Vocational training report NHPC TANAKPUR Uttarakhand

VOCATIONAL TRAINING
REPORT
NHPC (TANAKPUR)
2017
SUBMITTED TO: SUBMITTED BY:
PROF. JAIDEEP GUPTA SHADAB KHAN
11510697(ME)

ACKNOWLEDGEMENT
I would like to thank NHPC tanakpur Ltd. for providing me anopportunity
for summer training.
I am thankful to all the members working here for creating a friendly
atmosphere throughout my training period.
I wish to express my thanks to Mr. Ramprasad for allowing me to do the
training.
My sincere gratitude to Mr. Anurag Bhardwaj, Manager (HR) for his
constant support and words of appreciation during training.
Especially I am thankful to Mr. siddiqui, Officer(HR) who guided me a lot
throughout the training and also helped in timely completion of this
project.
I am also grateful to my Parents and God for providing me constant
inspirationduring my training and in preparing the project report
Shadab khan

ABSTRACT
Hydro power plants in general and hydro turbine in particular like any other real
Systems are nonlinear and have time-varying parameters to some extent. The
hydrodynamics Of the tunnel, penstock and turbine are complex due to
nonlinear relationship, which exists between the water velocity, turbine
inlet pressure and developed power. The performance of hydro turbine is
strongly influenced by the characteristics of water inertia, water compressibility
and penstock-wall elasticity. The dynamic characteristics of a hydro turbine
power depend heavily on changes in set point and load disturbances. Thus the
hydro turbine exhibits highly nonlinear, non-stationary system whose
characteristics vary significantly with the unpredictable load.
A key item of any hydro power plant is the governor. Hydro turbine governing
system provides a means of controlling power and frequency. The speed
governor normally actuates the gates / vanes that regulate the water input to the
turbine. The hydro plants being site specific may have different configurations
of their layout; however the main motivation of dissertation is confined to a
small hydropower scheme, which can be as high head or low head. Small hydro
power schemes with high head and thus connected to reservoir with long
length penstock experience severe control problems due to occurrence of
transients. This is due to pressure wave rise on sudden change of gate position,
which in turn is adjusted to meet the load demand. A low head hydro plant
Connected as single machine infinite bus system experiences a critical
low stability margin.
The study for such systems is a useful starting point for designers to evaluate
the dynamic performance under alternative / new controller concepts.
Subsequently, advanced control techniques are required to realize the full
potential of the plant over a wide range of operating conditions to capture full
plant characteristics. The mathematical models of various elements of hydro
power plant like hydraulic structures / components and electrical systems can be
integrated to represent the plant as a single entity.
To obtain accurate representation of the integrated system, the plant model can
be identified either in open-loop or closed-loop using its input-output data. This
will facilitate the implementation of new /alternative control approach to the
plant model for effective operation during disturbance. The approach has
discussed above may be considered for model identification for real existing
hydro power plants using its input-output data only.

CONTENT
1.Introduction
2.Location
3.Hydrology
4.Spillway
5.Sluices
6.Power channel
7.Power channel
8.Forebay
9.Penstock
10.Tail Race channel
11.Power house
12.Turbine
12.Generator
13.Bus duct
14.Generator Transformer
15.Switch yard
16.Eot

17.Allocation of power generation
18.Design energy
19.Elevations in power house
20.Equipments at various elevations
21.Checks before the starting of generating
system
22.Summary of the start sequence
23.Synchronization of the machine
24.Stopping sequence
25.Tripping of machine on fault
26.Restarting of machine after prolonged
shutdown
27.Operation regime
28.Troubleshooting

INTRODUCTION
***************************
The River Sharda originates in the region of higher Himalayas, from the Glacier of Zaskara
range, at about 5250 meter. In the upper reaches, in the hills, it is called Mahakali. The river
emerges into plains at Barmdeo, 5 Km upstream of Tanakpur and is called Sharda. The river
is among the major rivers and has a large hydro potential.
The Tanakpur Power Station is located on the right bank of the river Sharda in the state of
Uttarakhand. It is a run-of-the river power station. The Project comprises a (i) Barrage for
diverting Sharda river waters into the power channel (ii) a surface power house with a total
installed capacity of 94.2 MW (derated from original rating of 120 MW due to a compromise
that had to be made on the designed head), near the Banbassa Barrage, for utilizing the
available head for power generation; (iii) about 1.15 Km long tail race channel for discharging
back the water from the generating machines in to the Sharda River ; (iv) 220 KV /132 KV
switching station adjacent to the power house and (v) 220KV double circuit transmission line
to Bareilly C. B. Ganj, 132KV single circuit transmission line to Mahender Nagar for evacuation
of power.
The Power Station has 3 Kaplan turbines of 31.4 MW each. The (Kaplan type) Hydro turbines
for the Tanakpur Power Station are supplied by M/s BHEL. The turbine and generating
equipment were manufactured against our purchase order in October 1985. The turbine is
designed for direct coupling with three phase 50 cycles/sec generators. The Generators are
of the Umbrella type which are also supplied by M/s BHEL.
The elements of water path of turbine viz. spiral casing, stay ring, guide apparatus, runner and
draft tube have been worked out to get minimum overall dimensions of the unit, with high
efficiency and good anti cavitation properties. Main attention in designing the machines was
focused to obtain high hydraulic and operational qualities of the equipment and its complete
reliability.
The project area falls under gradation 4 on Richter’s scale and is not seismically active.
Monsoons are heavy and covers the months of July to October, winter extends up to February
and summer from March to June. The max. and min. temperatures are 400
C and 140
C
respectively. Average rainfall is 1500mm.
During monsoon, in order to have silt-free water for the power house, a silt excluder
device is provided in the under sluice parts of the barrage and silt ejector is provided
on the power channel.

SALIENT FEATURES
************************
LOCATION
State in which located Uttarakhand
District Champawat
River Sharda
Barrage Apprx. 2 KM D/S of the town Tanakpur
Power House Apprx. 1.2 Km U/S of existing Sharda Barrage
HYDROLOGY
Catchment area 15,100 Sq.km
Design flood 19900 Cumecs.
Mean annual rainfall 1500 mm
BARRAGE
Total length 475.3m
Spillway Bays length. 279.5m
Crest Level Under sluice-
237.5 m,
Spillway-
238.1m

No. of bays. 22 (Under
sluice – 9,
Spillway – 13)
Max. discharge capacity 19900
Cumecs
Max. barrage pond level 246.7 m
Silt Excluder Tunnels 6 no. size 2.2
m X 3.2 m
Guide Bund (Downstream) Left Bank -
177m, Right
Bank -177 m
Afflux Bund (Upstream) Left Bank- 2.2
Km, Right
Bank- 2.2 Km

SPILLWAY
No. of spillways
13
Size of spillway gates 18.3mx 8.9m
Weight of each gate
69.271 MT
Crest level of spillway bay 238.1m
SLUICES
No. of sluices 9
Size of under sluice gates
18.3mx9.5
m
Weight of under sluice gate 73.687 MT
Size of intake gate 5.1x 7.027
m
HEAD REGULATOR
Location
Length
Right bank
of the river
78.45m
No.& Size of gate /wt.
6 Nos, 11.2
m x 5.5m
each,
36.087 MIT
Discharge capacity.
680
cumecs
Energy Dissipation
Arrangement
Stilling
basin with
blocks

SILT EJECTOR
No. & Type 48, Hopper type
Size of desilting basin 90mX120m
No. of flushing tunnels 4 nos
POWER CHANNEL
Length

6.4 Km(from
head regulator
to forebay)
Max. discharge capacity 566 cumecs
Shape Trapezoidal
Depth 6-9 m
FOREBAY
Size 64.2mX91.0m
Bed level 231.10 m

BYPASS SPILLWAY
No. and size of bay 5 nos. of 9.5 m each
Max. discharge capacity 566 cumecs
Length of spillway 59.5 m
Crest level 243.2 m

PENSTOCK
Number 3Nos.
Diameter 6.5 m
Length 68 meter
Size of intake gates 5.1X7.11 m
Center line of intake 234.933 m
TAIL RACE CHANNEL
Length 1150meter.
POWER HOUSE
Type Surface
Design head 24.25 m
Installed capacity 94.2 MW
(3 units of 31.4 MW each – Derated capacity)
Dimensions 102.30x45.20x47.70m
Turbine Kaplan.
Unit design discharge
188.67 cumecs
TURBINE
Type of turbine Kaplan
Rated net head 24.25 m
Rated output 32 MW (Derated from rated output of 41.34 MW)
Rated discharge for 188.67 M3
/sec

rated out put & head
Rated speed 136.4 rpm
Rated average efficiency 92.2%
Discharge dia of runner 6200 mm
Runaway spped on cam 280 rpm
Runaway speed off cam 375 rpm
Direction of rotation Clockwise ( viewed from top)
P.P Set delivery pressure 40 Kg/cm2
Maximum hydraulic thrust 480 T
No. of guide vanes 24

GENERATOR
Type Umbrella
Rated out put 45 MVA
(at 0.9 p.f lagging)
Rated voltage 11 KV
Frequency 50 Hz.
No. of poles 44
Stator Connection Star
Rated Current 2361.8 A
Excitation at rated load 900 A
Slip ring brushes Total 24 ( 12 per ring)
Thrust Bearing Type Spring Mattress ( 10 pads; 91 springs per pad)
Air gap 14 mm

BUS DUCT
Type designation - Isolated Phase Bus Duct
Rated voltage KV 11
Highest voltage for
equipment Um
KV 12
Rated frequency Hz 50
Main bus A 3000
GENERATOR TRANSFORMER
Rated voltage 220 ( +10%) KV
Rated MVA 49.5 MVA
No. of Transformers 3 Nos.
Type of cooling OFWF
Insulation class A
% Impedance 12.32 %
(at principal tap)
Vector group Ynd11

SWITCH YARD
Voltage level 220KV / 132 KV
No. of bays 7
Unit bays 3
Line bays 3 ({Line-I/II(220 Kv) & Nepal Line(132 Kv)}
Bus coupler bay 1
Type of breaker SF6 (Single pole operation,pneumatic closing-spring
tripping)
Size of switch yard 168 M X 111 M

EOT
Number 2 Nos.
Capacity 125/30/ Ton
TRANSMISSION LINE
Tanakpur to Bareilly 220KV Double Ckt Line
Length of the line 106 Km.
Tanakpur to Nepal 132 KV single Ckt line
Length of the line 15 Km.
DESIGN ENERGY 452.19 MU
COMMISSIONING DATES
Unit-I ( 31.03.1992) , Unit-II (4.4.1992), Unit-III
(4.4.992)
BENEFECIARY STATES 1) Uttarakhand ( 12% free power)
2) Uttar Pradesh

ALLOCATION OF POWER GENERATED FROM TANAKPUR POWER STATION
S.No. State MW Share % Share
1 Chandigarh 1 1.3
2 Delhi 12 12.8
3 Haryana 6 6.4
4 H.P 4 3.8
5 J&K 7 7.7
6 Punjab 17 17.9
7 Rajasthan 11 11.5
8 UP 21 22.6
9 Uttarakhand 15 15.9
Note:The power allocation for different states will be pro-rata (%share) of net power transmitted
by TPS after deduction of power transmitted to Nepal.
SCHEDULE OF POWER TO BE TRANSMITTED TO NEPAL( MONTH-WISE)
SL.NO. MONTH
ENERGY SUPPLIED (MU) PEAK LOAD (MW)
SCHEDULE SCHEDULE
1 January 4.5000 12.00
CONSTRUCTION COST
3) Rajasthan
4) Punjab
5) Jammu& Kashmir
6) Himachal Pradesh
7) Haryana
8) Delhi
9) Chandigarh
10) Nepal ( receives 75 MU free power per year
funded by Ministry of External Affairs )
Rs. 400 crores.(Including Transmission cost and
IDC).

2 February 4.0000 12.00
3 March 4.5000 12.00
4 April 5.0000 14.00
5 May 6.0000 16.00
6 June 6.5000 16.00
7 July 7.0000 16.00
8 August 7.0000 16.00
9 September 7.0000 16.00
10 October 7.0000 14.00
11 November 6.0000 12.00
12 December 5.5000 12.00
TOTAL 70.0000 168.0000
DESIGN ENERGY (MONTH WISE) FOR TANAKPUR POWER STATION
S.NO MONTH DESIGN ENERGY (MU)
1. April 19.71
2. May 28.94
3 June 42.29
4 July 66.59
5 August 66.59
6 September 64.44
7 October 51.92
8 November 31.12
9 December 24.13
10 January 21.25
11 February 17.12
12 March 18.09

ELEVATIONS IN POWER HOUSE
*************************************
S.NO. ELEVATION DESCRIPTION
1 EL 247.5 ROAD FORMATION LEVEL
2 EL 246.375 M FULL SUPPLY HEAD OF POWER CHANNEL
3 EL 246.4 M BYE-PASS GATE OPERATION
4 EL 246.0-246.2 M NORMAL FOREBAY LEVEL FOR OPERATION OF UNITS
5 EL 243.2 M CREST LEVEL OF BYEPASS SPILLWAY
6 EL 234.933 CENTRELINE OF PENSTOCK INTAKE
7 EL 231.10 BED LEVEL OF FOREBAY
8. EL 234.0M ROOF TOP OF POWER HOUSE (1ST
FLOOR)
9 EL 227.7 M MACHINE FLOOR
10 EL 223.30 M MAX TRC WATER LEVEL
11 EL 222.0 M MIN TRC WATER LEVEL
12 EL 218.853 M BED LEVEL OF TRC AT ENTRY
13 EL 218.848 M BED LEVEL OF TRC AT REGULATOR SIDE
14 EL 222.0 M TURBINE FLOOR
15 EL 217.5 M CENTERLINE OF SCROLL CASING
16 EL 215.56 M CENTRE LINE OF RUNNER
17 EL 211.25 M COOLING WATER FLOOR
18. EL 210.5 M DRAFT TUBE GALLERY
19 EL 210.5 M DAINAGE/DEWATERING FLOOR
20 EL 202.5 M DEWATERING HEADER
21 EL 200.5 M DEWATERING PIT FLOOR
22 EL 200.0 M DRAINAGE PIT FLOOR
23 EL 198.80 M DEEPEST FOUNDATION LEVEL

EQUIPMENTS AT VARIOUS ELEVATIONS
******************************************
1) EQUIPMENTS AT EL 227.7 M (MACHINE HALL ELEVATION)
S.No. Location
Equipments
1. Machine Hall Instrument Panel, Alarm Panel, Unit Relay Panel-1&2,
Temperature& Measurement Panel, Unit Control &
Indication Panel, Thyristor Bridge, AVR cabinet, Field
Breaker cabinet, Field Flashing cabinet, Governor
System (Electrical Cabinet& Hydromechancial
cabinet).
2. Control Room Fire alarm control panel, fire annunciation panel, PLCC
Panel Nepal (ABB Make), PLCC CB ganj lines
(PUNCOM Make), Remote OLTC & cooler control
cubical (Nepal Line) 220KV/132KV, 50MVA auto
transformer, 132KV Nepal feeder, Time synchronizer
panel, Event logger panel, Disturbance recorder panel,
Auto synchronizer, 220V DC distribution board, CMR
panel, control desk, Bus coupler panel, CB ganj line
1&2 panel, Synchronizer panel.
3. Transformer Yard Generator Transformer# 1,2&3,
SST#1&2, UAT#1,2&3,Gantry crane.
4. Pump House (Fire
Fighting)
Main fire pumps#1&2, One jockey pump, Water
Storage Tank.
5. LT Panel Room SSB#1&2, 220 V Float charger and Boost charger, 48V
Float charger and Boost charger, Halon system for
control room fire fighting system.
6 Ventilation room Blowers(3 No.)

7. Battery Room 220 V Battery Bank (Old/New), 48 V Battery Bank.
Note: See Annex-1&Annex-2 for schematic drawing.
2) EQUIPMENTS AT EL 222.0 M (TURBINE FLOOR)
S.No. Location Equipments
1. Turbine Floor Brake dust collector system,Interpad cooler system,
LAVT Cubicle,NG Transformer cubicle, Excitation
transformer,CGLS system, Braking &Jacking system.
2. Compressor Room HP Compressors (Two), LP Compressor(Two),HP Air
Receiver, HP to LP Air Receiver,LP Air Receiver
3. Mechanical Workshop HMT milling machine (FN3U), BMC shaping machine,
HMT LTM20 lathe machine, BMC saw machine, Grinder
(Kulkarni), HMT drilling machine.
4. Panels SSB panel , UAB #1to3.
5. OPU Oil pressure unit (OPU) receiver, Two OPU pumps.
6. Co2 System(Fire
Fighting)
Co2 cylinder bank 1&2, Co2 fire extinguishing control
panel, smoke alarm system panel.
7. Other Systems Cable spreading room, cable gallery, medium velocity
water fire extinguishing system.

Note: See Annex-3 for schematic drawing.
3) EQUIPMENTS AT EL 211.25 M (COOLING WATER FLOOR)
S.No. Location Equipments
1. Cooling floor Two Cooling pumps for each unit, One oil leakage
pump for each unit.
2. Panels Cooling water pumps control panel.

TANAKPUR HYDROPOWER STATION,BANBASA
DAILY /SHIFT –WISE CHECK LIST
DISCHARGE.: …………………….. DATE:……………………..
FOREBAY LEVEL: ………………… TIME OF CHECKING…
WHETHER CONDITION: ……………
S.NO DESCRIPTION OF
EQUIPMENT
UNIT#1 UNIT#2 UNIT#3 REMARKS
1 Load on the machines in MW
2 Condition of D/T gallery EL210.5
3 Leakage from D/T manhole (front
and back)
COOLING WATER FLOOR EL 211.25M
1 Cooling water pump #1
2 Cooling water pump #2
3 O.L.U working in AUTO/MANUAL
4 Condition of duplex strainer#1
5 Condition of duplex strainer#1
6 Pressure at the inlet of strainer
7 Pressure at the outlet of strainer
8 Draft tube pressure
9 Cooling water header pressure
10 Condition of D/T valve pit pump
11 Condition of motorized valve in
cooling water circuit
TURBINE PIT EL 218.70 M
1 Condition of top cover drainage
pump
2 Shaft seal water pressure
3 GV shear pin air pressure
4 Oil leakage from TGB

S.NO DESCRIPTION OF EQUIPMENT UNIT#1 UNIT#2 UNIT#3 REMARKS
MACHINE FLOOR EL 227.70M
1 Hot air temp.
2 Cold air temp.
3 Thrust bearing pad temperature
4 Generator guide bearing (GGB) pad
temperature
5 Generator guide bearing (GGB) oil
temperature
1 Governor servomotor opening
pressure
2 Governor servomotor closing
pressure
3 Water pressure /vaccum below top
cover
4 Water pressure below top cover
GAUGE #1
GAUGE #2
GAUGE #3
7 Water pressure in spiral casing
8 Healthiness of PP set motor #1
9 Healthiness of PP set motor #2
10 Pressure in the accumulator
11 Oil level in the accumulator
12 Oil level in the sump
13 Leakage from idealer valve #1
14 Leakage from idealer valve #2
15 Healthiness of HS lube pump
16 Healthiness of CGLS
17 Flow meter in the air cooler
18 Flow meter in the oil cooler
19 Air pressure in breaking system
20 Water leakage from any valve (Give
location)
21 Healthiness of L.P compressor #1
22 Healthiness of L.P compressor #2
23 LP air tank pressure
24 Healthiness of H.P compressor #1
25 Healthiness of H.P compressor #2
26 H.P air pressure
27 Condition of MW system in cable
for any leakage etc.
28 Check ET for any abnormal sound
29 Condition of generator barrel door
30 Condition of UAT breaker.
31 Condition of ESV

6 Turbine guide bearing (TGB) pad
temperature
7 Turbine guide bearing (TGB) oil
temperature
8 Cooling water inlet temperature
9 Cooling water outlet temperature
10 Draft tube pressure
11 PP set pressure
12 Spiral casing pressure
13 Shaft gland isolating seal air pressure
14 Shaft seal cooling water pressure
15 Governor pressure on EHG cabinet
16 Balance position
17 Bridge current in AVR panel (a)
18 Bridge current in AVR panel (b)
19 Bridge current in AVR panel(c)
20 Pressure of runner servomotor
opening
21 Pressure of runner servomotor
closing
22 Any sparking on slip ring brushes
23 Head light glowing
24 Check any alarm in UCB panel
25 Healthiness of blower #1
28 Healthiness of sprinkler in cooling
pond
29 Water level in cooling pond

HEALTHINESS OF PUMPS ((EL 210.60 M)
1 90 HP VT Dewatering pump #1
S.NO DESCRIPTION OF
EQUIPMENT
UNIT#1 UNIT#2 UNIT#3 REMARKS
TRANSFORMER DECK (EL 227.70 M)
1 No of coolers working
2 Healthiness of oil circulation
temperature
3 Transformer winding
temperature
4 Transformer oil temperature
5 Humming sound from
temperature
6 Check for any sparking or
heating of transformer
jumpers
7 Any water leakage from any
point
8 Any oil leakage from any
point
CONTROL ROOM
1 Regular checking of control
desk and control panels
2 Indication of Annunciation
panel
3 Healthiness of relay Panels.
4 Cleanliness of control desk.
5 Cleanliness of relays.
6 Healthiness of PLCC of line #1
7 Healthiness of PLCC of line #2
8 Healthiness of PLCC of Nepal
line
9 Healthiness of AC
10 Healthiness of List
LT ROOM
1 Battery charger in
Float/Boost mode.
2 Healthiness of SST#1 circuit
breaker
3 Healthiness of SST#2 circuit
breaker
4 Healthiness of HALON system

5 90 HP VT Drainage pump #2
6 90 HP VT Drainage pump #1
7 35 HP submersible pump #1(Drainage
pit)
pit)
pit)
OTHERS ISSUES/CHECKING
1 Illumination at different floors
2 Opening of any hatch cover
3 General cleanliness

PRESTART CHECK LIST
********************************
1 No work permit should be outstanding.
2 Gen.schedule should be approved from NRLDC
3 Oil level in TGB/GGB should be normal.
4 All relevant oil/air/water lines should be charged and cooling water header
pressure should be normal.
5 D.C control circuit voltage check relay healthy.
6 Gov. Oil pressure and level should be normal.
7 Master stop relay reset/Controlled action shutdown relay reset/Emergency
shutdown relay reset. Electrical lockout relay’s reset.
8 ESV ckt. should be healthy.
9 Top cover pump AC supply should be normal.
10 HS pump AC supply ON.
11 DC supply to all Protection/controlled relay panel should be normal.
12 Brake air pressure normal and brakes in released position.
13 Guide vanes in closed position with lock disengaged.
14 Penstock & Draft tube gates are open.
15 Air pressure to shaft gland isolating seal released.
16 Penstock drain valve should be closed.
17 Fire fighting system should be healthy.
18 No alarm/annunciation is present.
19 Transformer oil flow/ oil pressure normal.
20 Generator HV circuit breaker open.
21 Generator Field breaker open.
22 Prestart check indication “unit ready to start”-ON.
23 For auto start from control room
1. Gov. & exciter should be in auto.
2. Unit selection in local.

CHECKS BEFORE STARTING OF THE GENERATING UNIT-SYSTEM WISE
(AFTER LONG OUTAGE/SHUTDOWN/MAINTENANCE WORK)
The following checks are to be made before starting of machine:
General Checks:
1) Verify from the shut down register that no work permit is outstanding.
2) Ensure that load schedule is approved from NRLDC.
3) Ensure that the machine is free from any fault and can be run on load.
4) Check that penstock drain valve & DT dewatering valve is closed.Air release valve
of spiral casing is opened and also check that Guide Vanes are closed and unlocked.
GENERATOR:
First make a general check of all the equipment. Ensure that tools, tackles, ladders,
platforms are removed from inside and around the component/ equipment. Ensure all
the manhole covers e.g. spiral casing, draft tube, generator barrel doors are closed
and securely fastened. Ensure that no body is inside the generator barrel.
Check that oil levels in bearings are normal as per level indicators.
Ensure normal water flow to generator air coolers.
Ensure that slip rings and carbon brushes are secured to their respective positions. This will
avoid sparking etc. Ensure that brake pads are in released condition.
CO2 SYSTEM:
Ensure that the CO2 cylinder banks in the system are in auto mode. Also check that no
annunciation is appearing on CO2 control panel.
THRUST BEARING:
Check the oil level of the chamber. In case the oil level is low, check for leakage and then
top up the oil to desired level.
Check the inlet and outlet valve of the unit for their open position.
Ensure water supply to TGB/GGB is normal.

BRAKE AND JACK:
Ensure correct air pressure (5-6 kg/cm2) in the system.
CGLS SYSTEM:
Check the availability of the supply on the panel. Charge the main pipe line up to
required pressure of 150 kg/cm2 & check for any leakage in distributer/feeders.
COOLING WATER SYSTEM:
Ensure that all the cooling water valves of the unit supplying water to the stator air
cooler, generator guide bearings, thrust bearings, Main transformers, shaft seal are
open. Also ensure that the outlet valves of the respective cooling water circuits are
open. Check that the pressure of 5-6Kg/cm2 is available at Turbine floor. In case of
reduction in pressure at any of the supply points, corrective measures should be taken
after finding the reason so as to avoid rise in temperature.
DEWATERING & DRAINAGE SYSTEM:
Dewatering & drainage system should work on ‘auto’ mode. Ensure the pumps are on
‘Auto’ mode. If the system is operated manually, ensure the proper operation of the
pump so that flooding doesn’t take place.
HP COMPRESSED AIR SYSTEM:
Ensure the settings of the compressor to operate at defined start and trip values.
Ensure the safety valve functions properly. Moisture should be drained from the
compressor air receiver. Selector switch should be on ‘Auto’ mode.
LP COMPRESSED AIR SYSTEM:
Ensure the settings of the compressor to operate at defined start and trip values (If in
auto mode).If in manual mode the receiver pressure should be monitored at regular
intervals. Ensure the safety valve functions properly. Moisture should be drained from
the compressor air receiver. Selector switch should be on ‘Auto’ mode.

PROTECTION SYSTEM:
All relay flag should be reset and there should not be any flag/alarm indication.
COMMUNICATION SYSTEM:
Communication (PLCC etc.) system should be in order.
DRAFT TUBE GATES:
Draft tube gates should be open.
PENSTOCK:
Penstock should be initially filled slowly with penstock by pass arrangement in order
to avoid sudden rush of water inside the penstock.
PENSTOCK GATES:
Penstock gates should be open.
SWITCHYARD:
Ensure 415V supply to the breaker/isolator motors in the switchyard. Check SF6
pressure in all the SF6 breakers. Check for satisfactory functioning of the isolators
from control room and locally with the concerned breaker in open position. Then the
control switch may be put back on remote control. Do not operate the breakers locally.
Check that closing spring of the breakers is in charged position.
TURBINE:
Check that all shear pins of guide vanes are intact. Ensure that the oil level in TGB is
normal. In case of higher oil level check for the water content in oil due to leakage from
oil coolers. Check for the open position of valves supplying clean water to turbine shaft
seal. Ensure that the stopper for servomechanism is disengaged.

OIL LEAKAGE UNIT:
Check that the control gear of the OLU of turbine is in ‘Auto’ mode.
LEVEL & PREESURE IN OPU:
Ensure that the control switches of the control panel for OPU are kept in auto mode
thereby indicating that out of the two oil pumps one will act as duty pump and other as
standby.
The following valves should be in ‘OPEN’ condition.
Main valve connecting oil pressure unit to the governing system.
The valves of the oil pipe line connecting both the pumps and air oil accumulator.
The valve of the pipe line connecting governor slide valve and main oil tank.
All the four valves in the servomotor.
Valve of oil pipe line connecting servomotors and oil leakage unit.
The valve connecting the pressure relay of the air oil accumulator.
The following valves should be in ‘CLOSED’ condition.
The valves connecting the OPU oil tank to pipe lines of oil handling system.
The valve connecting the OPU oil tank to pipe line for oil sampling.
The drain valve of the OPU oil tank.
GOVERNOR:
Ensure the control knob of the governor initially at the manual mode.
Main oil valve connecting OPU to governing system is open and oil pressure in the
cabinet is normal. If the pressure is less, check for rated pressure in of 40kg/cm2 in
OPU. If need be, take necessary measures and bring pressure at 40kg/ cm2 & oil level
at normal. Clean the filters in the mechanical cabinet of the governor.
STATIC EXCITATION SYSTEM:
Ensure for 220V DC supply from battery bank to the excitation panel for excitation
build up during black starting of the machine. Check DC supply for its control and

protection circuit. Ensure the field breaker is ‘OFF’. Ensure that all the protections of
Excitation system are in reset condition.
AC SUPPLY FOR PUMPS OPERATION:
It should be ensured that supply to the control panel of OPU is available from LT
control panel.
COOLING FOR GENERATOR GUIDE BEARING:
Check for the cooling water supply to the oil coolers and ensure 5-6 kg/cm2 pressure at the
inlet of oil cooler.
OIL LEVEL IN GUIDE BEARING:
Check the oil level in guide bearing. Top up, if required.
BRAKE AND JACK SYSTEM:
Rotor should not be in jacked position. Brake must be released.
EMERGENCY SLIDE VALVE:
E.S.V. should be reset.
MAINTENANCE SHAFT SEAL POSITION:
Maintenance shaft seal should be in deflated condition.
SHAFT SEAL WATER PRESSURE:
Ensure that the water supply at 2-3kg/cm2 is maintained to the shaft seal.

TOP COVER DRAINAGE PUMP:
Check that the drainage of top cover water through submersible pumps is functional.
TRANSFORMER:
Check the cooling water supply to the Generator Transformer.
The fire fighting system (sprinkler) of the GT should be in healthy condition.
Transformer cooling oil pumps should be ‘ON’.
Buchholz Relay Connection should be intact.
Oil level in conservator should be normal.
Color of silica gel in breather should be blue to ensure that it is moisture free.
Insulation resistance of winding and core should be checked.
BDV of oil should be taken. The value should be as per prescribed limits.
SF6 CKT BREAKER:
Check that SF6 pressure is normal.
EARTHING SWITCH POSITION-OFF:
Position of the earthing switch should be ensured as ‘OFF’
ISOLATOR POSITION-CLOSE:
Check for satisfactory functioning of isolators in remote and local mode with respective
breaker in open condition. Isolator should be in closed position.
BREAKER POSITION-OFF:
Breaker should be in ‘OFF’ position.
VENTILLATION SYSTEM:

For proper ventilation of the power house, blower fans should be ‘ON’
AIR CONDITIONING SYSTEM:
Air conditioning system should be ‘ON’
PLCC SYSTEM:
Make sure that the PLCC system should be functional.
EMERGENCY LIGHTING:
Emergency lighting circuit should be functional.
DG SET POWER:
DG power should be available, if required.
FIRE FIGHTING SYSTEM:
Ensure the proper functioning of the Fire fighting system.

SUMMARY OF THE START SEQUENCE
***************************************
Check that penstock drain valves are closed & guide vanes are closed.
Filling of pipeline and draft tube flooding:
Close all drain and isolating valve such as draft tube, penstock, spiral casing etc.
Open the air release valve of spiral casing .
Slowly raise the draft tube gates to open the air release port and kept in this position till the air
release is completed. Lift the gate in full open position thereby filling the draft tube.
Open bypass of hydraulic drive penstock gate so that penstock is flooded with water up to the
penstock gate and when pressure on both sides of the gate equals then open the intake gate
to full open position.
Open cooling water supply valves, isolating valves for turbine bearing oil cooler etc. While
opening the valves, care should be taken to open them slowly. Release air from generator air
cooler.
Open the water supply valve to shaft sealing .The pressure should be between 2 to 3
kg/cm2.Care is to be taken to see that pressure in the sealing should be more than the
pressure below the sealing.
Operation of the governor:
Check the oil level and oil pressure in the governor oil pressure accumulator. The
pressure in the accumulator should be 40 kg/cm2.
Ensure all Pre-start checks before starting the unit.The relay which indicates that the unit is
ready for start will be energized and unit ready to start indication will appear on the control
desk.
STARTING OF MACHINE
Open the guide vane with governor in manual mode.
After getting 80% speed, governor may be switched to auto mode.
The switch auto/manual in AVR should be in auto mode.
The local remote selector should be in remote position.
The generator start/stop control switch is turned to start position.
The excitation circuit breaker /field circuit (NC) breaker will close manually by field circuit
breaker control switch on control desk and voltage built up will reach up to a preset level of 11
KV.

The speed of machine viz. the frequency of the incoming machines can be adjusted with the
help of control switch meant for that installed on the control desk.
The incoming voltage of the generator can be adjusted with the help of control switch meant
for that installed on the control desk.
The generator is now ready for synchronization.
SYNCHRONIZATION OF MACHINE
When the machine has built up the required voltage and its frequency is 50 Hz,
synchronization can be done with the help of synchronization switch. The
synchronization can be done in two ways
Manual Synchronizing
Auto synchronizing
MANUAL SYNCHRONIZING (Currently only manual syn.is there)
Keep the Guide vane limiter to appx. 30%.Switch the synchronizing switch to
main/check position.
Adjust the generation voltage and match it with running voltage through switch voltage
level control for AVR on the control desk. The incoming voltage (machine voltage)
should be slightly higher than running voltage system. Turn synchronoscope switch
on synchronizing panel to ‘ON’ position. It will bring synchronoscope in the circuit. The
movements of synchronoscope needle in clockwise or anticlockwise direction will
indicate whether machine is fast or slower than the system.
Increase or decrease speed of machine by operating switch (speed power control
switch) and match the speed of the machine with grid. Ensure that the synchroscope
needle is moving very slowly clockwise. Wait for one or two rotations of synchroscope
needle. Carefully watch the clockwise movement of synchroscope needle. Keep the
left hand on breaker control switch and right hand on speed controller.
During the clockwise movement of synchroscope needle when it is at a position (very
near to 12 o’clock position), flip the breaker control switch to close position. This will
synchronize the machine with the grid.

Quickly take some load by giving short flips of speed controller towards increase
side. Delay in this operation may cause the motoring action of the machine.
Never close the main breaker of the machine in hurry. Wait for next rotation delaying the next
operation. Never try to close the breaker when synchroscope needle is moving fast in the clock
wise direction. Never try to close the breaker when the needle is very near to 12 O’clock
position but have a tendency to move anti clockwise. Each wrong synchronizing gives a
big jerk to the machine, which is harmful to the machine.
Switch off the synchroscope. Change synchronizing switch to off position. Set load on
the machine according to declared capacity. MVAR sharing of the machine can be
varied through voltage level controller switch.
When the machine is synchronized, shift all the auxiliaries of the machine from station
service transformer to unit auxiliaries’ transformer.
Note down the synchronizing time.

STOPPING SEQUENCE
************************
In case one unit has to be stopped then it should be ensure that the actual generation
does not deviate from scheduled generation ( Within +5% in a time block).No UI penalty should
be imposed. If switching of generation from one unit to other first synchronize the other unit
and then stop the running machine so as not to lose any UI charges due to delay in
synchronizing the other unit.If switching off the unit due to less inflow get the schedule
approved from NRLDC.
Following sequence shall be followed for stopping the unit when running on load.
1) Reduce the output of generator slowly till it is almost zero (at least 5 MW).
2) Trip HVCB.
3) Trip field circuit breaker and the closing of guide vanes starts.
4) Guide vanes close and the machine retards.
5) Ensure HS lubrication pump starts at 30% speed.(Normally in Auto)
6) Ensure brakes are applied after start of HS pump.(Normally in Auto)
7) Brake dust collector to be started if not in auto.
8) Machine comes to stand still.
9) HS Lubrication pump stops.
10) Generator brakes released.
11) Brake dust collector to be stopped if not in auto.
12) Shut off cooling water supply to stator, generator transformers and
bearings.(If unit to be stopped for more than 2 hours).
13) Shut off inter pad cooling system.(If running)
14) Engage G.V. lock.(If unit to be closed for long period)
15) Make a record of time of opening of Generator C.B. and stopping of machine
16) Close penstock gate when either leakage from guide vanes is expected or
the unit has to be closed for long period.

TRIPPING OF MACHINE ON FAULT
***********************************
1. Protection relay operates leading to operation of Trip Relay.
2. Generator C.B. is opened.
3. Generator Field breaker is opened.
4. Closing command is given to guide vanes and inlet penstock gates(in case of Electrical
Lock-out and S/D trip).
5. Stop sequence starts as in case of manual stopping of the machine.
6. Note down the operated protection relays, flags after ensuring that machine has stopped.
7.Take print out of Sequential Event Recorder/Event Logger (SER/EL) and record the tripping
time.
8.In case of tripping of lines, communicate with remote end and get information about
operation of relays at receiving end. Also take print out of Fault Disturbance Recorder
(DR).
9.Intimate maintenance staff giving as much detail as known.
10.Analyze the fault as to ascertain the cause of tripping.
11. Prepare unit for re-starting after rectification of faults.
12. Shift Incharge to prepare tripping report as per format and send as per the mailing list.
13. Breakdown report/ Restoration and analysis report to be send by Incharge (Electrical
Maint.) as per format.
In case of tripping of machine it should be ensured that UI penalty should be
minimum.Take revision of schedule if it is expected that the fault cannot be rectified
immediately.The revision is effective from the 4th
time block when revision is send, so revision
should be send immediately.

RESTARTING OF MACHINE AFTER PROLONGED SHUT DOWN
****************************************************************
The following checks have to be made when the machine is to be started after prolonged shut
down.
1)The insulation resistance and polarization index values of the stator and rotor shall be
checked. The IR value of each phase of stator winding should be compared with the
commissioning values and P.I. values should be equal to or greater than 2 (two). The rotor IR
value should be 5 (five) mega ohm when measured at slip rings after removing the brushes.
If the IR and PI values are low, the machine must be put on dry run.
2)The bearing oil/OPU Oil has to be circulated through centrifuge for at least 24 hours.
3)Check the operation of brakes.
4) Cleaning of governor oil filter to be performed.
5) Air removal from coolers by passing water for two hours.
6) Start the HS pump before rotating the machine.

INSTRUCTIONS FOR NORMAL OPERATION OF UNITS
******************************************************
► Machine should be run as per the schedule approved by NRLDC and any variation in load
shall be done as per the revised schedule.
►Monitor all parameters of the unit, feeders, grid conditions and auxiliaries.
► Check that no alarm is appearing on the alarm facia of each machine/feeder
► Ensure that the DC supply through distribution board is available to all the control and
annunciation panel of the running machine and in no case will it be switched off.
► While generating active power, due consideration for generation of reactive power may also
be given depending upon the system conditions but should not be exceeded beyond the
permissible limits of the stator(2362 A for rated power at 0.90 p.f lag) and rotor current (900 A
at rated load).
► Any annunciation appearing on the panel shall be accepted and recorded before resetting.
In case of non-resetting of the annunciation, remedial measures must be taken to rectify the
fault before tripping of the machine.
► Ensure that any equipment under maintenance has a warning board “DANGER/MEN AT
WORK” hung on to avoid any operation by mistake.PTW should be given before performing
any maintenance work in machine.
►All parameters of the machine and feeder on hourly basis as per format must be recorded
during each shift and signed.
►Water quality should be monitored , especially during monsoon period. If silt level above
3500 ppm intimate Shift Coordinator/ HOD(Operations).
►Water level at forebay should be constantly monitored and sudden variations in levels
should not be allowed.The level should be kept between 246.0m to 246.2 m.
►In order to avoid imposition of UI penalty the actual generation should be kept within + 5%
of scheduled generation for a block of 15 minutes and within +1% for the whole day.
Note: The operating regime of the generating units are enclosed alongwith detailed
chart of values for important operation parameters.

SCHEDULING OF POWER
*******************************
The scheduling of power is regulated by CERC/REB/RLDC/IEGC
regulations/notifications.This has to be read with the provisions of the Indian Electricity
Grid Code.The methodology of scheduling and calculating capacity index shall be as
under:
i. The generator shall make an advance declaration of capacity of its generating station.
The declaration shall be for that capacity which can be actually made available for a period of
time not less than 3 hours within a 24 hours period for pondage and storage type of stations
and for the entire day for purely run-of-river type stations.
ii. The generator shall intimate the declared capacity (MW), for the next day, either as
one figure for the whole day or different figures for different periods of the day along with
maximum available capacity (MW) and total energy (MWh) ex-bus to the Regional Load
Despatch Centre.
The declaration should also include limitation on generation during specific time
periods, if any, on account of restriction(s) on water use due to irrigation, drinking water,
industrial, environmental considerations etc.
iii. While making or revising his declaration of capability, the generator shall ensure that
the declared capacity during peak hours is not less than that during other hours. However,
exception to this rule shall be allowed in case of tripping/re-synchronisation of units as a result
of forced outage of units.
iv. Generation scheduling shall be done in accordance with the operating procedure, as
stipulated in the Indian Electricity Grid Code.
v. Based on the declaration of the generator, the Regional Load Dispatch center shall
communicate their shares to the beneficiaries out of which they shall give their requisitions.
vi. Based on the requisitions given by the beneficiaries and taking into account technical
limitations on varying the generation and also taking account transmission system constraints,
if any the Regional load dispatch center shall prepare the economically optimal generation
schedules and drawal schedules and communicate the same to the generator and the
beneficiaries.
The Regional load dispatch center shall formulate the procedure for meeting contingencies
both in the long run and in the short run (Daily scheduling).
vii. The scheduled generation and actual generation shall be ex-bus at the generating
station. For beneficiaries, the scheduled and actual net drawals shall be at their respective
receiving points.
viii. For calculating the net drawal schedules of beneficiaries, the transmission losses shall
apportioned to their drawal schedule for the time being .However, a refinement may be
specified by the commission future ,depending upon the preparedness of the respective
Regional load dispatch center.
ix. In case of forced outage of a unit, the Regional Load Dispatch Centre shall revise the
schedules on the basis of revised declared capability. The revised declared capability and the
revised schedules shall become effective from the 4th time block, counting the time block in
which the revision is advised by the generator to be the first one.
x. In the event of bottleneck in evacuation of power due to any constraint, outage, failure
or limitation in the transmission system, associated switchyard and sub- stations owned by
the Central Transmission Utility or any other transmission licensee involved in inter-state
transmission (as certified by the Regional Load Despatch Centre) necessitating reduction in
generation, the Regional Load Despatch Centre shall revise the schedules which shall

become effective from the 4th time block, counting the time block in which the bottleneck in
evacuation of power has taken place to be the first one. Also, during the first, second and third
time blocks of such an event, the scheduled generation of the generating station shall be
deemed to have been revised to be equal to actual generation, and the scheduled drawals of
the beneficiaries shall be deemed to have been revised to be equal to their actual drawals.
xi. In case of any grid disturbance, scheduled generation of all the generating stations
and scheduled drawal of all the beneficiaries shall be deemed to have been revised to be
equal to their actual generation/drawal for all the time blocks affected by the grid disturbance.
Certification of grid disturbance and its duration shall be done by the Regional Load Despatch
Centre.
xii. Revision of declared capability by the generator(s) and requisition by beneficiary(ies)
for the remaining period of the day shall also be permitted with advance notice. Revised
schedules/declared capability in such cases shall become effective from the 6th time block,
counting the time block in which the request for revision has been received in the Regional
Load Despatch Centre to be the first one.
xiii. If, at any point of time, the Regional Load Despatch Centre observes that there is need
for revision of the schedules in the interest of better system operation, it may do so on its own
and in such cases, the revised schedules shall become effective from the 4th time block,
counting the time block in which the revised schedule is issued by the Regional Load Despatch
Centre to be the first one.
xiv. Generation schedules and drawal schedules issued/revised by the Regional Load
Despatch Centre shall become effective from designated time block irrespective of
communication success.
xv. For any revision of schedules generation,including post facto deemed revision,there
shall be a corresponding revision of scheduled drawals of the beneficiaries.
xvi. A procedure for recording the communication regarding changes to schedules duly
taking into account the time factor shall be evolved by the central transmission utility.
xvii. Purely run-of-river power stations since variation of generation in such stations may
lead to spillage shall be treated as must run stations. The maximum available capacity, duly
into account the over load capability, must be equal to or greater then that required to make
full use of available water.
xviii. Run-of-river power station with pondage and storage type power stations.
These hydro stations are designed to operate during peak hours to meet system peak
demand. Maximum available capacity of the station declared for the day shall be equal to the
installed capacity including overload capability, minus auxiliary consumption and
transformation losses, corrected for the reservoir level. The Regional Load Despatch Centres
shall ensure that generation schedules of such type of stations are prepared and the stations
dispatched for optimum utilization of available hydro energy except in the event of specific
system requirements/constraints.

EMERGENCY CONDITIONS
***************************
1) If fire is in the machine or Transformer
Give stop command.
Release CO2 or water through mulsi fire system as per the provision.
Intimate fire station.
Intimate Operation In charge/Project Head.
Try to isolate other equipment from the source of fire.
2) Flooding of Power House
Raise Alarm.
Intimate Operation In charge/Project Head.
Try to stop the source of leakage water.
If the leakage is from the machine immediately close the intake gate after opening the
generator circuit breaker and giving stop command to the machine.
Open the interconnection valve of drainage and dewatering pit.
Ensure that Power Supply to Drainage & Dewatering pumps is not shut down.
Run the available drainage / dewatering pumps or any other available pumps to pump
out the water.
3) Abnormal Vibration

Intimate Operation In charge.
If sudden increase of vibration(even though vibration level is low) and/or vibration level
is above 200 microns (peak-to-peak) (radial vibration measured at TGB and GGB)
inform maintenance.In case of abnormal noise and rising trend of bearing temperature
immediately stop the machine.

OPERATING REGIME
**********************
ALLOWABLE OPERATING REGIMES OF HYDRO GENERATORS
The generator is designed to operate electrically and mechanically within the prescribed limits
given below. Adherence to these limits will ensure maximum life of the machine.
The generator capability curve(See Annex. 4) provides the operating regime of generator.
Voltage
Generator can develop maximum output at rated p.f. with permissible change in voltage within
+/- 5% of the rated value.
Frequency
Operation of generator at rated frequency beyond +/- 3% of rated value is not permitted.
Power Factor
The generator is allowed to operate continuously at lagging p.f. provided the rotor current
doesn’t exceed its rated value(900 A at rated load).
Cooling air temperature
Operation of generator with cooling air temperature exceeding 40 C is not allowed except
when the machine is under dry out. Operation of generator at a cooling temperature less than
10 C is not permissible as per manufacturer’s instructions.
Unbalanced loading

During unbalanced loading of the generator, the current in any phase should not exceed the
rated current and the ratio of the negative sequence components of the system of currents to
the rated current should not exceed 8%.
Asynchronous operation
Asynchronous operation of the generator is not allowed. If it happens, it should be
disconnected from the bus bar at once as in case of emergency.
Vibration
Allowable vibration peak-to-peak displacement of different generator components in radial
direction during unexcited condition at rated speed is as follows:
S.No. Place of measurement Allowable Vibration
1. Thrust bearing bracket 0.05 mm
2. Slip-rings 0.3(Throw) mm

Recommended setting of various Devices (As per OEM)
*********************************************************************
1 Hot Air Thermometer alarm contact 70C
2 Hot Air Thermometer shutdown contact 80C
3 Thrust pad dial Thermometer alarm contact 75C
4 Guide pad dial Thermometer alarm contact 75C
5. Thrust pad Thermometer shutdown contact 85C
6 Guide pad Thermometer shutdown contact 85C
7 Thrust bearing oil Thermometer alarm contact 60C
8 Thrust bearing oil Thermometer shut down contact 70C
9 Pressure gauge for HS lub system ‘interlock contact’ 75 Kg/cm2
10 Pressure switch for HS lub system ‘interlock contact’ 75 Kg/cm2
11 CO2 fixed temperature thermostat 90C
Note: The actual settings should be on lower side depending on unit conditions.
OPU Related Operation Parameters
***********************************************
S.No. Device Parameter Unit-I Unit-II Unit-III
ALARM TRIP ALARM TRIP ALARM TRIP
1. 71 G-4 Oil Receiver
Level High
Level
switch-
High
Level
switch-
High
Level
switch-
High
2. 71 G-3 Oil Receiver
Level Low
Level
switch-
Low
Level
switch-
Low
Level
switch-
Low
3. 63 G-
2a&
63 G 2b
OPU Oil
pressure
very low
31 30.5 31 30.5 31 30.5
4. 23 G-6 Oil sump
temp. High
65C 65C 65C
5. 71 G-2 OIl level in
sump tank
Low
level
Low
level
Low
level

6. 63 G-1a M/c starting
interlock
make contact at
& below 37.5
kg/cm2
make contact at &
below 37.5
kg/cm2
make contact at &
below 37.5
kg/cm2
7. Safety valve
setting
44 kg/cm2 44 kg/cm2 44 kg/cm2
OPERATION PARAMETERS
****************************
S.No. Operation Parameter Normal Value Max. Permissible limit/ Alarm
Value/Trip Value
1. Stator Winding Temperature 90  C 120 C
2. Rotor Winding Temperature 95 C 125 C
3. Generation Voltage 11 kV 11 kV(+/-) 5%
4. Generation Current 1850 A 2362(0.90 Lagging P.F)
5. Field Voltage 340 V
6. Field Current 900 A at rated load
530 A at no load &
rated voltage
7. Frequency 50.00 Hz. 50 Hz(+/-) 3%
9. Generator Speed 136.4 rpm 136.4 rpm (+/-) 3 % (normal)
115% speed- Unit tripping
135% speed – Elect.
Overspeed trip
150% speed- Mech.
Overspeed trip
280 rpm- runaway( on-cam)
370 rpm runaway (off-cam)
10. Power Factor 0.9 lagging
11. Brake operating air pressure 5 kg/cm2 7 kg/cm2(Max.)
12. Brake application speed 30% of Syn. speed 70 rpm (Max.)
13. Jacking Oil pressure 85 bar
14. Cooling water pressure 7 kg/cm2

15. MVAR-Generator 4.8 MVAR 14 MVAR
16. Gen. Air/ Oil circulating cooling
water inlet temp.
20-35C
(depending on
weather)
water outlet temp.
30-45 C
(depending on
weather & load)
water inlet pressure
5-6kg/cm2 7 kg/cm2(max.)
5 kg/cm2(min.)
19. Shaft seal cooling water
pressure
2-3 kg/cm2
20. Thyristor convertor bridge
current
200-250 A

Value/Trip Value
21. Runner blade angle () Depends on load &
guide vane opening
Range of movement=20.5 
22. Governor Oil pressure 18-20 kg/cm2 15 kg/cm2(min. recomended)
23. SST Winding Temperature 50-60 C 80 C
24. SST Oil Temperature 50-55 C 70 C
25. UAT Winding Temperature 50-60 C 80 C
26. UAT Oil Temperature 50-55 C 70 C
27. 220/132 kV Auto transformer-
Winding Temperature
50-60 C 80 C
28. 220/132 kV Auto transformer- Oil
Temperature
50-55 C 70 C
29. Line Current(CB-Ganj-I/II) 140 A/Line 280 A
30. Line Active Power (CB-Ganj-I/II) 48 MW 96 MW
31. Line Reactive Power (CB-Ganj-
I/II)
5 MVAR/Line 40 MVAR
32. Line Voltage (CB-Ganj-I/II) 220 kV 245 kV(Max)/200kV(Min)
33. Line Current(Nepal feeder) 28 A 98 A
34. Line Active Power (Nepal feeder) 5 MW 20 MW
35. Line Reactive Power (Nepal
feeder)
2.5 MVAR 9.5 MVAR
36. Line Voltage (Nepal feeder) 132 kV 145 Kv(Max.)/120 Kv(Min)
37. Water level (Barrage) 246.7 m
38. Water Level (Forebay) 246.0 m-246.2 m 246.4 m(Bye-pass)
39. Water level ( TRC) 221-223 m depends on generation(No. of
units running)
40. Discharge( Sharda River) Upto 150000
cusecs (flood)
41. Discharge (Head Regulator) 20000 (max.) cusec depends on load
42. Silt in ppm 100-1000 ppm-
Summer/Winter
1000-3500 ppm-
Rainy Season
5000 ppm max.

Value/Trip Value
43. H.P Pressure Receiver 40-42 kg/cm2 44 kg/cm2
44. L.P Pressure Receiver 6-7 kg/cm2
45. L.P Station Receiver 6-7 kg/cm2
46. Water pressure in spiral casing 2-3 kg/cm2 4.7 kg/cm2(max.)
47. Water pressure / vacuum below
top cover
-1 to +1 kg/cm2
48. Shaft gland water pressure 2-3 kg/cm2
49. 220 V DCDB Load Voltage 220 V 220 V+- 10%
50. 220 V DCDB Load Current 25 A 40 A
51. 220 V DCDB Battery Voltage 220 V 220 V+- 10%
52. 220 V DCDB Battery Current 25 A 40 A
53. Max . guide vane opening () Depends on load Upto 46.2  & guide vane
servomotor movement =660
mm
54. Working air pressure of isolating
seal
3.0- 5.0 kg/cm2 6.0 kg/cm2(Max.)
55. Max. Runner blade opening Depends on load From – 8.2 to +13.0 degrees
.Servomotor movement = 105
mm.

PROTECTIVE DEVICES
********************************
1. MAIN RELAYS IN POWER HOUSE
The tripping circuits of Generators are of three types namely
A. Electrical S/D & Lock-out Circuits.
B. Non Electrical S/D & Lock-out Circuit.
C. Non Lock-out Circuits.
A. Electrical S/D & Lock-out Circuits
The Generator due to Electrical faults is tripped through relay 86A. The tripping of this
relay is accompanied with the tripping of any one or more of the following relays.
DESCRIPTION RELAY
1. Gen field fail Protection with U/V. 40G/27X
2. Reverse power Protection... 37X
3. Gen. spilt phase diff.Protection 87SA/B/C
4. Generator stator main E/F protection. 64GI
5. Generator Transformer Overall Diff. protection . 87GT
6. Generator-Transformer HV REF Protn. 64RHv
7. Generator-Transformer HV Un.EF protn /Gen over flux protn. 51NX/99T
8. Gen Transformer Buchh, no oil flow & no water flow protn... 30A/B,30K/L
9. Emergency shutdown. 86B
10.Gen Transformer on fire/Gen on fire 64GX
11.Gen. Diff protn. 87GX
12.Excitation TR O/C Protn.Trip Stage1/StageII K220/K224
13.UAT Buchh. Trip Aux 130A
14.UAT O/C protn. 50/51ABC
15.UAT REF protn. 64R
16.Gen.link line Diff. protn. 87LA/B/C
17.Generator E/F protn 64F
18.LBB protn. 50Z
19.Voltage balance scheme 160A/B/C
The operation of this relay is due to electric faults and tripping of this
relay causes the tripping of Main Circuit Breaker, Field circuit breaker and Unit Auxiliary
Transformer Breaker. The operation of this relay shuts down the unit and energises
emergency shutdown relay(86B).

B. Non-Electrical S/D & Lock out Tripping Circuits
The tripping due to the mechanical faults cause Non-Electrical Lock out through
operation of relay no 86B. This tripping causes opening of Main Generator Circuit
breaker, Field C.B and L.T. breaker of Unit Auxiliary transformer and shuts down the
unit. The machine is stopped. It operates controlled action shutdown relay(86A). The
detailed causes of tripping along with relays placed in U.C.B are as follows:
DESCRIPTION RELAY
1. Turbine guide bearing Temp.very high 38TB-TX
2. Gen. Guide bearing Temp. very high 38GB-TX
3. Gen thrust guide bearing Temp. very high 38TH-TX
4. Gen air cooler inlet air temp.very high 49AH-TX
5. Gen Tr. wdg Temp. very high 30F
6. Gen Tr .oil temp very high 30D
7. Governor oil press. Unit oil press Very low. 63G-2X
8. Unit over speed Elect/Mech.speed 12X3AX/12MX
9. Governor failure 2GFT
10.Controlled action shutdown. 86A
C. Elect.Non-Lock out Trip
This tripping is caused through relay No. 86C. In this tripping, the Main Generator Circuit
breaker and Unit Auxiliary L.T. breaker is tripped. Penstock gate is not closed. The machine
keeps on spinning on no-load. This tripping is caused due to operation of following: relays:
DESCRIPTION RELAY
1. Gen. Backup Imp protn. 21AB/BC/CA
2. Gen over voltage protn. 59DI
3. Gen. –ve Ph sequence protn. 46T/A
5. Gen.loss of field protn. 40G
6. No load Tripping protn 5NLT
8 Excitation TR O/C instantaneous. K219
9. Bus bar protn. Contact. 96

TROUBLE SHOOTING
**********************
The tripping of machine can be initiated due to fault in the turbine, generator, auxiliaries
or grid. On receiving the trip command the following sequence is initiated: -
(i) Generator C-B opened
(ii) Generator field breaker opened.
(iii) Closing command is given to guide vanes .
(iv) Stop sequence is initiated.
After the tripping it is mandatory to check/note the operated protection relays and take a print
out of the sequential event recorder. In the event of tripping of lines, data about the operation
of relays at the receiving end and the disturbance recorder print out are also required. The
maintenance staff is provided with all the above details to enable them to analyse the problem
and take remedial action.
The various types of faults in some components are described below: -
TURBINE:
The following chart provides a guide to fault diagnosis with probable cause and proposed
rectification action: -
Defect Probable cause Rectification
Guide vanes slow to
operate
Low hydraulic pressure
Servomotor leakage
Oil temperature too low
Check performance of
hydraulic power unit
Replace hydraulic pump if
necessary
Replace hydraulic servo
motor seals
Check oil temperature /take
remedial action.

Oil viscosity too high
Filter oil. If necessary,
change oil to a lower
viscosity.
Jerky operation of hydraulic
servomotor
Air in servomotor
Tight servomotor bearings
or seals
Bleed hydraulic system
Clean /replace hydraulic
servomotor seals if
necessary.
Noisy operation of
servomotor
Loose trunnion mountings
and/or pivot bearings.
Check trunnion mounting for
security and restore the
tolerances as required.
Hydraulic servomotor not
cushioning correctly
Cushion requires
adjustment
Cushion housing damaged
Adjust cushion
Repair/replace hydraulic
cushion
Scored hydraulic
servomotor rod
Foreign matter in bearing or
gland seal
Damaged wiper seal
Dirty hydraulic oil
Remove bearing and seal.
Clean bearing and replace
seal if necessary.
Replace wiper seal
Clean hydraulic servomotor,
filter oil, and change oil if
necessary.
Scored hydraulic
servomotor bore
Foreign matter in piston
bearings and seal
Dirty hydraulic oil
Clean /replace bearings and
seals, filter oil.
Filter oil, clean oil, Change
fluid and oil filters
Oil leakage from hydraulic
servomotor gland seal
Worn or damaged seal Replace seal, check rod for
scores, dents, etc. Rectify
damage to cylinder rod,
clean oil.

Guide vane mechanism will
not cycle
Obstruction inside guide
vane assembly
Guide vanes incorrectly
aligned
Regulating ring jammed or
seized
Clear all obstructions
Check alignment
Check regulating ring for
damage and repair if found
damaged.
Individual guide vane not
cycling.
Obstruction in guide vane
assembly
Guide vane lever is loose
Check G.V. key and guide
vane alignment.
Runner not rotating Obstruction in turbine
runner case
Turbine/Generator
misalignment
Blockage to runner
Check alignment
Check runner clearance
Excessive vibration Operating outside of the
normal operating “envelope”
Guide vanes have slipped
Rotating element out of
balance
Check operating
parameters related to
balancing.
Check G. V’s alignment

Obstruction in turbine
waterways
Bearing failure
Turbine misalignment
Bearing housing or shaft
flanged fasteners failed
Check rotating mass
balance
Clear obstructions
Repair /replace bearing
Check alignment
Check for failed or loose
fasteners
Excessive noise by turbine. Operating outside of the
normal operating “envelope”
(cavitation sounds like
gravel in turbine)
Guide vane slipped
Rotating element out of
balance
Loose parts or fasteners
Check operating
parameters related to
balancing.
Check G.V’s alignment
Check rotating mass
balance
Check for failed or loose
fasteners
OPU:
FAULT DIAGNOSIS
The following chart provides a guide to fault diagnosis with probable cause and proposed
rectification action: -

Low hydraulic reservoir oil
level
Hydraulic installation
leaking
Indication fault
Check complete hydraulic
installation for leak with
system pressurized.
Rectify leakage & clean up any
split hydraulic fluid.
Replenish hydraulic reservoir
Check operation of level
switches
High oil temperature Control system
hunting/oscillating
Hydraulic pump
overheating
Check solenoid valves are
not hunting.
They can generate heat in the
oil system as oil crosses the
control valve lands.
Replace defective hydraulic
pump as necessary.
Hydraulic pressure too high Indication fault
Hydraulic pressure high
on pressure gauge
Check hydraulic pressure on
gauge, if pressure is normal;
check that pressure switch is
adjusted to the correct
pressure.
If hydraulic pressure on gauge is
above required pressure, check
that unloading valve is correctly
adjusted.
Hydraulic services slow or
jerky in operation.
Air in system Check hydraulic pressure is
normal
Bleed complete hydraulic
installation.
Guide vane “Auto” hydraulic
circuit fails to operate
Defective solenoid valve Ensure that hydraulic
pressure is normal
Replace defective solenoid.
Guide vane fails to close
and open in manual
Defective solenoid
valve.
Ensure that hydraulic
pressure is normal .
Replace defective solenoid
Guide vane “Start” and
“stop” hydraulic circuit fails
to operate
Defective selector valve Ensure that hydraulic
pressure is normal

Check that solenoid valve is
energized Replace valve if
necessary.
COOLING WATER SYSTEM:
Water system high
differential pressure
Blocked strainer
Indication fault
Manually changeover
strainer duties & clean
strainer
Check differential pressure
gauge .If necessary replace
or re-set differential
pressure switch.
Overheating water pump
drive motor
Blocked air vents
Motor overworking
Water pump “jammed”
Clean motor & ensure that
all air ventilation holes are
clear.
Check current
consumption is below
stated on nameplates
(Amps)
Strip water pump &
inspected for damage
Replace water pump as
necessary
Replace drive motor as
necessary
Noisy water pump Loose assembly
Loose coupling
Air in system
Water pump “Jammed”
Check water pump for
correct assembly &
security
Check water pump
coupling for security
Bleed system free of air
Strip water pump &
inspect for damage &
debrisReplace water
pump as necessary

Replace drive motor as
necessary
Water system low flow rate
i.e. “No-Flow” alarm
Air in system
“Duty” strainer blocked
Heat exchanger blocked
Indication fault
Bleed system free of air
Select “standby” strainer
& not any change in flow
rate. Clean “Duty”
strainer.
Clean heat exchanger.
Check Raw water flow
relay & replace as
necessary
Water pump delivery
pressure low
Indication fault Ensure that the calibration &
isolation valve to pressure
gauge is correctly selected.
Ensure that the pressure
gauge is bled free of air.
Replace pressure gauge
with a re-calibrated gauge
Header tank level low Float operated ball valve
stuck.
Supply cut-off
Excessive system leakage
Check float operated ball
valve for correct operation
Ensure the supply is
selected ON & check that
supply line is not blocked.
Inspect complete potable
water system for leakage,
including possible leakage
at turbine bearing oil
coolers.
Rectify all leaks
immediately.

GENERATOR:
The generator is equipped with the following protective devices/relays: -
(i) Stator earth fault protection
(ii) Rotor earth fault protection
(iii) Generator differential protection
(iv) Under impedance protection
(v) Negative phase sequence current protection
(vi) Loss of excitation protection
(vii) Over voltage protection
(viii) Shaft current protection
(ix) Frequency protection
(x) Reverse power protection
(xi) Neutral voltage protection
(xii) Overload protection
(xiii) Unit computer fault during start/stop protection
Similarly in the transformer the following protections are included.
- Block differential relay
- Restricted earth fault relay
- Over flux relay
- Over current relay
- Breaker failure relay, etc.
The fault which causes a trip can be indicated either in the control room or in the unit control
panel.
In case of non-response of any component to the order of start sequence an alarm from the
step time is generated and the stop sequence is initiated.
A few common electrical protections provided in the generating equipment are discussed in
brief: -
1.Observation: - Rotor earth fault alarm (on first earth fault) and facia annunciation.
Cause(s): Earthing of pole coils including excitations bus bars, etc.
Measure:
Inspection of pole coils, pole-coil-ends-holder and excitation bus bar for insulation
deterioration. Measurement of AC or DC voltage drop across the pole needs to be carried out.

If measured value(s) differ from the value during commissioning for one or more poles
(normally three consecutive poles will show anomalous reading if the middle pole is faulty),
then there must be an earth fault in that pole.
Do repair/ replacement as is recommended in maintenance manual, recheck the AC
or DC voltage drop across each pole coil and the IR value of the excitation circuit when
isolated from the excitation output end. If AC or DC voltage drop and IR values are
found very near the value at the time of commissioning, system can be put back in
service.
2.Observation:
Loss of excitation tripping/ alarm accompanied by over speeding trip/ alarm
- Excitation field breaker
- Excessive reactive power.
- Generator output pulsation.
- Main C.B trip and other trip/ alarm.
Cause(s):
Loss of excitation due to failure of tripping of field breaker by accident or by malfunctioning.
Fault in the excitation equipment leading field current to a value below the set limit.
Measure:
Inspect/ check the excitation circuit and equipment components. Repair/ replace the faulty
parts if needed. Check the field breaker, roll the machine and build the excitation in manual
mode in a small go at a time. Run the machine for some time. Switch over to auto excitation
mode and observe the excitation performance. If found satisfactory then generator can be
synchronized.
3.Observation:
- Stator earth fault tripping/ alarm along with other tripping/ alarm such as.

- M.C.B
- Electrical lockout and other trip/ alarm as per the loading condition of the machine.
Cause(s):
Stator coil/ bars insulation layer might be damaged and earthing of the coil/ bar at a particular
part or parts might have occurred.
Measure:
Inspect the stator coils/ bars and over hang. If the fault is severe then burning patches near
the bars and core (at fault spot) can be seen along with insulation burning smell. If the fault is
mild, the change in the color shade (near the faulty part) is observed.
In this case repair/ replace the faulty coil/ bar, re-check the IR value of the stator coils. If found
O.K, dry out the generator winding (if necessary). At appropriate insulation resistance (IR)
value of the generator stator coil (each phase), the generator can be put back in service.
4.Observation:
- Generator differential protection tripping/ alarm.
- MCB tripping.
- Electrical lockout tripping/ alarm and other protections that are operating on the same
input quantities (like over current protection) and other trip/ alarm as per the loading of
the machine.
Causes:
Fault within the domain of the protection (within the range of CTs physical location) might
have occurred, causing diverting the current (through fault path) or might shift the phase angle
due to fault. The domain is mainly the generator stator winding and the protection is meant to
detect phase to phase fault only. Normally the fault will be accompanied by stator earth fault.
IR between phases as well as to ground should be measured in all cases of protection.
Measure:

Within the domain of the protection, thorough inspection of the circuit is done. Some times the
C.T could be faulty. Repair/ replace the faulty component. Check the protection by primary
injection test limit if found O.K, run the machine to put in service.
5.Observation:
Under impedance protection trip/ alarm followed by other overlap protections and locking
tripping/ alarm.
(This protection is used for protection of generator against uncleared on the high voltage bus
or grid. Also useful when the GCB is opened and the stator of the generator is isolated from
grid.) By setting the relay to cover the generator also, this can provide a backup protection to
generator. Therefore, generator needs to be checked as well.
Cause(s):
- Undesired fault on the HV side or failure of primary protection of generator and a fault
in generator.
Measure:
Check the transmission line fault details. The chances are that many main protections at our
end/ remote end have failed. To ensure safe operation (the chances are remote that there will
be a generator fault), inspect physically the generator’s outgoing bus bars/ link lines for short
circuit as well temporary shorting. Repair / replace the faulty component if necessary. Check
the protection for malfunctioning and analyze/ correct if necessary. Check the protection by
fault simulation. If found O.K, put the protection in service.
6.Observation:
Negative phase sequence tripping/ alarm followed by other protection provided in a typical
protection design for the generator.
Cause(s):
The protection is operative when there is considerable imbalance of power/ current in the
phases of the generator or when there is a broken wire condition, generally on the
transmission line. Due to imbalance, the negative sequence component rotates at twice the
synchronous speed (with respect to the rotor) in causing extra eddy current losses and thereby

additional heating of the rotor is caused. The imbalance also causes pulsating magnetic fluxes
and the unequal magnetic pull between rotor and stator, which causes unequal mechanical
forces acting on the rotor/ shaft.
Measure:
Check the causes for unbalance load or the broken wire condition as recommended in
standard practices and set right. Check the functioning of the protections and if malfunctioning
is found, check the cause for malfunctioning. Repair/ replace the faulty component if
necessary. Check the protection by fault simulation. If found O.K, put the protection in service.
7.Observation:
Over voltage protection tripping/ alarm followed by lock at trip.
Cause(s):
High voltage in the grid, either due to load throw-off or surge in the grid.
- Faulty function of AVR
- At the time of high surge there is change in the noise level of generating machine. (The
voltage surge can be confirmed from the disturbance recorder).
Measure: -
The high voltage surge is also accompanied by some power imbalance. Restart the machine
and put back in service.
In case there is fault in the AVR (the AVR malfunctioning/ tripping and indication shall confirm).
Check, analyze and repair/ replace the faulty component. Test the functioning of the AVR as
described in the AVR maintenance manual. If found O.K, put back AVR in service.
8.Observations:
Shaft current protection tripping/ alarm.

Cause(s):
Failure of bearing insulation.
Measure:
(i) Check the insulation provided to isolate electrically, the bearing pad(s) (it should
be as per the commissioning value or as mentioned in the maintenance manual).
If necessary replacement of the insulation is to be done.
(ii) Check the shaft earthing (done through slip ring) to the appropriate (low) value.
Take the measure to restore the earthing value as recorded.
(iii) In case the C.T. is faulty replace the same.
9.Observation:
Frequency protection tripping/ alarm [the normal operation is recommended from 49.5 Hz
(lower limit) to 50.5 Hz (upper limit) frequency bond.] followed by other indication as provided
in the protection system.
Causes:
(i) For high frequency: When the load demand is less in comparison to generation or
there may be tripping of feeder, the frequency of the generator may go beyond the
upper limit.
(ii) For low frequency: When the load demand is more than the generation, the
frequency will dip.
Measure:
(i) For higher frequency: Inform the grid controller and reduce generation/ stop the
machine, if trip is not provided. Confirm the causes of tripping. If it is due to grid
disturbance then reset the tripping. In case the protections have operated due to
malfunctioning, analyze/ repair/ replace the faulty component. Test the protection
and put in service.
(ii) For low frequency: In case the protection has operated due to grid disturbance,
follow the normal procedure to restore. In case the protection has malfunctioned
analyze/ repair/ replace the faulty component. Test the protection and if found
satisfactory put the protection in service.

Note: Both frequency settings are incorporated in a single relay and the upper and lower
frequency limit settings are independent. The timers are used for delaying the tripping when
the frequency variations are for a specified short duration. No tripping is provided in most
cases.
10.Observation:
Reverse power protection tripping/ alarm along with other indication as provided in the
protection system.
Causes:
Sudden closure of guide vanes under synchronized condition.
Measure:
Check the governor thoroughly for its correct operation under various running and loading
condition. Repair/ rectify the fault if required. Test the operation of governor on off load as
recommended in the testing procedure. If found O.K, put the governor in service.
11.Observation:
Neutral voltage protection tripping/ alarm along with other indication as provided in the
protection system.
Causes:
The protection is basically the stator earth fault protection
There are two variations of the neutral voltage protections.
(a) When the generator is connected to transformer.
(b) When the generator is directly connected to the distribution bus.

The case ‘(a)’ should be considered, which is commonly used in the generating station of
installed capacity of several megawatts.
Measure:
Same as described in the stator earth fault. Checking of the malfunctioning of the protection
should be done when there is no actual earth fault found after protection operation. If
necessary the repair/ replacement of the faulty component is done to put the protection in
service.
12.Observation:
Local breaker backup protection trips along with certain other primary protection trip.
Causes:
The primary protection has failed to trip the generator circuit breaker/ feeder circuit breaker
concerned. All the other breakers connected to the same bus must have tripped.
Measure:
Do the necessary maintenance of the breaker and adjust the various operating parameters,
ensure the correct operation by operating the breaker for its desired operation. Test for the
pole- discrepancy (in case multi pole) and for the phase discrepancy of the breaker if found,
attend to the same and check the protection again. If the breaker is all right, the problem could
be anywhere in the protection circuit from the primary protection up to the breaker tripping coil.
13.Observation:
Restricted earth fault tripping/ alarm of generator transformer along with other indication as
provided in the protection system.
Causes:
The winding of the generator transformer may be grounded due to insulation deterioration.

Measure:
Check the generator transformer (IR, winding resistance, magnetizing current, etc.). If
faulty, replace it with healthy spare transformer.
14.Observation:
Over fluxing tripping/ alarm of transformer along with other tripping and locking as provided
in the protection system.
Causes:
The transformers are designed to operate at certain maximum value of the flux density
in its case. When it over shoots the value of the maximum allowable flux density, the
overheating of the core takes place and under such conditions if the transformer is
allowed to operate, fast deterioration of its life takes place. The protection is used with
delay timer.
Measure:
Avoid the operation with higher excitation of upper limit and also when the frequency is low.
Under these conditions when alarm starts repeating, the load on the transformer is reduced to
set appropriate operating level.
15.Observation:
The fault is observed (during starting of the machine and also during stopping of the machine)
by observing the character display on the front of the CPU board presents a stop code to
assist in tracing faults.
(i) When start command is given by computer and instantly fault occurs in this computer then
in this case machine is started manually.
(ii) When machine is running normally and instantly fault occurs in controlling computer then
in this case machine will trip.

(iii) When stop command is given by computer and instantly fault occurs in this computer then
in this case machine is stopped manually.
Causes:
Faults in the computer’s common central parts such as the memory stop the system. These
faults trip the RUN relay, the contacts of which are available on the main’s switch unit.
Measure:
- Cleaning all cards
- Tightening of connected cables
- Resetting of relays
Some of the other electrical faults, their causes & measures are described.
EXCITATION SYSTEM:
Static excitation with redundant thyristor bridge system is used .
i) Low measuring voltage (alarm)
Cause:
Supervision of the measuring circuit to the voltage regulator has been activated.
Measures :
Automatic change over to the field current regulator will take place and the operation may
continue in this mode of regulation. Check the fuses to the voltage measuring transformers.
Also check the output signal from the voltage measuring unit.
Change over to voltage regulation is blocked until the fault has been attended.
ii) Low supply voltage (tripping)

Cause:
Supervision of the supply to the converter has beer activated.
Measures:
Check the miniature circuit breaker for synchronization voltage to the trigger pulse
unit. Try closing the miniature circuit breaker. If it trips again, there has been a short-
circuit and the circuit must be checked for faults.
Check the MCCB for the adapting transformer. Try closing it. If it trips again, there has been
a short-circuit and the circuit must be checked for faults.
If the excitation equipment is supplied from the generator terminals and the miniature circuit-
breaker for the synchronization voltage has tripped, the circuit must be investigated for faults
before starting up again. This due to the fact that the synchronization voltage drops out when
the machine is dead, and the breaker can not trip when the machine is not under voltage.
Check the output signal from the trigger pulse unit.
Check the fuses to the excitation transformer.
iii) Low auxiliary voltage Generator (alarm)
Cause:
The internal supervision of the auxiliary power to the measuring board for the generator
voltage has been activated
Measures:
Automatic change-over to field current control is obtained.

Check the miniature circuit-breaker for auxiliary power supply to the unit. Try closing the
miniature circuit-breaker. If it trips again there has been a short- circuit and the circuit must
be checked for faults. Measure the internal auxiliary supply of the board.
iv) Low auxiliary voltage grid (alarm)
Cause:
The internal supervision of auxiliary power to the measuring board for the grid voltage has
been activated
Measures:
Check the miniature circuit-breaker for auxiliary power supply to the unit. Try closing the
miniature circuit breaker. If it trips again there has been a short-circuit and the circuit must be
checked for faults. Measure the internal auxiliary supply of the board.
V) Low auxillary voltage supervision unit (alarm)
Cause:
The internal supervision of the auxillary power to the supervision unit has been activated.
Measure
Check the minature circuit breaker of the unit. Try closing it.
If it trips again there has been a short circuit and the circuit must be checked for faults.
vi) Thyristor fault (alarm and / or tripping)
Cause:
The 50 HZ current pulsation protection has been activated on account of a branch in the
thristor bridge not conducting. If the equipment is fitted with a redundant bridge only an alarm
is obtained and operation can continue. In case of a thyrsitor fault occurring in the second
bridge as well, the machine is tripped.

Measure
If the equipment is provided with a redundant bridge the machine should be stopped at a
suitable moment and the cause of the fault investigated.
Check the fuses in the converter.
Check the trigger pulse circuits to the thyristors.
vii) High temperature excitation transformer (alarm and/or tripping)
Cause :
The transformer’s temperature relay has been activated.
Measure :
Upon an alarm, reduce the field current to avoid tripping. When high MVAR are in demand,
excessive excitation may be required. Check that the transformer’s ambient temperature is
not abnormally high, and that its ventilation ducts are not clogged. If the alarm does not cease
within 15 minutes, the machine should be stopped and the transformer checked.
viii) High voltage fuse failure (Tripping)
Cause
High-voltage fuses for the excitation transformer have tripped.
Measure:
Check the high-voltage fuses in the circuit, and replace those that have blown. Make sure you
first isolate and earth the equipment in prescribed manner.
Check the following with regard to any short-circuit damage.
- Cables & bus bars to the transformer

- Transformer
- Cable/bus bars to the converter
- Converter
- Converter fuses
In doubtful cases, the circuit should be voltage-tested before starting up again.
AC/DC Converter power supply failure ( alarm / tripping ) :
CAUSE: - The voltage supervision of the AC/DC converter has been activated.
MEASURE:- If there is a redundant power supply unit an alarm is obtained and operation can
continue. Otherwise tripping is initiated. Check the input and out voltage of the converter, and
the internal fuse.
High temperature rotor winding ( alarm / tripping ) :
CAUSE: - The temperature in the rotor winding has risen to a dangerous high value.
MEASURE: - When the alarm level has been reached the field current should be decreased
to a value that is allowed for the machine. A high temperature can be due to overloading of
the machine for a longer period, incoming cooling air temperature to the generator is too high
or that the cooling of the rotor has in another way drastically been deteriorated. If the
temperature still is over the alarm level the machine should be stopped in a controlled way,
before trip level is reached and load rejection will take place.
Check the output signal from the measuring units for the field current and field voltage.
Check the cooling circuits of the generator
Over load ( tripping ) :
CAUSE: - The overload protection has been activated due to excessive field current for too
long a period.
MEASURE: - If the machine was in the operational mode VOLTAGE CONTROL, the voltage
in the network has probably dropped to such a value that the machine has been reactively
overloaded. If the machine was in the operational mode FIELD CURRENT CONTROL, the
field current has probably been adjusted to an excessive value. The machine can be started
up again, but observe the value of the field current, generator voltage and reactive power.
A fault in the field current regulator may have occurred, in which case this has to be checked.
Over current ( tripping ) :

CAUSE: - The instantaneous over current protection has been actuated due to a short-circuit
in the circuit.
MEASURE: - Search for faults in the main circuit after short-circuit. The circuit may have to be
voltage-tested before starting up again. Also check all fuses included.
Fuse failure in thyristor bridge ( alarm and / or tripping ) :
CAUSE: - One of the high-speed fuses in the thyristor bridges has been tripped. If the
equipment is provided with a single converter bridge, the machine is tripped. If the equipment
is provided with a redundant thyristor bridge an alarm is obtained, the ordinary bridge is
blocked and a change-over to the redundant bridge takes place. At a fuse failure in the
redundant bridge the machine is tripped.
MEASURE: - Check the fuses in the converter. Also investigate the reason for the fuses
tripping, e.g. a short-circuit in the field circuit.
N.B- The fuses cannot be replaced during operation, and therefore, the converter must be de-
energized and earthed in the prescribed manner before work on the main circuit.
DC Short-circuit ( tripping ) :
CAUSE: - The over current protection by measuring current ripple (300 or 360 Hz) has been
actuated due to a short-circuit in the DC circuit. The protection indicates a short-circuit on the
DC side of the converter when the field current limiter is in operation, or when the machine is
in the operating mode FIELD CURRENT CONTROL. Although no over currents appears, the
machine loses it’s excitation and loss-of-synchronism may appear.
MEASURE: - Look for shot-circuits on the DC side of the converter. In doubtful cases, megging
between plus and minus poles should be carried out, but not with a higher voltage than the
blocking voltage class of the thyristors involved. Also check the fuses in the converter.
Long field flashing ( tripping ) :
CAUSE:- Upon starting-up, the machine will not accept voltage.
MEASURE:- Check that the machine is rotating with rated speed.
Check that the field breaker is operating when an order is given.
Check the supply voltage to the field flashing unit.
Check the fuses for the excitation transformer.
Check the fuses in the thyristor converter.

Check the auxiliary supply to the trigger pulse equipment.
Check the low-supply-voltage trigger unit.
Field over voltage ( alarm / tripping ) :
CAUSE: - High voltage in the field circuit, caused by induced fault currents from the stator
circuit. Discharge thyristor or over voltage thyristor short-circuited.
MEASURE: - If the machine tripped as a result of external faults e.g. stroke of lighting or
breaker operation, a fresh start can probably be made without further checks. If the machine
tripped without being caused by external faults, the field over voltage thyristor and the
discharge thyristor must be measured and checked.
Rotor earth fault ( alarm / tripping ) :
CAUSE: - An earth fault has occurred in the field circuit or in the power supply to the thyristor
converter.
MEASURE: - If the protection is not connected for tripping the machine, the latter should be
stopped at a suitable time. Since the field circuit is not earthed operation can continue, but if
further earth fault occurs, large fault currents and magnetic unbalance in the machine may
appear.

Hydropower is the cheapest way to generate electricity today. No other energy
source, renewable or non-renewable can match it.
Producing electricity from hydro plants is cheap because, once a dam has been
built andthe equipment installed, the energy source-flowing water is
free.Although hydro plants do present a few environmental problems the
inherent technical, economic andenvironmental benefits of hydroelectric
power plants make it a important contributor to the future world energy.
It was a great honor for me to have four week training from such a prestigious
government undertaking projectwhich is awarded as a mini Ratna class I by
government of India. It was a great experience to see the formal work which
showed the status of a government Profile.

Vocational training report NHPC TANAKPUR Uttarakhand

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