Total no of trips at NTPC coal stations 2013 Presentations/Day-2 at PMI... · VINDHYACHAL 2005-06...

0

100

200

300

400

500

600

2001-02 2011-12

516

357

63 83

Total Trippings

No of units

STRIVING TOWARDS ZERO HUMAN ERROR

powering India’s growth

Total no of trips at NTPC coal stations

Breakup of Trips at NTPC coal stations

0

20

40

60

80

100

120

140

160

180

ELEC SG/TG C&I OPN(HE) OTHER

174 163

82

32

65

124

100

57 44

32

2001-02 2011-12



Source: Yearly Trip analysis reports of NTPC

coal stations

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

18.00

6.32 7.36 7.71

8.70

16.10

8.61 7.00

10.00 9.69 10.56

12.32

Average % Trips Due to Human Factors

Avg. Tripping Due To Human Error:9.49%




coal stations


Presented by: Nilesh dangayach Abhishek jain

Presentation Outline

Compilation of trips due to human error

Categorization on the basis of direct cause

Event investigation and Root Cause Analysis

Identification of the dominant factors

Case studies

Implementation of corrective measures

Conclusion



Compilation Data



Source: Trip reports of NTPC coal stations.

Base years: From 2001-02 to 2011-12 (11 years)

Number of trips attributed to human error = 322

Selected batch size representing the whole batch = 101

S. N. TRIPPING DETIALS PLANT YEAR DIRECT CAUSE

1

While replacing resin from stator water SPU, wrong v/v

operation for draining SPU. Primary water tank level

reduced and unit tripped on Bushing Flow Low.

RAMAGUNDAM 2001-02 Slips, lapse, omission

2 Generator Field breaker operated instead of operating

other nearby switch for MVAR raise/lower. VSTPS 2001-02

Wrong desk

operation

3

Unit running on single TDBFP, its LOP made off from desk

in place of MDBFP LOP starting. Unit tripped on all BFP

tripped.

VSTPS 2001-02 Wrong desk

operation

4 While changing Active processor to standby processor PA

fans IGV become zero. VSTPS 2001-02 Lack of knowledge

5

“Turbine not working” alarm was appearing continuously

and persisted for 11 secs after some time. Unit tripped on

RH protection.

VSTPS 2001-02 Lack of Knowledge

6 Fire occurred due to oil leakage from TDBFP governing oil

supply line. Unit hand tripped and ALL TG LOPs stopped. VSTPS 2001-02

Wrong desk

Operation.

7 While isolating starting ejector, steam v/v closed first

instead of air v/v. Unit tripped on Low Vacuum. VSTPS 2001-02 Slips, lapse, omission

8 TG LO FILTER C/O VSTPS 2001-02 Slips, lapse, omission

9 Faulty card changing by c&I, wrong card changed. Unit

tripped on flame failure. VSTPS 2001-02 Slips, lapse, omission

10

During load throw off seal steam header pressure became

low, alarm appeared and unit tripped on low vacuum after

some time.

KORBA 2002-03 Lack of knowledge




11

After Oil injection test of main turbine, while resetting turbine tripped, as the Aux. trip oil blocking lever got released inadvertently before resetting the trip device.

KORBA 2002-03 Slips, lapse, omission

12 Due to frequent chocking of cooler, all BCPs tripped. RIHAND 2002-03 Lack of knowledge

13 Reverse operation of speeder gear lead to Unit tripping. VSTPS 2002-03 Lack of knowledge

14 Primary water c/o lead to unit tripping on high

conductivity. DADRI 2002-03 Slips, lapse, ommision

15 Howell Level saturated at max. and unit hand tripped due

to shaft vibn high. DADRI 2002-03 Slips, lapse, omission

16 Throttle Pressure lowered fast and unit tripped on flame

failure due to flame disturbance. UNCHAHAR 2002-03 Wrong desk operation

17 TG lo cooler c/o turbine tripped on LO pr low KORBA 2003-04 Slips, lapse, omission

18

D/A level controller kept in manual , ALL CEPs tripped

on hotwell level very low subsequently all BFPs tripped on

seal water pr low, Unit tripped.

RAMAGUNDAM 2003-04 Lack of knowledge

19 Unit tripped during station to UT c/o RIHAND 2003-04 Slips, lapse, omission

20 During Boiler washing ,water splashed on hydrastep

vessel, unit tripped on false drum level high. RIHAND 2003-04 Local wrong operation




21 Wrong isolation of 48V DC lead to unit tripping RIHAND 2003-04 Wrong Local

operation

22

ID Fan C tripped on R-phase over current protection though the

current was normal. Other ID fan was tripped inadvertently while

stabilizing unit. Unit tripped on Both\ID Fans off.

SINGRAULI 2004-05 Wrong desk operation

23 Load reduced due to reduction in TSE margin. Unit tripped on drum

level low. RAMAGUNDAM 2004-05 Wrong desk operation

24

During Mill F energy measurement VT fuses of 6.6 KV unit bus

tripped on under voltage. Unit tripped on Loss of fuel due to

tripping of auxiliaries.

DADRI 2004-05 Lack of knowledge

25 Unit tripped on drum level low as one BFP got unloaded. FARKKA 2004-05 Wrong desk operation

26

There was a dip of 16 MW in load set point when frequency

influence was made ON. Boiler master command dipped & unit

tripped on flame failure.

UNCHAHAR 2004-05 Wrong desk operation

27

Leak off steam control valve pump tripped. When it was again

started by C&I, control valve opened full, as control loop had

remained in auto. Seal steam pressure could not be maintained and

unit tripped.

UNCHAHAR 2004-05 Wrong desk operation

28 Unit tripped on Both ID Fans tripped. EPBs of both UPS found

pressed. Tripping of UPS caused tripping of both ID Fans and MFT. TALCHAR 2004-05 Wrong local operation

29 Unit tripped due to PA fan tripping. EPB of PA fan found pressed. TALCHER 2004-05 Wrong local operation

30 Contractor personnel working in U#6 C&I module disturbed U#4

module by mistake. TALCHER 2004-05 Wrong local operation




31 Protection acted due to inadvertent flushing of air line of the air

flow transmitter of unit 3 in place of unit 1.

TALCHER-

THERMAL 2004-05 Wrong local operation

32

While providing connection to energy meter in 6.6 KV bus 5A ,

PT link was inadvertently removed, tripping the bus on under

voltage.

TALCHER-


33

During work in unit-1 PLC, power supply breakers of unit-2 were

switched off inadvertently. MFT actuated due to loss of 220v DC

supply to PLC-4.

TALCHER


34 During TD BFP charging unit tripped on low condenser vacuum. SINGRAULI 2005-06 Slips, lapse, omission

35 Running Seal oil pump tripped due to wrong selection of seal oil

pump, unit manually tripped SINGRAULI 2005-06 Wrong desk operation

36 Fire protection operated during working of faulty channel. KORBA 2005-06 Wrong local operation

37 Drum Level very high operated due to wrong FRS valve

operation RAMAGUNDAM 2005-06 Wrong Desk operation

38 Running unit 6.6Kv Bus DC supply made off during working in

overhauled unit. RAMAGUNDAM 2005-06 Wrong Local operation

39 One BFP tripped, S/B BFP did not come ,Unit tripped on drum

level low. RIHAND 2005-06 Slips, lapse, omission

40 Mill SAF B U/P to C&I, SAF A discharge damper closed by

mistake, all mills tripped which lead unit tripping on loss of fuel. RIHAND 2005-06 Wrong local operation




41 All CC pump tripped during service cooler charging. RIHAND 2005-06 Slips, lapse, omission

42 PA B Fan tripped while making canopy of motor on high

vibration ,wrongly snatched vibration pick up. RIHAND 2005-06 Wrong Local operation

43 HT bus dead due to flashover, by mistake running equipment CW

2B bkr isolated. VINDHYACHAL 2005-06 Wrong local operation

44 Tripped on MS temperature low during working of thermocouple

-1 multi meter connected to thermocouple-2 VINDHYACHAL 2005-06 Slips, lapse, omission

45 Rotor Earth Fault Measurement Trouble Relay supply made off

instead of protection bypass VINDHYACHAL 2005-06 Slips, lapse, omission

46 110V AC CSP Running unit supply made off while isolating

supply of overhauled unit. VINDHYACHAL 2005-06 Local wrong operation

47 APH EPB tripped by mistake lead to Both ID fan tripping on

overload VINDHYACHAL 2005-06 Local wrong operation

48 Unit tripped on low lube oil pressure during MOT filter

changeover FARRAKA 2005-06 Slips, lapse, omission

49 Unit tripped on drum level low protection during HP heater

charging FARRAKA 2005-06 Slips, lapse, omission

50 Due to running equipment CG 5D isolation, bus dead lead to

flashover which resulted unit tripping FARRAKA 2005-06 Local wrong operation




51 Running mill lop stopped from desk, lead to mill tripping resulted in

unit tripping on flame failure. UNNACHAR 2005-06

Wrong Desk

operation

52 Unit tripped on drum level low due to closing of FRS valve instead of

CBD valve. KAHALGAON 2005-06

Wrong Desk

operation

53 Vacuum breaker valve open from local KAHALGAON 2005-06 Local wrong

operation

54 Drum level low due to delay in increasing BFP scoop SINGRAULI 2006-07 Wrong desk

operation

55

Unit tripped on flame failure when mills d, e & f out of six running

mills were tripped as one of the running TDBFP B tripped on over

speed and drum level was decreasing even when MDBFP took auto

start.

RAMAGUNDAM 2006-07 Wrong desk

operation

56 Turbine tripped on fire protection channel-2 due to mot level very

low (actual). RAMAGUNDAM 2006-07 Lack of knowledge

57

UAT-1B was out of service (maintenance work). While starting BFP-

B from station bus, station bus-b tripped. BFP-3B was also started at

the same time, which was in lighted up condition.

FARAKKA 2006-07 Wrong desk

operation

58

Lub oil pumps a& b of both TDBFPS' EPB found in pressed

condition. Both TD BFP tripped on lub oil header pressure low

protection. MDBFP took start, but tripped on overload.

FARAKKA 2006-07 Wrong local

operation

59 Furnace pressure went high while coal flow was being regulated to

adjust load according to frequency. UNCHAHAR 2006-07

Wrong desk

operation

60 Unit tripped on generator cold gas temp. Very high protection as

ECW pumps tripped due to low ecw tank level . UNCHAHAR 2006-07 Lack of knowledge




61 UAT-B tripped on differential protection due to shorting of the differential protection

CT core terminals of the UAT-B breaker during energy meter replacement. UNCHAHAR 2006-07 Lack of knowledge

62 Condenser vacuum lost while isolating and draining HPH 5&6 due to passing of HPH 6

shell vent to condenser. UNCHAHAR 2006-07 Slips, lapse, omission

63 Unit tripped on HPT exhaust steam temperature high protection. The HPBP pressure set

point put on auto instead of putting HPBP valves on auto.

TALCHER

KANIHA 2006-07 Wrong desk operation

64

Unit tripped on Excitation system problem during testing by BHEL. Change over from

channel-2 to channel-1 of excitation system by BHEL expert without ensuring the null

balance between channel 1 & 2.

TALCHER

KANIHA 2006-07 Wrong desk operation

65

TG Trip on turbine trip signal alarm appeared although seal oil temp. after cooler was

normal. 1/3 seal oil temp. after cooler very high alarm had appeared. While bypassing

the seal oil temp. after cooler very high protection, turbine tripped on the same

protection.

TALCHER

KANIHA 2006-07 Lack of knowledge

66

LT Bus 5D was being changeover done after unit synchronization. During LT

changeover bus 5D became dead. As EMCC was from bus 5D, both APHS tripped.

Both ID Fans tripped & unit tripped

BADARPUR 2006-07 Wrong desk operation

67

Unit was being normalized after synchronization. While changing D/A steam supply

from tank heating to dome heating, turbine side aux. steam valve was closed

inadvertently. Unit tripped on Condenser Vacuum low protection.

BADARPUR 2006-07 Wrong local operation

68

During changing over from SOP to MOP, the SOP discharge v/v was being closed.

During closing of valve, dip in relay oil pressure occurred resulting in closing of ESVs

& unit tripped on ESV/IV closed protection.

BADARPUR 2007-07 Slips, lapse, omission

69 Condenser vacuum low. Vacuum protection was normalized before resetting

corresponding relays causing unit trip. BADARPUR 2006-07 Lack of knowledge

70

On stopping of BFP-2C, BFP-2B got unloaded (scoop position came down from 78%

to minimum). Desk engineer tried to increase BFP-2B scoop position, but it did not

increase. Unit tripped on drum level low protection. It was found that selector switch of

BFP-2B which was supposed to be at deselected mode as the pump is already started,

was in selec mode.

DADRI-COAL 2007-08 Wrong desk operation




71 Unit tripped on "Furnace Pr. lo-lo" protection. It is suspected that either operating staff

inadvertently might have forgotten to put blade pitch master controller on auto. FARAKKA 2007-08 Lack of knowledge

72

While selecting MDBFP scoop (to reduce it), feed water master got selected as these

two very near in the computer screen and were visually identical. Immediately, feed

water flow came down drastically. Unit tripped on drum level low-low.

RAMAGUNDA

M 2007-08 Wrong desk operation

73

Unit was synchronised & running at 63 MW and was under stabilasation. Unit tripped

on Hydrogen cold gas temperature high protection. It was observed that Hydrogen

cold gas temperature rise overlooked

SINGRAULI 2007-08 Lack of knowledge

74

Unit was at 20 MW. While the load was being Increased, condenser vacuum started

falling and subsequently unit tripped on condenser vacuum low protection. The

atmospheric vent valve of HP flash tank remained in open condition causing drop in

condenser vacuum.

TANDA 2007-08 Slips, lapse,

omission

75

Standby CEP was under permit. Suspected that EPB of running CEP was accidentally

pressed. Mills were hand tripped for reducing load. As Deaerator level dropped feed

water flow was also reduced. Unit tripped on drum level low protection.

TANDA 2007-08 Wrong local and desk

operation

76

Unit tripping on “All BFP trip protection” as all of running BFPs tripped on

“discharge pr. Low” protection due sudden increase in FW flow while operating FRS

control valve.

BADARPUR 2008-09 Wrong desk operation

77 Unit tripped while carrying out supply changeover from Station source to UAT (UAT

breaker was not in service position) KHALGAON 2008-09

Slips, lapse,

omission

78 Unit tripped on “Drum Level high’ protection” as BFP controls shifted to manual. KHALGAON 2008-09 Wrong desk operation

79

Unit tripped on Drum level low protection due to tripping of one out of two running

BFP (EPB pressed).One BFP was under PTW and Drum level could not be maintained

with one BFP.

KORBA 2008-09 Wrong local operation

80 Unit tripped while changing over supply from station bus to unit bus. SINGRAULI 2008-09 Wrong desk operation




81 Unit tripped on opening of TDBFP exhaust valve from local on condenser

vacuum low ("LP turbine exhaust steam pressure > 0.25 bar" protection).

TALCHER

KANIHA 2008-09

Slips, lapse,

omission

82 220 KV bus charged without ensuring earth switch position unit tripped on

generator differential protection due to 40 KV jerk in system BADARPUR U #2 2010-11

Slips, lapse,

omission

83

Feed water inlet stop valve was inadvertently closed while trying to reset a

fault in HPH 6 extraction block valve. Unit tripped on drum level low

protection

DADRI U#4 2010-11 Wrong desk operation

84 Instead of unit VI primary water pumps isolation was done in Unit-V

primary water pumps by mistake. Unit tripped on primary water flow low. DADRI U#5 2010-11 Wrong local operation

85 Human error in load rising after unit synchronizing. Unit tripped on IP top-

bottom difference temp.>45 deg. DADRI U#5 2010-11 Lack of knowledge

86 Tripping of running seal air fan and non start of standby fan. Unit tripped

on furnace pr low due to tripping of all running mills DADRI U#5 2010-11

Slips, lapse,

omission

87

some welding work was going on at a higher elevation and falling of

welding splatters on the trestle led to fire in boiler side equipment control

cables leading to tripping of mills, and ID/FD fans and unit tripped on

flame failure

DADRI U#5 2010-11 Local wrong operation

88

Loosening of trip oil transmitter cable by contract worker by mistake.

Which lead to Sensing of trip oil pressure zero and EHC output becoming

zero.

DADRI U#5 2010-11 Local wrong operation

89

Rupture of TDBFP-B diaphragm due to closure of exhaust valve and

subsequently while normalizing TDBFP condenser got connected to

atmosphere.

DADRI U#5 2010-11 Lack of knowledge

90 PA header pressure low led to all mills trip during mill changeover. Unit

tripped on furnace pr. low DADRI U#6 2010-11

Slips, lapse,

omission




91

Erection work on CW pump -4 was going on. It is suspected that somebody might have

pressed the EPB of running CW pump, inadvertently causing unit tripping on condenser

vacuum low protection.

DADRI U#6 2010-11 Local wrong

operation

92 Closure of VFDs and IGVs while putting the furnace pressure on auto when it was not steady.

Unit tripped on furnace pr. high DADRI U#6 2010-11 Lack of knowledge

93 Generator tripping on seal oil temperature high due to high DM cooling water temperature.

Due to chocking of all PHE’s DADRI U#6 2010-11

Local wrong

operation

94 Inadequate handling of EHC controls during pressure variations. Turbine was hand tripped as

EHC o/p became zero DADRI U#6 2010-11 Lack of knowledge

95 Poor flame conditions went un noticed leading to flame failure trip. DADRI U#6 2010-11 Lack of knowledge

96

The root cause of unit tripping was low water level in expansion tank causing tripping of

running stator water pump and standby pump also could not start leading to tripping of the

unit.

FARAKKA U#1 2010-11 Lack of knowledge

97 The unit tripped because of boiler tripping on “Furnace Pressure lo - lo” protection caused

due to inadvertent switching off of running PA fan B. FARAKKA U#4 2010-11 Wrong desk operation

98 Improper mechanical isolation of CEP led to the air ingress in condenser during suction

strainer opening for cleaning. Unit tripped on condenser vacuum low.

KAHALGAON

U#1 2010-11

Slips, lapse,

omission

99 Stopping the running Gas cooler pump by mistake. Pump B did not took start as its control

supply was found in OFF condition. Unit tripped on both gas cooler pumps off

KAHALGAON

U#4 2010-11 Wrong desk operation

100

While opening the Korba Bhilai Line 1 breaker during a load flow disturbance, it's isolator

was opened by mistake. This resulted in Bus Bar Differential Protection acted.Unit 4

connected to the Bus tripped.

KORBA U#4 2010-11 Slips, lapse,

omission

101

400KV Tie breaker developed oil leakage and it was being isolated to attend the leakage.

During an open command to it's isolator, heavy arcing observed in B phase isolator and a

heavy fault with severe voltage dip occurred.Units 1&2 tripped on pole slip protection. Unit 4

triped as it's running feeders tripped and unit 3 tripped on FD fan lub oil pump tripping.

RIHAND

U#1/2/3/4 2010-11

Slips, lapse,

omission



27%

24% 27%

22% Inadvertant operation from control desk

Inadertant operation at local

Slips, Lapses, omission

Lack of knowledge

Total 101 trips



Main categories contributing to trips

attributed to human error

22%

8%

35%

35%

Inadvertant operation from control desk

Inadertant operation at local

Slips, Lapses, omission

Lack of knowledge

Total 38 trips

Categorization for Vindhyachal specific

cases



Event investigation and

Root cause Analysis



Old view of human error

(persons approach)

Human error is the cause of accidents.

To explain failure, you must seek failure.

You must find people’s inaccurate assessments wrong decisions, bad

judgments.

Modern view of human error

(systems approach)

Human error is a symptom of trouble deeper inside a system.

To explain failure, do not try to find where people went wrong.

Instead, find how people’s assessments and actions made

sense at the time, given the circumstances that surround them.

Opposing Views



Traditional Root

Cause Analysis

Investigation by systems approach



Swiss cheese model of Human error



Systems approach........

ORGANIZATIONAL INFLUENCES (latent)

1. Resource acquisition /management

2. Organizational climate

3. Organizational Process

UNSAFE SUPERVISION

(latent)

1. Inadequate supervision

2. Planned inappropriate operations

3. Failure to correct problems

PRECONDITIONS FOR UNSAFE ACTS (latent)

1. Substandard conditions of operators

Mental/physiological status and limitations

2. Substandard practices of operators

Crew resource management, Personal readiness

UNSAFE ACTS

(active)

1. Errors

Decision errors, Skill based errors, Perceptual errors

2.Violations

Routine, Exceptional

HFACS

Human factor analysis and classification

system



Survey Methodology

Discussions with operation executives and workmen.

In person interviews with senior executives.

Brainstorming



Factors that came out strong from

survey



1. Lack of failsafe design and controls

2.Inadequate training

3.Inexperienced manpower

4.Non adherence to standard procedures



13%

28%

26%

33% Lack of failsafe design and controls

Inadequate training

Inexperienced manpower

Non adherence to standard procedures

Total 101 trips

“Reverse engineering” Human Error

based on Root Cause

Case study (Lack of failsafe design)

• Case (1):

• Year: 2010-11

• First up: “FURNACE FLAME FAILURE”

• Root cause:

PA Header Pr set point was changed inadvertently from 805mmwc to 30mmwc from a work station through key board, which led to unloading of PA fans and subsequent unit tripping on “Flame failure” protection.

• Recommendations:

Direct value entry of some critical parameters is being disabled. They will be changed by Raise / Lower button only.

PA header pressure set point should not reduce below alarm value once unit is synchronized; it should be included in interlock.

• Case (2):

Year:2010-11

• First up: “Condenser Low Vacuum”

• Root cause:

• Rupture of TDBFP-B diaphragm due to inadvertent closure of exhaust valve and subsequently while normalizing TDBFP condenser got connected to atmosphere.


• Since exhaust valve is very near to casing drains valve in MIMIC so for distinguishing them size of exhaust valve increased to double.

• Close command to TDBFP exhaust valve should not be extended once TDBFP is working, it should be included in interlock.



Design Changes Required

• Confusing displays and controls need to be rectified and for new projects especial attention is to be given to graphics/controls design.

• Certain interlocks and logics are to be reviewed to make the system failsafe.

• Certain alarms upper/lower limits are to be revised from time to time as per system requirement.

• Annunciation system needs to be improved particularly in new units .



S.N OBSERVED PROBLEM MIMICS/ALARMS/LOGICS

MODIFIED

1 TD BFP steam exhaust valve was very near to casing drain valves in display.

Size of exhaust valve in MMI increased to double.

2 MOT Level low alarm at 650 mm; close to trip value 600 mm

Provided alarm in event log at 680/660mm

3 CFT tank level low alarm at 650mm Provided alarm in event log at

690/670/650

4 DM make up high no alarm Provided alarm at more than 20T/hr

5 Seal air fan current high alarm was 400amp Provided at 200amp/220amp

6 CF current high alarm was at starting current 400 amp

Provided at more than 200 amp

7 FD/PA fans tripping on overload Blade pitch locking Provided at 80%

8 Machine came in speed controller without operator notice

Emergent alarm Provided at alarm window

Changes Implemented at Vindhyachal stage 2



Training and development



Case study (inexperienced manpower)

• Case (1):

• Year : 2011-12

• First up: “Furnace Pr. High”

• Root cause:

Both RC feeders of one of the running ball & tube mill tripped as both the bunkers got empty. Mill was kept in service as it can be run for 10 minutes without any feeder. In the meanwhile Pressurization in Ball & Tube Mill took Place and unit tripped on furnace pr. HI HI

• Remedial measures taken/to be taken:

1. Mill should be tripped immediately if there is no chances of restarting of any feeder immediately.

2. Training is required on “Safety First” .

• Case (2):

• Year : 2011-12

• First up: “Turbine Manually Tripped”

• Root cause:

Aux steam source was changed from U5 to U#2 during stabilization of unit after capital overhaul. Sudden change over of seal steam source caused fall in cold header steam temperature and that led to high bearing vibration of turbine.

• Remedial measures taken/to be taken: Extra caution is to be exercised in maintaining seal steam/aux steam temperature during source changeover/start up/ stabilization of the unit.



Three step development program for

new entrants

Skills testing

Departmental basics

Procedures/manuals/trip reports

Basic knowledge of power plant

Introduction to LMI’s/OD/OGN

Scrutiny at each phase



Entry point

Implementation of the Three step development

program

1. Training/learning targets are to be included in the performance appraisal (KPA) of new entrants.

2. Assessment of the progress is to be monitored by the senior executives through regular interviews.

3. Same (assessment) will be included in the KPA targets of the senior executives.

4. Hard copy of the manuals will be readily made available to all the new entrants as per requirement.



A few cases of casual approach

Case 3: Date 11.06.2010

First up: Furnace Pressure Very Low

Root cause: PA fan was inadvertently stopped while stopping one of it's LOP during a

Lub Oil Pump changeover.

Case 1: Date 21.04.2010 First up: Turbine Tripped On Trip Oil Pressure Low Root cause: Unit tripped while changing over the auxiliary supply to UAT. During changeover the switch over travelled and a reverse command was given to the switch. Bus 9BA tripped due to this Unit tripped on trip oil pressure low protection due to tripping of running CF pump.

Case 2: Date 02.04.2010 First up: Primary Water Flow Low Root cause: Instead of unit VI primary water pumps isolation was done in Unit-V primary water pumps by mistake.



“The HEAT is on”

What does HEAT mean? H = Human E = Error A = Avoidance T = Techniques



1. S.A.F.E.R- Summarize, Anticipate, Foresee, Evaluate, Review

Also known as Tailboards (Job Briefs)

2. S.T.A.R. – Stop, Think, Act, Review

Also known as “Self-Verification”

3. Three-way communication

Always Take feedback from receiver

4. Two-Minute Rule:

Improves situational awareness of the job site.

5. Stop When Unsure

When unsure, stop and get help from other people.

6. Questioning Attitude

Promotes a preference for facts over submission and opinion

7. Procedure Use and Adherence

“Tools for human performance

improvement (HPI)



Standard Procedures as safety barrier



Case study

(non-adherence to standard procedures)

• Case (1):

• Year: 2007-08

• First up: “All BFP tripped”

• Root cause:

Unit was on partial load after DDCMIS commissioning. EBD v/v got opened on drum level high interlock and drum level start decreasing. FW flow was increased to maintain drum level. In the process D/A level became very low and unit tripped on ALL BFP TRIP protection.


1 . New changes introduced in logics should be well documented and communicated to user/operator.

• Case (2):

• Year: 2012-2013

• First up: “Turbine Hand Tripped”

• Root cause:

MOT duplex filter severe choking due to contaminated oil transfer.


1. Whenever oil is being topped up in MOT,CFT,TDBFP,MDBFP lube oil tank of any unit, oil is being checked for moisture, MI, viscosity etc. Practice is being followed even for fresh drums.

2. Always oil is being transferred by using COPU/MOT centrifuge.



• Compilation of human error related trip reports has been done and

approval has been taken for the distribution of the same in booklet form to all operation staff.

• Standard procedures (unit specific) have been developed and made readily available to the working executives.

• Occurrence reports for the critical activities/events are being developed by the executives involved and the same is shared through the operation web page.

• Weekly exception reports including any pending issues are developed by UCE and mailed to the department head and seniors to keep them informed.



Strengthening procedures at Vindhyachal

STRIVING FOR ZERO HUMAN ERROR


Conclusion

Zero error

Thank U

0

100

200

300

400

500

600 516

367 350 322 267 244 257 280 258

303 357

Total no of trips at NTPC coal stations in past 10

years



Average tripping per year 286.6


coal stations

0

5

10

15

20

25

30

35

40

45

32 27 27 28

43

21 18

25 25

32

44

Trips Due to Human Error

Average tripping due to human error:28.11




coal stations

ABSTRACT

• Today the biggest hurdle in our way is the number of forced outages per

year which hurts our organization not only in terms of financial losses but

also in terms of its reputation among its customers as a reliable power

producer. Although we have been able to reduce the number of forced

outages considerably during the past several years still we have a long way

to go to achieve the target of ‘Zero Forced outage’. The breakup of forced

outages is done in various categories one of which involves HUMAN

ERROR. This paper addresses the issue of forced outages attributed

particularly to the human error. Inputs to the paper are taken from the yearly

trip reports of NTPC coal stations, trip data is compiled and cost analysis is

done to assess the scope for improvement. The focus remains on adopting

modern approach in finding the root cause of the incident. It shows how to

concretely "reverse engineer" human error by rebuilding systematic

connections between human behaviour and features of the tasks and tools

that people worked with, and of the operational and organizational

environment in which they carried out their work.

Cost analysis of unit outage

Type of Cost/unit size 500 MW 210 MW

Loss on account of DC (incentive loss)

500*10³*4*0.75=1500000 210*10³*4*0.75=630000

UI loss 500*10³*2/3*4.21=1403333 210*10³*2/3*4.21=589400

Fuel cost 35*40196=1406860 25*40196=1004900

Total loss 4310193 2224300

Yearly cost 14*4310193=60342702 14*2224300=31140200

Scope of improvement

914.8 lacs/year

Source: EEMG NTPC Vindhyachal/UI cost as per CERC guidelines


Assumptions: (1) UI loss accounted for an avg. 40 min as the time taken for DC revision (2) Total no of trips divided as per the ratio of 500/210 MW units in total fleet


TYPICAL INVESTIGATION ERRORS

(DUE TO HINDSIGHT BIAS)



• Reactions arise from our ability to look back on a sequence of events, of which we know the outcome.

Retrospective

• They focus on those people who were closest in time and space to causing or potentially preventing the mishap.

proximal

• Identify what they could have or should have done – now that knowledge of the event shows the consequence of what they did

Counterfactual and judgemental

Generic approaches to minimizing

human error

• Design strategies

• Exclusion: makes it impossible to commit error used in cases in

which the potential human error can lead to catastrophic consequences.

• Prevention: makes it difficult to commit that identified human

error. used where the risk of human error is not as critical.

• Fail safe: mitigates the consequences of human error instead of

trying to prevent it from occurring in the first place.

Case study (inadequate training)

• Case (1):

Dadri Unit V Date: (12/05/2010)

• First up: “IP TOP-BOTTOM CASING TEMPERATURE DIFFERENCE HIGH”

• Event description:

Unit tripped on HP or IP top bottom casing temperature difference > 45 Deg C. The trip logic requires load more than 100MW and during that time load was being raised after synchronisation and had crossed 100MW.

• Root cause: human error in load raising


Large number of fresh ETs working in operation and having experience of less than one year has to be given in-depth orientation of the process interlocks and protections.


• Case (2):

Dadri Unit VI Date: (05/08/2010)

• First up: “TURBINE HAND TRIPPED”

• Event description:

With rise of throttle pressure, unit came from pressure to load controller. While trying to normalize a fixed command was given to EHC but the deviation was not matched. This resulted in complete unloading of the machine and the unit was hand tripped.

• Root cause:

Inadequate handling of EHTC controls during pressure variations


Training on governing system to operation engineers to avoid human error.


Why training needs to be strengthened

• Fast track expansion of the company demands new entrants to take Higher responsibilities early in their career.

• Present training facilities are inadequate to keep pace with faster development needs.

• No. of less experienced people have increased in the present manpower mix.

• Experienced people are under heavy work load, and find it difficult to spare time for new entrants.



Lack of experienced manpower

• Manpower mix needs to be balanced especially in new projects where system is still unstable and prone to failures.

• Lateral entry of more experienced personnel may be increased in line with the fast track capacity addition program of the company.

• Experienced manpower may be retained after retirement through contracting agencies.

• Promotion/appraisal, incentive policies may be changed to retain quality manpower



Case study (non-adherence/lack of standard

procedures)

• Case (1):

Vindhyachal Unit IX

• Date: (24/11/2010)

• First up: “Furnace Pr Hi Hi”

• Root cause:

Both ID fans unloaded as per feed forward logic while taking trial of blade pitch of FD 9A which returned from PTW.


1. All such type of operation is being done in steps and preferably taking system in

manual.

2.changes introduced in logics of new units should be well communicated to user/operator.


• Case (2):

Vindhyachal Unit X

• Date: (26/07/2012)

• First up: “TURBINE HAND TRIPPED”

• Root cause:

Turbine hand tripped due to MOT duplex filter severe choking due to contaminated oil transfer.


Whenever oil is being topped up in MOT,CFT,TDBFP,MDBFP lube oil tank of any unit, oil is being checked for moisture, MI, viscosity etc. Practice is being followed even for fresh drums.


Standard Procedures as a safety barrier

• Standard procedures to be developed and made readily available to the working executives.

• Increased involvement of working executives in procedure development is required.

• Time pressure should be eased in case of critical activities so as to avoid any lapse in following standard procedures.

• Procedures needs to be updated continuously based on the design changes and any new developments.



Critical Equipment Isolation/Normalization @site

Nomenclature At switchgear

S.A.F.E.R

• The critical steps Summarize

• Errors for each critical step Anticipate

• Probable and worst case consequences should an error occur during each critical step

Foresee

• Controls and contingencies at each critical step to prevent, catch and recover from errors.

Evaluate

• Previous experience and lessons learnt relevant to the specific tasks and critical steps Review

3-way communication

UNSAFE ACTS

Violations Errors

Exceptional Routine Perceptual

Errors Skill-based

Errors Decision Errors

Unsafe

Acts

Skill-based Errors

•Breakdown in visual scan

•Failed to prioritize attention

•Inadvertent use of controls

•Omitted step in procedure

•Omitted checklist item

Decision Errors

•Improper procedure

•Misdiagnosed emergency

•Wrong response to emergency

•Exceeded ability

•Poor decision

Perceptual Errors (due to)

•Misjudged parameters

•Complex situation

•Visual illusion

Violations

•Violated rules/regulations

•Not current/qualified for the

job

•Intentionally exceeded the

limits of the system

PRECONDITIONS FOR

UNSAFE ACTS

Substandard Conditions of Operators

Substandard Practices of Operators

Preconditions for

Unsafe Acts

Unsafe Acts

Physical/ Mental

Limitations

Crew Resource

Management

Personal Readiness

Adverse Physiological

States

Adverse Mental States

Non-Supervisory Tolerance of Unsafe Acts

SUBSTANDARD CONDITIONS OF THE

OPERATORS

Adverse mental states

•Channelized attention

•Complacency

•Distraction

•Mental fatigue

•Get-home-itis

•Loss of situational awareness

•Misplaced motivation

•Task saturation

Adverse physiological states

•Medical illness

•Physical fatigue

Physical/mental limitation

•Insufficient reaction time

•Incompatible intelligence/aptitude

SUBSTANDARD PRACTICES OF THE

OPERATORS

Crew resource management

•Failed to communicate/co-ordinate

•Failed to provide back-up

•Failed to use all available resources

•Failed to conduct brief

•Failure of leadership

Personal readiness

•Fatigue due to Excessive work

UNSAFE SUPERVISION

Unforeseen Known

Unrecognized Hazardous Operations

Inadequate Documentation/

Procedures

Inadequate Supervision

Planned Inappropriate Operations

Failure to Correct Problem

Supervisory Violations

Unsafe Supervision

Preconditions for

Unsafe Acts

Unsafe Acts

Inadequate supervision

•Failed to provide guidance

•Failed to provide oversight

•Failed to provide training

•Failed to track performance

Planned inappropriate operations

•Failed to provide correct data

•Failed to provide adequate brief

time

•Improper manning

•Provided inadequate opportunity

for rest

Failed to correct problems

•Failed to correct document in error

•Failed to initiate corrective action

•Failed to report unsafe tendencies

•Failed to identify at-risk systems

Supervisory violations

•Failed to enforce rules and

regulations

•Authorised unqualified personnel for

the job

•Authorised unnecessary hazardous

procedure

Organizational Climate

Resource Management

Operational Process

ORGANIZATIONAL INFLUENCES

Organizational Influences

Unsafe Supervision

Preconditions for

Unsafe Acts

Unsafe Acts

RESOURCE ACQUISITION/MANAGEMENT

Human resources

•Selection

•Staffing/manning

•Training

Monetary/budget resources

•Excessive cost cutting

•Lack of funding

Equipment/facility resources

•Poor design

•Purchasing of unsuitable equipments.

ORGANIZATIONAL CLIMATE

Structure

•Chain of command

•Communication

•Delegation of authority

•Formal accountability for actions

Policies

•Hiring

•Promotion

•Appraisal

Culture

•Norms and rules

•Values and beliefs

ORGANIZATIONAL PROCESS

Operations

•Deficient planning

•Time pressure

•Incentives

•Measurement/appraisal

•Schedules

Procedures

•Standards

•Documentation

•Instructions

•Clearly defined objectives

Over sight

•Risk management

•Safety programs

Size of exhaust valve in MMI increased to double

TD BFP Exhaust

Valve

Total no of trips at NTPC coal stations in past 10

years

0

100

200

300

400

500

600 516

367 350 322 267 244 257 280 258

303

Average tripping per year 286.6




coal stations

Trips Due to Human Error

Average tripping due to human error:28.11




coal stations

0

5

10

15

20

25

30

35

40

45

32 27 27 28

43

21 18

25 25

32

Average % Trips Due to Human Factors

0.00 2.00 4.00 6.00 8.00

10.00 12.00 14.00 16.00 18.00

6.32 7.36 7.71

8.70

16.10

8.61 7.00

10.00 10.56

Tripping Due To Human Error:9.15%




coal stations

No of units each year

0

10

20

30

40

50

60

70

80

90

63 65 69 71 74 75

79 81 83 86



0

100

200

300

400

500

600

2001-02 2011-12

516

357




coal stations

Total no of trips at NTPC coal stations

Main categories contributing to trips

attributed to human error

27%

24% 27%

22% Inadvertant desk operation

Faulty local operation/lack of supervision

Non-adherence to standard procedures

Lack of knowledge / training

Total 101 trips



Categorization for Vindhyachal specific

cases

22%

8%

35%

35%

Inadvertant desk operation

Faulty local operation/lack of supervision

Non-adherence to standard procedures

Lack of knowledge / training

Total 38 trips



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