THDC SUMMER TRAINING

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Abhilash Rwaat Abhilash Rwaat C C h h a a p p t t e e r r : : E E r r r r o o r r ! ! N N o o t t e e x x t t o o f f s s p p e e c c i i f f i i e e d d s s t t y y l l e e i i n n d d o o c c u u m m e e n n t t . .

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0 SUMMER TRAINING REPORT | ABHILASH RAWAT

SUMMER TRAINING REPORT | ABHILASH RAWAT

THDC

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A A B B H H I I L L A A S S H H R R A A W W A A T T – –

1

1 TABLE OF CONTENT

TABLE OF CONTENT

SERIAL SERIAL NUMBER NUMBER TOPICS PAGE TOPICS PAGE NUMBER NUMBER 1

1 Submission Submission Details Details 22

2

2 Acknowledgement Acknowledgement 33

3

3 Introduction Introduction 44

4

4 THDC THDC India India Limited Limited Projects Projects 55 5

5 Salient Salient Features Features Of Of Tehri Tehri Dam Dam 66

6

6 _{Location Of Equipments (Elevation Wise)}_{Location Of Equipments (Elevation Wise)} ₇₇ 7

7 _{Hydro Generator}_{Hydro Generator}

A. Rating A. Rating

B. Layout &Structural Detail B. Layout &Structural Detail C. Stator

C. Stator D. Rotor D. Rotor

E. Upper &Lower Bracket E. Upper &Lower Bracket F. Bearing & Breaking System F. Bearing & Breaking System G. Cooling System

G. Cooling System

H. Fire Extinguishing System H. Fire Extinguishing System

12 12

8

8 _{Generator Transformer}_{Generator Transformer}

A. Rating A. Rating

B. General Construction Features B. General Construction Features C. Transformer Cooling System C. Transformer Cooling System D. Generator Transformer Protection D. Generator Transformer Protection

16 16

9

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2

2 SUBMISSION DETAILS

SUBMISSION DETAILS

Name of the

Name of the Organization

Organization

Tehri Hydro Development Corporation Ltd.

Location of Powerhouse

Tehri-Garhwal, Uttarakhand, India

Mentor

Shri Arun Kumar,

Senior Manager (Operation)

Duration

June 23

st

, 2014 to August 2

th

, 2014

Title Of Report

Summer Training Report Tehri HPP

Name

Abhilash Rawat

College

THDC Institute Of Hydropower & Technology

University

Uttarakhand Technical University

Discipline

Electrical Engineering

Roll.no

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3

Acknowledgement

I am very grateful to

I am very grateful to Shri Sajeev R, AGM(Operation)

Shri Sajeev R, AGM(Operation)

Tehri

Tehri HEP,

HEP, THDC

THDC

India Limited for

India Limited for guiding

guiding and providing me

and providing me information about the

information about the

various

various equipments

equipments at

at Tehri

Tehri Hydro

Hydro Power Plant.

Power Plant.

I I would like to

would like to acknowledge my deep gratitu

acknowledge my deep gratitude to

de to Shri Arun Kumar

Shri Arun Kumar

,, Senior

Senior

Manager(Operation)

Tehri

Tehri HEP for

HEP for his

his guidance

guidance which h

which helped

elped me to

me to

understand

understand the

the role

role of

of a

a Electrical

Electrical engineer

engineer as

as well

well as f

as for

or explaining

explaining

the functions

the functions of various

of various equipments required for the

equipments required for the smooth operation

smooth operation

of Hydro Power Plant

I I would

would like to thank

like to thank HR Department, Rishikesh, THDC India Limited

HR Department, Rishikesh, THDC India Limited

for

giving

giving me

me opportunity of

opportunity of Summer Training. I

Summer Training. I am also indebted to

am also indebted to

acknowledge

acknowledge the

the Executives

Executives of

of Tehri

Tehri Power

Power House

House who

who gladly

gladly shared

shared

their vast knowledge about generation of electricity.

I would like to thank my Institution,

I would like to thank my Institution, THDC Institute of Hydropower

THDC Institute of Hydropower

Engineering & Technology

, Tehri, Uttarakhand and the Faculty members

for providing opportunity and valuable guidance render

for providing opportunity and valuable guidance rendered during summer

ed during summer

training.

I also extend my heartfelt thanks to my family and well wishers.

Abhilash Rawat

THDC Institute Of Hydropower &

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4

4 INTRODUCTION

INTRODUCTION

The Tehri Dam is a

The Tehri Dam is a multi-purpose rock and earth-fill embankment dam at the confluence of Bhagirathimulti-purpose rock and earth-fill embankment dam at the confluence of Bhagirathi and Bhilangna River at Tehri in Uttarakhand, India. Tehri Hydro Power Projects comprises of three and Bhilangna River at Tehri in Uttarakhand, India. Tehri Hydro Power Projects comprises of three phases. Phase 1: Tehri HEP (4X250MW) was completed in 2006, Phase 2: Koteshwar HEP phases. Phase 1: Tehri HEP (4X250MW) was completed in 2006, Phase 2: Koteshwar HEP (4X100MW) wa

(4X100MW) was completed in 2s completed in 2012. 012. The Tehri DaThe Tehri Dam withholds a resm withholds a reservoir for irrigatiervoir for irrigation, municipalon, municipal water supply and the generation of

water supply and the generation of 1,400 MW of hydroelectricity.1,400 MW of hydroelectricity.

Third phase: (4X250MW) Pumped storage Plant of hydroelectricity generation is under Third phase: (4X250MW) Pumped storage Plant of hydroelectricity generation is under construction. This dam is world’s 3

construction. This dam is world’s 3rdrd largest rock fill dam. The complex will afford irrigation to an largest rock fill dam. The complex will afford irrigation to an area of 270,000 hectares (670,000acres), irrigation stabilization to an area of 600,000 hectares area of 270,000 hectares (670,000acres), irrigation stabilization to an area of 600,000 hectares (1,500,000acres

(1,500,000acres), and supply of 270 m), and supply of 270 million gallons of illion gallons of water per day to thwater per day to the industrialize aree industrialize areas ofas of Delhi, Uttar Pradesh and

Delhi, Uttar Pradesh and Uttarakhand.Uttarakhand.

4x250 MW Tehri HPP stage -1 comprises an underground powerhouse of size 196x20x61.7m and 4x250 MW Tehri HPP stage -1 comprises an underground powerhouse of size 196x20x61.7m and is designed to accommodate four no. 250MW generating units coupled to vertical Francis turbines is designed to accommodate four no. 250MW generating units coupled to vertical Francis turbines working under a net head of 188 m along with its mechanical and electrical auxiliaries. A separate working under a net head of 188 m along with its mechanical and electrical auxiliaries. A separate cavern

cavern of of size size 161x17x28.9 161x17x28.9 m m has has been been designed designed to to accommodate accommodate eight eight numbers numbers of of 15.75/420kv15.75/420kv , three phase Generator Transformer at EL 605 m out of which four numbers for Tehri HPP stage-1 , three phase Generator Transformer at EL 605 m out of which four numbers for Tehri HPP stage-1 has been installed and four no. of Generator Transformer for future PUMP STORAGE PLANT has been installed and four no. of Generator Transformer for future PUMP STORAGE PLANT (PSP). 7 Bays of 420kV Gas Insulated Switchgears and associated equipment have been installed (PSP). 7 Bays of 420kV Gas Insulated Switchgears and associated equipment have been installed at EL 618m. Provisions for future extension for PSP has been made for 04 numbers incoming bays at EL 618m. Provisions for future extension for PSP has been made for 04 numbers incoming bays and 01 no. outgoing bays besides a provision for one starting bus to be added in future for back to and 01 no. outgoing bays besides a provision for one starting bus to be added in future for back to back starting of PSP , if required. Two circuits of 420kv Gas Insulated Bus Ducts (GIB) have been back starting of PSP , if required. Two circuits of 420kv Gas Insulated Bus Ducts (GIB) have been extended to the Port yard from where two nos. 400kv overhead lines of length 182 & 184 km each extended to the Port yard from where two nos. 400kv overhead lines of length 182 & 184 km each are taking off to

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5

5 THDCIL

THDCIL

Project

At

A

Glance

Sl

Sl No. No. Projects/State Projects/State InstalledInstalled

Capacity(MW) Capacity(MW)

Remarks River/Basin Remarks River/Basin

PROJECT UNDER OPERATION PROJECT UNDER OPERATION i.

i. Tehri Tehri Dam Dam & & HPPHPP Uttarakhand Uttarakhand 1000 1000 Commissioned Commissioned inin 2006-07 2006-07 Bhagirathi Bhagirathi ii.

ii. Koteshwar Koteshwar HEPHEP Uttarakhand Uttarakhand 400 400 Commissioned inCommissioned in 2011-12 2011-12 Bhagirathi Bhagirathi Total 1400 Total 1400

PROJECT UNDER CONSTRUCTION PROJECT UNDER CONSTRUCTION

i. i. ii. ii. Tehri PSP Tehri PSP Uttarakhand Uttarakhand Vishnugad Vishnugad Pipalkoti HEP, Pipalkoti HEP, Uttarakhand Uttarakhand 1000 1000 444 444 F

Fiirrsst pt puummp sp sttoorraagge se scchhee in central sector

in central sector

ROR scheme on ROR scheme on Alaknanda

Alaknanda RiverRiver

Bhagirathi Bhagirathi Alaknanda Alaknanda Total 1444 Total 1444

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6

6 Salient Features

Salient Features

a)

a) Geographical Geographical Features:Features:

1. 1. LOCATION

LOCATION

•

State

: :

Uttarakhand

•

District

: : Tehri

Tehri Garhwal

Garhwal

•

Dam

:

: At

At the

the confluence

confluence of

of river

river Bhagirathi

Bhagirathi and

and Bhilangana

Bhilangana

•

Power

Power House

House

: : Bhagirathipuram

Bhagirathipuram

•

River

: :

Bhagirathi

2. 2. DAM

DAM

•

Type

: :

Earth

Earth &

& Rock

Rock filled

filled

•

Top

Top Level

Level

: :

EL-839.5 meter

EL-839.5

meter

•

Height

: :

260.5meter

•

Width

Width at

at river

river bed

bed

: :

1125meter

•

Length

Length at

at TOP

TOP

: :

592.25 592.25 meter

meter

•

Width

Width at

at top

top

: :

25.5 25.5 –

– 30.5

30.5 meter

meter

3. 3. RESERVOIR

RESERVOIR

•

Max.

Max. water

water level

level

:

El-835.5

El-835.5 meter

meter

•

Normal

Normal reservoir

reservoir level

level

: :

EL-830

EL-830 meter,

meter,

•

Min.

Min. draw

draw down

down level

level

: :

EL-740

EL-740 meter

meter

•

Gross

Gross storage

storage

: :

3540

3540 MCM

MCM

•

Dead

Dead storage

storage

: :

925MCM

•

Water

Water spread

spread at

at FRL

FRL

: :

42 42 Sq.km

Sq.km

•

Water

Water spread

spread at

at MDDL

MDDL : :

18 18 Sq.km

Sq.km

4. 4. HYDROLOGY

HYDROLOGY

•

Catchment

Catchment area

area

: :

7511

7511 Sq.

Sq. Km

Km

•

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7

7 Location of Major Equipment

Location of Major Equipment

Elevation wise

E.L. means Elevation with reference to sea

E.L. means Elevation with reference to sea level (E.L. 0 meters)level (E.L. 0 meters) Power House

Power House:: E.L.- 578 m E.L.- 578 m : :

Waste Water Clarification Unit

Waste Water Clarification Unit- Waste water disposal system. Sludge dewatering Tank, Lime- Waste water disposal system. Sludge dewatering Tank, Lime dosing pump and tank, Alum dosing tank and pump, polyelectrolyte, Agitator 1,2,3,4, Air dosing pump and tank, Alum dosing tank and pump, polyelectrolyte, Agitator 1,2,3,4, Air Compressor, Sludge dewatering pump-1,2, Filter feed pump-1,2,

Compressor, Sludge dewatering pump-1,2, Filter feed pump-1,2, Backwash Pump-1,2.Backwash Pump-1,2. E.L.- 584 m

E.L.- 584 m:: Cooling

Unit-Cooling Unit- Filtration system, Ejector, Generator and Turbine cooling water system & cubicleFiltration system, Ejector, Generator and Turbine cooling water system & cubicle (ejector and filter control) for all 4 units, Generator Transformer cooling system, Generator rotor (ejector and filter control) for all 4 units, Generator Transformer cooling system, Generator rotor jacking, Brake d

jacking, Brake dust collecting fan, tuust collecting fan, turbine head coverbine head cover drain, turbine lear drain, turbine leakage unit, oil cookage unit, oil cooling pumpling pump Draft tube manhole, Drainage Leakage valve control cabinet, Hydraulic Service Seal Valve, Main Draft tube manhole, Drainage Leakage valve control cabinet, Hydraulic Service Seal Valve, Main Inlet Valve, MIV Leakage Unit, Filtration Unit.

Inlet Valve, MIV Leakage Unit, Filtration Unit. Drainage Pump Station-I(DPS-I)-:

Drainage Pump Station-I(DPS-I)-: Pump number 1 and 2Pump number 1 and 2 E.L.-591.6 m

E.L.-591.6 m::

Dewatering Pump

Station-Dewatering Pump Station- Pump number 1, 2 and 3Pump number 1, 2 and 3

Runner Seal, Shaft Seal water connection point, Spiral casing for each unit, Turbine Guide Bearing Runner Seal, Shaft Seal water connection point, Spiral casing for each unit, Turbine Guide Bearing cooling system.

cooling system. E.L.-595.5 m E.L.-595.5 m::

Generator Lower Bracket Barrel

Generator Lower Bracket Barrel: Stator air cooler, Turbine oil cooler, Emergency closing valve,: Stator air cooler, Turbine oil cooler, Emergency closing valve, Rotor braking system and rotor lifting unit,

Rotor braking system and rotor lifting unit, Generator Thrust bearing.Generator Thrust bearing. Oil Pressure Unit-(MIV)

Oil Pressure Unit-(MIV) Air Air oil oil vessel, vessel, Air Air vessel, vessel, two two induction induction motors motors attached attached with with pumppump immersed underneath sump oil section to maintain oil and

immersed underneath sump oil section to maintain oil and air pressure for vessels.air pressure for vessels. Turbine Generator coupling chamber

Turbine Generator coupling chamber : Lower Guide bearing, servo motors for opening and: Lower Guide bearing, servo motors for opening and closing of wicket gates

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E.L.-600 m E.L.-600 m Excitation floor:

Excitation floor:, RTU excitation, , RTU excitation, Independent Excitation Transformer, Static Excitation System, SelfIndependent Excitation Transformer, Static Excitation System, Self Excitation Transformer, Unit Auxiliary Transformer, Unit Auxiliary switchgear, Voltage Transformer Excitation Transformer, Unit Auxiliary Transformer, Unit Auxiliary switchgear, Voltage Transformer Cabinet, Transformer cooling water system.

Cabinet, Transformer cooling water system. 17.5 KV Isolated Phase Bus duct

17.5 KV Isolated Phase Bus duct: LAVT : LAVT cubicle, Dyncubicle, Dynamic Brakamic Braking Cubicling Cubicle, Neutral e, Neutral GroundingGrounding Transformer

Transformer

Oil Pressure Unit-(Turbine):

Oil Pressure Unit-(Turbine): Air Air oil oil vessel, vessel, Air Air vessel, vessel, two two induction induction motors motors attached attached with with pumppump immersed underneath sump oil section to maintain oil and

immersed underneath sump oil section to maintain oil and air pressure for vessels.air pressure for vessels. Mechanical Turbine Governor:

Mechanical Turbine Governor: actuator cubicle actuator cubicle (hydro-mechanical cabinet)(hydro-mechanical cabinet)..

Compressor Room:

Compressor Room:Two air compressors pump number 1 & 2, works in two stages.Two air compressors pump number 1 & 2, works in two stages. E.L.-605 m:

E.L.-605 m: Machine Hall:

Machine Hall: Unit Control Board (UCB), Generators Turbine Unit upper cabinet with name plateUnit Control Board (UCB), Generators Turbine Unit upper cabinet with name plate details, MIV vault opening for all 4 units, Dewatering Pump station service switchgear and details, MIV vault opening for all 4 units, Dewatering Pump station service switchgear and Transformer, Overhead Travelling crane (

Transformer, Overhead Travelling crane ( E.L.-626.10m)E.L.-626.10m) Transformer Hall:

Transformer Hall: Power Transfer Vault total 8 in numbers, 4 for Generator Transformer of TehriPower Transfer Vault total 8 in numbers, 4 for Generator Transformer of Tehri HEP, 4 for Generator Transformer of Tehri PSP, 4 numbers of Generator Power Transformer of all HEP, 4 for Generator Transformer of Tehri PSP, 4 numbers of Generator Power Transformer of all units of HEP, Generator Transformer Cooler control cabinet.

units of HEP, Generator Transformer Cooler control cabinet. Station Service Transformer tapped to unit #

Station Service Transformer tapped to unit # 4.4. E.L.-618 m:

E.L.-618 m:

GAS INSULATED SWITCHGEAR (GIS):

GAS INSULATED SWITCHGEAR (GIS): Transformer bushing, PDM (Partial DischargeTransformer bushing, PDM (Partial Discharge Maintenance), Circuit Breakers, Isolators, Earthing Switches, Gas Insulated Bus duct (GIB) of

Maintenance), Circuit Breakers, Isolators, Earthing Switches, Gas Insulated Bus duct (GIB) of 840m840m tunnel till IFB bu

tunnel till IFB building, ilding, 4 Bus Bars-BB4 Bus Bars-BB11,BB12,BB21,B11,BB12,BB21,BB22; Bus coupleB22; Bus coupler.r. E.L.-706m:

E.L.-706m:

Butterfly Valve Chamber:

Butterfly Valve Chamber: The Butterfly Valve Chamber houses 4 nos. butterfly valves of 5000mm The Butterfly Valve Chamber houses 4 nos. butterfly valves of 5000mm size. Penstock Assembly Chamber is an

size. Penstock Assembly Chamber is an underground cavern parallel to BVC, Fire underground cavern parallel to BVC, Fire Fighting System,Fighting System, Drainage Pump Station no.3

Drainage Pump Station no.3 (DPS-III).(DPS-III). Station Control Area (Control Building):

Station Control Area (Control Building): It is an underground multi-storey building having lowest floor It is an underground multi-storey building having lowest floor at 600.0m and top floor at El. 622.0m.

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E.L.-605 m:

E.L.-605 m: Mechanical Maintenance Mechanical Maintenance Department, Hydro Mechanical DepartmentDepartment, Hydro Mechanical Department E.L.-608 m:

E.L.-608 m: Station Relay Room, CCR( UPS room), Computerised Control System room ( CCS), Station Relay Room, CCR( UPS room), Computerised Control System room ( CCS), Monitoring System, Control Panels and

Monitoring System, Control Panels and Computers, Main Mosaic Mimic Board.Computers, Main Mosaic Mimic Board. E.L.-611 m:

E.L.-611 m: Video Conference Hall, Conference Hall, Visitors Room. Video Conference Hall, Conference Hall, Visitors Room. E.L.-615 m:

E.L.-615 m: Air Conditioning and Air Ventilation Room, Electrical Maintenance Group Room, Cable Air Conditioning and Air Ventilation Room, Electrical Maintenance Group Room, Cable Room.

Room.

E.L.-618 m:

E.L.-618 m: Station Control Area Service Switchgear(Auxiliary supply L.T. room), 11KV switchgear Station Control Area Service Switchgear(Auxiliary supply L.T. room), 11KV switchgear panel- main bus bar, Battery Bank Ist and IInd bus bars DC, SCA Transformers, L.T. Panel (415V), panel- main bus bar, Battery Bank Ist and IInd bus bars DC, SCA Transformers, L.T. Panel (415V), Machine Testing Laboratory and Library.

Machine Testing Laboratory and Library.

Power House

:: E.L.- 584 m E.L.- 584 m:: Cooling

Unit-Cooling Unit- Cooling water system is provided in the power house for cooling of generating unitsCooling water system is provided in the power house for cooling of generating units and generator transformers. It is provided fully independent open circuit cooling system for each and generator transformers. It is provided fully independent open circuit cooling system for each unit, and double-loop cooling water system for each transformer. Cooling water for users is taken unit, and double-loop cooling water system for each transformer. Cooling water for users is taken from the penstock and the draft tube. Water for ejector operation is fed from the penstocks, while the from the penstock and the draft tube. Water for ejector operation is fed from the penstocks, while the drawn-in water is taken from the draft tubes and passes through the deaerators to get the water free drawn-in water is taken from the draft tubes and passes through the deaerators to get the water free of air bubbles accumulated there during passing the

of air bubbles accumulated there during passing the runner chambers.runner chambers. Main Inlet Spherical Valve (MIV)

Main Inlet Spherical Valve (MIV): The spherical valve is : The spherical valve is of the horizontal shaft type of the horizontal shaft type and comprises:and comprises: split body, split rotor, rotor trunnions, service and maintenance seals, bearings, lock and other split body, split rotor, rotor trunnions, service and maintenance seals, bearings, lock and other components and parts. The spherical valve gets closed both when there is no flow in the penstock components and parts. The spherical valve gets closed both when there is no flow in the penstock (i.e. when the wicket gates are closed) and under flow conditions by the counterweights attached to (i.e. when the wicket gates are closed) and under flow conditions by the counterweights attached to the levers. The spherical valve is opened by two swinging servomotors operated by the valve oil the levers. The spherical valve is opened by two swinging servomotors operated by the valve oil pressure system. The spherical valve is to be opened after filling up the spiral case with water and pressure system. The spherical valve is to be opened after filling up the spiral case with water and pressure differential across the valve maximum 0.3 MPa.

pressure differential across the valve maximum 0.3 MPa. Draft Tube Manhole:

Draft Tube Manhole: Hydro Turbine

Hydro Turbine: Four numbers of Vertical Francis Turbine are installed in power house. Each: Four numbers of Vertical Francis Turbine are installed in power house. Each machine has a rated capacity of 255 MW and can be operated in the head range of 122.6-230.1 m. machine has a rated capacity of 255 MW and can be operated in the head range of 122.6-230.1 m. The unique feature of the design of Francis turbine is that single runner is capable of operation The unique feature of the design of Francis turbine is that single runner is capable of operation under large head variation of over 100.0m.The direction of rotation is anti-clock wise when viewed under large head variation of over 100.0m.The direction of rotation is anti-clock wise when viewed from the top.

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E.L.-591.6 m E.L.-591.6 m::

Dewatering Pump Station:

Dewatering Pump Station: Dewatering system is provided in the power house for dewatering ofDewatering system is provided in the power house for dewatering of penstock, spiral case and draft tube between penstock / main inlet valve and draft tube gate for penstock, spiral case and draft tube between penstock / main inlet valve and draft tube gate for access to turbines and MIV’s for inspection and maintenance. In emergency the pumps of the

access to turbines and MIV’s for inspection and maintenance. In emergency the pumps of the systemsystem can be used for

can be used for dewatering the flooded areas of the power dewatering the flooded areas of the power house.house. E.L.-595.5 m

E.L.-595.5 m::

Oil Pressure Unit-(MIV):

Oil Pressure Unit-(MIV): Oil pressure system for servomotors of each valve consists Oil pressure system for servomotors of each valve consists of oil pumpingof oil pumping unit equipped with two 11.2 ltr/sec, 55 KW oil pumps, sump tank, control cubicle and other unit equipped with two 11.2 ltr/sec, 55 KW oil pumps, sump tank, control cubicle and other necessary equipment and auxiliaries. For the opening of the valve is

necessary equipment and auxiliaries. For the opening of the valve is provided with oil pressure of 60provided with oil pressure of 60 kgf/square cm. This oil pressure is supplied by oil pumps. The pressure oil system consists of oil kgf/square cm. This oil pressure is supplied by oil pumps. The pressure oil system consists of oil sump, oil pumping unit, valves, fittings, instrumentation and automatic operation. Two oil pumping sump, oil pumping unit, valves, fittings, instrumentation and automatic operation. Two oil pumping set are mounted on oil sump, one acting as main and other as standby. The pump shall be of set are mounted on oil sump, one acting as main and other as standby. The pump shall be of variable displacement type suitable for auto start/stop operation with the

variable displacement type suitable for auto start/stop operation with the help of pressure switches.help of pressure switches. E.L.-600 m:

E.L.-600 m:

Excitation System

:: Each generator is equipped with two modern static excitation systemsEach generator is equipped with two modern static excitation systems known as parallel/self excitation system and independent excitation system. Parallel/self excitation known as parallel/self excitation system and independent excitation system. Parallel/self excitation system is meant for excitation of the generator in generation mode as well as in synchronous system is meant for excitation of the generator in generation mode as well as in synchronous condenser mode.

condenser mode.

The excitation system is intended for providing the

The excitation system is intended for providing the following functions:following functions:



 Start Start up, up, field field flashing flashing and and switching switching to to the the system system by by precise precise synchronizing.synchronizing.



 Operation Operation of of the the generator generator at at loads loads varying varying from from no no load load to to maximum maximum load load for for the the generator.generator.



 Operation Operation in in the the synchronous synchronous condenser condenser mode mode both both with with inductive inductive and and capacitive capacitive load.load.



 Field Field forcing forcing at at the the set set voltage voltage response response and and de de excitation excitation at at disturbances disturbances in in the the power power gridgrid causing voltage rise or drop in

causing voltage rise or drop in the system.the system.



 Rotor Rotor field field suppression suppression by by the the field field circuit circuit breaker breaker at at protection protection operation operation with with simultaneoussimultaneous inversion of the rectifying unit.

inversion of the rectifying unit.



 Operation Operation on on joint joint control control maintaining maintaining even even distribution distribution of of the the reactive reactive load load betweenbetween machines.

machines.



 Limiting Limiting the the ratio ratio of of ceiling ceiling field field current current to to nominal nominal field field current current by by two two (2) (2) per per unit unit without without timetime delay as well limiting of

delay as well limiting of over load by the over load by the time-inverse characteristime-inverse characteristics.tics.



 Limiting Limiting minimum minimum field field current current with with set set point point depending depending on on generator generator active active power power in in thethe mode of VAR load demand from the grid.

mode of VAR load demand from the grid.



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11

11 Governor

Governor

: A governor is incorporated in the turbine generator to ensure constant speed. It senses: A governor is incorporated in the turbine generator to ensure constant speed. It senses change in speed & then controls wicket gate opening automatically through servomotors so as to change in speed & then controls wicket gate opening automatically through servomotors so as to oppose changes in turbine speed. Turbine governors are equipment for the

oppose changes in turbine speed. Turbine governors are equipment for the control and adjustment ofcontrol and adjustment of turbine power output and grid load as fast as possible.

turbine power output and grid load as fast as possible. The governor consists of the following units:

The governor consists of the following units: 1. Electronic Unit

1. Electronic Unit

2. Hydro mechanical unit. 2. Hydro mechanical unit.

Governor for each unit consists of a digital programmable electronic part for control and Governor for each unit consists of a digital programmable electronic part for control and regulating function and a hydraulic part act as a power amplifying servo unit. The governor regulating function and a hydraulic part act as a power amplifying servo unit. The governor performs the following tasks for the

performs the following tasks for the regulating and control of the regulating and control of the generating unit:generating unit: Speed Frequency control

Speed Frequency control Power Control

Power Control

Governing during synchronous condenser mode operation Governing during synchronous condenser mode operation

The electronic governor has provision for both automatic operation as well as manual control The electronic governor has provision for both automatic operation as well as manual control through the hydraulic actuator. The governor comes into action when the turbine ‘start’ signal is through the hydraulic actuator. The governor comes into action when the turbine ‘start’ signal is given from the unit control board/control room. It then regulates the speed of the generating unit given from the unit control board/control room. It then regulates the speed of the generating unit in operation. The governor is of proportional differential (PD) action type. The governor has high in operation. The governor is of proportional differential (PD) action type. The governor has high sensitivity, quick response to

sensitivity, quick response to speed/load changes.speed/load changes.

Hydraulic actuator unit of governor consists of oil pumping unit, oil pressure accumulator, oil Hydraulic actuator unit of governor consists of oil pumping unit, oil pressure accumulator, oil leakage unit, amplifier and solenoid operated

leakage unit, amplifier and solenoid operated distributing valve etc. the hydraulic actuator distributing valve etc. the hydraulic actuator unit hasunit has following features:

following features:



 Two numbers remotely controTwo numbers remotely controlled (from control room) shut down devicelled (from control room) shut down devices for normal ands for normal and emergency closure of wicket gates.

emergency closure of wicket gates. For emergency closure both solenoid operated valvesFor emergency closure both solenoid operated valves are fed from two

are fed from two independent 220 V DC sources.independent 220 V DC sources.



 Independent emergency solenoid vIndependent emergency solenoid valve which operates alve which operates in emergency condin emergency conditions and senditions and send the pressurized oil directly to the

the pressurized oil directly to the wicket gate servomotors by passing the governor.wicket gate servomotors by passing the governor.



 Control devices for the manual operaControl devices for the manual operation allowing openintion allowing opening and closing of wickg and closing of wicket gates to anyet gates to any position.

position.



 Wicket Wicket gate maxgate maximum opimum opening limening limiting deiting device.vice.



 Transmitter Transmitter for wicfor wicket gate ket gate and limiteand limiter positior position.n.



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12

12 HYDRO GENERATOR

HYDRO GENERATOR

Hydro generator (CB 870/300-28) is a vertical shaft, alternating current, 3-phase synchronous Hydro generator (CB 870/300-28) is a vertical shaft, alternating current, 3-phase synchronous machine of semi umbrella type with combined thrust and lower guide bearing located below the rotor machine of semi umbrella type with combined thrust and lower guide bearing located below the rotor and upper guide bearing above the rotor. Guide bearing are arranged in the oil bath of upper and and upper guide bearing above the rotor. Guide bearing are arranged in the oil bath of upper and lower brackets and thrust bearing in oil bath of lower bracket. The generator is designed for nominal lower brackets and thrust bearing in oil bath of lower bracket. The generator is designed for nominal output of 250 MW and maximum continuous output of 275 MW at 0.9 lagging power facto the output of 250 MW and maximum continuous output of 275 MW at 0.9 lagging power facto the rotational speed of the machine is 214.3 rpm and runaway speed is 410 rpm.

rotational speed of the machine is 214.3 rpm and runaway speed is 410 rpm.

Key parameters of hydro generator are as follows

::

1-1- Nominal Nominal output output 278/250 278/250 MVA/MWMVA/MW

2-2- Maximum Maximum continuous continuous output output 305.8/275 305.8/275 MVA/MWMVA/MW

3-3- Power Power factor factor 0.9 0.9 lagginglagging

4-4- Frequency Frequency 50_+3% 50_+3% HzHz

5-5- Rated Rated terminal terminal voltage voltage between between phases phases 15.75 _+5%15.75 _+5%

6-6- Nominal Nominal speed(Rotational speed(Rotational speed) speed) 214.3 214.3 rpmrpm

7-7- Runaway Runaway speed(over speed(over speed) speed) 410.3 410.3 rpmrpm

8-8- Rotational Rotational direction direction Counter Counter clockwise clockwise If If looked looked from from toptop

9-9- Fly Fly wheel wheel effect effect 24000 24000 t.m^1/2t.m^1/2

10-10- Inductive Inductive reactance, reactance, unsaturated: unsaturated: RelativeRelative i)

i) Synchronous, Synchronous, by by direct direct axis, axis, Xd Xd 1.01.0 ii)

ii) Transient, Transient, by by direct direct axis, axis, Xd Xd 0.290.29 iii)

iii) Sub Sub Transient, Transient, by by direct direct axis, axis, Xd Xd 0.1290.129 iv)

iv) Negative Negative phase phase sequence sequence 0.20.2 v)

v) Zero Zero phase phase sequence sequence 0.090.09

11-11- Maximum Maximum efficiency efficiency under under rated rated load load with with pf=0.9 pf=0.9 98.23%98.23%

12-12- Voltage across slip ring with rated load and 120Voltage across slip ring with rated load and 120 Degree

Degree C C temperature temperature of of field field winding winding 300V300V

13-13- Field Field current current rated rated load load 1600A1600A

14-14- Field Field voltage voltage ratio ratio under under field field forcing forcing 2.5 2.5 p.u.p.u.

15-15- Voltage Voltage rise rise after after 100% 100% load load rejection rejection with with pf=0.9 pf=0.9 28%28%

16-16- Total Total weight weight of of generator generator 1300 1300 tt

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13

13 General lay out and structural details:

General lay out and structural details:

Hydro generator has umbrella- type vertical design with two guide bearing arranged in oil baths of Hydro generator has umbrella- type vertical design with two guide bearing arranged in oil baths of upper and lower bracket and thrust bearing in oil bath of lower bracket. Hydro generator shaft upper and lower bracket and thrust bearing in oil bath of lower bracket. Hydro generator shaft consists of rotor hub, thrust bearing hub and shaft extension. Hydro generator rotor gob is directly consists of rotor hub, thrust bearing hub and shaft extension. Hydro generator rotor gob is directly joint to turbine s

joint to turbine shaft.haft.

STATOR

Stator frame is form construction made of steel sheet rolled metal. It consists of horizontal shelves, Stator frame is form construction made of steel sheet rolled metal. It consists of horizontal shelves, vertical rip and sheeting. Stator frame has a ring shape and consists of four sections, which are vertical rip and sheeting. Stator frame has a ring shape and consists of four sections, which are welded at site. There are a number of apertures in stator frame for winding terminals and air coolers. welded at site. There are a number of apertures in stator frame for winding terminals and air coolers. Stator core is assembled of varnished laminations, stamped of 3432-type coiled cold –rolled Stator core is assembled of varnished laminations, stamped of 3432-type coiled cold –rolled electrical steel with 35mm thickness. Core is arranged to stacks by height, with ventilation ducts electrical steel with 35mm thickness. Core is arranged to stacks by height, with ventilation ducts between them for provision of effective stator ventilation.

between them for provision of effective stator ventilation. Stator winding is wave – bar – type.

Stator winding is wave – bar – type.

Stator winding consists of 696 Rebel bars. Stator winding consists of 696 Rebel bars.

Main insulation is thermosetting – “Monolit”- type, made of F-class materials with epoxy binding Main insulation is thermosetting – “Monolit”- type, made of F-class materials with epoxy binding agent. Fastening of winding bars is

agent. Fastening of winding bars is provided by slot wedges with use provided by slot wedges with use of flexible polyurethane gasketof flexible polyurethane gasket between the upper bar and

between the upper bar and slot wedge.slot wedge.

ROTOR

Rotor of hydro generator consists of rotor

Rotor of hydro generator consists of rotor hub, thrust bearing hub and shaft hub, thrust bearing hub and shaft – extension with planted– extension with planted upper guide bearing hub, spider, stacked rim, twenty-eight poles. Rotor

upper guide bearing hub, spider, stacked rim, twenty-eight poles. Rotor rim is assembled ofrim is assembled of segments, stamped of steel with 4mm thickness.

segments, stamped of steel with 4mm thickness. Pole cores are assembled of punched steel sheetPole cores are assembled of punched steel sheet with 2 mm thickness. This sheet

with 2 mm thickness. This sheet has insulating coating in order to has insulating coating in order to decrease the losses. They aredecrease the losses. They are pressed by steel pole end plates with pressing studs. Pole coils are made of copper band. Turn to pressed by steel pole end plates with pressing studs. Pole coils are made of copper band. Turn to turn insulation is glass type

turn insulation is glass type with epoxy binding agent (class F with epoxy binding agent (class F materials).materials). The main insulation of poleThe main insulation of pole core is glass textolite (Class F

core is glass textolite (Class F material). Poles are fastened to rotor rim material). Poles are fastened to rotor rim with T-shape tales andwith T-shape tales and counter wedges. During installation of poles on rotor rim, the pole coil should be drawn in to pole counter wedges. During installation of poles on rotor rim, the pole coil should be drawn in to pole shoe with springs.

shoe with springs.

UPPER BRACKETS

Upper brackets supports to stator. It has central part and twelve arms. Oil bath of upper guide Upper brackets supports to stator. It has central part and twelve arms. Oil bath of upper guide bearing is located in central part of bracket. Ten oil coolers and guide bearing are built into central bearing is located in central part of bracket. Ten oil coolers and guide bearing are built into central part. Upper flooring of generator is disposed on top of bracket arms. It consists of support beams part. Upper flooring of generator is disposed on top of bracket arms. It consists of support beams and steel sheets. Felt gaskets are installed between flooring sheets and support beams in order to and steel sheets. Felt gaskets are installed between flooring sheets and support beams in order to decrease the noise in machine hall. Upper hood with brush rocker is installed on central part of decrease the noise in machine hall. Upper hood with brush rocker is installed on central part of

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bracket. There are twelve support jacks on upper bracket arms supported into foundation for bracket. There are twelve support jacks on upper bracket arms supported into foundation for suppression of horizontal

suppression of horizontal displacement.displacement.

LOWER BRACKET

Lower bracket is radial – type welded construction with central part and twelve arms, which supports Lower bracket is radial – type welded construction with central part and twelve arms, which supports to foundation. Oil bath of lower guide and thrust bearing is located in central part of bracket. Twelve to foundation. Oil bath of lower guide and thrust bearing is located in central part of bracket. Twelve oil coolers are built in to it. Lower bracket is the support for unit shaft. Bracket is installed on it. There oil coolers are built in to it. Lower bracket is the support for unit shaft. Bracket is installed on it. There are twelve support jacks o

are twelve support jacks on lower bracket arms for supn lower bracket arms for suppression of radial disppression of radial displacement. lacement. Sole plates ofSole plates of lower bracket fasten to foundation by

lower bracket fasten to foundation by means of studs and anchor plates.means of studs and anchor plates.

BEARINGS

Upper and lower guide and thrust bearings are lubricated without use of separate installed oil Upper and lower guide and thrust bearings are lubricated without use of separate installed oil circulation pumps. Upper guide bearing is located in central part of upper bracket above stator and circulation pumps. Upper guide bearing is located in central part of upper bracket above stator and rotor of hydro

rotor of hydro generator.generator. Thrust bearing has rotating disk Thrust bearing has rotating disk (runner) with polished bottom surface and(runner) with polished bottom surface and twelve fixed pads on rigid

twelve fixed pads on rigid supports. Friction surface of pads is supports. Friction surface of pads is coated with linings on TEFLON basis.coated with linings on TEFLON basis. Thrust bearing pads are installed by means of flexible disk supports on bolts with spherical heads. Thrust bearing pads are installed by means of flexible disk supports on bolts with spherical heads. These bolts allow adjusting the height of supports and providing the equal load on each pad. These bolts allow adjusting the height of supports and providing the equal load on each pad. Support bolt with spherical head allow the pads to self – adjust into operation position.

Support bolt with spherical head allow the pads to self – adjust into operation position. ThrustThrust bearing runner has the insulation against shaft current.

bearing runner has the insulation against shaft current. Lower guide bearing and thrust bearing areLower guide bearing and thrust bearing are located in oil bath in central part of lower bracket under rotor. Twelve oil coolers are installed in oil located in oil bath in central part of lower bracket under rotor. Twelve oil coolers are installed in oil bath of lower guide and

bath of lower guide and thrust bearing. Cooling water circulates by U-shape tubes of thrust bearing. Cooling water circulates by U-shape tubes of these coolers.these coolers. Guide bearings consist of set of pads located around the hubs fastened on shaft. Guide bearings consist of set of pads located around the hubs fastened on shaft. Upper and guide bearing pads have the same design. Guide bearings contain twelve pads. Friction Upper and guide bearing pads have the same design. Guide bearings contain twelve pads. Friction surfaces of bearings pads are coated with Б

surfaces of bearings pads are coated with Б -83 babbit. Self adjusted pads have the insulation-83 babbit. Self adjusted pads have the insulation against the shaft current. Oil baths of bearing are covered with special seal shields, which prevent against the shaft current. Oil baths of bearing are covered with special seal shields, which prevent the penetration of oil vapor

the penetration of oil vapor and splashes into generator.and splashes into generator.

BRAKING SYSTEM

Electrical and Mechanical (auxiliary) braking is used for regular braking. When hydro generator is Electrical and Mechanical (auxiliary) braking is used for regular braking. When hydro generator is disconnected from grid, turbine wicket gate is closed and rotation speed is reduced down to 50% of disconnected from grid, turbine wicket gate is closed and rotation speed is reduced down to 50% of rated value, short-circuiting of main terminals of stator winding and current supply into rotor winding rated value, short-circuiting of main terminals of stator winding and current supply into rotor winding from brake thyristor co

from brake thyristor converter occurs. nverter occurs. When rotation speeWhen rotation speed reduced down to 10% of rated vad reduced down to 10% of rated value,lue, the mechanical breaking is automatically switched on. In case of

the mechanical breaking is automatically switched on. In case of electrical braking system failure, orelectrical braking system failure, or electrical damage of generator, the mechanical breaking is automatically switched on, when rotation electrical damage of generator, the mechanical breaking is automatically switched on, when rotation speed will become 10% of rated value. Twenty – four pneumatic brakes provide the mechanical speed will become 10% of rated value. Twenty – four pneumatic brakes provide the mechanical breaking. They are installed under rotor rim

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15

15 COOLING SYSTEM

COOLING SYSTEM

Cooling system of generator active parts is of air-type with cooling of heated air in air coolers with Cooling system of generator active parts is of air-type with cooling of heated air in air coolers with water cooling. Air circulation through generator is carried out by closed cycle inside generator pit by water cooling. Air circulation through generator is carried out by closed cycle inside generator pit by means of crowding action of rotor arms, ventilation ducts in rotor rim, centrifugal ventilators on end means of crowding action of rotor arms, ventilation ducts in rotor rim, centrifugal ventilators on end surfaces of rim and poles. Baffles are installed below and above rotor for ordering of air motion and surfaces of rim and poles. Baffles are installed below and above rotor for ordering of air motion and decrease of ventilation losses. Heated air from

decrease of ventilation losses. Heated air from stator winding end zone and stator winding end zone and ventilation ducts in statorventilation ducts in stator core is going to stator frame and cooling by passing through air coolers, which are installed on stator core is going to stator frame and cooling by passing through air coolers, which are installed on stator frame sheeting. Then it come out to generator pit and again is drawn into rotor.

frame sheeting. Then it come out to generator pit and again is drawn into rotor.

FIRE EXTINGUISHING SYSTEM

Fire extinguishing is carried out with water, which is supplied by two collectors to end parts of Fire extinguishing is carried out with water, which is supplied by two collectors to end parts of winding and spraying by 450 special nozzles.

winding and spraying by 450 special nozzles. Water flow through one nozzle is about 0.08 l/sec;Water flow through one nozzle is about 0.08 l/sec; total water flow is 34 l/sec. switching on of water supply into collectors is performed by fire total water flow is 34 l/sec. switching on of water supply into collectors is performed by fire extinguishing control unit.

extinguishing control unit. Fire extinguishing control unit provides both manual and automaticFire extinguishing control unit provides both manual and automatic switching on water supply; possibility of

switching on water supply; possibility of check of automatic water supply system. It check of automatic water supply system. It has the pressurehas the pressure gauge, which indicates the presence of water pressure in fire extinguishing pipe line and electric gauge, which indicates the presence of water pressure in fire extinguishing pipe line and electric contact pressure gauge, which indicates the presence of water pressure in fire extinguishing contact pressure gauge, which indicates the presence of water pressure in fire extinguishing collectors.

collectors. Automatic

Automatic switching switching on on water water supply supply is is carried carried out out by by pneumatic pneumatic driven driven valve. valve. Pneumatic Pneumatic valve valve isis controlled by electric signal, which is supplied by fire alarm detector(four VMX 1000 F 90 controlled by electric signal, which is supplied by fire alarm detector(four VMX 1000 F 90 temperature detectors and four IMX 1001 E type

temperature detectors and four IMX 1001 E type smoke detectors installed on wall of generator pit) ,smoke detectors installed on wall of generator pit) , or from control board.

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16

16 306 MVA GENERATOR TRANSFORMER

306 MVA GENERATOR TRANSFORMER

Generator transformer is an

Generator transformer is an oil-filled, three-phase, double-winding, delta-star group 11 connectedoil-filled, three-phase, double-winding, delta-star group 11 connected transformer:

transformer:

Key parameters of Generator Transformer are: Key parameters of Generator Transformer are:

1-1- Rating Rating 306 306 MVAMVA

2-2- Rated Rated voltage voltage of of H.V. H.V. winding winding 420 420 kVkV

3-3- Rated Rated voltage voltage of of L.V. L.V. winding winding 15.75 15.75 kVkV

4-4- Rated Rated current current in in H.V. H.V. winding winding with with tap tap changer changer in in normal normal position position 420.6 420.6 AA

5-5- Rated Rated current current in in L.V. L.V. winding winding with with operating operating cooling cooling system system 11217.1 11217.1 AA

6-6- HV-LV HV-LV impedance impedance at at nominal nominal tap tap 14.5%±10%14.5%±10%

7-7- Type Type of of cooling cooling OFWFOFWF

8-8- Permissible oil temperature rise above ambient temperaturePermissible oil temperature rise above ambient temperature (+30

(+30°°C) C) in in normal normal operation operation 4040°°C.C.

9-9- Permissible Permissible winding winding temperature temperature rise rise 5353°°C.C.

10-10- Full Full weight weight of of transformer transformer with with oil oil 284.6 284.6 tt

11-11- Oil Oil weight weight 54.47 t,54.47 t,

12-12- Volume Volume 62600 62600 ll

13-13- HV HV insulation insulation level level SI SI 1050 1050 LI LI 1300- 1300- AC AC 3838

14-14- LV LV insulation insulation level level LI LI 95 95 AC AC 3838

15-15- Core Core and and winding winding weight weight 179100 179100 KgKg

16-16- Flow Flow rate rate of of each each oil oil pump pump 2530 2530 LpmLpm

17-17- Flow Flow rate rate of of each each oil oil pump pump 2300 2300 LpmLpm

GENERAL CONSTRUCTION FEATURES

The tank cover mounts the H.V. and L.V. bushings. The 420 kV bushings HV are of special oil-SF The tank cover mounts the H.V. and L.V. bushings. The 420 kV bushings HV are of special oil-SF66

construction. Flange connection consists of two parts. One is standard transformer bushing; the construction. Flange connection consists of two parts. One is standard transformer bushing; the other is connection device from SF

other is connection device from SF66 switchgear side intended for connection with switchgear switchgear side intended for connection with switchgear

equipment. Main bushings of incomers consist of resin-impregnated base with grading layer for equipment. Main bushings of incomers consist of resin-impregnated base with grading layer for monitoring. On the 15.75 kV side the oil-filled L.V. bushings with porcelain insulation parameters monitoring. On the 15.75 kV side the oil-filled L.V. bushings with porcelain insulation parameters 24kV/12.5 kA are installed.

24kV/12.5 kA are installed.

The conservator is mounted above the tank cover on a separate support structure. The pipe The conservator is mounted above the tank cover on a separate support structure. The pipe connecting the conservator to the tank contains the Buchholtz relay. The Buchholz relay is isolated connecting the conservator to the tank contains the Buchholtz relay. The Buchholz relay is isolated from the conservator with an isolating gate valve and with an isolating butterfly valve from the from the conservator with an isolating gate valve and with an isolating butterfly valve from the transformer tank.

transformer tank. At

At variation variation of of load load and and temperature temperature of of the the transformer transformer the the oil oil level level varies varies (breathes). (breathes). In In order order toto avoid ingress of moisture with air into the transformer during “breathing”, the silica gel dryer is avoid ingress of moisture with air into the transformer during “breathing”, the silica gel dryer is installed. Additional protection of oil is achieved by provision of enclosure made of air-filled installed. Additional protection of oil is achieved by provision of enclosure made of air-filled oil-resistant nitrite rubbe

resistant nitrite rubber. The enclosure r. The enclosure is floating on the oil surface of this floating on the oil surface of the conservator followe conservator following theing the oil level. The enclosure is connected with the dryer, therefore, the air increasing in it is always dry. oil level. The enclosure is connected with the dryer, therefore, the air increasing in it is always dry. Such system prevents from direct contact of transformer oil with ambient air thus decreasing Such system prevents from direct contact of transformer oil with ambient air thus decreasing potential of oil contamination due to

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Oil level behind the enclosure in the dryer is measured by oil gauge of magnetic type. The gauge Oil level behind the enclosure in the dryer is measured by oil gauge of magnetic type. The gauge driving magnet turns following the float and by its magnetic field makes the driven magnet and driving magnet turns following the float and by its magnetic field makes the driven magnet and indicator disk with contacts turn. At decrease of level to El.65 mm the indicator reaches the “Empty” indicator disk with contacts turn. At decrease of level to El.65 mm the indicator reaches the “Empty” position and the signal “Low Level Alarm” is given. The signal will be also given if the enclosure has position and the signal “Low Level Alarm” is given. The signal will be also given if the enclosure has been torn and

been torn and fell down. fell down. Oil temperature in the Oil temperature in the transformetransformer is r is measured by an measured by an alcohol thermometeralcohol thermometer installed on the tank cover. Brass bulb thermometers with visual readings are installed in special installed on the tank cover. Brass bulb thermometers with visual readings are installed in special pockets arranged in the hot

pockets arranged in the hot spots of the cooling system.spots of the cooling system.

Pipelines from the pump sets can be closed with gate valves located below the conservator. The Pipelines from the pump sets can be closed with gate valves located below the conservator. The pipes can be cross-connected by opening the bypass. Provision is made for a valve on the tank pipes can be cross-connected by opening the bypass. Provision is made for a valve on the tank cover, plugs on the conservator and pipe inlet from the cooler for air release from the top points. Oil cover, plugs on the conservator and pipe inlet from the cooler for air release from the top points. Oil filling pipe with gate valve is connected to the

filling pipe with gate valve is connected to the conservator. The transformer windingconservator. The transformer windings have insulations have insulation levels designed for operation on the system with effective neutral grounding (networks with large levels designed for operation on the system with effective neutral grounding (networks with large ground fault currents). In this connection, the windings have “incomplete” insulation of the neutral ground fault currents). In this connection, the windings have “incomplete” insulation of the neutral and the transformer must always operate with solidly grounded neutral.

and the transformer must always operate with solidly grounded neutral.

Transformer cooling system

OFWF(Oil Forced Water Forced) cooling system comprises two water/oil coolers (one main and one OFWF(Oil Forced Water Forced) cooling system comprises two water/oil coolers (one main and one standby). Hot oil is taken from the upper part of the transformer and forced by the pump through standby). Hot oil is taken from the upper part of the transformer and forced by the pump through water/oil cooler for cooling and goes to the lower part of the transformer. Two oil pumps (pump water/oil cooler for cooling and goes to the lower part of the transformer. Two oil pumps (pump No.1, pump No.2) are mounted before the cooler on the oil inlet side The transformer cooling No.1, pump No.2) are mounted before the cooler on the oil inlet side The transformer cooling system is of two loops configuration. Water from ejectors AT el-584 m passes through automatic system is of two loops configuration. Water from ejectors AT el-584 m passes through automatic filters to the water-to-water coolers of the primary loop where it cools the clean water of the second filters to the water-to-water coolers of the primary loop where it cools the clean water of the second loop and thereafter it drains to down stream. Water of the secondary loop is fed from the clean water loop and thereafter it drains to down stream. Water of the secondary loop is fed from the clean water system. Clean water is conveyed to the

system. Clean water is conveyed to the make up tank.make up tank.

Water of the secondary loop is handled by two pumps located at El.600.00 m in bus duct galleries. Water of the secondary loop is handled by two pumps located at El.600.00 m in bus duct galleries. Normally one pump operates; the other pump goes into operation automatically as stand by. Water Normally one pump operates; the other pump goes into operation automatically as stand by. Water flows in the primary and secondary loops are controlled by the flow meter with remote indication. flows in the primary and secondary loops are controlled by the flow meter with remote indication. Water temperature of the secondary loop is monitored by the electro contact thermometer. Design Water temperature of the secondary loop is monitored by the electro contact thermometer. Design water flow in the primary loop is 250m

water flow in the primary loop is 250m33/hr. The rate of water flow in the secondary loop is 135m/hr. The rate of water flow in the secondary loop is 135m33/hr./hr. Check temperature of water at the heat

Check temperature of water at the heat exchanger outlet: raw water – maximum 30exchanger outlet: raw water – maximum 30°°C, clean water–C, clean water–

maximum 35

maximum 35°°C. There are two oil coolers in the system; one of them is standby. The oil coolerC. There are two oil coolers in the system; one of them is standby. The oil cooler

should reduce oil temperature by 10-15

should reduce oil temperature by 10-15°°C and maintain temperature of the upper oil strata at 50-C and maintain temperature of the upper oil strata at

50-55 55°°C.C.