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 Bharahrmadeov, 5 Km upstream of Tanakpur and is called Sharda. The river is among the major rivers of India and has a large hydro potential.

The Tanakpur Power Station is located on the right bank of the river Sharda in the state of Uttaranchal. 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 (Nepal) 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 have been 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 Semi 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 efficiency of the equipment and its complete reliability.

The project area falls under Zone 4 (High damage risk zone) on Richter’s scale and is not seismically activeof seismic division of our country. Monsoons are heavy and spread over the months of July to October, winter season extends up to February and summer from March to June. The mean max. and min. temperatures are 400C and 140C respectively. Average annual rainfall is 1500 mm.

During monsoon, in order to have silt-free water for the power house, a silt excluder device is provided in the under sluice portion of the barrage and silt ejector is provided on the power channel.

SALIENT FEATURES ************************

LOCATION

State in which located Uttaranchal

District Champawat

River Sharda

Barrage Approx. 2 Km D/S of the town Tanakpur

Power House Approx. 1.2 Km U/S of existing Sharda Barrage

HYDROLOGY

Catchment area 15,100 Sq.km

Design flood 19900 Cumec

Mean annual rainfall 1500 mm

BARRAGE

Total length 475.3 m

Spillway Bays length. 279.5 m

Crest Level Under sluice-237.5 m, Spillway-238.1m

No. of bays. 22 (Under sluice – 9, Spillway – 13)

Max. discharge capacity 19900 Cumec

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 –177 m, 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 18.3 mx9.5 m

Weight of under sluice gate 73.687 MT

HEAD REGULATOR

Location

Length

Right bank of the river

78.45 m

No.& Size of gate /wt. 6 Nos, 11.2 m x 5.5 m each, 36.087 MT

Discharge capacity. 680 cumec

Energy DissipationArrangement Stilling basin with blocks

SILT EJECTOR

No. & Type 48, Hopper type

Size of desilting basin 90 mX120 m

No. of flushing tunnels 4 nos

POWER CHANNEL

Length 6.4 Km(from head regulator to forebay)

Max. discharge capacity 566 cumec

Shape Trapezoidal

Depth 6-9 m

FOREBAY

Size 64.2 mX91.0 m

Bed level 231.10 m

BYPASS SPILLWAY

No. and size of bay 5 nos. of 9.5 m each

Max. discharge capacity 566 cumec

Length of spillway 59.5 m

Crest level 243.2 m

PENSTOCK

Number 3 Nos.

Diameter 6.5 m

Length 54.2 m

Size of intake gates 5.1 m X 7.11 m

Center line of intake 234.933 m

TAIL RACE CHANNEL

Length 1150 m

POWER HOUSE

Type Surface

Design head 24.25 m

Installed capacity 94.2 MW (3 units of 31.4 MW each – Derated capacity)

Dimensions 102.30 m x 45.20 m x 47.70 m

Unit design discharge 188.67 cumecs

EOT

Number 2 Nos.

Capacity 125/30 / Tonne

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 rated out put & head

188.67 M3/sec

Rated speed 136.4 rpm

Rated average efficiency 92.2%

Discharge dia of runner 6200 mm

Runaway speed 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 UmbrellaRated out put (at 0.9 p.f lagging) 45 MVA

Rated voltage 11 KV

Frequency 50 Hz.

No. of poles 44

Stator Connection Star

Rated Current 2361.8 Amp.

Excitation at rated load 900 900 Amp.

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 11 kV

Highest voltage for equipment (Um) 12 kV

Rated frequency 50 Hz

Main bus 3000 Amp.

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(at principal tap) 12.32 %

Vector group YNd11

SWITCH YARD

Voltage level 220KV / 132 KV

No. of bays 7

Line bays 3 ({Line-I/II(220 kV) & Nepal Line(132 kV)}

Bus coupler bay 1

Type of breakerSF6 (Single pole operation, pneumatic opening-spring closing)

Size of switch yard 168 m X 111 m

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

TRANSMISSION LINE

Tanakpur to Bareilly 220 KV kV Double Ckt Line

Length of the line 106 Km.

Tanakpur to Nepal 132 KkV sSingle Ckt line

Length of the line 15 Km.

DESIGN ENERGY 452.19 MU

COMMISSIONING DATES Unit-I ( 31.03.1992) , Unit-II (04.04.1992), Unit-III (04.04.1992)

ALLOCATION OF POWER GENERATED FROM TANAKPUR POWER STATION

S.No. State MW Share % Share1 Chandigarh 1 1.32 Delhi 12 12.83 Haryana 6 6.44 H.P 4 3.85 J&K 7 7.76 Punjab 17 17.97 Rajasthan 11 11.58 UP 21 22.69 Uttaranchal 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. MONTHENERGY TO BE SUPPLIED (MU) PEAK LOAD (MW)

SCHEDULE SCHEDULE1 January 4.5000 12.002 February 4.0000 12.003 March 4.5000 12.004 April 5.0000 14.005 May 6.0000 16.006 June 6.5000 16.007 July 7.0000 16.008 August 7.0000 16.009 September 7.0000 16.0010 October 7.0000 14.0011 November 6.0000 12.0012 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 19.712. May 28.943 June 42.294 July 66.595 August 66.596 September 64.447 October 51.928 November 31.129 December 24.1310 January 21.2511 February 17.1212 March 18.09

Total452.19(MU)

ELEVATIONS IN POWER HOUSE*************************************

S.NO. ELEVATION DESCRIPTION1 EL 247.5 M ROAD FORMATION LEVEL32 EL 246.4 M BYE-PASS GATE OPERATION43 EL 246.0-246.2 M NORMAL FOREBAY LEVEL FOR OPERATION OF

UNITS4 EL 245.48 M FULL SUPPLY HEAD OF POWER CHANNEL5 EL 243.2 M CREST LEVEL OF BYEPASS SPILLWAY6 EL 234.933 CENTRELINE OF PENSTOCK INTAKE7 EL 231.10 BED LEVEL OF FOREBAY8. EL 234.0M ROOF TOP OF POWER HOUSE (1ST FLOOR)9 EL 227.7 M MACHINE FLOOR10 EL 223.30 M MAX TRC WATER LEVEL11 EL 222.0 M MIN TRC WATER LEVEL12 EL 218.853 M BED LEVEL OF TRC AT ENTRY13 EL 218.848 M BED LEVEL OF TRC AT REGULATOR SIDE14 EL 222.0 M TURBINE FLOOR15 EL 217.5 M CENTERLINE OF SCROLL CASING16 EL 215.56 M CENTRE LINE OF RUNNER17 EL 211.25 M COOLING WATER FLOOR18. EL 210.5 M DRAFT TUBE GALLERY19 EL 210.5 M DRAINAGE/DEWATERING FLOOR20 EL 202.5 M DEWATERING HEADER21 EL 200.5 M DEWATERING PIT FLOOR22 EL 200.0 M DRAINAGE PIT FLOOR23 EL 198.80 M DEEPEST FOUNDATION LEVEL

EQUIPMENTS AT VARIOUS ELEVATIONS******************************************

1) EQUIPMENTS AT EL 227.7 M (MACHINE HALL ELEVATION)

S.No. LocationEquipments

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 gGanj 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 gGanj line 1&2 panel, Synchronizer panel ., Vibration monitoring system.

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 Equipments1. 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. CoO2 System(System (Fire Fighting)

CoO2 cylinder bank 1&2, CoO2 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 Equipments1. 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,BANBASADAILY /SHIFT –WISE CHECK LIST

DISCHARGE.: ……………………cumec.. DATE:……………………..FOREBAY LEVEL: ………………… TIME OF CHECKING…WHEATHER CONDITION: ……………

S.NO DESCRIPTION OF EQUIPMENT

UNIT#1 UNIT#2 UNIT#3 REMARKS

1 Load on the machines in MW2 Condition of D/T gallery

EL210.53 Leakage from D/T manhole

(front and back)COOLING WATER FLOOR EL 211.25M

1 Cooling water pump #12 Cooling water pump #23 O.L.U working in

AUTO/MANUAL4 Condition of duplex strainer#15 Condition of duplex strainer#16 Pressure at the inlet of strainer7 Pressure at the outlet of strainer8 Draft tube pressure9 Cooling water header pressure10 Condition of D/T valve pit pump11 Condition of motorized valve in

cooling water circuitTURBINE PIT EL 218.70 M

1 Condition of top cover drainage pump

2 Shaft seal water pressure3 GV shear pin air pressure4 Oil leakage from TGB

S.NO DESCRIPTION OF EQUIPMENT

UNIT#1 UNIT#2 UNIT#3 REMARKS

1 Governor servomotor opening pressure

2 Governor servomotor closing pressure

3 Water pressure /vaccumvacuum below top cover

4 Water pressure below top cover GAUGE #1

5 Water pressure below top cover GAUGE #2

6 Water pressure below top cover GAUGE #3

7 Water pressure in spiral casing8 Healthiness of PP set motor #19 Healthiness of PP set motor #210 Pressure in the accumulator11 Oil level in the accumulator12 Oil level in the sump13 Leakage from idealer valve #114 Leakage from idealer valve #215 Healthiness of HS lube pump16 Healthiness of CGLS17 Flow meter in the air cooler18 Flow meter in the oil cooler19 Air pressure in breaking system20 Water leakage from any valve

(Give location)21 Healthiness of L.P compressor

#122 Healthiness of L.P compressor

#223 LP air tank pressure24 Healthiness of H.P compressor

#125 Healthiness of H.P compressor

#226 H.P air pressure27 Condition of MW system in

cable for any leakage etc.28 Check ET for any abnormal

sound29 Condition of generator barrel

door30 Condition of UAT breaker.31 Condition of ESV

S.NO DESCRIPTION OF EQUIPMENT

UNIT#1 UNIT#2 UNIT#3 REMARKS

MACHINE FLOOR EL 227.70M1 Hot air temp.2 Cold air temp.3 Thrust bearing pad temperature4 Generator guide bearing (GGB)

pad temperature 5 Generator guide bearing (GGB) oil

temperature6 Turbine guide bearing (TGB) pad

temperature7 Turbine guide bearing (TGB) oil

temperature8 Cooling water inlet temperature9 Cooling water outlet temperature10 Draft tube pressure11 PP set pressure12 Spiral casing pressure13 Shaft gland isolating seal air

pressure14 Shaft seal cooling water pressure15 Governor pressure on EHG

cabinet16 Balance position17 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

opening21 Pressure of runner servomotor

closing22 Any sparking on slip ring brushes23 Head light glowing24 Check any alarm in UCB panel25 Healthiness of blower #126 Healthiness of blower #227 Healthiness of blower #328 Healthiness of sprinkler in cooling

pond29 Water level in cooling pond

S.NO DESCRIPTION OF EQUIPMENT

UNIT#1 UNIT#2 UNIT#3 REMARKS

TRANSFORMER DECK (EL 227.70 M)1 No of coolers working2 Healthiness of oil

circulation temperature3 Transformer winding

temperature4 Transformer oil

temperature5 Humming sound from

temperature6 Check for any sparking or

heating of transformer jumpers

7 Any water leakage from any point

8 Any oil leakage from any point

CONTROL ROOM1 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 #17 Healthiness of PLCC of

line #28 Healthiness of PLCC of

Nepal line9 Healthiness of AC10 Healthiness of List

LT ROOM1 Battery charger in

Float/Boost mode.2 Healthiness of SST#1

circuit breaker3 Healthiness of SST#2

circuit breaker

4 Healthiness of HALON system

S.NO DESCRIPTION OF EQUIPMENT

UNIT#1 UNIT#2 UNIT#3 REMARKS

HEALTHINESS OF PUMPS ((EL 210.60 M)1 90 HP VT Dewatering pump #12 90 HP VT Dewatering pump #23 90 HP VT Dewatering pump #34 90 HP VT Dewatering pump #45 90 HP VT Drainage pump #26 90 HP VT Drainage pump #17 35 HP submersible pump

#1(Drainage pit)

8 35 HP submersible pump #2(Drainage pit)

9 35 HP submersible pump #3(Drainage pit)

OTHERS ISSUES/CHECKING1 Illumination at different floors2 Opening of any hatch cover3 General cleanliness

PRESTART CHECK LIST********************************

1 No work permit should be outstanding.2 Gen.schedule should be approved from NRLDC3 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 autoauto mode.2. Unit selection in local mode.

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.Airclosed. 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.

CO22 SYSTEM:

Ensure that the CO22 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 distributerdistributor/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 of 40.0 kg/cm2 and 44.0 kg/cm2 .. Ensure the safety valve functions properly. Moisture should be drained from the compressor air receiver in each shift. 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 A.C 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 6 kg/cm2 at (20 C).. Operating air pressure is 15 kg/cm2 .

EARTHING SWITCH POSITION-OFF:

Position of the earthingearthing 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 housepowerhouse, 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.Theunit. 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 KkV.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 SynchronizingAuto 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 ensured 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 pumppump 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 bearingsBearings.(If unit to be stopped for more than 2 hours).13) Shut off inter pad cooling system.(If running)14) Engage G.VGuide vane. lock.(If unit to be closed for long period)15) Make a record of time of opening of Generator C.B.circuit breaker and stopping of machine16) 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) 1. Protection relay operates leading to operation of Trip Relay.2) 2. Generator C.B. is opened.3) 3. Generator Field breaker is opened.4) 4. Closing command is given to guide vanes and inlet penstock gates(in

case of Electrical Lock-out and S/D trip).5) 5. Stop sequence starts as in case of manual stopping of the machine. 6) 6. Note down the operated protection relays, flags after ensuring that

machine has stopped.7) 7.Take print out of Sequential Event Recorder/Event Logger (SER/EL) and

record the trippingthe tripping time.8) 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) 9.Intimate maintenance staff giving as much detail as known.10)10.Analyze the fault as to ascertain the cause of tripping.11)11. Prepare unit for re-starting after rectification of faults.12)12. Shift InchargeIn charge to prepare tripping report as per format and

send as per the mailing list.13)13. Breakdown report/ Restoration and analysis report to be send by

InchargeIn charge (Electrical Maint.) as per format.

In case of tripping of machine it should be ensured that UI penalty should be minimum.Takeminimum. Take revision of schedule if it is expected that the fault cannot be rectified immediately.Theimmediately. The revision is effective from the 4th time block when revision is sendt, so revision should be sendt immediately.

RESTARTING OF MACHINE AFTER PROLONGED SHUT DOWN/MAINTENANCE

****************************************************************

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) If the machine is being run after annual maintenance or long period of shutdown the machine should be put on mechanical run for at least 12 hours. IR and PI to be checked after dry run and if IR/PI readings found OK (clearance from maintenance) then machine can be synchronized.3) If machine is run after maintenance then speed should be increased slowly in steps. Vibration at TGB/GGB should be continuously monitored alongwith bearing temperatures. In case of any sharp rise of bearing temperature / sudden increase of vibration or abnormal noise/smell from machine, immediately stop the machine. Diagnose the fault before starting machine.24)The bearing oil/OPU Oil has to be circulated through centrifuge for at least 24 hours.35)Check the operation of brakes.46) Cleaning of governor oil filter to be performed.57) Air removal from coolers by passing water for two hours.68) 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 current (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 Vibration1. Thrust bearing bracket 0.05 mm2. Slip-rings 0.3(Throw) mm

Recommended setting of various Devices (As per OEM)*********************************************************************

1 Hot Air Thermometer alarm contact 70C

2 Hot Air Thermometer shutdown contact 80C

3 Thrust pad dial Thermometer alarm contact 75C4 Guide pad dial Thermometer alarm contact 75C5. Thrust pad Thermometer shutdown contact 85C6 Guide pad Thermometer shutdown contact 85C7 Thrust bearing oil Thermometer alarm contact 60C8 Thrust bearing oil Thermometer shut down contact 70C9 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 90CNote: The aActual settings shallould be on lower side depending on unit conditions.be kept below above limit but may differ between two units depending upon unit characteristic and condition.

OPU Related Operation Parameters***********************************************

S.No. Device Parameter Unit-I Unit-II Unit-IIIALARM 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

65C 65C 65C

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 V6. Field Current 900 A at rated

load530 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 tripping135% speed – Elect. Overspeed trip150% speed- Mech. Overspeed trip280 rpm- runaway( on-cam)370 rpm runaway (off-cam)

10. Power Factor 0.9 lagging11. Brake operating air pressure 5 kg/cm2 7 kg/cm2(Max.)12. Brake application speed 30% of Syn.

speed70 rpm (Max.)

13. Jacking Oil pressure 85 bar14. Cooling water pressure 7 kg/cm215. MVAR-Generator 4.8 MVAR 14 MVAR16. Gen. Air/ Oil circulating

cooling water inlet temp.  20-35C (depending on weather)

17. Gen. Air/ Oil circulating cooling water outlet temp.

30-45 C (depending on weather & load)

18. Gen. Air/ Oil circulating cooling 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

S.No. Operation Parameter Normal Value Max. Permissible limit/ Alarm 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 C24. SST Oil Temperature 50-55 C 70 C25. UAT Winding Temperature 50-60 C 80 C26. UAT Oil Temperature 50-55 C 70 C27. 220/132 kV Auto transformer-

Winding Temperature50-60 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 A30. 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 A34. Line Active Power (Nepal

feeder)0-520 MW 20 50 MW

35. Line Reactive Power (Nepal feeder)

2.5 MVAR 9.5 MVAR

36. Line Voltage (Nepal feeder) 132 kV 145 KkvV(Max.)/120 KvkV(Min)

37. Water level (Barrage) 246.7 m38. 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.)

cusecdepends on load

42. Silt in ppm 100-1000 ppm-Summer/Winter1000-3500 ppm-Rainy Season

5000 ppm max.

S.No. Operation Parameter Normal Value Max. Permissible limit/ Alarm Value/Trip Value

43. H.P Pressure Receiver 40-42 kg/cm2 44 kg/cm244. L.P Pressure Receiver 6-7 kg/cm245. L.P Station Receiver 6-7 kg/cm246. Water pressure in spiral

casing2-3 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/cm249. 220 V DCDB Load Voltage 220 V 220 V+- 10% 50. 220 V DCDB Load Current 25 A 40 A51. 220 V DCDB Battery Voltage 220 V 220 V+- 10% 52. 220 V DCDB Battery Current 25 A 40 A53. 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 CircuitsThe Generator due toin case of major Eelectrical faults is tripped through relay 86A. The tripping of this relay is accompanied due to 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... 37X3. Gen. spilt phase diff.Protection 87SA/B/C4. Generator stator main E/F protection. 64GI5. Generator Transformer Overall Diff. protection . 87GT6. Generator-Transformer HV REF Protn. 64RHv7. Generator-Transformer HV Un.EF protn /Gen over flux protn. 51NX/99T8. Gen Transformer Buchh, no oil flow & no water flow protn... 30A/B,30K/L9. Emergency shutdown. 86B10.Gen Transformer on fire/Gen on fire 64GX11.Gen. Diff protn. 87GX12.Excitation TR O/C Protn.Trip Stage1/StageII K220/K22413.UAT Buchh. Trip Aux 130A14.UAT O/C protn. 50/51ABC15.UAT REF protn. 64R16.Gen.link line Diff. protn. 87LA/B/C17.Generator E/F protn 64F18.LBB protn. 50Z19.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 initiates shuts down sequence of the unit and energisesenergies emergency shutdown relay(86B).

B. Non-Electrical S/D & Lock out Tripping CircuitsThe tripping due to theIn case mechanical faults, cause Non-Electrical Lock out is initiated 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.Itstopped. It operates controlled action shutdown relay(86A). The detailed causes of tripping along with relays placed in U.C.B are as follows:

DESCRIPTION RELAY1. Turbine guide bearing Temp.very high 38TB-TX2. Gen. Guide bearing Temp. very high 38GB-TX3. Gen thrust guide bearing Temp. very high 38TH-TX4. Gen air cooler inlet air temp.very high 49AH-TX5. Gen Tr. wdg Temp. very high 30F6. Gen Tr .oil temp very high 30D7. Governor oil press. Unit oil press Very low. 63G-2X8. Unit over speed Elect/Mech.speed 12X3AX/12MX9. Governor failure 2GFT10.Controlled action shutdown. 86A

C. Elect.Non-Lock out TripThis 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 with guide vane in opening position. This tripping is caused due to operation of following: relays:

DESCRIPTION RELAY1. Gen. Backup Imp protn. 21AB/BC/CA2. Gen over voltage protn. 59DI3. Gen. –ve Ph sequence protn. 46T/A5. Gen.loss of field protn. 40G6. No load Tripping protn 5NLT8 Excitation TR O/C instantaneous. K2199. 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

Oil viscosity too high

Check performance of hydraulic power unitReplace hydraulic pump if necessary

Replace hydraulic servo motor seals

Check oil temperature /take remedial action.

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

Clear all obstructions

Check G.V. key and

guide vane alignment.

Runner not rotating Obstruction in turbine runner case

Turbine/Generator misalignment

Blockage to runner

Clear all obstructions

Check alignment

Check runner clearanceExcessive vibration Operating outside of the

normal operating “envelope”

Guide vanes have slipped

Rotating element out of balance

Obstruction in turbine waterways

Bearing failure

Turbine misalignment

Bearing housing or shaft flanged fasteners failed

Check operating parameters related to balancing.

Check G. V’s alignment

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 balanceLoose parts or fasteners

Check operating parameters related to balancing.

Check G.V’s alignment

Check rotating mass balanceCheck for failed or loose fasteners

OPU:

FAULT DIAGNOSIS

The following chart provides a guide to fault diagnosis with probable cause and proposed rectification action: -

Defect Probable cause Rectification

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:

Defect Probable cause Rectification

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 damageReplace water pump as necessaryReplace drive motor as necessary

Noisy water pump Loose assembly

Loose coupling

Air in system

Water pump “Jammed”

Check water pump for correct assembly & securityCheck water pump coupling for securityBleed system free of air

Strip water pump & inspect for damage & debrisReplace water pump as necessaryReplace drive motor as necessary

Water system low flow rate i.e. “No-Flow” alarm

Air in system

“Duty” strainer blocked

Bleed system free of air

Select “standby” strainer

Heat exchanger blocked

Indication fault

& note any change in flow rate. Clean “Duty” strainer.

Clean replace 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 operationEnsure 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 trip / alarm.

- 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 fusesIn 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.