ratio : 0.3


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SoilDensity γs 21 KN/m^3Shear Modulus G 30000 KN/m^2Poisson's ratio Μ 0.35Modulus of Elasticity Es 81000 KPa

5.2.4.7 Methodology

Vibration analysis of the machine foundation has been performed on the basis of elastic half space analog method.For this analysis, information of machine regarding weight, unbalanced force and operating as well as peakingspeed are needed. Present analysis has been performed relying on the available machine specification. Since themass has been the dominant aspect for the vibration control, so while analyzing the machine foundation to restrictits deflection on vertical, horizontal as well as rocking direction, the undamped case is taken into considerationwithout the use of any damper or dashpot. Also the amplitude of the vibration in various modes such as verticaloscillation, sliding oscillation and rocking mode are checked against their permissible values in the case ofresonance as well.

The ratio of force transmitted to the total unbalance force should be less than unity and the frequency ratioshould be greater or less than square root of 2. This result may provide the transmissibility to the unbalanceforce. This should be usually satisfactory enough to withstand the vibration of the machine foundation by theground.

5.2.4.8 Information needed for the design

The following information is required and must be obtained for design of a machine foundation:

1. Static weight of the machine and accessories.

2. Magnitude and characteristics of dynamic loads imposed by the machine operation and their point ofapplication.

3. The soil profile of the site and dynamic soil properties such as dynamic shear modulus and damping.

4. Trial dimensions of the foundation. This will give the total static weight.

5. An acceptable method of analysis i.e., a mathematical model to determine the response of the foundation-soilsystem.

5.2.4.9 Present status of the design of machine foundation

The machine foundation was preliminarily analyzed and designed for stability so that it was safe against sliding,overturning, eccentricity, bearing etc. In final design, safety against uplift and safety against accidental loads and uplift(e.g. Impacts due to braking of blades of turbines) shall be checked once the machine details are obtained. Moreover,the amplitudes of vibration in various modes such as vertical oscillation, sliding oscillation, rocking mode has been keptin control with the help of massive foundation concrete block even at the time of resonance/amplification.

5.2.4.10 Results

Table 5-2 : Stability Analysis


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S.N. Excitation Parameter Check Remark

Permissible Calculated

1 Normal Eccentricity 1.705 1.09 Safe

Bearing 100 20.9 Safe

Sliding 1.5< 5.43 Safe

Overturning 1.5< 14.277 Safe

2 Horizontal Eccentricity 1.705 0.97 Safe




3 Vertical Eccentricity 1.705 0.78 Safe




4 Unbalanced Eccentricity

Bearing

Sliding

Overturning

5 Uplift

a Normal Eccentricity

Bearing

Sliding

Overturning

b Earthquake Eccentricity

Bearing

Sliding

Overturning

6 Accidental Eccentricity

Bearing

Sliding

Overturning

Table 5-3: Vibration Analysis

S.No. ConditionsAmplitude atResonance

PermissibleAmplitude TR β Remarks

1. Vertical Oscillation 0.0021mm 0.4mm0.952 1.586

GoodGoodSatisfactory

2. Horizontal Oscillation 0.0120mm 0.4mm3. Rocking Mode 0.5mm


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4. Top Displacement 0.083mm Satisfactory

5.2.5 Tailrace Culvert

During the analysis of tailrace canal, it requires the detailed information about the probable load and loadcombinations that are assumed to be critical from the hydraulic design considerations. Load considered for detaildesign are hydrostatic load on side wall and bottom slab, lateral soil pressure load on side walls, overburden loadon top slab of canal, vehicle load for certain section of the road crossing.

Earthquake load hasn’t been considered due to buried structure. Load combination includes live load (hydrostaticload and live load on top slab), dead load (soil load and self weight) are considered as per IS 1893- 2002.

The tailrace is designed to accommodate up to full design flow i.e. 0.81 m3/s. Effect of Belkhu khola HFL is takeninto account for finalizing the size of conduit. The tailrace arrangement consists of a concrete box culvert of 1.4 mwide and 1.2 m deep that extends from the tailrace gate to the left bank of Belkhu Khola. The total length ofrectangular shaped tailrace channel is 36.63 m including all and culvert bed slope of 1:500 (V: H).

. The thickness 0.2m for the top slab is considered where the road crossing occurred. Concrete grade of C25 hasbeen carried out. The poison’s ratio for concrete has been taken as 0.2.

In order to take into the account of the behaviour of whole structures in the monolithic form under the abovementioned loading combinations, the whole arrangement of tailrace culvert has been taken into consideration.Finally, the 3D-Model has been prepared in the Structural Analysis Program Software (SAP-2000). In addition, theloads as mentioned above have been applied on the structures resembling the real loading condition. Analysis isperformed for different load combinations as per IS 1893- 2002. For this among the load combinations the worstcondition (envelope) is taken into consideration. Member sizing and spacing of reinforcement has been performedby successive 3D-model analysis and corresponding design. The RC design has been performed in spread sheetwith the help of analysis result obtained from the software SAP2000.

The failure of structure was checked against the permissible limit of tensile, compressive and shear stresses.Successive iterations have been done in the sections of structure in order to bring the stresses within these limits.

The design has been done according with limit stress design method of IS456:2000 and other associatedliteratures whereas detailing has been done according to IS13920:1993.


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6. HYDROMECHANICAL WORKS

6.1 IntroductionAs the detailed design will be consider during construction. Moreover this chapter only describes various types ofgates, stoplogs, valves, trashracks, penstock pipe, bifurcation, branch pipes including all accessories to be used inthis project.

6.2 Gate Stoplog and TrashrackThere are different types of gates and stoplogs used to control the flow and remove the debris/silt from thewaterway and its accessories. The size of each hydro-mechanical component has been determined with referencefrom the hydraulic design calculation. Each gate has been provided with the sealing arrangement, hoisting, steelsupports, dogging device, appurtenant parts and guide frame including track, seal beam, lintel etc. as required.

6.3 Coarse TrashrackA coarse trashrack has been proposed at intake infront of the intake gate. It is provided to prevent the entry ofbed load greater than 100 mm as well as debris, floating materials etc. into the canal. It will be placed at an angleof 81 degree with the horizontal. However, during the low flow season if bed loads are deposited over thetrashrack it will be cleaned manually. Other details are as follows;

Design Data:Width 4.3 mHeight 0.5 mDesign head 3.5 mSpacing 100 mmInclination 81° to the horizontalQuantity 1 Set

6.4 Intake GateOne set of manually operated chain pulley hoisting gate has been proposed at intake. The gate will be used forregulating the inflow during the high flood season. Other details are as follows;

Design Data:Width 4.3 mHeight 0.5 mDesign head 3.5 mSealing 4 way UpstreamQuantity 1 Set

6.5 Gravel Trap Flushing GateOne set of manually operated screw spindle hoist has been proposed for the gravel flush. Other details are asfollows;


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Design DataWidth 1.0 mHeight 0.5 mDesign head 3.0 mSealing 4 way UpstreamQuantity 1 Set

6.6 Canal Inlet GateOne set of manual chain pulley operated hoist gate has been proposed and it is used for the flow control on thewaterway. Other details are as follows

Design Data:Width 0.75 mHeight 1.13 mDesign head 1.5 mSealing 3 way UpstreamQuantity 1 Set

6.7 Fine TrashrackOne set of fine trashrack at forebay has been proposed. It prevent to enter the particle more than 25 mm sizefrom the forbay to the pressure steel pipe.

Design Data:Width 2.3 mHeight 2.5 mDesign head 4 mSpacing 25 mmInclination 81° to the horizontalQuantity 1 Set

6.8 Sand Flushing GateOne set of manually operated screw spindle hoist has been proposed for the sand flush. Other details are asfollows;

Design DataWidth 1.0 mHeight 0.5 mDesign head 4.0 mSealing 4 way UpstreamQuantity 1 Set


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6.9 Tailrace GateOne set of manual chain pulley operated hoist has been proposed at the tailrace and it is used to protect thewater backflow from the tailrace. Other details are as follows;

Design DataWidth 1.4 mHeight 1.8 mDesign head 1.5 mSealing 4 way DownstreamQuantity 1 Set

6.10 Steel Penstock PipesMild steel headrace and penstock pipes of 750 mm diameters are proposed for this project. The thickness variesfrom 6 mm to 8 mm. The prefabricated pipes or fabricated at the site of up to 2m length will be welded togetherat the site. There will be an anchor block at every horizontal and vertical bends in the penstock alignment and thepipe will be supported on the saddle support at every 8 m of distance approximately. The pipe will be placed onthe top of 6mm thick mild steel saddle plates and wear plates. The summary of the required penstock pipe andrequired steel works details hereunder;

Thickness of Pipe (mm) Pipe diameter (m) Length of pipe (m) Total weight (ton)

8 mm Bellmouth 1.4 dia. To 0.75 dia. 0.8 0.35

6 0.75 1226 138

8 0.75 280 42

10 0.75 360 68

10 0.53 22.50 3.2

16 mm Bifurcation 0.75 dia. To 0.53 dia. 2 1.2

Saddle Plate (6 mm) 4.6

Total 1891.3 257.35

Expansion Joints 10 (nos)


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7. TRANSMISSION LINEThe power generated from Upper Belkhu Khola Small Hydroelectric Project shall be connected to 11 kVbusbar of Jahare Substation. Project will construct single circuit 11 kV transmission line with ACSR Dogconductor (Length-8 km approx.) from power house to Jahare Substation.

7.1 Energy Meter and Metering EquipmentTwo sets of energy meter (one main meter and the other check meter) including CT, PT shall be installedat11 kV busbar of Jare Substation at Company’s cost as required by NEA. The energy meter shall be bi-directional and shall be able to record the energy exported to NEA and energy imported from NEA. Theenergy meter and metering equipments (CT, PT) shall be indoor or outdoor type. The connection point isshown in Single Line Diagram.

The rated secondary current of current transformer (CT) shall be 5- 1 A and rated secondary voltage ofPotential transformer (PT) shall be 110 V. The accuracy of both metering CT and PT shall be 0.2 or as advisedby NEA. The accuracy of both main and check energy meter shall be 0.1 or as advised by NEA. The main andcheck meter shall be supplied by the separate core of CT and PT. The detail specification of metering unit(Energy Meter, CT and PT) shall be as per the specification provided or approved by NEA.


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8. POWER FACILITIES-ELECTRICAL EQUIPMENT

8.1 POWER HOUSE MECHANICAL EQUIPMENTThis chapter deals with the power generation from the project. For the option selected, gross power andenergy has been calculated. The net saleable energy for revenue generation has been calculated deductingoutage, self consumption and transmission losses to be borne by the power plant according to the connectionagreement made with Nepal Electricity Authority (NEA)

8.1.1 General

The study of Upper Belkhu Khola Small Hydroelectric Project reveals that the installation of twoTurbine-Generator units will be more economical for the following reasons:

The reliability and efficiency of the plant will be better than single unit. The repair and maintenance works of the power units can be performed in the yearly dry

season in such a way that no energy loss will occur.

The load bearing capacity of the road and bridge will be the determining factor for selection ofgenerating equipment size and capacity.

The powerhouse mechanical equipment of the Project mainly consists of the following:

Turbine Governor Turbine Inlet Valve Flywheel Cooling water supply system Drainage and dewatering system Compressed air system Grease lubricating system Oil handling system Ventilation and air conditioning system Fire protection system Powerhouse overhead travelling crane.

8.1.2 General design criteria

Dimensioning, design and layout of various components and installations considered following features andaspects:

Ratings to safely cope with all normal and fault conditions, avoiding any overstressing of material andequipment.

Equipment to be of standard design, providing highest degree of safety, reliability, availability and easein operation

Equipment arrangements to consider the adequate space and access for the transport, installation,commissioning, operation and maintenance.

8.1.3 Turbine

The selection criterion for turbine for hydropower plants are tabulated as below:


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I. Net HeadII. Range of discharge through the turbineIII. Specific speedIV. EfficiencyV. Cavitations problem

Gross head

The gross head of the site provided to us is 150.10m. From the table given below, we have four choicesnamely, Fransis, Pelton, Michell-Banki and Turgo. So we go for next criterion for the selection of turbine thatis discharge.

Figure 8-1 Range of Gross Heads

Discharge

We have design discharge per unit as 0.81m3/s which is low and discharge available during the driest monththat is during April is:- 0.23 m3/s.

Figure 8-2 ALSTOM Turbine selection chart

From this chart we can select both Fransis and Pelton turbine.


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Gross head



Discharge





39


Gross head



Discharge





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Figure 8-3 Application Zone in Selecting the Turbine Type

From this chart we can select horizontal Pelton turbine.

Efficiency

Pelton versus Fransis efficiency graph given below shows that there is large variation in the efficiency ofFransis turbine when its load is varied from 40% to 85% of design discharge whereas there isn’t muchvariation in the efficiency of Pelton turbine with its load variation. Moreover, the Fransis turbine must beoperated above 50% of the nominal load. In upper belkhu more than 6 month the discharge will be less than0.6 m3/s and this period So Pelton turbine is selected for this project. If we selected fransis turbine efficiencyis very less.


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Figure 8-4 Efficiencies; Pelton vs Francis

Cavitations problem

This problem is mostly seen in case of Fransis turbine. So it requires frequent maintenance and increasesoperation and maintenance cost.For the given head and discharge, two units of pelton turbine with horizontal shaft will be used. The reasonfor selecting pelton turbine is presented as below:

1. The operation and maintenance of the plant will be easier.2. The average efficiency is high in general and most suitable for part load operation.3. Less space is required for installation.

Each turbine is controlled by an electro-hydraulic governor relaying on a pressurized oil system for regulationof the turbine Nozzle. The turbine will be directly coupled to the generator through an intermediate shaft.Such provision will allow removal of turbine runner without dismantling parts of the generator. The turbineshall have oil-lubricating guide bearings.The main characteristics of the horizontal Axis Pelton turbine will be as follows:

Type Horizontal Axis PeltonNo. of units 2Rated output per unit 560 kW

Rated gross head 150.1 m

Rated discharge for each unit 0.405 m3/s Ratedspeed 750 rpm

No. of pole 8

Runaway speed 1425 rpm

Rated efficiency 90%

8.1.4 Turbine Governor

Each turbine is equipped with Proportional Integral Derivative (PID) type electro-hydraulic servo system forneedle and jet deflector. Governors will permit independent unit operation and will ensure stable governing in


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Cavitations problem







No. of pole 8






41


Cavitations problem







No. of pole 8






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parallel operation. In combined operation, they can regulate the required power even during fluctuation of thereservoir level. In case of frequency fluctuation in the system, an automatic switch-over to speed control willbe initiated to stabilize the power system frequency. In addition a simplified opening controller enables acontinuation of turbine operation, in case the speed and power controller with the electronic feed-backdevice fails.

8.1.5 Turbine Inlet Valve

One inlet valve is provided for each generator unit. All the valves are arranged in conjunction with expansionjoints. The valve should be designed for opening at equalized pressure and closing against the maximum headand flow. A valve of fail-safe close type should be furnished with rubber service seal, metal to metalmaintenance seal operated by water pressure, linear servomotor for opening, operated by means of oilpressure from the governor hydraulic unit, counter weight for closure and bypass with electrical actuator.

The valve should be designed to facilitate maintenance and replacement of the different valve elements andoperating mechanism, which might be worn out and need to be replaced.

8.1.6 Cooling water supply system

The cooling and service water system will supply water in sufficient quantity to the following components:

Main generator coolers Bearing oil coolers Governor oil coolers Turbine shaft sealing Washing and cleaning points

The system taps water from the tailrace pit for the cooling purpose. The water system is served by a filterstation comprising:

Two pre-filter in each supply line Two self-cleaning rotary strainers Valve and piping AC and DC pump

8.1.7 Drainage and Dewatering System

The drainage and dewatering system will serve the following purpose:

to drain the powerhouse seepage water to dewater the power conduit to drain the powerhouse in the event of emergency

The system will consist of drains leading to the drainage pit. Two drainage pumps and two dewateringpumps with associated valves and pipe works will be located in the drainage sump. These pumps willdischarge to the tail water. To dewater the penstock and power conduit, a drain valve with piping workjust upstream of main inlet valve will be provided for each unit. The details of drainage and dewateringsystem shall be carried out in next phase of study.


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8.1.8 Mechanical Workshop

The mechanical and electrical workshop is equipped with a number of machine tools and tools for pneumaticand electric appliances for the maintenance of the mechanical, electrical equipment and hydraulic steelstructure at the site. In additional, it also has adequate space for storing spare runner and other turbine andgenerator related accessories, for instance nozzle, deflector) complete set of all wearing parts for the turbineguide bearing, complete turbine guide bearing, complete bearing oil cooler, relay of each type, set of speedsensing device for governor, hydraulic control valve of each type, governor oil pump, set of completelubrication fittings, complete set of ring and gasket for butterfly valve servomotor, one complete set of relayfor generator protection and other parts as recommended by the specific manufacturer later on. Theworkshop is located near the erection bay.

8.1.9 Grease lubricating system

A centralized automatic grease lubricating system will be provided for each generating unit for automaticallyinjecting pre-set amount of lubricants for bushing and all working parts of the turbine inlet valves operatingmechanism. A stand by hand operated pump for normal service is provided. The system will have a means ofcontrolling the volume of grease to each grease point and of assuring that each grease point is lubricated insequence in the greasing cycle. This system will be finalized in next phase of study.

8.1.10 Oil handling system

An oil handling system will consist of an oil purifier capable of removing all contamination such as watersolids, sludge etc. from lubricating oil system as well as high pressure oil system. It will also have oil pumpswith appropriate length of flexible hose pipes. The capacity of the oil handling system will be determined inthe next phase of study.

8.1.11 Ventilation and air conditioning system

The purpose of ventilation system for the powerhouse is as follows:

to provide adequate fresh air to the working personnel to remove heat generated by mechanical and electrical equipment to provide smoke exhaust ventilation in case of fire to minimize the circulation of smoke and

production of combustion

The ventilation and air conditioning system consists of fresh air handling unit and air conditioningunit.

8.1.12 Fire Protection System

The power plant and its major equipments need to be protected against the fire hazards. The power plant isguarded against the fire with the following two levels of operations:

Fire detection

Fire fighting

The fire detectors, for instance, heat detector, ionization detector, optical detector, smoke detector are to


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be installed in the plant. These detectors initiate the fire alarms installed at appropriate locations. The firefighting system for the power plants comprises fire hydrants for generators/ transformers and the installationof portable fire extinguishers for other rooms. Water fire extinguishing system is installed for each unit ofgenerator and transformer, manual operated type for generators and automatic system with spray nozzles (ahigh pressure water deluge sprinkle system) for transformer respectively. In addition to this every generatorhas CO2 fire extinguishing system.Water for above system is obtained from the pressurized water storage tank somewhere near thepowerhouse. The portable extinguishers are of dry chemical heavy-duty type and air pressurized type.

8.1.13 Powerhouse Overhead Travelling Crane

One single girder Electric Overhead Traveling (EOT) crane with a hook capacity of 10 tons is proposedinside the powerhouse. This crane is used for lifting and handling any equipment during installation,maintenance and operation of the plant. It is anticipated that the generator, rotor and shaft are the heaviestpart to be lifted by the EOT crane. It has a single travelling trolley for the main hoist and auxiliary hoist.Operation of this crane ensures loading and unloading of the heaviest single part at the powerhouse. Also,erection of all the components should be ensured by installing this crane. Capacity of the main hoist shouldbe 30% above the single heaviest part of equipment inside the powerhouse, which obviously is the rotor of asingle generator. The crane will be equipped with two different levels of speeds; one for longitudinal traveland other for the cross travel. All the units will be handled by this crane. It should be noted that additionallifting devices such as monorails, chain blocks wheeled platform/trolleys etc are required for lifting andmoving equipment in areas which are out of reach of the overhead crane. Access will be provided to theoverhead crane by staircase for maintenance.In addition, the crane has an emergency stop button switch. Provision for manual operation of auxiliary hoistis also provided in case of emergency.

8.2 POWER HOUSE ELECTRICAL EQUIPMENT

8.2.1 General

The powerhouse electrical equipment of Upper Belkhu Khola Small Hydroelectric Project will mainly includegenerators, transformers, switchgears, protection scheme, control system, earthing system, lighting system,communication system etc. The ratings of the equipment are designed safely to cope with all normal andfault conditions, avoiding any overstressing of equipment. Also equipment will be of standard design,providing highest degree of safety, reliability, availability and ease in operation.The total generating capacity of the Upper Hadi Khola power plant is 996W. Based on power optimizationof the plant, two generating units are selected. The details of the electrical equipment are discussed in thissection. The main features of the upper belkhu khola power plant are as follows:

Two sets of generators will be connected individually to 400 V medium voltage bus bar through 3phase (Rated maximum voltage 0.6KV) air circuit breaker via cable. The generator circuit breakerwill protect the generator during fault and abnormal conditions and facilitates for synchronization at400V bus.

Indoor type 400 V standard single generating bus configuration will be adopted.

The station transformer will be connected to 400V bus bar to supply the auxiliary and ancillary inthe power plant.


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The 400 V bus bar will be connected to a three phase, 0.4/11 V, 1250KVA step up main powertransformer through 11 kV vacuum circuit breaker and power cable.

The high voltage bus bar is connected to 11 kV transmission line. The metering CT, PT, main meterand check meter of Upper Belkhu khola will also be located in the Jare Substation.

8.2.2 Generating Equipment

Almost all of the hydraulic turbine-driven generators used are synchronous alternating-current machines,which produce electrical energy by the transformation of hydraulic energy. The electrical and mechanicaldesign of each generator must conform to the electrical requirements of the power distribution system towhich it will be connected, and also to the hydraulic requirements of its specific plant.

Generator

The unit rating of the turbine-generator has been selected based on the criterion that the minimum threeunits and capacity of each unit does not exceed 1.0% of the total NEA’s forecasted load of the system. Thisassumption is based on the following consideration:

To limit the transportation sizes and weights

To minimize the power shortage during maintenance or forced outage of a unit;

To provide sufficient flexibility during operation;

To be able to maintain the system stability during the tripping of a unit.

Two units of horizontal shaft, three phase Synchronous generator will be installed to generate996 kW power. The rated output of each generating unit will be 625 kVA. The shaft of the generators willbe directly coupled to the Francis turbines runner. Each generating unit will be provided with Exciter andAVR. The stator winding of the generator shall be star-connected and neutral shall be grounded with neutralgrounding resistor to limit the unbalance fault current. The insulation materials shall be of class F and thetemperature rise shall be limited to 800 C. The cooling system and fire protection of the generator will be assuggested by the manufacture.The main parameters of generator will be as follows:

Type Synchronous, 3-phase, horizontal shaft, salient pole revolving fieldNo. of units Two RatedOutput 625 KVARated generation voltage 0.4 KVRated power factor 0.80 (lagging)Rated efficiency 0.96Rated frequency 50 HzRated speed 750 rpmNo. of poles 8Stator/ rotor insulation Class FStator connection Star with neutral earthedExcitation Brushless

Generator Leads


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The purpose of generator leads is to connect the generator stator coil with the medium voltage bus bar,which is connected with main step up transformer. The term “generator leads” applies to the circuitsbetween the generator terminals and the low voltage terminals of the generator step up transformer. Theequipment selected depends upon the distance between the generator and transformer, the capacity of thegenerator, the type of generator breakers employed, and the economics of the installation. There are twogeneral classes of generator leads: those consisting of metal-enclosed buses and those consisting of medium-voltage cables.

8.2.3 Excitation System

The excitation system installed for generator excitation will be of brushless type and will consist of analternating current exciter (A.C. Exciter), rotating rectifiers, field circuit breaker, excitation transformerand voltage regulating equipment. The excitation system shall have sufficient capacity that the generator iscapable of supplying continuous rated load at rated voltage, power factor and frequency. Provision shall bemade for both automatic and manual control of exciter voltage.

The A.C. Exciter shall be directly coupled to the generator shaft. The A.C. Exciter shall be three phaserotating armature type generator and shall be self-ventilating air cooled type. Sufficient numbers of rotatingdiodes; rectifier shall be installed in the rotor so that excitation current for generator shall be suppliedthrough the main shaft insulated conductor strip. Initial charging DC current field of exciter shall besupplied from station DC source via AVR. For continuous operation, it shall be supplied from excitationtransformer connected on 0.4 kV main circuits via AVR. The insulation shall be of class ‘F’.

The voltage regulating equipment will consist of an automatic voltage regulator (AVR) equipped withreactive power limiter, reactive power control equipment, thyristors and other accessories. The AVR willbe of high speed, quick response type.The general requirements for AVR shall be as follows:

The voltage control under steady state condition shall be +- 5 % of rated terminal voltage.

Over voltage resulted due to sudden load rejection at any load shall not exceed above 30 % of thevoltage held before the occasion of sudden load rejection.

The AVR shall suppress the residual voltage through field discharge switch

8.2.4 Power Transformer

One step-up transformer will be provided to step up the generation voltage 0.4 kV to thetransmission voltage 11 kV. The transformers will be located at the outdoor switchyard. On the highvoltage side HV bushings will be provided. The Lightning arrestors will be provided in 11 kV line side toprotect the equipment against over- voltages caused by lightning and switching surges. Connections of highvoltage terminals of the transformers, switchgear and protection equipment, located at the switchyard willbe made by ACSR dog conductors. The neutral of the HV side of the transformer will be solidly grounded.The generated power will be delivered to NEA’s Jahare Substation at Dhading District.

The main parameters of the power transformer are summarized below:Number of unit One (1)Type 3-phase, oil-immersedInstallation OutdoorRated capacity 1250 KVARated H.V. (Secondary) 11 kV Rated


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L.V. (Primary) 0.4 kVEfficiency 0.99Cooling ONANRated frequency 50 HzL.V. winding connection DeltaH.V. winding connection StarVector group YNd11Tap changer Off-load, ±5 % in steps of ± 2.5 %Material of conductor Copper

8.2.5 Station Supply Transformer

A 3-phase, 25 kVA, 400 V / 400-230 V transformer will be provided for station supply. The primary side ofstation transformer shall be protected by Drop Out fuse and the secondary side shall be protected byMCCB. Ratings of station supply transformer will be as follows:

Number 1Type Indoor typeRated capacity 25 KVARated primary voltage 400 VRated secondary voltage 400-230 VPrimary connection DeltaSecondary connection StarVector group Dyn11Rated frequency 50 Hz

8.2.6 General Layout of Electrical Equipment

Indoor type 0.4 kV standard single generating bus configuration shall be adopted.

The generators shall be connected individually to 0.4 kV generation bus bar through 600V vacuumcircuit breakers. The vacuum circuit breakers shall protect the generator during fault and abnormalconditions and facilitate for synchronizing at 0.4 kV bus.

The high voltage side of Main transformer will be connected to 11 kV transmission bus bar via 12 kVvacuum circuit breaker.

8.2.7 Auxiliary Systems

Essential auxiliaries are those without which the generator units cannot be kept in operation, namelygovernor, the cooling water pumps, the lubrication oil pumps and the Excitation systems. The switchgear isfed from two alternate sources, namely, from station service switchgear or from the emergency dieselgenerator. The two incoming circuit breakers are interlocked to prevent inadvertent paralleling of twoalternate sources.

Operational auxiliaries are those without which over a longer period of time the powerhouse will cease to beoperational, such as dewatering pumps, switchgear and governor air compressors and battery chargers. Theseloads will be normally fed through the 400/230V Motor Control Centres (MCC).


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The selected scheme for the auxiliary services, as shown in the Single Line Diagram is based on thefollowing criteria:

Failure of LV main feeder or circuit breaker should not cause the failure of the auxiliary system. Maintenance on switchgear will be possible without interruption to essential auxiliary services.

The physical layout of the powerhouse should be taken into account, so that the suggested scheme is bothpractical and cost effective.

Based on the above criteria, several alternative sources of supply will be provided

The Station transformer will be of 400/400-230 V, 25 KVA capacity. Indoor and outdoor lighting system will be implemented to provide the adequate illumination level

over different places. A diesel generator, sized to feed the essential loads, will provide station emergency power

supply in the event of unavailability of the generating unit and an overall system outage

8.2.8 DC Auxiliaries

For the utmost reliability, the Control, Protection, Alarm equipment will be fed from a DC supply. The DCsupply is provided by main and redundant battery sets and each set supplied by a battery charger. The basicconcept being that, the failure of DC supply system should not affect the operation of the control andprotection relay system and consequently the powerhouse. For the purpose of this study, a DC batterysupplied emergency lighting has been selected. Battery and charger sizes will be determined during subsequentdesign phase. The batteries for the control, protection and emergency lighting will be 9 in number each ofrating 12V, 150Ahr supplying 110V.

8.2.9 Control and Protection Systems

The unit electronic governors and the unit control panels will be arranged on the generator floor. Bothmanual and automatic control will be provided. For the testing of the unit during commissioning andmaintenance, it will be possible to control a unit in either automatic or manual mode from the panel.However, unit synchronization will not be permitted from the unit control panel. When the unit is ready forsynchronizing, the automatic or manual synchronization will be possible only from the Control Room.

The powerhouse and switching equipment will be controlled from the control desk located in the ControlRoom. The station control console with its own control and monitoring instruments, the synchronizer, thestation annunciators, the metering panels, the protective relay panels and the temperature recorders will belocated in the powerhouse Control Room.

Protection system will be provided to isolate faulty systems as quickly as possible, to limit damage and tomaintain healthy systems in stable operating conditions. The system will feature a high degree of selectivityand discrimination between faulty and healthy circuits. The protection system will be provided for turbine,generator, transformer and transmission line.

Turbine protection

The turbine shall be protected against following conditions:

Bearing temperature extremely high/low Governor oil pressure extremely high/low Failure of governor Over speed Oil level of pressure oil tank low or high


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Regulating pond/ reservoir water level below the setting etc.

Generator Protection

Generator shall be provided with following protection schemes:

Field loss protection Reverse power protection Over voltage and under voltage protection Over current protection Ground over current protection and earth fault protection Over frequency and under frequency protection Out of synchronization protection etc.

Power Transformer Protection

The main transformer shall be provided with following protection schemes:

Primary side over current protection Secondary side over current protection Earth fault protection Buchholz relay protection

Transmission line protection

The basic concept of protective relay schemes on a high voltage system is to minimize damage to systemequipment, to minimize the effects of the system disturbances, and to ensure that no single contingency willdisable the protection on any element of the system. Thus protective relays must be capable of reliableoperation to sense and isolate all faults rapidly. They must also possess a high degree of security againstunwanted operations. For maximum reliability, all circuits of the system should be protected by protectiveschemes, which is capable of independent detection and isolation of all faults without undue disturbance tothe system. Breaker failure protection will be provided to trip all necessary circuit breakers or the unit in theevent of a particular breakers failure to clear the fault.

A basic concept of protection, comprising line protection using over current and earth fault relays plussequential tripping schemes for breaker failure is recommended for the 11 kV transmission line andtransformers.

The transmission line and associated equipments at both ends shall be protected with the followingprotection schemes:

Over current protection Ground fault protection Lightning protection by Lightning arrester For the protection of other components, general practice will be adopted.

8.2.10 11 kV Switchgear

Outdoor type single bus 11 kV system supported by lattice structure with support insulators will beconstructed. The 11 kV switchyard shall comprise of 11 kV bus bar, vacuum circuit breaker, disconnectingswitches, current transformers, potential transformers and lightning arresters.The rating of the equipment will be a follows:


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11 kV Circuit Breaker

11 kV vacuum Circuit Breakers (VCB) shall be installed at powerhouse switchyard and at connection pointas shown in Single Line Diagrams. The 11 kV VCB will be outdoor type.It shall be possible to close and trip the breaker from control room with "Local/Remote" selector switch in"Remote" position. The breaker shall be provided with mechanical ON-OFF indicator at the front properlymarked and ON (green colored) and OFF (red colored) push-button/handles for control, key switch for"Local/Remote" and "Manual/Automatic" selection.The technical details of VCB will be as follows:

Type 3-phase, OutdoorVoltage rating:Nominal system voltage 11 kVRated maximum voltage 12 kVCurrent rating:Rated continuous current 630 ARated short circuit breaking current 25 kAOne min. power frequency withstand voltage (rms) 28 kVImpulse withstand voltage (peak) 75 kVFrequency 50 HzRe-closing duty cycle 0-0.3sec-CO-3min-CO

11 kV Disconnecting Switch

1. The 3-pole disconnecting switches will be gang operated type so that all the poles make and breaksimultaneously.

2. The disconnecting switches will be designed for upright mounting on steel structure.3. The disconnecting switches will have padlocking arrangement in both "open" and "closed"

positions.4. All current carrying parts will be of non-ferrous metal or alloy. All live parts shall be designed to

avoid sharp points and edges.5. All metal parts will be of such material and treated in such a way as to avoid rust, corrosion and

deterioration due to atmospheric conditions. Ferrous parts shall be hot-dip galvanized.6. Bolts, nuts, pins, etc. will be provided with appropriate locking arrangement such as locknuts,

spring washers, key, etc.7. Bearing housing will be weatherproof with provision for lubrication. The design, however, shall be

such as not to require frequent lubrication.8. The main contacts will be of silver-plated copper alloy and controlled by powerful springs

designed for floating and pressure point contact.9. The contacts will have sufficient area and pressure to withstand the electromagnetic stresses

developed during short circuit without excessive heating liable to pitting or welding.10. Contacts will be adjustable to allow for wear, shall be easily replaceable and shall have minimum

movable parts and adjustments.11. The disconnecting switches for the transmission line will be provided with the earthing switches.

The technical details of disconnecting switch will be as follows:


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Type 3-pole, Single throw, outdoorVoltage rating:Nominal system voltage 11 KV Ratedmaximum voltage 12 KVFrequency 50 HzInsulation levelBasic impulse level (BIL) 75 KV Powerfrequency withstands voltage (1 min.) 28 KVCurrent rating:

Rated continuous current at 40oC ambient temp. 630 A

Rated short-time withstand current (r.m.s.) 25 KAOperating Mechanism Manually gang operated

11 kV Current Transformer

1. The current transformers will be of epoxy encapsulated/cast in resin type, mounted on stationaryportion of the switchgear and shall be easily accessible for maintenance and testing purposes.

2. The current transformers will be capable of withstanding the short circuit stress corresponding to afault level of the system.

3. This ratio and ratings of the current transformers willl be suitable to meet the requirements ofmetering and protection of the corresponding feeder.

4. The current transformers will conform to the latest edition of IEC. Unless specified otherwise,insulation, temperature rise and all other phases of manufacture and testing will conform to that givenin the standards. A type test certificate of a CT of similar design for temperature rise test will befurnished along with the Contract.

5. Facilities for shorting and grounding the terminals will be provided at the terminal block.6. Technical particulars of the CT will be as indicated in the enclosed appendices.

The technical details of current transformer will be as follows:

Type Outdoor, Oil immersedVoltage rating:Nominal system voltage 11 KV Ratedmaximum voltage 12 KV Impulsewithstand voltage (peak) 75 kV Powerfrequency withstand voltage (1 min.) 28 KV Frequency

50 HzShort time thermal ratings 10 kA for 1 secCurrent ratio 75/5 A, 75/5-5 ABurden 50 VA for protection and general Metering, 15VAfor Main & Check meteringAccuracy 5P20 for protection and 0.5 for metering

11 kV Potential Transformer

1. The potential transformers will be epoxy encapsulated/cast in resin design.


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2. A manually operated disconnecting device will be mounted on the primary side of potentialtransformer. This device shall be designed to operate externally without access into the line portionof the switchgear.

3. The connections from main circuit to potential transformers will be capable of withstanding shortcircuit of the system.

4. The high voltage winding of the potential transformer will be protected by current limiting fuses. Lowvoltage fuses, sized to prevent harmful overload, shall be installed.

5. The technical particulars of the potential transformer will be as indicated in the enclosed appendices.6. The manufacture, testing, insulation and temperature rise of the potential transformer will conform to

the latest revision of the relevant IEC.

The technical details of potential transformer will be as follows.Type Outdoor, Oil ImmersedRated primary voltage 11 KV /√3Rated secondary voltage 110 V/ √3Impulse withstand voltage (peak) 75 kV Frequency 50 Hz

Burden 50 VA for protection and generalmetering, 15 VA for Main &

Checkmetering

Accuracy 3P for relay and 0.5 for metering

11 kV Lightning Arrester

The Lightning arresters will be provided for protecting the substation equipment including maintransformer against possible lightning strokes and other abnormal voltages.

The technical details of Lightning arrester will be as follows:

Type Outdoor, gapless ZnO arresterFrequency 50 Hz System voltage 11 kVRated voltage 9KV9 kV Impulse withstand voltage (BIL) 75 kVPower frequency withstand voltage 28 kVNominal discharge current 10 kA

0.4 kV Switchgear

0.4 kV switchgear which is provided for the generator circuits and main transformer primary circuit will be

of self-supporting, indoor and metal enclosed cubicle type.

0.4 kV Circuit Breaker

Two numbers of 0.4 kV draw out type Air Circuit Breaker (ACB) will be installed. The ACB Will be ofthree phase with single throw in operation.

The technical details of ACB will be as follows:Type 3-phase, single throw in operation, indoor, drawout type


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Quantity required: 2Voltage rating:Nominal system voltage 0.4 kV Ratedmaximum voltage 0.6 kVCurrent rating:Rated continuous current 1250 ARated short circuit breaking current 25 kAOne min. power frequency withstand voltage (rms) 28 kVImpulse withstand voltage (peak) 60 kVFrequency 50 Hz

0.4 kV Current Transformer

The technical details of current transformer will be as follows:Type IndoorVoltage rating:Nominal system voltage 0.4 kVRated maximum voltage 0.6 kVImpulse withstand voltage (peak) 60 kVFrequency 50 Hz Current ratio 1000/5 ABurden 50 VAAccuracy 5P20 for relay and 0.5 for metering

0.4 kV Potential Transformer

The technical details of potential transformer will be as follows:Type IndoorRated primary voltage 0.4 kV /√3Rated secondary voltage 110 V/ √3Impulse withstand voltage (peak) 60 kVFrequency 50 HzBurden 100 VAAccuracy 3P for relay and 0.5 for metering

8.2.11 Battery and Battery Charger

Company will sign Power Purchase Agreement (PPA) with NEA on Take or Pay basis. Company will claimfor the energy sold to NEA throughout the month which shall be recorded by the energy meter at Jaharesubstation. Hence Isolated mode operation facilities will be installed in the project.

8.2.12 Communication System

A dedicated telephone line will be established for the voice and data communication between Power houseand Jahare Substation.

8.2.13 Grounding

The basic objective of the power house grounding is:

to provide low resistance grounding;

to limit the step and touch potentials within the acceptable limits as indicated in IEEE 80;

to limit the ground potential rise during ground fault occurrence and to limit over voltages;

to assure the proper operation of the protective relay system.

The grounding grid shall be designed in such a way that the resistance of the grounding grid shall not exceed1ohm.


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9. COMPUTATION OF PROJECT OUTPUT

9.1 BASIC FOR COMPUTATION

The computation of the project output is generally based on the available river flow. The powergeneration is calculated on the basis of the available monthly average flow in the river and 10% ofthe least flow is deducted for the downstream release for the protection of the environment andaquatic ecosystem. The overall efficiency of turbine (91%), generator (96%) and transformer (99%)has been adopted to be 86.49% for the computation of the energy. The net head used in energycalculation has been calculated considering the minor and major losses in the water way system.

9.2 ENERGY COMPUTATION

The Upper Belkhu Khola Small Hydroelectric Project is a run of river type project with designdischarge of 0.81 m3/s at 40% dependability. The power plant runs under a rated head of 144.96 mto generate 6,244 MWh energy after outage per year. The installed capacity of the Project has beenset to 996 kW considering gross head of 150.10 m. Two generating equipment will be used in thepowerhouse to generate optimum energy. The energy calculation has been done considering 5%as outage energy. The total dry season energy has been calculated as 1164 MWh and the total wetseason energy is calculated as 4768 MWh per year. The energy calculation is given inTable 9-1 Monthly Available Estimate of the Energy (MAE)

Table 9-1 Monthly Available Estimate of the Energy (MAE)Energy Computation of Upper Belkhu Khola SmallHydroelectric Project.Water level atforebay 905.00 maslTurbine axislevel 754.9 masl

Gross head, m 150.1 m

Turbineefficiency 91.00%GeneratorEfficiency 96.00%

Transformor 99.00%

Overall efficiency 86.49%

Dry seasonoutage 5%

Wet seasonoutage 5%


Downstreamrelease 0.024 m3/s

Installed Capacity 996.00 KW


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Table for energy calculation

Month

No.of

Days Flow*

Riparian

FlowAvailable Flow

PlantDischa

rge

TotalHeadloss

Nethead Power Energy

EnergyOutage

ContactEnergy

Revenue

(m3/s)(m3/s

) (m3/s) (m3/s) m m (kW) (KWh) (KWh)Jan 31 0.433 0.024 0.41 0.41 1.95 148.15 514 382,510 19,125 363,384Feb 28 0.327 0.024 0.3 0.3 1.44 148.66 383 257,362 12,868 244,494Mar 31 0.269 0.024 0.25 0.25 1.26 148.84 311 231,062 11,553 219,509Apr 30 0.235 0.024 0.21 0.21 1.14 148.96 268 192,608 9,630 182,977May 31 0.363 0.024 0.34 0.34 1.64 148.46 427 317,700 15,885 301,815Jun 30 0.809 0.024 0.79 0.79 4.93 145.17 968 696,808 34,840 661,967Jul 31 3.102 0.024 3.08 0.81 5.15 144.95 996 741,117 37,056 704,062Aug 31 4.667 0.024 4.64 0.81 5.15 144.95 996 741,117 37,056 704,062Sep 30 3.723 0.024 3.7 0.81 5.15 144.95 996 717,210 35,861 681,350Oct 31 1.736 0.024 1.71 0.81 5.15 144.95 996 741,117 37,056 704,062Nov 30 0.824 0.024 0.8 0.8 5.03 145.06 985 709,090 35,454 673,635Dec 31 0.579 0.024 0.56 0.56 2.90 147.2 694 516,075 25,804 490,271

365 1.42 6,243,776 312,189 5,931,587


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10. CONSTRUCTION PLANNING

10.1 GENERAL

This chapter of the report describes the approach used to develop the construction schedule. Theschedule was prepared using timeline Gantt charts presenting all the major activities.

The main objectives of this study are:

To make reasonable assumptions concerning the construction methodology achievable atthe site conditions prevailing at the area considering remoteness and inaccessibility,

To develop a construction schedule for the project implementation estimating probable jobcompletions targets and identify the critical activities to be taken extra care.

The construction activities will comprise river diversion for weir and river crossing structureconstruction, construction of power canal, gravel trap, desanding basin, forebay, headrace pipe,powerhouse, access road and tailrace canal. The construction will also include theelectromechanical installations comprising turbines, generators and accessories like governors,exciters and auxiliary equipment. In addition, mechanical parts like gates, valves, hoistingdevices etc. will also be required.

10.2 ACCESS

For the construction of any hydropower project, heavy machines and equipment will be required.Hence, for the transportation of such machines, the area must be accessible through a motorableroad.The project area is accessible from Kathmandu through Prithvi Highway at Adamghat and fromAdamghat towards the south the road is bifurcated. Through this bifurcated earthen road thepowerhouse site as well as Intake site is accessible. The total length up to the Intake site is about18 km. A permanent bridge over Dariyal Khola makes the site accessible round the year. Road upto Majuwa is available and thus little extension about 550 m to the proposed headworks will berequired. The road up to the powerhouse site has already been excavated by the project. The roadfrom Adamghat to the project site is needed to be upgraded so that heavy loaded vehicle can berun. For this the present road is needed to be widened and earthen road is needed to upgrade atleast by gravelling with proper drainage system.

10.3 INFRASTRUCTURE FACILITIES

The Contractor will construct a camp for its work force comprising skill and unskilled labours. Toavoid haphazard camps and to maintain environmental integrity, the contractor will berequired to construct well managed camps. It is envisaged that two such camps will be requiredone each for the intake site and the powerhouse site. The Employer will also be required toconstruct camps and colonies, which could be later converted to permanent facilities foroperation and maintenance.


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10.4 CONSTRUCTION POWER

Currently there is no availability of electricity at the project site. Therefore construction powerrequirement will be fulfilled by using diesel generators. The cost estimate has been doneaccordingly.Construction camp will be required for the employer’s staffs and contractor’s staffs. The camp sitewill be located near the powerhouse site and weir site. The camp will comprise of an office, livingquarters, a store and a workshop. It is envisaged that permanent structures of camp at thepowerhouse site will be used for accommodation of the operation maintenance staff once theconstruction is completed. Much of the construction camp will be built with pre-fabricated units,which will be dismantled once the project is completed. About 30 days will be required tocomplete the construction camp.

10.5 CONSTRUCTION MATERIALS

The major construction materials required for the project consist of the following:

Cement / reinforcement bars

Fuels

Coarse aggregate which will be produced on site and will be mainly quarried materials frombank of Belkhu Khola.

Fine aggregate will be retrieved from the Belkhu river banks (Granitic sand) and alsoprocessed from the designated burrow areas located in the vicinity of the project area.

10.6 CONTRACT PACKAGEThe construction work can be broadly classifiedinto

Civil –Lot –I Hydro Mechanical – Lot –II Electro- mechanical and Transmission Line - Lot -III works

For civil works, generally one main contractor will be selected so as to achieve the necessary levelof coordination between different team of workers which will ensure the timelyaccomplishment of the jobs. The electro-mechanical works will be mostly carried out in thecontractor’s workshop, hence, could be divided into sub- lots. It is proposed to have three electro-mechanical contracts, the first one for major equipment like turbines, generators and accessories,the second one basically for mechanical equipment like gates, hoists, valves, penstock pipes etc andthe third one for transmission line. The works of improving the existing trail could be awarded tobe carried out simultaneously. In general, the following contract packages are envisaged;

Civil works Design, manufacture, supply and installation of electromechanical equipment. Design, manufacture, supply and installation of hydraulic steel structures.


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Supply and installation of transmission and substation facilities

10.7 CONSTRUCTION SCHEDULEAttached on Annex-A


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11. COST ESTIMATE

11.1 CRITERIA AND ASSUMPTIONSAll the criteria and assumptions adopted for cost estimation are to be mentioned includingfollowing:

Consideration of the natural conditions prevailing at the site, construction scale, and levelof construction technology available in Nepal.

To the extent possible, construction equipment available in Nepal is used. A brief description of project with location is mentioned. The cost estimate is based on 2015 prices. Exchange rate applied to calculation is 1 USD = 105 NRs. Identifiable Nepalese taxes, custom duties, royalties etc. for goods, materials and services

are included in cost estimation.

11.2 ESTIMATING METHODOLOGYThe following methodology is applied for estimation of cost of each component of the project.

A. For civil works: The cost estimates are based on unit rates developed from prevailing labor rate,

construction equipment rate and materials taking also into account the local situation andbill of quantities derived from design drawings.

Due consideration are be given to local labors. The rates of locally available labors areobtained from 'District rates' of Dhading district and are be used after appropriateadjustments.

The rates of construction equipment are taken from Heavy Equipment Division/Department of Roads.

The construction material to be used for construction work are divided into Material locally available Materials to be imported from India Materials to be imported from Overseas

The rates of construction materials are derived accordingly as their source of supply. Whilecalculating the construction materials rate, sufficient attention is also be given to mode oftransportation and their corresponding costs.

Since the estimate is prepared for contract/tender purpose contractor's overhead andprofitis included in the item rate.

Value Added Tax (13%) is also included in the Cost Estimate wherever applicable.

B. For Generating Equipment:

The cost estimate for generation equipment is based on quotations received from reputedIndian /European/ Chinese Manufacturer, Company. The cost include cost of controldevices/system, auxiliary etc. transportation and erection.

C. Hydraulic Steel Works:

The cost of hydraulic steel works are based on international market price. Transportation,fabrication and erection cost are also be added.


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D. Transformers, Switchyard and Transmission Line:

The cost of transformer and switchyard are based on capacity, while for estimate of cost oftransmission line cost is calculated from per km rates of transmission line. References of cost istaken from current rates used by Nepal Electricity Authority for same type/voltage oftransmission lines taking into account different types of towers required, the conductors andtypes of terrains being crossed.

E. Access Road:

Due attention is given to the cost of construction of access road to the powerhouseand improvement of the existing or under construction road to the Intake site. The length andtype of access roads to be constructed or to be improved are derived from the preliminarydesign. Costs per km of different types of roads are assumed on the basis of prevailing practicesof the Department of Roads.

F. Camp and Other Facilities:

The costs of construction and refurbishment of camps and permanent buildings required foroperation and the cost of construction power facilities required are included in cost estimation.

G. Land acquisition and Environmental Mitigation:

Cost of land acquisition for construction of the permanent structures and environmentalimpact mitigation costs are also included in the estimate.

11.3 BASE COST AND TOTAL PROJECT COSTThe total of all costs indicated above will constitute base cost of the project. The followingcosts are added for obtaining the total capital cost of the project:

An allowance of 2.5% of the total construction cost for Engineering and Management hasbeen included to cover the following:

Detailed field investigations

Preparation of detailed designs, construction drawing and tender documents

Prequalification, Evaluation and Award of Contracts

Administration and Supervision of construction works

Testing and commissioning

Reviewing and approving contractor’s submittals

Owner's Project Development Cost @ 2% of base cost;

Contingencies to account for unforeseen cost increases due to uncertainties in siteconditions and indecency of study levels @ 5% on Civil ,1.5% on HM and EM of base cost.

Contingencies to account for price escalation @ 2.5% on Civil and @2 % on HM and EM.

The cost of insurance @1% of the base cost.


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On the basis of the analysis described above, the cost of the Upper Belkhu KholaSmall Hydroelectric Project (996 kW), including contingencies, owner's development,engineering and contract administration costs, has been estimated at NRs 185.01 million. Thesummary of abstract of cost estimate is given in Table 11-1 Project Cost Summary.

Table 11-1 Project Cost Summary

Upper Belkhu Khola Hydroelectric Project (UBKHP)Project cost summary

1 USD= NRs.105ItemNo.

Description Amount(NRs)

Amount(USD)

A General itemsA.1 Mobilization and demobilization cost including temporary

construction camps 800,000 7,619A.2 Insurance of works, materials, equipments, personnel and third

party, and all other insurance items covered by the Contract

1,850,131 17,620A.3 Accomodation for the personnel of the

Employer/Engineer,temporary site office for the Engineerincluding all facilities as described in the specifications

600,000 5,714A.4 Cost of corporate office at Kathmandu including office vehicles 800,000 7,619A.5 Construction power 600,000 5,714

Total cost for general items 4,650,131 44,287B Civil works

B.1 Headworks 20,183,731 192,226

B.2 Penstock pipe 18,556,099 176,725

B.3 Powerhouse and tailrace 12,801,798 121,922

B.4 Switchyard 569,343 5,422

B.5 Permanent construction facilities 1,600,000 15,238

B.6 Access road 1,500,000 14,286

B.7 River diversion works 600,000 5,714

B.8 Dewatering from tunnel & other structures 400,000 3,810

Total cost for civil works 56,210,971 535,343C Hydro-mechanical works 38,802,821 369,551D Electromechanical equipment 40,340,000 384,190E Transmission line including substation 12,857,804 122,455F Total Base Cost 152,861,727 1,455,826G Land acquisition @ 5% of B 2,810,549 26,767H Contingencies

Civil Contingencies surface works @ 5% 2,605,549 24,815H-E/M Contingencies @ 1.5% 1,380,009 13,143

I Engineering, administration and management @ 2.5% 3,921,183 37,345J Project Development Cost @ 2.0% of Total Base cost 3,057,235 29,117K Taxes and Duties


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Upper Belkhu Khola Hydroelectric Project (UBKHP)Project cost summary

1 USD= NRs.105ItemNo.

Description Amount(NRs)

Amount(USD)

Custom Tax (1%) and Local Tax (1 .5%) of Hm, Em & TL cost 2,334,516 22,233

L Total Cost 168,970,767 1,609,245M Value Added Tax @ 13% 12,394,449 118,042N Price Contingencies for civil works @ 2.5% 1,780,274O Price Contingencies for H-E/M works @ 2% 1,867,613 17,787P Total Project Cost 185,013,103 1,762,030

Cost per kW 185,756 1,769Plant Capacity, kW 996


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12. FINANCIAL ANALYSIS AND PROJECT EVALUATION

12.1 ASSUMPTIONSFinancial projection of the project is done on the basis of estimated cost of the project basedon technical details of Q-40 design described above. Financial projection is done with followingassumptions:

Contract energy per unit ( KWh) and rate for dry and wet session would be as per thePPA dated 03-11-2068 with NEA , and same would be annual energy sale net of outage,

The total estimated cost of the projected would be Rs. 185.01 million,

The exchange rate used is Rs. 105 per USD,

Debt to equity ratio would be 70:30,

The bank interest of 12%, with one percentage documentation fee,

Discount rate would be the bank borrowing rate of the project,

Construction period for the project is estimated of 18 months,

With relatively short construction period of 18 months, the bank interest rate wouldnot change,

Loan repayment would be done within 10 years of commercial operation (COD),included therein 18 months of construction period, interest during the constructionperiod will be capitalized,

Due to significant exchange rates fluctuate and other risk factors, Civil contingencyestimated at @ 5% on Civil, 1.5% on HM and EM of base cost.

Contingencies to account for price escalation @ 2.5% on Civil and @2 % on HM andEM.

No royalty payment to Government of Nepal,

Expenses increased by 4% per annum,

O/M- Cost 0.5 % and Insurance cost 0.5% of project cost.

Other constraints/variables would remain the same.

12.2 FINANCIAL PROJECTIONFinancial projection is done on the basis of discounted cash flow technique in combination withfollowing financial analysis tools:

Net Present Value

Break Even Point

Simple Pay Back Period

Discounted Pay Back Period

Total Debt Service Cover

Internal Rate of Return, and

Return on Equity


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12.3 CONCLUSIVE FINANCIAL INDICATOR

Financial Analysis for the Project:-

NPV Benefit (NRs. 000) – 179,900.00NPV Cost (NRs.000)-144,579.00NPV- Benefit -Cost (NRs.000)-35,321.00Benefit Cost Ration – 1.24IRR on Project -15.14%

Financial Analysis for the Shareholder:-

NPV Benefit (NRs. 000) – 73,677.00NPV Cost (NRs.000)-46,168.00NPV- Benefit -Cost (NRs.000)-27,509.00Benefit Cost Ration – 1.60IRR on Project -16.32%


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13. CONCLUSIONS AND RECOMMENDATIONS

13.1 CONCLUSIONSThe Upper Belkhu Khola Small Hydroelectric Project has been studied to the detailed level.Moreover there may some changes after detailed field investigations like topographical mapping,geological/geotechnical investigations and hydrological data collection, layout and design workswere carried out during the construction period and appropriate project cost estimate wasdeveloped. As the same after receiving the detail data from Electro mechanical section theremay be change some modification in power house. Likewise the site verification of therespective component and lay out model may be affected the cost of the project. Financialevaluation was also carried out to determine the viability of the project.

The following conclusions were drawn from the study:

The Upper Belkhu Khola Small Hydroelectric Project utilizing 0.81 m3/sec of designdischarge and gross head of 150.10 m generates about 996 kW of electric power. Thedesign discharge will be diverted from the river by constructing an overflow weirequipped with a trench gallery on the top. The discharge will be controlled by a vertical liftgate provided at the right end of the trench canal. Then after the design discharge will beconveyed to the powerhouse via different structures viz. open rectangular canal, graveltrap, settling basin, forebay (Head pond) and penstock pipe to generate the power. Aftergeneration of the power the water will be discharged back to the Belkhu Khola via atailrace canal.

The project will have two pelton turbines installed with a total optimum capacity of 996kW for production of 6,244 MWh of average energy annually, out of which 1,164 MWh willbe in dry season and 4,768 MWh will be in wet season.

The power generated from the project will be evacuated to the national grid of INPS via8.0 km long 11 kV transmission line to the Jahare substation of NEA.

The construction period for the project is about 1.5 years.

The project would cost NRs 185.013 million at 2015 price level including the entirerelevant contingency.

The project would yield financial internal rate of return (IRR) 15.14 % at 12.0 % interestrate.

The project is financially 70:30 debt equity ratio and 10 years loan repayment period at abank interest rate of 12.0%

13.2 RECOMMENDATIONS

Based on the above conclusions, the following recommendations have been made:

From the technical, economic, and financial point of view the project shall go on forimplementation as soon as possible.

Detailed field investigations in the area of pipe alignment, forebay tank and powerhouseareas should be carried out to obtain information on permeability and bearing capacity of


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the soil and rock to ascertain the stability of the structures prior to the construction worksduring construction supervision time.

In order to get adequate quality and quantity of concrete aggregates, a detailedconstruction material survey and their laboratory tests should be carried out duringconstruction time.


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APPENDIX

ANNEX-A-CONSTRUCTION SCHEDULE


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ANNEX-B-FINANCIAL ANALYSSIS

UPPER BELKHU KHOLA HYDROELECTRIC PROJECT DETAILED … Design Study- Report… · excavated by the...

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