Post on 11-Nov-2014
description
Mr. Mayur Dhanaji Rane
NPTI-PSTI Bangalore
22/03/2013
400 KV/ 220 KV Nelamangala
Report
2
National Power Training Institute
Power System Training Institute
400 /220 KV Nelamangala Station
Submitted By: -
Mr. Mayur Dhanaji Rane (1540)
Guided By:-
Mr. K. Vetrivel Mr. M. N. Murthy
Assistant Director, Director, PSTI,
PSTI, Bangalore Bangalore
3
Index
Sr. No Contents Page No.
1 Introduction 4
2 Single Line Diagram of the 400KV/220KV
Substation
5
3 Bus Bar Scheme 6
4 Substation Auxiliaries 8
5 Capacitive Voltage Transformer 10
6 Current Transformer 13
7 Circuit Breaker 15
8 Isolator 17
9 Transformer 18
10 Reactor 21
11 220V Battery Charger Room 23
12 Control Room 24
13 Earthing 25
14 Bibliography 27
4
1. Introduction:-
It is 400 \ 220 KV station at about 25 kms North West of Bangalore city in
Bangalore- Tumkur road (national high way no.4) established in a 118 acre plot.
After establishing a major power generating station at Sharavathi river fall, the
power supply was stepped up to 220 KV and 4 numbers of 220 KV lines transferred
power to Bangalore. But often the lines were tripping and sometimes a cascading effect
resulted in entire grid failure plunging whole \ parts of Karnataka into darkness. This was
very often leading to failure of Southern grid even. This grid-failure had to be minimized.
Besides the 400 KV power supply from generating stations like GOOTY (Andhra
Pradesh) was to be integrated into southern grid. All these and further system studies on
Southern grid of India by CEA (Central electricity Authority) necessitated a 400 KV
station in this zone.
These reasons resulted in this Nelamangala station established in the paths of the
existing Sharavathy-Bangalore 220 KV lines. It was constructed on TURN-KEY basis by
L&T under planning and technical supervision of PGCIL (Power Grid Corporation of
India limited). It is presently owned, operated and maintained by KPTCL (Karnataka
Power Transmission Corporation limited) After establishment of this station there has not
been any grid failures of the type described before and thus the purpose has been
effectively served.
5
2. Single Line Diagram of the 400KV/220KV Substation:-
6
3.Bus Bar Scheme:-
7
8
4. Substation Auxiliaries:-
160KN Anti Fog Insulator Aluminium with Dead End Jumpers
Aluminium T Clamp Fix and Sliding Clamps
T Connector Circuit Breaker Clamps
9
Spacers for Double moose rigid type Spacer for Double type sliding type
Line Spacer for Moose Twin Double Tension for Moose
Double Suspension hardware fitting Types of Jumpering
10
5. Capacitive Voltage Transformers:-
The CVT’s are also used to serve as coupling condensers for connecting PLCC
equipments. Wave traps prevent telecommunication signals getting into the station side
equipments.
There are potential transformers in the form of CVT (Capacitor Voltage
transformer) to measure the incoming line voltage. The CVT’s also serve as coupling
condensers for connecting PLCC lines in one or two phases of the lines. Wherever PLCC
lines are connected one can see Wave traps to block communication signals reaching the
220 KV bus. Wave traps are tuned inductors to allow a particular frequency (here it is 50
c\s power) the first line control is through double break isolators coupled with grounding
switch.
400 kV
1. Core 1 3P Protection (connected in star)
2. Core 2 3P Directional Earth Fault Protection (connected in open delta)
3. Core 3 0.5 Protection & Metering (connected in star)
Here Core 1 is used for Protection purpose hence connected in Star
11
Core 2 is used for Directional Earth Fault Protection hence connected in Open Delta.
The formation of the star / neutral point or open delta connections of the secondary
windings of the three phases of the VTs has been made correctly and that the neutral end
of the star connected winding and one end of the open delta connected winding have been
earthed in the Marshalling Kiosk / Junction Box.
Ratings
Make Alstom
Type CVEB:400/1425
Frequency 50 Hz
Number of cores 3
Rated Voltage HV 400KV/√3
LV 110V/ √3
HF Capacitance 8800 pF
Primary Capacitance C1 9312pF
Secondary Capacitance C2 160000pF
12
Insulation Level 630/1425 KV
HSV 420 KV
Burden 200 VA
Class 3P
Insulation Class A
13
6. Current Transformer:-
400 kV Bays
CT Ratio: 500 – 1000 – 2000.
1. Core 1= PS Differential Protection Main – 1 / Distance Protection Main - 1
2. Core 2= PS Differential Protection Main – 2 / Distance Protection Main 2,Over
current, Earth fault and LBB Protections.
3. Core 3= 0.5 Metering
4. Core 4= PS Bus Bar Protection (Main Zone) except for CTs in Tie CB Bay
5. Core 5= PS Bus Bar Protection (Check Zone) except for CTs in Tie CB Bay.
14
The secondary windings of different phases of Current Transformers are generally
star connected. A typical wiring connection for Core – 1 of Current Transformers in the
Bay Marshalling Kiosk / Junction Box.
Rating
Rated Voltage 400 KV
Insulation Level 630/1425 KV
Rated Current 2000 A
Knee Point Voltage 1500 V
Burdon 40 KV
Number of cores 5
Insulation Level 630/1425 KV
Frequency 50 Hz
Class Protection PS
Metering 0.5
Ratio Available 2000-1000-500/1A
Total Weight 2450Kg
15
7. Circuit Breaker:-
The breakers are of single phase double pole types i.e. an interrupter and a
capacitor circuit held in porcelain bushings and working in parallel. The interrupter is of
double break type i.e. there are two female contacts on either ends inside the interrupter
with two male contacts striking into these contacts. The circuit closing or opening is in
two stages with a few mili-seconds of time gap between the two actions. The breaking \
making zone held in porcelain bushings is filled with high pressure (here it is 6 kg \ cm²)
SF6 gas for arc quenching .The gas is hermitically sealed with a pressure indicator. The
movements of the contacts are by AIR-PRESURE-TRIP with a simultaneous SPRING-
LOADING. Later the spring loading is used for closing the contacts. For air-pressure
operation the air at a particular pressure (here it is 15 kg’s per cm²) is held in high
pressure tanks. Any fall in air pressure is taken care of by an automatically working air
compressor. For the purpose of safety of the breakers, fall of gas \ air pressure beyond
certain threshold levels results in locking up of the breaker for breaking or closing
operations. (LOCK IN: The breaker fails to obey any commands ie neither opens or
closes) This interrupter is in parallel with a suitably designed capacitor circuit to raise the
potentials of the contacts so that the potential difference between male and female
contacts is reduced considerably and so the arcing is very much reduced.. In certain
breakers (Triple pole type) a third circuit is inserted to contain the effects of surge
currents of some lengthy lines they are called PIR (Pre-inserted resistance) type. Here the
initial circuit closing action is through a resister and a little later the interrupter contacts
move. (After about 12 milli seconds) But now-a-days due to development of fast acting
breakers PIR type breakers are no longer used. Most of the breakers are of auto-reclosure
16
type. In India the reclosing is for single phase faults only. The GOS’s (Group operating
switches) have an additional grounding switch for the incoming lines. In the latter the
interlocking mechanism is such that the grounding switch can be operated only if the
isolator is open. As done in all stations load breaking or closing is through breakers and
isolators are used for no load closing \ opening.
The following typical connections are made at the circuit breaker end.
a) DC positive & DC negative for local operation.
b) DC positive for remote closing.
c) DC positive for remote tripping.
d) Remote closing signal.
e) Remote tripping signal.
f) Protection trip signal.
g) Trip circuit supervision.
h) ON / OFF indications (Lamp & Semaphore).
i) Auto Trip / Spring Charged Lamp indication.
j) Air pressure / Oil pressure / spring charging limit switch contacts for auto reclose
Blocking.
k) Contacts of pressure switches for annunciations of low SF6 gas / air / oil pressure
Alarms & lockout conditions and for loss of N2 pressure.
l) Contact for annunciation of pole discrepancy trip alarm.
m) Auxiliary contacts as required for various control circuits.
Rating
Type 400-SFM-40A
Lightning Impulse withstand voltage 1425 kVP
Rated Short Circuit breaking current 40 KA
Rated Operating pressure 15.5 Kg/cm2-g
First pole to clear factor 1.3
Rated line charging current 600 A
Gas Weight 21 Kg
Rated Voltage 420 KV
Rated Current 2000 A
Rated frequency 50 Hz
Operating Voltage 220 V DC
Total weight 9600 Kg
17
8. Isolator:-
The male and female contact arms on the polycone insulators / insulator
stacks in case of single break Isolator. In case of double break Isolator, 6 nos. fixed
contacts and 3 nos. moving contacts are fitted on the polycone insulators / insulator
stacks.
The following typical connections, as applicable, are made at the isolator and earth
switch end.
a) DC positive & DC negative for local operation.
b) Interlocking supply.
c) DC positive for remote closing.
d) DC positive for remote opening.
e) Remote closing signal.
f) Remote opening signal.
g) OPEN / CLOSE indications (Lamp / Semaphore).
h) Contact for annunciation of pole discrepancy trip alarm.
i) Auxiliary contacts as required for various control circuits.
Operation of Isolator and earth switch for following:
i) Smooth operation.
ii) Complete insertion and making of contacts in close position.
iii) Complete opening of contacts in open position.
iv) Functioning of mechanical interlock between main Isolator and earth switch.
v) Setting of end stoppers in close and open conditions.
vi) Operation of auxiliary switches.
18
9. Transformer:-
The 7 numbers of 167 MVA single phase AUTO- TRANSFORMERS. (When the
HV \ LV transformation ratio is less than two we go for an auto-transformer) Six of them
are interconnected to form two numbers of three phase 500 MVA star-star-delta
transformers – that is the reason of being called ICT-1 and ICT-2 (Interconnected
transformer N0.1 etc.). The seventh one located in between ICT-1 and ICT-2 is so wired
as to serve as an alternate transformer for any one of the 6 single phase transformers and
is used as such for maintenance purposes. Transfer-buses are constructed both on 400
and 220 KV sides for facilitating the alternate transformer insertion and is actually put
into action by operating appropriate isolators.( without physical shifting of the
transformers)
The delta (connection established externally) winding is left out for the intended
purpose of stability of the ICT’s only and remains un
TERTIARY windings of EHV
The station auxiliary distribu
(each used alternatively) transformers fed from an exclusive 11 KV feeder from the
nearby regular Nelamangala sub
alternate supply.
Rating Details
S
N Parameters
a) Type
b) i) Rating
ii) Rated Capacity (MVA)
c) Rated voltage (kV)
d) Highest system voltage (kV)
e) System frequency (Hz)
f) Type of cooling
g) Vector Group
i) System of grounding
j) Insulation Level of winding:
19
delta (connection established externally) winding is left out for the intended
purpose of stability of the ICT’s only and remains un
TERTIARY windings of EHV \ UHV transformers” by the author.
The station auxiliary distribution transformers consist of two numbers of 350 KVA
(each used alternatively) transformers fed from an exclusive 11 KV feeder from the
nearby regular Nelamangala sub-station. A diesel generator is also used to provide
Parameters 500 MVA, 400/220/33 kV
Type 3 phase Auto transformer with loaded
i) Rating
ii) Rated Capacity (MVA)
LV
Rated voltage (kV)
Highest system voltage (kV)
System frequency (Hz)
Type of cooling ONAN / ONAF / ODAF
Vector Group
System of grounding
Insulation Level of winding:
delta (connection established externally) winding is left out for the intended
purpose of stability of the ICT’s only and remains un-tapped. Please read “Trends in
UHV transformers” by the author.
tion transformers consist of two numbers of 350 KVA
(each used alternatively) transformers fed from an exclusive 11 KV feeder from the
station. A diesel generator is also used to provide
500 MVA, 400/220/33 kV
3 phase Auto transformer with loaded
tertiary winding
HV - 500 MVA
MV - 500 MVA
LV - 167 MVA (LOADED)
ONAN - 60% of ODAF
ONAF - 80% of ODAF
ODAF - 100%
400/220/ 33
420/245/36.3
50
ONAN / ONAF / ODAF
4x33.3% Unit cooler
YNaOd11
Solidly grounded
delta (connection established externally) winding is left out for the intended
tapped. Please read “Trends in
tion transformers consist of two numbers of 350 KVA
(each used alternatively) transformers fed from an exclusive 11 KV feeder from the
station. A diesel generator is also used to provide
20
i)
400 kV:
a) 1.2/50µs full wave impulse
voltage withstand level
1300 kVp
b) 1.2/50µs chopped wave
impulse voltage withstand
level
1300 kVp
c) Switching impulse withstand
voltage 1050 kVp
220 kV:
a) 1.2/50µs full wave impulse
voltage withstand level
1050 kVp
b) 1.2/50µs chopped wave
impulse voltage withstand
level
1050 kVp
33 kV:
a) 1.2/50µs full wave impulse
voltage withstand level
250 kVp
b) 1.2/50µs chopped wave
impulse voltage withstand
level
250 kVp
ii)
Power frequency withstand
voltage (kV)
400 kV (line-neutral)/(line-line)
220 kV
33 kV
HV neutral
570 kV rms
<460 kV rms
95 kV rms
38 kV rms
k) Impedances ( % )
HV & MV - 12.5% (Tolerance - ±10%)
HV & LV - 45% (Tolerance - ±15%)
MV & LV - 30% (Tolerance - ±15%)
l) Tapping range
Auto transformer with On Load Tap Changer for high
voltage variation of
-10 to +10 % in 16 equal steps, of
1.25% each, provided on common
end of series winding.
m) Type of tap changers ON LOAD TAP CHANGER (Resistance
Transition type).
n) Connection HV & MV: Star Auto with neutral
LV; Directly earthed delta.
o) Tap control
Full capacity - on load tap changer suitable
for group / independent, remote /local
electrical and local manual operation and
bi-directional power flow.
p) Short circuit level for the
system
Voltage,kV S C MVA S C current, kA
400 10000 40 for 3 sec
220 10000 40 for 3 sec
132 5000 40 for 3 sec
66 & below 3000 25 for 3 sec
q) Creepage distance for bushing
(mm)
Voltage,kV Total Creepage mm/kV
HV 400 10500 31
MV 220 6125 25
LV 52 1300 25
N 36 900 25
r) Service Outdoor
s) Duty Continuous
t) Overload capacity As per IS:6600 / IEC354 / IEC 60076-7
u) Partial Discharge level 100 pico-columb, Max.
21
v) HV/MV winding neutral end 36 kV porcelain without arcing horns
w)
Bushings:
Winding
Rated kV
HV
420
MV
245
LV
52
NEUTRAL
36
Mounting
P F Volt Full Chopped Switching
Rated STC,3s
DRY/WET mpulse Impulse Impulse
Amp kA
630/630 1550 1550 1050
1250 40
460/460 1050 1050 ---
2000 40
95/95 250 250 ---
3150 25
75/75 170 170 ---
2000 25
---- TANK mounted ----
The fire extinguishing is Nitrogen perching. (Earlier it used to be water quenching
called water-emulsification system) Now a day the nitrogen perching fire protection
system has been made compulsory for all 100 MVA and above capacities transformers.
(In Karnataka at least for sure) The process consists of compressed nitrogen gas held in
high-pressure tanks and connected by piping arrangements to the main transformer tank
near the top plate. The action is initiated following the actions of FOUR relays
(Buchholtz, OTI , WTI and PRV trips) acting either together or one after the other. At
this juncture arrangement is made for prevention of oil flow from the conservator)
When the transformer catches fire the high-pressure nitrogen is released into the
tank and the fires are quenched as it is cut off from oxygen supply (the oil drain valve at
the bottom of the transformer tank should be opened out at this stage before it is too hot
and un-approachable by humans. In a later improvement even this action is automated.),
In order to prevent accidental actuation of this fire quenching activity during routine
works, the controls for this action is held in a metallic enclosure with a transparent glass
cover normally and suitably labeled. One will have to break open the glass and operate
the controls when the fire extinguisher is available for manual operation. Etc The entire
fire extinguisher (piping, control box etc) is red-painted.
22
10. Reactor:-
The 11 numbers of 400 KV lines 5 of the incoming ones are provided with 50
MVA star-connected switchable shunt reactors. In the cases of some unduly lengthy lines
(in excess of 150 KM’s) shooting up of voltages due to their capacitance reactance are
found to be very harming. So the capacitance reactance harming effect is offset by
purposely introducing an inductive reactance load in the form of shunt or parallel reactors
to these lines. {The criteria here is one 50 MVA reactor for all lines exceeding 150 KM’s
in length. } As regards the neutrals (Please note that the word ‘neutral’ to an electrical
engineer is meant to indicate the junction point of a star circuit) some of the reactors are
earthed directly while some are earthed through NGR’s (Neutral Grounding Reactors—
Single phase reactors) The reactors were switched on (or switched out) and included as
an inductive load whenever a length line like GOOTY BANGALORE line is closed into
or taken out of the station bus. That is why they are called switchable reactors. Once the
purpose is over the reactors are switched off. This procedure was before synchronization
of all 400 KV lines. Now they are used as loads to control the bus voltage and included
whenever voltage increase much beyond 400 KV.
Rating
Rated MVAR 50
Rated Voltage 420KV
Rated Current 68.7A
BIL Line 1300KVp
Neutral 550KVp
Phases 3
Connection Star
Type of Construction Gaped type
Cooling ONAN
Total Mass 108700Kg
23
11. 220V Battery Charger Room:-
The station is having 220, 48 volts (lead-acid batteries) station battery
sets energizing DC bus bars of 220, and 48 volt bus bars respectively. As required by
rules all the batteries are housed in separate rooms in the ground floor. All the DC
operating equipments (all relays) of 220 KV systems are energized by 220 volts DC. The
48 volts DC energies the communication lines emanating from the station. The DC
rectifiers (working on boost, float & trickle modes) that converts AC into DC and charge
all the batteries. They draw AC power from an AC bus bar energized by the station
auxiliary distribution transformers. There are two exclusive 11 KV lines strung from a
nearby 66 \ 11 KV Nelamangala Sub-station to provide power supply to the distribution
transformers. From these AC \ DC busses control cables are run to provide required AC \
DC power supply to various AC \ DC equipments spread out in the station yard The
batteries consisting of (as per standard practice in almost all the stations of Karnataka)
two-volt cells of various ampere-hour capacities are connected in series to form the
required voltage ratings. From the past mistakes it has been found that the control room
staff should always be looking at a clearly visible signs of DC presence or absence. For
the purpose a two lamp (each lamp is connected between positive or negative and earth)
method of DC indication is provided and exhibited conspicuously. There are two sets of
220 and 48 volts batteries here. Since there are several cells, they are checked by what is
called PILOT CELLS basis. All the cells are numbered and number plates are fixed to
each of them. One day the pilot cells are (for example) cell no.1, 14, 16, 25, 36 etc.
Specific gravity of acid and voltage of each of these cells are checked and maintenance
works if necessary are done. The next day another set of pilot cells (cell no’s 2,
15,17,26,37 etc) are taken up. Thus in a specific period of say one month all the available
cells are subjected to checking and maintenance.
The DC rectifiers convert AC into DC and charge all the batteries. The silicon
based rectifiers work on boost, float & trickle charge modes. This is decided on the
current requirement of the cells at various stages of charging For example for the 220
volts charger, the three modes of charge are boost at 52 amperes, float at 50 amperes and
trickle charging is at 630 mili amperes. They draw AC power from an AC bus bar
energized by the station auxiliary distribution transformer. From these AC \ DC busses
control cables are run to provide required AC \ DC power supply to various AC \ DC
equipments spread out in the station yard The batteries consisting of (as per standard
practice in almost all the stations of Karnataka) two-volt cells of various ampere-hour
capacities are connected in series to form the required voltage ratings of 220, 48 volts
DC.
24
12. Control Room:-
All the equipments-operation can be locally controlled as well as remote controlled
from a control room and SCADA (Supervisory Control and Data Acquisition) operable.
An RTU (Remote terminal unit) is also established to convey all the relevant data to the
State load dispatch centre and can also be ON LINE controlled from there.
No
Of Operation of Check Points
1
Trip protections such as
Buchholz, OSR, etc.
provided on transformers
Operation of
relevant
auxiliary
relays
Alarm
annunciation
Operation
of Master
Trip Relay
Tripping of
HV & LV
CB’s
2
Alarm protections such as
high oil & winding
temperature, low oil level,
etc. provided on transformers
Operation of
relevant
auxiliary
relays
Alarm
annunciation
3
Trip protections such as
differential, over current,
earth fault, etc. provided in
C&R Panels for transformers
Alarm
annunciation
Operation
of Master
Trip Relay
Tripping of
HV & LV
CB’s
4
Trip protections such as
distance, over current, earth
fault, etc. provided in C&R
Panels for feeders & other
circuits
Alarm
annunciation
Operation
of Master
Trip Relay
Tripping of
relevant
CB
5 Alarms provided in circuit
breakers
Operation of
relevant
auxiliary
relays
Alarm
annunciation
6 Lockouts provided in circuit
breakers
Operation of
relevant
auxiliary
relays
Alarm
annunciation
Trip circuit
faulty
indication
CB
operation
blocked
25
13. Earthing:- Earth matt normally made out of about 70mm x 6mm GI flat is constructed at
about a metre below the ground level to which all the metallic items which do not carry \
convey electricity are connected (equipment grounding).This earth matt design (normally
consisting of welded GI flats of rectangular blocks) depend upon levels of fault currents
that come into play at time of faults. The size of GI flat, rectangles size and total area of
the earth matt is now-a-days decided by a software design in KPTCL. The design also
gives out the number of CAST IRON pipe groundings to be provided and connected to
the earth matt. Apart from the earth matt groundings certain equipments are also provided
individual groundings.
Over the entire substation stone gravel of different sizes is spread mainly to reduce
the dangerous effects of STEP-POTENTIAL and TOUCH-POTENTIAL, on humans
(operating personnel) who may be present in the station yard. These potentials, occur
during creation of EPR (Earth potential rise) zones that are created during phase to
ground faults of any feeder.
Sr.
No. Purpose
Description & Size
of Material for 400
kV Sub
Stations
1
Main Earthing Conductor
for
Earth Mat.
40 mm dia.
M.S. Rod
2
Earthing Conductor for
Risers (for equipments &
structures).
100 × 12 mm
M.S. Flat /
75 × 12 mm
G.I. Flat
3
Earthing of LT panels,
DC panel, C& R Panels,
marshalling boxes,
Compressors, MOM
boxes,
junction boxes, lighting
panels, etc.
50 × 6 mm
M.S Flat
4 Earth Electrodes
40 mm dia.
M.S. Rod,
3250 mm
long
5 Earthing conductor along
racks of cable trenches
50 × 12 mm
M.S. Flat
The neutrals of all voltage levels of transformers / reactors had earthed through
Independent earthing. All these earthing points had interconnected with the sub
Station earth mat. Each earthing lead from the neutral of the power transformer / reactor
Should be directly connected to two earth electrodes separately which, in turn, should
26
Connected to the earth mesh. The transformer / reactor tanks as well as associated
Accessories like separate cooler banks shall also be connected to the earth mat at two
points. Capacitor Voltage Transformers & Lightning Arresters shall be earthed through
two independent risers directly connected to earth electrodes which should in turn be
connected to the substation earth mat. The distance between the electrodes should not be
less than 4 meters. All other equipments such as Circuit Breakers, CTs, Isolators, Post
Insulators, etc. had earthed at two points.
27
14. Bibliography:-
1. EHV substation construction manual
2. O & M Manual of substation.
3. IS 3043: Indian Standard Code of Practice for Earthing.
4. Erection & Installation Manual for Transformers: M/s BHEL.