STUDY OF DIFFERENT COMPONENTS &

PRODUCTION PROCEDURE OF

POWERHOUSE AT BAIRA SIUL HYDROELECTRIC

POWER STATION, SURANGANI,N.H.P.C. LIMITED

SUMMER TRAINING REPORT

BAIRA SIUL H.E. POWER STATION(3 x 60 MW)

N.H.P.C. LIMITED

Submitted by:

SUMMER TRAINING REPORT

BAIRA SIUL H.E. POWER STATION(3 x 60 MW)

N.H.P.C. LIMITED

This is a dedication to the brilliance of human effort…

To create, through human ingenuity, diligence and modern technologies…

A source of energy that is clean, cheap and inexhaustible…

For the benefit of millions of people all over India,

This energy is the awesome power of water -

Which is one of nature’s greatest gifts for the welfare of mankind,

And when the power of nature is harnessed it helps create prosperity

In the form of electricity and water

This noble objective can only be achieved through partnership…

Of Nature and Man…

ACKNOWLEDGEMENT

I wish to thank Sh. Himanshu Shekhar, Chief Engineer(In

charge), Baira Siul H.E. Power Station, N.H.P.C. Ltd., for providing me

an opportunity to undergo my summer training in such a prestigious

organization. I also express my sincere thanks to all my guides &

staff of this power station for providing me their valuable support

and guidance throughout my training.

Trainee,

RESERVOIR

DISC VALVE HOUSE

PENSTOCK

H

R

T

SIUL WEIR

BAIRA RIVER JOINER NALLAH

DROP SHAFT

SPIRAL CASING/ GUIDE VANES

RUNNER

BHALEDH WEIR

BHALEDH FEEDER TUNNEL

GENERATOR

60 MW,

EXCITATION

TRANSFORMER11 KV / 220 KV

SWITCHYARD

PONG FEEDER - I & II

DRAFT TUBE

TAIL RACE

SIUL RIVER

FLOW CHART OF BAIRA SIUL POWER STATION

Selection of site: Preliminary investigations regarding catchments area, average rainfall, ground gradient, geology of foundation, availability of raw material for constructions work are required. The important factors governing selection are as follows: -

1. LOCATION OF DAM: From the cost point of view, the smaller the length of dam, the lower will be the cost of construction. Therefore, the site has to be where the river valley has a neck formation. In order to have capacity, a valley, which has a large storage capacity on the upstream of the proposed dam site, is probably the best. It is desirable to locate a dam after the confluence of two rivers so that advantage of both the valleys to provide larger storage capacity is available.

2.CHOICE OF DAM: The most important consideration in the choice of the dam is safety and economy. Failure of dam may result in substantial loss of life

and property. The proposed dam must satisfy the test of stability for : (a)shock loads which may be due to earthquakes or sudden changes in reservoir levels and (b)usually high floods. The dam should, as far as possible be close to the turbines and should have the shortest length of conduit.

3.QUANTITY OF WATER AVAILABLE: This can be estimated on the basis of measurement of stream flow over as long a period as possible. Storage of water is necessary for maintaining continuity of power supply throughout the year. Sufficient storage of water should be available since rainfall is not uniform throughout the year and from one year to another.

4.ACCESSIBILITY OF SITE: The site should be accessible from the viewpoint of transportations of man and material, so that the overall cost for construction, of the project is kept low.

5.DISTANCE FROM THE LOAD CENTRE: The distance should be as small as possible so that the cost of transmission of power is minimum. Availability of construction material and general know-how should also be considered in site selection.

.

Classification of Hydro plants:

The Hydro power plants can be classified in terms of location and topographical features, the presence or absence of storage, the range of operating head etc.

Classification based on plant capacity :

(i) Micro hydel plant :less than 5 MW(ii) Medium capacity plant :5-100 MW(iii) High capacity plant :101 MW-1000 MW(iv) Super capacity plant :Above 1000 MW

Classification based on construction:

Run-off-river plant without pondage: A run-off-river plant is one in which a dam is constructed across a river and the low head thereby created is used to generate power .It is typically a low-head plant and is generally provided with an overflow weir, the power station being an integral part of the dam structure. These plants thus use water as and when it is available. The firm capacity of such plants is very low if the supply of water is not uniform throughout the year. Run-off-river with pondage: The pondage increases the usefulness of this type of plant. The main requirement for the plant is that the tailrace should be such that floods do not raise the tailrace water level; otherwise the operation will be affected adversely. With pondage it is possible to meet hour-to-hour fluctuations of load throughout a week or longer periods depending upon its size.

Valley dam plant: The main features of a valley dam plant are a dam in the river, which creates a storage reservoir that develops the necessary head required for the turbines. The plant can be used efficiently throughout the year as it has large storage capacity. Its firm capacity is relatively high. The following are the main components of a valley dam plant: (a) The dam with its appurtenant structure like spillways etc. (b) The intake with gate , stop logs and racks etc. © The penstocks (d) The power plant with its components. Diversion canal plant: The characteristic of this plant is that the waters of the river are diverted away from the main channel through a diversion canal, known as power canal. These plants are usually low-head or medium-head plants. They do not have any storage reservoir. The powerhouse requirements of pondage are met through a pool called fore bay, which is located just before the power plant. The main components of a diversion canal plant are:(a) Diversion Weir(b) Diversion Canal Intake with its ancillary works©Bridges or culverts etc. of the diversion canal; and

(d) Fore bay and its appurtenance

. High head diversion plant: The main feature of this plant is the development of high head resulting from the diversion of water. The main point of difference between high head and low head diversion plants is the elaborate conveyance system for the high head plants. The main components of this type of plant are as follows:(a) Diversion Weir (b) The Canal tunnel intake©The head-race(d)Surge tank(e) Penstock(f) Tail-race

Classification Based on operation:

Base load plant: These plants operate on the base portion of the load curve of the power system if they are of large capacity. As these loads operate throughout the year at approximately full capacity, the load factor of such plants is high. Peak load plant: These plants supply power to the system corresponding to the load at the top portion of the load curve. Run-off river plants with pondage can be used for such purposes. The load factor of such plants is relatively low as they operate only for a short period of the total operating time.

Pumped storage plant: Pumped storage plants are a special type of power plants which work as ordinary hydro power plant for part of the time and when such plants are not producing power they can be used as pumping stations which pump water from tail race to head race. During this time, these plants utilize power available from the grid to run the pumping set. Thus, pumped storage plants can operate only if these plants are interconnected in a large grid.

Classification based on Head:

Another way of classifying hydro-stations is based on the hydraulic heads available:

Low head plants with head less than 70 mMedium head plant: Between 70 m-300 mHigh head plant: Above 300 m

Layout of a Hydro station:

The main components of a hydro station are as follows:

(i) Reservoir: The main function of the reservoir is to store water during rainy season and use it during dry season.

(ii) Dam: A dam is a barrier constructed in the normal path of the river. A dam serves two functions:(1) It develops a reservoir which has a capacity to store water; and (2) It helps to increase the working head of the power plant. A dam can have a moderate head and a large storage capacity or a high head with small storage capacity.

(iii) Spillways: A spillway acts as a safety valve for a dam. The capacity of spillway should be such that it discharges major floods without damage to the dam but at the same time it keeps the reservoir level below the predetermined maximum level.

(iv) Intake: In a hydroelectric plant, the intake allows the water to flow into the conduit or penstock under controlled conditions. Thrash racks or screens are used to prevent debris passing into the water passage. Debris is allowed to move, will damage the turbine blades or choke the nozzle of the impulse turbine.

(v) Forebay: A forebay is a large body of water just above the intake and is used as a regulating reservoir. The river water is distributed to various penstocks leading to the turbines through the forebay. A forebay is a naturally provided storage, which is able to absorb the flow variations due to variation in the system loads.

(vi) Penstock: The pipe between surge tank and turbine is known as penstock. These are made of steel through reinforced concrete. Penstocks supply water from the forebay to the turbine. If the distance between the forebay and turbine is short separate penstocks are used for each turbine. Penstocks are provided with head gates at the inlet, which can be closed during repair of the penstock. Normally for high head plants, the permissible velocity of water through the penstock is 8 m/s, for medium head it is 4 m/s and for low head it is 2 m/s.

(vii) Surge tank: A surge tank or a surge tower is a structure introduced in the system in between the dam and the power house (preferably on high ground, to reduce the height of the tower) to provide better regulation of flow of water when the load on the system fluctuates. The surge tanks are associated with high head schemes where water is taken to the powerhouse through the tunnels. However if powerhouse is located close to the head works surge tanks are not required. When the load on the system decreases turbine gates close partly, increasing the water level in the surge tank. This produces a retarding head and the velocity of water in the penstock decreases, which is a desirable feature. Slowly the level of water in the surge tank starts falling and fluctuates

up and down till its motion is damped out by friction. On the other hand, when the load on the system increases, the governor opens the turbine gates, additional the surge tank supplies water, the water level of the tank lowers and an accelerating head is produced which increases the flow of water in the penstock. When the discharge of water matches the with the turbine demand, the level of water in the surge tank stops lowering. The surge tank thus helps in stabilizing the velocity and pressure in penstock and reduces the water hammer effect.

(viii) Prime mover: The turbine acts as a prime mover coupled to the hydro-generator. The water flowing through the turbine blades rotate s the turbine and hence in turn rotate the generator. Mainly there are four types of turbines:

(i) Francis Turbine, patented by Francis in 1849(ii) Pelton Turbine, patented by Pelton in 1889(iii) Propeller and Kaplan Turbine, patented by Kaplan in 1913(iv) Deriaz Turbine, patented by Deriaz in 1945

(ix) Powerhouse: Apower house consists of two section, the substructure and super structure. The substructure supports the hydraulic and electric equipment and the super structure houses and protects these equipments from weather. The substructure consists mainly of the foundation of building, the draft tubes, scroll cases and setting of the turbines when they are of the reaction type. The super structure consists of the main building above the generator floor, housing the generator and the power equipment including switchgears. The main transformer for stepping up the voltage is normally located outside the building. the high voltage switchyard is also outdoor.

(x) Draft tube: The draft tubes are either straight, conical draft tubes with a circular section or they are elbow shaped tubes with gradually increasing area, the shape changing from circular at the runner section to rectangular at the outlet section. Draft tubes are used for reaction turbines i.e. For Francis and Kaplan Turbines and serve mainly two functions: (i) they achieve the recovery of velocity head at runner outlet which otherwise would have gone waste as an exit loss. (ii) It permits the setting of the runner of the turbine wheel at a level above that of the water in the tailrace under high water and flood conditions without losing the advantage of the elevation difference. The height of the draft tube is decided by the need to avoid cavitations. Cavitation occurs is harmful as it causes pitting of the turbine runner flowing water when a cavity or void filled with air and water vapor is formed.

NHPC-A PROFILE

A land of continental dimensions, blessed by the monsoons, the snow capped Himalayas and rich river valleys; India is a veritable fountainhead of Hydropower. India has an identified Hydropower potential estimated at 84044 MW at 60% load factor. Bulk of this potential still remains to be tapped. In terms of potential India ranks sixth in the world at 600 Billion units annually and is equivalent to 148700 MW at today average load factor-seven times the present the Hydro capacity installed. National Hydroelectric Power Corporation was set up in 1975, as a Private Limited Company with an authorized capital of Rs. 200 Crores .It became a Public Limited Company in 1986. In its existence of over twenty-five years NHPC has become the premier organization in India, responsible for harnessing vast Hydro-potential in the country to improve power scenario. As on date, it has seven generating stations housing 25 generating units, having combined installed capacity of 2175 MW.Individual unit capacity, ranging from 20-180 MW are under operation. Projects of total capacity of 1770 MW are under construction. Corporation is also investigating 10 projects of total capacity of 17789 MW.It is having ambitious plans to become 10000 MW plus Hydro-power generating Company by year 2012.

Case Study Of Baira-Siul Hydroelectric Project

INTRODUCTION: Baira Siul power station was the first project of National Hydroelectric Power Corporation to go on stream. It is situated in Chamba district (Surangani) of Himachal Pradesh.The Project was commissioned in 1981-82 at a cost of Rs.153 Crores, and went into commercial production on April 1, 1982. Although its first unit started working from Feb 1980.It supplies power to the Northern grid at Talwara through 96 km.long, 220KV double circuit transmission line. From here it is channelised to Delhi, Punjab, Haryana and Himachal Pradesh. Topography of the terrain is very steep and rock is geologically very weak and unstable. Consequently there are massive landslides on access roads both during summer and winter rain. Project area is highly seismic and prone to frequent earth shocks due to constraints of steep hillside and narrow valley. There I s extreme paucity of suitable land for construction of infrastructures. It envisages utilization of combined inflow of three tributaries of Ravi river i.e. Baira, Siul, Bhaled for generation of power on run of the river basis. Years ago, what is now the Baira-Siul Power Project, used to be a fierce dense jungle clinging tenaciously to the mountain walls. The initial developmental work required 165 Km. of macadamized road to carry supplies and heavy equipment, besides bridges. The target of annual power generation of this project is approx. 750 MU. Today it is generating (60 X 3) 180 MW of power lightning the dreams of people and marching ahead for a more prosperous and well-lit India.

METHODOLOGY OF PRODUCTION:

Introduction: The water of Ravi River through its different tributaries provides the requisite water for functioning of the Baira-Siul Hydroelectric Project. The entire sequence of methodology of production is as follows:

1. The water of Bhaled River is taken to Baira dam through a feeder tunnel from where both the Baira and Bhaled water flow towards the Head Race Tunnel.

2. Before reaching the Disc Valve House Siul River water is added to the water of both the rivers, through a drop shaft. Whence the combined water of all the three tributaries reach Disc Valve House where it is trifurcated.

3. There is a surge shaft near the Disc Valve House to accommodate the variation of water due to change in loads. It has a diameter of 4.75 m in the upper half with sandwiched steel liner and reinforced concrete lining.

4. Three headers take off from the surge shaft and lead to Disc Valve House at the outlet portal of HRT.

5. The water coming out of the Disc Valve House is equally distributed into the three penstocks, which enters into the spiral casing of the three Hydro turbines.

6. The stay and guide vanes properly guide the water, in order to minimize the losses, onto the runner. The water enters the runner from the guide vanes towards the center in radial direction and discharges out of the runner axially.

7. The difference of pressure between the guide vanes and the runner called the reaction pressure is responsible for the motion of the runner. The turbine shaft bolted with the runner rotates with the same angular velocity as the runner.

8. The water after completion of its job is discharged to the Tail Race through draft tube, which is of gradually enlarging section. From here, the water goes into the Tail Race Tunnel and then into the river. The free end of draft tube is submerged deep in the water, thus making the entire water passage, right from the Head Race up to the Tail Race totally enclosed.

9. The turbine shaft is flange coupled with the rotor shaft below the lower bracket. Thrust Bearing is at the top followed by Upper Guide Bearing (UGB) and Lower Guide Bearing (LGB) in sequence in the lower bracket. Balancing weights and brake pads are also positioned there.

10. The Hydro generators coupled to the turbine (prime mover), converts the mechanical energy of water to electrical energy.

11. The CT’s taps the electric energy generated and PT’s for use in the protective equipments and relays.

12. The generated 11 KV is taken to the transformer gallery. A set of three 3-phase transformers is used to step down the voltage from 11 KV to 0.4 KV and is used to provide power to the auxiliaries connected to each machine.

13. Bus Bars of 11 KV are also taken to three 1-phase transformers of 25 MVA for each machine to step up voltage from 11 KV to 220 KV from where it is taken to the switchyard and is then sent to the Power Grid for further distribution.

DAM AND DISC VALVE HOUSE

Baira Siul Hydroelectric Project uses the water of Baira, Bhaled and Siul rivers. The Baira dam rising 51 m above the riverbed sits astride the Baira River. It diverts the water of the Baira and Bhaled rivers through the intake structures to the main Head Race Tunnel. BAIRA DAM: Type : Earth Core Rock Filled Height above riverbed : 51 m Height above foundation : 85 m Top of dam elevation : 1125 m Approx. length at top : 160 m Width at top : 7.5 m Approx width at river : 200 m

BHALED WEIR: Length : 21 m Crest elevation : 1180 m SIUL WEIR: Length :30.60 m Crest elevation : 1129.5 m Gates : 4 nos. each 6.1 m wide The water of Bhaled River is brought to main Head Race Tunnel by Bhaled feeder tunnel. This aspect of Baira Siul Project makes it quite unique. BHALED FEEDER TUNNEL: Length : 7.83 km Shape : D Type Size : 2.13 m X 2.13 m Discharge : 20 cumecs The water goes to the Head Race Tunnel through spillway, which has two radial gates and discharges 2380 cubic mts. of water every second at peak capacity.

SPILLWAY : Width at crest : 28 m Gates : 2 nos. radial Type Size : 12 m X 12 m Crest elevation : 1110.15 m Maximum outflow : 2380 cumecs Length of Chute : 103.14 m

The length of the Head Race Tunnel is about 7.63 kms. The water flows through HRT to the Disc Valve House.Enroute, a concrete lined drop shaft

(100 m deep and of 3 m dia.) joins up, carrying the turbulent waters of the Siul River.

HEAD RACE TUNNEL: Length : 7.63 km Shape : Horseshoe Type Size : 5 X 4.08 m Discharge : 85 cumecs There are three 2600 mm dia. Disc valves installed in the three penstocks coming out from the trifurcation point. The centerline of the Disc Valve is at EL 1016.85. To cater to the elongation and contraction of mild steel pipes due to temperature and pressure variation, inside the Valve House area. Only a gap of 20 mm is provided in the joint installed on the upstream side of the Disc Valve House. This assembly is basically a dismantling joint. The different Types of Valves installed in the Disc Valve House are as Follows:

(1) BY PASS VALVE: Two 200 mm dia. wheel valve are installed on top of the disc valve by passing it. This is required for initial filling of the penstock pipe up to spherical valve so that there is no pressure difference between two sides when disc valve opens. (2) AIR RELEASE VALVE:

A 200 mm dia. two way spring loaded air release valve is installed on the downstream side of Disc Valve House for releasing and letting in the air from and to the penstock between spherical valve and disc valve during water filling and draining respectively. This valve closes by itself as soon as the penstock is full. (3) VACUUM BREAKING VALVE:

There are two vacuum breaking one-way valves, installed on the downstream side of the disc valve to let the air into the penstock. These valves are spring loaded. Sudden requirement of large quantity of air in penstock during closing of disc valve operates them for a very short period. Normally airflow from and into the penstock is regulated by release valve.

(4) DISC VALVE: This is horizontally pivoted 2600 mm dia. butterfly valve installed at the outlet of the hill rock. It consists of fabricated steel framework with machined steel rims at 11-degree angle to accommodate movement with seals in position. There are flow guides on either side of the disc to guide the flow of water above and below the disc. Two rubber seals are installed in the outer body of the valve on both the sides of the disc for obtaining sealing effect. The upstream side seal, which is of inflated type and hollow, is inflated by air pressure of 13 kg. /cm.cm.This is used only when working seal is to be replaced. Air at a pressure of 18 kg/cm.cm is fed to the repair seal to obtain the sealing effect by operating the electromagnetic relay either

electrically or mechanically. The working seal installed on the D/S side is made of solid rubber and will provide sealing effect at the rim of the disc when valve is in close position. The pivots consist of bronze bush with water sealing arrangement obtained through the rubber cup seals and rings.

POWER STATION

The Baira Siul Power House of NHPC has 5 floors: EL 831.30,EL 834.00,EL 838.80, EL 845.65 and EL 850.00 floor. The details of the position of the various floors is as under: 1.EL 831.30 FLOOR (one for each unit):

a) Spherical valve of 1800 mm diameter.b) By pass valve c) Sealing valve d) Oil leakage unit for spherical valvese) Penstock drains of 200 mm diameterf) Draft tube in two partsg) Dewatering and drainage sumps and pumps (common for all units)

2.EL 834.00 FLOOR (one for each unit):

A.TURBINE SIDE

(a) Francis turbines with 375 rpm, 60 MW, clockwise rotation inward flows.(b) Control mechanism of spherical valve© Centralized grease lubrication system for turbine and spherical valves(d) Top cover drain pump(e) Draft tube drain valve(f) O.L.U. for turbine(g) Control mechanism of thermo signalizing devices and T.G.B.(h) Pressure stats. for monitoring the pressure variation in penstock(i) Starters for drainage and dewatering pump

B. PUMP ROOM

(a)Cooling water pumps with their starters(b)Thrust bearing pumps(c) Thrust bearing oil cooling units and oil tanks(d)Cooling water piping(e)Fire protection pumps with the mechanical starters

3. EL 838.80 FLOOR:

(a) Thrust bearing oil filters (4 for each unit)(b)Electro contact manometers on thrust bearing oil-pipe-lines(c) Six 11 KV PANELS(d)400 V Unit Aux. Boards (one for each unit)(e) 400 V Station Service Board in 2 parts(f) Lighting distribution Board(g)3 pressure filters for shaft sealing of turbines(h)HP compressor units for turbine and spherical valve Opus

(i) L.P. compressor units for brake air and station service air supply(j) CO2 fire protection banks for generators.(k) Field discharge resistance units(l) Bus-ducts containing CT’s and PT’s(m) Neutral grounding transformers(n)Generator barrel containing 60 MW-11 KV star connected 3-phase AC

generator, water flow air coolers, L.G.B and U.G.B, Lower bracket with brake and jack pads and shaft coupling

(o) Spherical valve OPU and its starters(p)Master control switch

4.EL 845.65 FLOOR: A.MACHINE ROOM (one for each unit):

(a)Unit control board(b)Generator field rheostat(c) Automatic voltage regulator(d)Mech. and Elect. Cabinets of Governor (e)Turbine OPU and Pressure vessel with starters(f) Thrust bearing (g)Main exciter(h)Pilot exciter(i) Permanent Magnet Generator(j) Silencer(k)Brake air control panel(l) Thermo signalizing devices for LGB, UGB, TB and stator coolers(m) Workshop in service bay

B.TRANSFORMER DECK

(a)10 nos. 25 MVA, 11/220 KV 1-phase transformers(b)Station service transformers(c) Unit auxiliary transformers(d)Emulsifier system around SSTs and UATs (e)Air conditioning plants with its compressors

5.EL 850.00 FLOOR:

(a)Control desk for regulation of machines(b)Control panels containing protection relays and measurement meters(c) Synchronizing panels (d)Battery chargers and DC distribution panels(e)220 V DC station battery bank(f) PLCC equipment with its 48 V battery bank and chargers(g)3 fresh air blowers

DESCRIPTION OF VARIOUS PARTS

(1) SPHERICAL VALVE: To provide additional protection to the machine against the over speed during its tripping and sudden load rejection and to avoid frequent dewatering of the penstock at the time of minor maintenance of the turbine, a spherical valve of 1800 mm diameter is used for each unit in between the disc valve and the turbine. The body of spherical valve is in two halves bolted to each other with high tensile steel bolts. Recesses are provided in the body on either side to accommodate the bearings of tunions of rotor. The rotor of the spherical valve has two tunions welded on either side for pivoting it .The rotor has pipe with a diameter of 1800 mm for the flow of water when spherical valve is open. The valve installed on one side of rotor provides sealing effect called working seal. The movement of this valve is obtained by water pressure exerted in it. This water under pressure enters below valve through space between rotor and it. The metal-to-metal contact between surface of valve and stainless steel ring installed in the body constitute working seal. The repair seal on the upstream side of spherical valve is also metal-to-metal contact. Sealing is obtained by moving steel ring in the valve through 12 bolts on U/S joint of spherical valve.

These spherical valves are controlled through two servomotors with 920 mm stroke. These servomotors are installed on extended tunions of the rotor through levers .Due to the movement of the rotor by 90 degree, the valve opens or closes .

Control of Spherical Valve:

Three slide valves are used for the regulation of oil movement for the operation of by pass valve, seal valve and Main Slide valve respectively, in sequence, during the opening cycle of the spherical valve. The movement of the Main Slide valve causes flow of oil in the servomotors for opening of the spherical valve. Similarly during closing cycle, Seal valve, Main Slide valve for servomotors and the By Pass valve operate in sequence through above slide valves.

(2) BY PASS VALVE:

In order to equalize the pressure on both sides of the spherical valve, before its operation, a hydraulically

operated By Pass valve of 200 mm diameter is installed over the Spherical valve. When open, it feeds water from penstock via the Spherical valve body to the spiral casing.

(3) SEALING VALVE:

Similar to By Pass valve another valve of dia 200 mm is installed on the extended tunion of the rotor. This Valve is known as the Sealing valve.

(4) OIL LEAKAGE UNIT OF SPHERICAL VALVE:

The Oil Leakage Unit of the spherical valve installed near it is intended for collection of oil leakages from servomotor cup seals and returns oil from slide valves to control the cabinet of the Spherical valve. Thus oil collected in the tank of this unit is periodically pumped back to the sump tank of the OPU of the spherical valve. Over the OLU tank a fractional HP pump and star connected 3-phase motor are installed for pumping purposes. Level relay is also used for the automatic regulation of the pump.

SPECIFICATION:

Induction Motor:

Power :0. 55 KWSpeed :1400 rpmVoltage :415 VCurrent :1.5 APhase :3Frequency :50 HzInsulation: Class BType :AM80K4

(5) PENSTOCK DRAIN:

A Wheel valve of 200 mm diameter is installed on the last piece of penstock prior to 2.75/1.8 reducer. This high pressure Wheel valve is not to be operated when penstock is full. This valve is operated for drainage of balance water left in the horizontal section of the penstock.

(6) DRAFT TUBE AND DRAFT TUBE PIPES:

To facilitate the dismantling of runner, the upper portion of draft tube is in the form of two bolted conical pipes. These are named as Upper cone and Lower cone. The upper cone is bolted to lower ring of the turbine and the bottom cone to the embedded

portion of draft tube, with an adjusting ring in two parts. There are two manholes in the lower cone to facilitate inspection of runner and draft tube.

(7) DRAINAGE AND DEWATERING PUMPS:

There are three three-stage 35 HP turbine pumps installed on the 4 X 3 m dewatering sump having a depth of 6 m. The water from the draft tube of all the three units is fed to dewatering sump through a gallery at EL 826.00.Water from drainage sump is also fed to it through a 100 mm diameter Wheel valve installed in between the two sumps. Discharge from dewatering sump is thrown to tail race through a 250 mm dia. pipe. The dewatering of the penstocks between the Disc valve and the Spherical valve can also be achieved by operating the draft tube drain valve. Similarly 2 two-stage 10 HP vertical turbine pumps are installed on the 3 X 3 X 6 m drainage sump. The discharge of these pumps is also fed to the tailrace. The drainage sump caters for the general leakages in the Power House as well as the discharge from the drainage gallery at EL 831.30,water from P.R.V. sump, top cover drain and various leakages from turbine etc. The starters of these pumps is set in such a fashion that any of the two pumps will start automatically as soon as the water in the sump rises to a preset level (828 m). The selector switch has three positions main, off and stand-by. The stand-by pump has the level of 829.5 m.

(8) 60 MW FRANCIS TURBINE:

SPECIFICATIONS:

Type : Francis Diameter of runner : 2800 mm Speed : 375 rpm Runaway speed : 620 rpm

NET HEADS: Max. Head : 284 m Design Head : 260 m Min. Head : 251 m Rated output at Design Head : 63 MW For rated output the discharge through the turbine : 29 m-m-m/s Direction of rotation : Clockwise Max. axial load transferred on Generator thrust bearing from the turbine : 259 T Pitch circle dia. of G.vanes : 3300 mm

No. of guide vanes : 24 Height of guide app. : 286 mm Speed rise of the set at 100% : 30%

Pressure rise : 1.20 HmaxDia. of PRV : 1600 mmType of governor : Electro-HydraulicDia. of sph. valve : 1800 mmTotal wt. of turbine, sph valve

and their auxiliaries : 299 T

The different important parts of the turbine are:

A. SPIRAL CASING:

The spiral casing of the turbine is in two parts bolted to each other .The bottom half of the spiral casing is embedded .For A 40 mm thick mild steel plate is used for the construction of the spiral casing. Holes of suitable diameter are provided in spiral casing for the installation of.

a. Ejector mechanism for top cover drainage.b. Five holes at different elevations are for measurement of

pressure.c. Elliptical manhole for inspection. Stay ring of the turbine is on the internal part of the spiral

casing. A compensator joint has been installed in between spiral casing of turbine and spherical valve to accommodate the movement of the spherical valve, during operation, when pressure variations take place.

B. GUIDE APPARATUS:

The Guide apparatus consists of 24 guide vanes, top cover and lower ring. Guide vanes are made up of casted stainless steel. The surface of the top cover and lower ring in contact with the guide vanes are lined with stainless steel to provide longer life. The top and bottom journals of guide vanes are held in position by top bush housing and lower bush housing respectively. Individual guide vane is connected to the regulating ring of the guide apparatus through the link lever mechanism. Each guide vane can rotate about its pivot center, which is connected to the regulating ring of the guide apparatus through the link lever mechanism. The stroke of the servomotor governing the movement of the guide vane is 1300 mm. The height of guide vanes opening is 286 mm. The top and bottom clearance between guide vanes and lining is of the order of 0.1-0.3 mm to allow their movement. To avoid damage to guide vanes in case of any obstruction during their movement a shear pin is installed on the lever and its

strap. The percentage guide vane opening for the full load is approx. 65%.

C. TURBINE SEALING:

The turbine shaft sealing serves to prevent the water from below to flood the top covers. The face type sealing has 2 rubber rings as sealing elements. These rings are mounted on the body of the sealing in 2 parts and pressed against the stainless steel cylinder mounted on the flange of the shaft. Body of sealing is mounted on a base plate on 4 parts and bolted to top cover. Clean water at 1-1.5 kg/cm-cm is fed through radial hole in the body between these two rubber rings against cylinder. The dirty water is stopped from coming up by higher pressure of clean water. This difference should be 0.5-1 kg/cm-cm .The clear water also serves as cooling fluid and lubricator of rubber rings. A rubber ring is also fixed on the shaft flange, just below the base plate, which presses against the taper surface of top cover when machine is jacked. This interference provides sealing during the maintenance of turbine sealing.

D. GUIDE BEARING:

It is self lubricating type having 8 Babbitt lined segments. These segments are arranged against outer surface of bearing belt of shaft. These segments rest on a ring fixed to the bearing body and are kept pivoted against spherical end studs. Under stationary conditions segments are kept immersed in oil up to centerline of pivoting studs. When machine rotates, oil is sucked from the lower tank and after lubricating the surface goes back to lower tank through holes provided in outer body of bearing tank. Level relay installed in the outer tank regulates the min. and max. Level of oil.

E. TURBINE SHAFT AND RUNNER:

The turbine shaft with 650 mm with external dia. forged from high quality carbon steel. It is hollow with internal dia. of 400 mm. It has flanges at both ends. Upper flange is connected to flange of generator shaft with 16 fitted bolts and the lower flange is connected to runner with 12 fitted bolts and 4 free bolts. Turbine shaft has a bearing belt suiting to the height of guide bearing. Runner has 19 blades and is cast-welded construction. The nominal diameter of runner is 2800 mm.It is made of stainless steel to minimize the cavitations .Moving rings of lower and upper labyrinths are bolted to runner are made of stainless steel plates. Runner cone is fabricated from carbon steel plates and is bolted to runner.

(9) CENTRALIZED GREASE LUBRICATING UNIT (CGLU) :

C.G.L.U has one high-pressure pump with its fractional Horse Power motor, grease tank and two sets of feeders of which only one acts at a particular time. This unit serves both turbine and spherical valves. Once it is switched on it feeds grease to all the points .The backpressure switches off the plant automatically. The unit serves for lubrication of upper, middle and lower bearing of guide apparatus and bearings of spherical valves. Just after the lubrication unit, filters are installed on the lines, which filter the grease before feeding to main line. Feeders have been used to distribute the required amount of grease to different lubricating points.

SPECIFICATIONS:Induction Motor (C.G.L.U)

Type : BDA4Power :0.75 KWSpeed : 1450 rpmPhase : 3Frequency : 50 HzVoltage :415 VCurrent : 2.1 A (star)Bearings : 6204ZLubrication : Lithium 2

(10) OIL LEAKAGE UNIT FOR TURBINE:

The OLU is intended for collection of oil leakage from the servomotor cup seals, for drainage of oil from the servomotor guide case and oil pipelines and periodically pump the oil thus collected back to sump tank of oil pressure unit. It also works as pump for filling and draining the oil to/from TGB bank. The OLU consists of a tank and mounted on it is a pump and electric motor. In the tank a level relay is mounted for automatic control of pump.

(11) THERMO SIGNALIZING DEVICES: Gas filled temperature detection device, installed in 2 parts of TGB, are to measure temperature and are very sensitive and reliable. Temperature of pad is reflected in an indicator while the other end has a metallic tube for installation in the pad for sensing purposes. Two sets of electric contacts in the indicator are connected to alarm and trip circuits respectively for the protection of the gas-filled tube; it is covered with a metallic coil.

(12) THRUST BEARING OIL CIRCULATION AND COOLER UNITS:

I.WATER CIRCUITS: There is a ring formation around the three oil cooler units installed for cooling the oil being circulated in the thrust bearing of the machine. The ring consists of 4 valves. At any time only two valves are open as per the requirement. Discharge from the ring is connected to the discharge header of the machine in the same floor. This ring formation facilitates the back washing of the thrust bearing oil coolers. Individual cooler is fed from the ring through valves. There is a water flow relay installed in the discharge header of this coolers.2 coolers work when m/c is in operation.

II. OIL CIRCUITS : An oil tank (8 m X 3 m X 3 m). is installed at EL 836 on a cantilever deck on EL 834 Floor. This tank caters for the circulation of oil in the thrust bearing of the m/c. There are 2 37 KW pumps, which circulate the oil from this tank to the thrust bearing of the m/c at EL 845 Floor through oil coolers at EL 834 Floor, and oil filters installed at EL 838 Floor.Approx. 15000 liters of oil is filled in thrust bearing oil-circulating system.

(13) THRUST BEARING OIL FILTERS:

There are 4 filters installed on the pipeline with 100 mm dia. feeding cool oil from thrust bearing oil coolers to thrust bearing of m/c for each unit .On either side of each filter, there are wheel valves. At a time only 3 filters will be in operation and one filter is kept in spare.

(14) HIGH PRESSURE COMPRESSORS (HP COMPRESSOR):

There are two HP Compressors installed with their allied equipment on EL 838.80 Floor beyond unit-III adjacent to the pressure filters. The capacity of each of these two compressors is approx. 2000litres/min. Its working pressure is 42 kg/cm-cm. Output from these compressors is fed to the common air receiver through inline oil and water seperator. Any one of the two compressors can be set to work on auto and other on reserve. As soon the pressure in air receiver falls to 40 kg/cm-cm. The compressor starts automatically and stops when pressure rises to 42 kg/cm-cm. The reserve compressor works when pressure falls to 39 kg/cm-cm. Both the compressors stop automatically at 42 kg/cm-cm. If the pressure releases do not work at 42 kg/cm-cm, at 44 kg/cm-cm air starts leaking through safety valves installed on air receiver.

SPECIFICATIONS:Induction Motor :

M/c No. : BDH54Power : 11 KWSpeed : 1440 rpmPhase : 3Frequency : 50 HzCurrent : 22 AVoltage : 440 V

Compressor :Size : 51/2 & 3 & 15/8 X 4Type : 30Model No. : 15T2

(15) LOW PRESSURE COMPRESSOR (LP COMPRESSOR):

They are installed on EL 838.80 floor in the compressor room. There is one common control panel installed between these compressors for their regulation. Capacity of each compressor is 100 C.F.M.On the outlet pipeline of each compressor there is an after air-cooler installed for cooling the air before feeding it to respective air receiver. One non-return valve and one wheel valve are installed in between. Two 96 c.ft air receivers, installed on the 2 outlet pipelines are inter connected through a inter connected header of 150 dia. and they feed dry air at 7 kg/cm-cm to 222 c.ft. Capacity air receiver through a tee-off with a dia. of 150 mm. This feeds air to the brakes of all the machines and can stop them twice without further supply. The other two inter-connected air-receivers cater the general requirement of the compressed air in the powerhouse. The 2 compressors can be set to work on main and reserve format. Main compressor starts when pressure drops from 7 to 6 kg/cm-cm and reserve at 5.5 kg/cm-cm and they both stop automatically when pressure reaches to 7 kg/cm-cm. When compressor fails to stop at 7 kg/cm-cm and pressure rises further the air is released through the safety valves installed on the air receivers.

SPECIFICATIONS:Induction Motor:

Power : 22 KWSpeed : 1470 rpmPhase : 3Frequency : 50 HzCurrent : 41 AVoltage : 440 VRating : S1Synchronous speed : 1500 rpm

Insulation class : B

Compressor:Size : 5.5” X 5.5” & 4” X 4”Model no. : 3000Serial no. : 9432762

(16) GOVERNORS: It comprises of mechanical and electrical cabinets of EHG-40 Electro-Hydraulic Governor. Mechanical cabinet is connected to OPU & Guide apparatus servomotors of turbine through oil pipelines and feedback rope. It is also connected to electrical cabinet through control cables.

A.MECHANICAL CABINET:

It comprises of following:a. Electro Hydraulic Transducer with Hydro-amplifier.b. Main slide valve and Pilot slide valve.c. Gear for limiting gate opening according to head.d. Gate limiter. In addition, it carries the following meters and indicators as well as other accessories also to control the unit and governor operation. These are:

e. Main indicator to indicate the gate opening and gate limiter position,

ii. Electric-Tachometer to get the turbine speediii. Balance device to measure the governing current through the transducer.iv. Signal lamps to indicate the position of gate servomotor stopper.v. Control hand wheel of the gate limiter. viii. A pressure gauge indicating the pressure of the oil fed to the Hydro-amplifier of the transducer with the working pressure of 18-22 kg/cm-cm, achieved through a throttle installed in the oil pipeline from the OPU. .The opening of guide vane is limited to 65% -80 % by the mechanism of a gear used to limit the gate opening does these functions.

B.ELECTRICAL CABINET:

It has 7 horizontal blocks:1. Terminal block

2. Detector block3. Governor adjustment block4. Joint governing block5. Relay block protection unit6. Head adjustment unit

Function of the Governor: The circuit in detector block sense the frequency of the m/c and sends signals to the transducers in the mechanical cabinet for guide vane operation. This circuit also gets signals from Governor adjustment block for frequency/load control. The electric coil in the transducer is placed in the magnetic field of a ring shaped permanent magnet. Variation of signal current in this electric coil will move it around its vertical axis. This movement is amplified through hydraulic amplification system connected to transducer. This amplified movement is transferred to the main slide valve through leverages and pilot servomotors in the cabinet. Motion of main slide valve and consequent opening/closing of its ports cause the movement of oil under pressure to guide apparatus servomotors causing opening/closing of guide vanes. The hydraulic balance is achieved in the new position of electric coil in the transducer and thus guide vanes remain in position.

(17) OIL PRESSURE UNITS:

There are a no. of OPUs used for different systems. Their function is almost same in every case. The Oil Pressure Unit is intended to feed oil under pressure to the servomotors for their opening and closing through control cabinets. The OPU consists of an Air Oil Pressure accumulator, oil sump tank, 2 screw pumps driven by electric motors coupled through flexible coupling, automation gears, control and measuring equipment including starters. The air-oil pressure accumulator filled with oil and compressed air serves as source of energy for operation of servomotors by means of oil under pressure. The oil tank serves as the collector of oil flowing back to the OPU.Pressure relays are also installed on top of the OPU tank and are connected to the pressure vessel on tapping through a wheel valve. Each relay has individual needle type entry valve.

SPECIFICATIONS:

A.FOR SPHERICAL VALVE:Induction Motor:

Type : AM225S2Power : 37 KW

Speed : 2950 rpmCurrent : 62 AVoltage : 415 VPhase : 3Frequency : 50 HzInsulation Class : E

Pump:Type : Triple ScrewCapacity : 6 liters/sEff. Pressure : 40 kg/cm-cm

B.FOR TURBINE:Induction Motor:

Type : AM180L2Power : 22 KWSpeed : 2930 rpmCurrent : 38 AVoltage : 415 VPhase : 3Frequency : 50 HzInsulation Class : BPower factor : 0.88

Oil Pump:Capacity : 35 liters/sEff. Pressure : 40 kg/cm-cm

Pressure Vessel:Type : 1.6-1/40

Capacity : 16000 litersHydraulic test pressure : 60 kg/cm-cmWorking test pressure : 40 kg/cm-cm

(18) COOLING WATER PUMPS AND WATER PIPING: Four cooling water pumps of 175 HP each, is used. Each unit has a pipe of 400 mm dia. with a valve of 400 mm dia., supplying water from tailrace with the help of 175 HP pump. A gate valve of 350 mm dia. and a non-grease valve are used after the pump valve and before two-way strainer. After strainer, a valve of 355 mm dia., feeds the water to all section of generator. Another tee-off feeds water from individual pump to the main header for the unit as well as generator auxiliaries supplies. UATs and thrust bearing oil-cooling units are also supplied from the individual header through connection of 150 mm dia. One tapping of 50 mm dia. is used for oil cooler unit of turbine OPU. The 350 dia. cooling water header works as interconnection for inter changeability of 175 HP CWPs.Tappings from this header are used to feed LP compressor coolers, air

conditioning plants cooler and pressure filters. There is also a general water supply of 100 mm dia. tapping from this header.

SPECIFICATIONS:Induction Motor:

Type : MIA2201A-2Power : 132 KWSpeed : 1480 rpmPhase : 3Frequency : 50 HzStator : 415 V, 226 A, DeltaInsulation Class : B

Pump:Type : ASDCSize : 2500 S4A4Speed : 1450 rpmHead : 37 m

16) WATER FILTERS: There are 3 pressure water filters on EL 838.00 Floor. The

specifications of these filters are 60” dia. vertical section wash low water filters. The intake header has 150 mm diaphragm valve and outlet header has similar valve of 100 mm dia. for regulation of flow to turbine seals.

Water is filtered when it mixes with Alum in the pressure filters. The layers of various grade gravels and sand etc.separate out the suspended impurities and clean water is obtained. The impurity thus separated are removed from filter tank by reversing the flow of water in it and by opening the 150 mm dia. top drain valve near inlet.

SPECIFICATIONS:Type : Twin strainer OS/74-89

17) MASTER CONTROL SWITCH: The feedback rope is connected between the guide apparatus of the

m/c and the governor feedback shaft in the mechanical cabinet of the governor. The function of the feedback rope is to restore the governor main slide valve to the main position during process of governing and synchronous operation of PRV.Enroute master control switch is installed on feedback rope to open or close the contacts in it for automatic operation of m/c.

18) OIL LEAKAGE UNIT FOR SPH. VALVES:

The oil leakage unit of sph. valve installed on EL 831 Floor is intended for collection of oil leakages from servomotor cup-seals and return oil from slide valves on control cabinet of sph. valve. Thus, oil collected in the tank of this unit is pumped back to the sump tank of OPU of sph. valve installed at EL 838 Floor.

SPECIFICATIONS:Induction Motor:

Type : AM80K4Power : 0.55 KWSpeed : 1400 rpmVoltage :415 VCurrent : 1.5 APhase : 3Frequency : 50 HzInsulation Class : BDuty : S1

19) GENERATOR SYSTEM:

APPLICATION:Hydroelectric Generators are the most vital part of the powerhouse.

These generators convert the mechanical power output of the turbine (prime mover), to electrical power. The power output of the generator system installed here is about 180 MW.

SPECIFICATIONS:

STATOR:Slots : 192Winding : Double layer, wave connected bar

type short pitched, two parallel paths

Height : 2750 mmDia. at air gap : 4200 mmOutside Dia of frame : 6860 mmWt. of wound stator : 125 TNo. of sectors : 4Class of insulation : B

ROTOR:

Type : SalientNo. of Poles : 16Rated speed : 375 rpmRunaway speed : 620 rpmRated excitation current : 880 A

GENERAL:

Type of product : SV505/190-16Type of generator : SuspensionRated output : 66700 KWMax. cont. output : 76700 KWRated voltage : 11000 VRated Power factor (lag) : 0.9

Frequency : 50 Hz

Generator resistance at 15 deg. C : 1.Armature winding

per phase : 0.0027 Ohm2.Field winding per phase : 0.139 OhmCapacitance/phase toGround of the statorWinding : 0.3 microfaradInertia constant : 4.38 KW.Sec/KVA

a. Specification : Medium grade IS-1012/58b. Quantity (for fillingthrust bearing and guide bearing) : 250 m-m-m/hrOil pressure for jacking : 100 kg/cm-cmAdmissible vibration : 0.12 mmTotal wt. : 480 TNo. of finned tube airCoolers : 8

CONSTRUCTION:

Hydroelectric generators are salient pole machines having relatively slow speed. The generator system installed here is a standard type-high speed generator. This design has a top mounted thrust and guide bearing supported on a heavy bracket which must be capable of supporting the total wt. of the unit without distortion during unit operation.

Each major component is described below:

STATOR: The generator stator consists of stator foundation support members, a stator frame, stator core and the stator windings. The foundation members are embedded in the powerhouse concrete and provide support for the stator frame structural members. The stator frame structural members provide support for the stator core and other m/c components.

The stator core consists of thin steel laminations stacked on top of one another. The stator core is secured to the stator frame structural members to avoid mechanical vibrations during generating operations.

The stator windings are inserted into the stator core slots and terminated on collector rings called the ring bus, located at the top of the stator core.

ROTOR: The rotor is salient pole type and has 16 poles. The rotor hub is attached directly to the generator shaft. The purpose of the rotor hub is to mount and fasten the rotor spider. The rotor spider consists of several mechanical arms that radiate outward from the rotor hub. A continuous rotor rim is connected to the outside end of each rotor spider arm.

The field windings are wrapped around the outside of each rotor pole and connected to each other to form alternate north/south poles around the periphery of the rotor.

The damper winding consist of the copper bar that extend the length of the rotor pole face. The damper windings are used to dampen or restrict generator oscillation during steady state operation.

SHAFT: The generator shaft is flange coupled to the turbine shaft and conveys the mechanical power from the turbine to the generator rotor.

BRAKES: The hydro generators are provided with a mechanical friction braking system to help stop the generator rotation after the unit is tripped off line. These brakes are applied after the unit has slowed to less than 25% of the operating speed. Stopping the unit at this point avoids wear on the thrust bearing.

THRUST BEARING: Thrust bearing of m/c is of pivoted segmental pad type. The thrust collar is heat-fitted on the shaft. Mirror surfaced thrust disc is bolted to thrust collar with insulation in between for prevention of flow of bearing currents.8 thrust pads lined with Babbitt metal and pivoted on thrust bolts transfer the thrust of the m/c to the thrust columns of the building through upper bracket and stator frame. Thrust pads are pivoted on thrust bolts mounted on thrust frames. Spring action is provided by pad support put between pads and bolts. Radial and circumferential movements of pads during starting and operation of m/c are prevented by means of locking plates. For measurement of bearing pad temperature is RTDs are installed in 6 pads and TSDs are installed in 2 pads. Cooled oil from thrust bearing oil-cooling system is fed to thrust pad for cooling them when m/c is operating. Hot oil is returned to thrust bearing oil tank by gravity flow.

EXCITATION SYSTEM:Excitation system supplies and regulates the amount of DC current

sent to the generator field winding. The excitation system employed here is that of brush type rotating exciter. This exciter system utilizes commentators to change the exciter AC output to the DC required by the generator field winding. The amount of DC current supplied to the field winding is controlled by motor operated field rheostats, which have a very long response time.

20) FIRE PROTECTION SYSTEM:

There are 2 banks of carbon dioxide cylinders. The fire detectors operate at 80 deg. C .on outbreak of fire inside the generator, due to a fault in the winding causes flashover between phases or between turns, the CO2 gas under pressure of 40 kg/cm-cm discharges. The CO2 system is triggered by the operation of generator differential relay and/or generator split phase differential relay.

ROTOR WORKING:

Rotor has 16 salient poles. They are excited by means of DC fed to the field winding. This current is fed to the rotor via slip rings and carbon brushes. This DC current is provided by main exciter, which is excited by the pilot exciter. The pilot exciter is DC shunt generator, which generates its output because of residual magnetism of the magnetic poles. The stator forms the armature carrying a 3-phase winding wound for the same no. of poles as the rotor. All the 3 phases have identical windings with the same angular displacement between any pair of phases. The field winding mmf is distributed sinusoid ally along the air gap periphery and causes an induced emf to be produced in the stator winding. This mmf, generated by the field mmf only is called as the excitation emf or excitation voltage. Thus, there results an armature current in the armature windings. The mmf set up by this current is called as the armature reaction mmf. These two mmfs are rotating with synchronous speed so that their relative speed is zero with respect to each other. The phasor sum of these two mmf is the resultant air gap mmf. The two poles created on the stator by the armature mmf tend to produce an electromagnetic torque by attracting the rotor poles. This torque is in the opposite direction to that of the torque by the prime mover. So we can say that the machine, which is converted into the electrical form, absorbs the mechanical energy. The relation gives the frequency of the electrical power generated :

f = n x p/120 Where, f = frequency in Hz n = Speed in rpm p = No. of poles

The produced electrical energy is taken to the switchyard through step up transformer. From there it is sent to the power grid for further distribution.

21) TRANSFORMER GALLERY:At hydroelectric plants, large transformers perform the primary task of delivering power produced by the generators to the transmission system. other smaller transformers serve the power needs within the plant itself.Depending on the applications, the transformers are classified as follows:

A.25 MVA, 220 KV, GENERATOR STEP UP TRANSFORMER:SPECIFICATIONS:

MVA : 25 Frequency : 50 HzKV (No load) : HV 220/sqrt 3 LV 11Amp : HV 197 LV 2270Phase : Single PhaseImpedance voltage at 75 C : 14-16%Type of cooling : OFW Vector group : DY11

Guaranteed temp. rise of oil : 45 CGuaranteed temp rise of winding by resistance : 65 C

Diagram DRG No. : T628361 Maker’s Serial No. : 23816

Year : 1975

APPLICATION: The Generator Step Up (GSU) transformer transmits the energy produced by a hydroelectric plant to the utility network by converting the low voltage at which the generator produces power (11 KV) to a level that matches the transmission system (220 KV)ARRANGEMENT SCHEME:

3 Single-phase transformers of 25 MVA each are used for each unit. The three transformers are connected in delta/star fashion.

There are 9 such transformers in all. The arrangement scheme is shown in the fig.CONSTRUCTION:

The GSU transformer is a liquid immersed meaning that the core and coils are in oil filled tank. Oil is much more effective cooling and dielectric medium than air, hence it is employed for all the transformers with capacity over 10 MVA.The cooling is Oil Forced Water (OFW) type. The oil is circulated to external radiator to cool the core and coils during operation. The circulation of oil is forced through a 3.5 HP, 3 Phase, 440 V motor. Here water circulation should be started only after initiating the passage of oil through the tubes, in order to prevent the damage of tubes and hence the mixing of oil and water. PROTECTION:

a) Bucholoz’s Protection: It protects the transformer winding. The relay has got alarm as well as tripping contacts.

b) Oil Temperature Protection: It protects against the high oil

temperature. It also has the alarm and tripping contacts.

c) Winding Temperature Protection: It is against the high winding temperature with alarm and tripping contacts.

d) Water Flow Trouble: In case of cooling water supply fails this relay functions.

e) Oil Flow Trouble: It indicates the failure of 3.5 HP motor used for the circulation of oil through the coolers.

f) Restricted Earth Fault Protection: In case of damage to 220 KV winding this protection trips the unit through REF instantaneous relay. The feed to this relay is from core no.1 of 300/5 Amps. CTs provided in the 220 KV bushing.

The generated power is provided to these transformers in delta-connected fashion and the stepped up power is provided to the Switchyard via the star connected HV side.

B.1000 KVA, 11/0.4 KV UNIT AUXILIARY TRANSFORMER:

SPECIFICATIONS:KVA :1000

Frequency :50 HzVolts(No Load) :HV 11000 LV 415Amps :HV 52.5 LV 1391Phase :3Impedance :5.021 %Type of cooling :ONVector Group :DY11Guaranteed temp. rise of oil : 50 CDiagram DRG No. : T-S/386/WTMaker Serial No. : 12028

APPLICATION: Transformer are also used at Hydroelectric plant in the plant

electrical auxiliary systems, which require from 1-6% of the unit MVA.Electrical auxiliaries include unit auxiliaries (system, such as the excitation system or governor oil pressure system, that are directly associated with individual units). Generator system feed the unit auxiliaries.

ARRANGEMENT SCHEME:

A 1000 KVA, 11/0.4 KV, 3-Phase transformer is used as a unit auxiliary transformer for each unit. Thus, there are three such transformers in all. The primary terminals of the transformers are directly connected to high voltage 11KV bus bar of the power station.

CONSTRUCTION: Voltage on the hydroelectric plant auxiliary ranges from 11 KV to

the normal 415-208/110 V low voltage systems. These transformers are required to be liquid immersed i.e. oil filled, due to the high voltages of their primary terminals. The primary terminals are connected to high voltage 11 KV bus bars of the power station. These transformers must be located outdoors to minimize the fire hazard associated with a short circuit condition or tank rupture.

PROTECTION: The transformer has the following protection:a) Bucholoz’s Protectionb) Oil Temperature high Protectionc) Winding Temperature high Protection

C.1000 KVA 11/0.4 KV STATION SERVICE TRANSFORMER:

SPECIFICATIONS:KVA :1000 Frequency : 50 HzVolts(No Load) : HV 11000 LV 433Amps. : HV 52.5 LV 1333.3Phase : 3Impedance : 5.53%Type of cooling : ONVector Group :DY11

Guaranteed temp. rise of oil : 45 CDiagram DRG No. : TD-136Maker Serial No. : S10403/72

APPLICATION: These transformers are used to feed power to the power station

when the unit is not functioning.

CONSTRUCTION: These transformers are liquid immersed, i.e. oil filled and is similar

to the UATs.PROTECTION: These transformers have similar protection as for the UATs.

D. DIESEL GENERATOR SET (DG SET):

During emergency, when there is a need of power and no power is available DG set is used. There are two such sets provided in the powerhouse.

SPECIFICATIONS:KVA :500Volts :415Amps. :896Speed :1500 rpmPhase :3Frequency :50 HzConnection :starInsulation :Class FExcitation :40 V 2.5 ARating :CRHeater :2,250 W,230 V

E .BATTERY SUPPLY:For the emergency case battery supply is also available in the

powerhouse. On the occasion of failure of power supply from other media, the battery supply comes into action and continues the power supply without any interruption.There are 4 batteries set in the powerhouse, 2 of 48 V each and the other two of 220 V each. The 48 V set is used for local exchange and PLCC i.e.; local power line carrier system.

CAPACITY: 80 Ah

Fourth Set is installed at Jassure and Talwara for telecommunication purposes. CAPACITY: 200 Ah

22) 400 V UNIT AUXILIARY BOARD (UAB): There are 3 L.T distribution boards, one for each unit, to supply all

the auxiliaries of the unit. The auxiliaries are:1. Cooling water pumps2. OPU of the spherical valve3. OPU of the turbine

4. OLU 5. Oil circulating pumps for each of the 25 MVA generating

transformer (2 for each unit)6. UCB7. Thrust bearing pumps8. Central grease lubricating unit9. Turbine pit dewatering pumps

The board may get its supply either from SSTs or UATs, which are directly connected, to the output terminal of the generator through CTs placed on the phase side of the bus duct. But at any instant only one of the supplies is given To safeguard against intermixing of these 2 supplies a no. of lockout controls have been provided. The protection scheme includes the protection against

1. Over current [Relay CDG-31]2. Earth faults [Relay CDG-14]3. Restricted earth fault [Relay CAG-14]4. Over voltage [Relay VAG-21]

23) 400 V STATION SERVICE BOARD (SSB):

The 400 V station service boards have been provided in 2 parts- SSB A & SSB B.SSB A is connected with UAB-1 via tie-line breaker no. QF18M.On the other hand SSB B is interconnected with UAB-2 as well as with UAB-3 via tie-line breaker no. QF19M & QF20M respectively. These boards may also be supplied through SSTs via the breakers QF6M & QF7M.The 2 SSBs are also interconnected through a bus coupler via breaker no. QF5M (of 2000 A capacity). Whenever one of the SSTs fails, the bus coupler interconnects the two SSBs and the supply remains in continuation.

The various relays are also equipped for the protection purpose. The protection scheme includes the protection against

1.Over current [Relay CDG-31]2.Earth faults [Relay CDG-14]3.Restricted earth fault [Relay CAG-14]4.Over voltage [Relay VAG-21]

The supply to switchyard is fed through the breaker nos. QF21M for SSB A & QF24M for SSB B, while disc valve is fed through QF23M & QF22M for SSB A & SSB B respectively. An incoming line from the DG Set is also provided via the breaker QF8M.

24) LIGHT DISTRIBUTION BOARD (LDB):

The entire lightning system of powerhouse has been controlled through GEC supplied panels. Two circuits from each of the SSB is drawn through 100 A CB and fed into four 200 A TPN switch fuse units. The switch fuse unit feed a common busbar. The further distribution is made through 30 A and 15 A TPN switches fuse units .A distribution box of 25 mm-mm PVC for main circuits and of 15 mm-mm PVC for branch circuit has been used.

25) POWER LINE CARRIER COMMUNICATION (PLCC):

The term power line is used to represent the entire process of

communication through the high voltage overhead power lines as the means of transmission. PLCC is used in telemetering, power line protection, telecontrol etc.The power lines offer the following advantages:

1.Less attenuation of signal due to thicker cross section.2.Negligible leakage even under wet weather condition due to

high voltage insulation3.Cross-talk is avoided because of the good distance between the

phase lines4. Cost for extra lines is avoidedBut on the other hand, due to heavy voltage transmission,

communication through these lines may be dangerous to human life and also for the telephone system. Also, during transient operation the higher harmonic may interfere the communication signal. These harmonics generally lie in the range of the frequency of 100 Hz to 50 KHz. So carrier frequency is chosen in the range of 30 KHz to 500 KHz to avoid noise production. To prevent the interference of these carrier signals and also to prevent these signals due to a short because of the low impedance of transformer and generator connected at the end of the line, line-traps (wave-traps) are used which offer a very high impedance to carrier frequency and a low to the power frequency. Similarly coupling capacitors are also used which are so designed as to offer a very low impedance to carrier frequency and a high impedance to the power frequency.

The 2 most common coupling methods are center-phase to ground and adjacent-phase to phase. The former is employed here. In this method only one phase line is used and ground is used as the returning part so that 3 separate carrier sets may be connected to the 3-phase lines.

For efficient coupling at carrier frequency the reactance of the coupling capacitor is cancelled by inductances in the line matching unit and the impedance of the power line (300 Ohm to 500 Ohm approx.) is matched. The line-matching unit is normally located close to the coupling capacitor in the Switchyard.

There are 2 methods for transmitting the carrier signals over the power lines between the different stations in the power grid. These are fixed frequency system and wave changeover system. The former type is employed here, in which transmission of signal in different sections is carried out by different carrier frequencies. In this method the signal is sent between 2 consecutive stations by the allotted carrier frequency. The carrier frequency is demodulated at the second station and the signal is used to modulate the carrier frequency allotted for the second station and is retransmitted on this second carrier and so on. So there is simultaneous transmission of signals in different sections and the quality of reception is better as the signals are amplified at each station. However it is costlier as two carrier sets are required at each intermediate substation.

The ground wire for the protection of power line against the lightning strokes may also be used as a transmission medium by insulating the conductors from the tower with insulators having breakdown voltage of 15-25 KV. So this insulation behaves as a short for the voltages above this range,

which is the case with lightning strokes, but for below voltages it behaves as an insulator.

In this Project the PLCC exchange has 10 line cards and each line card has 3 lines and 1 call office.

The connection for Pong grid is at frequency 140 KHz while for Jassure it is 185 KHz.

PROTECTIVE RELAYS:

The purpose of the Protective relay and the protective relay system is to operate the correct circuit breaker so as to disconnect only the faulty equipment from the system as quickly as possible. It does not eliminate the possibility of false because its action starts only after the occurrence of fault. It can be ideal if protection could anticipate and prevent faults, however only the gas detector relay (Bucholoz relay) falls under this category.

Though in low voltage system of lesser importance, fuses, MCBs and MCCBs serve the purpose. However protective relaying is indispensable in the high voltage system. The types of fault that can occur are so vast that just one type of relay cannot protect the system against all those faults. Hence, we have to employ a variety of relays. Isolation of a faulty section is only slightly more important than the non-isolation of a healthy section, because of the huge losses we may incur due to a grid collapse initiated by indiscriminate tripping.

Protection requirement of generators & transformers are well kept in mind while finalizing a scheme for a powerhouse. Some of the important protections are discussed below:

A. GENERATOR PROTECTION:

i) Differential Protection:

This protection is the most important protection. There are two types of relays available, high impedance type & low impedance type. Any one can be used according to the CT selected to match the relay. This protection is only for phase fault and earth fault cannot be detected by it because of a very small change in the stator current during the earth fault, when the neutral grounding impedance restricts the earth fault current. But, in case of any arcing even the differential relay can operate.

ii) Stator Earth Fault Relay:

0-95% winding fault is sensed using the neutral over voltage. If faults between 95% & 100% winding are not detected there may not be any immediate damage because of a very small current involved. However if other faults occur in the stator winding that can cause extensive damage to the stator core. Therefore it is essential to protect the generator against such faults near the neutral also. Using both neutral over-voltage as well as the third harmonic contents of neutral and line voltages provide 100% winding protection.

iii) Unbalance Generator Load Protection (Negative Phase sequence Protection):

This protection is essential to protect the generator against the negative sequence currents, which cause rotor heating. Also this protection covers the broken wire condition that has not developed into an earth fault. This protection is a back-up protection for the generator against faults in winding as well as unclear system faults.

iv) Backup Protection (Over-current & Under-impedance):

A back-up impedance protection is provided to protect the generator against unclear line faults. Thee under impedance protection operate under certain conditions. In addition to the impedance protection & over-current protection is also essential for providing a complete back-up protection because increase in current to the tune of 50% of the rated current without corresponding drop in voltage may not create an under-impedance condition. Such an eventuality may arise, either due to overloading or mal-operation of excitation system.

An over-current relay on each phase can be provided so that above situation related to overloading can be cared, also 2 over-current relay and 1 earth-fault relay is an equally suitable protection.

v) Rotor Earth Fault Relay:

There may be Ground faults or short between the turns of the field windings, caused by the severe mechanical and thermal stresses acting upon the winding insulation. The system is not grounded normally and, so, a simple line-to-ground fault does not produce any fault current. A second fault to earth will short-circuit part of the field winding and thereby produce an unsymmetrical field system which gives rise to unbalanced forces on the rotor and results in excess pressure and bearing & shaft distortion if the fault is not removed quickly. So it is essential to take correct measures as soon as the first fault occurs.

vi) Loss of Excitation:Generally an under-impedance relay is used for the protection

against loss of excitation; the field current being used as the parameter. An under voltage condition coupled with a leading stator current beyond a set limit is clear indication of loss of excitation. In other words an under voltage condition and a simultaneous under impedance condition within set charters a tic indicates loss of excitation.

vii) Generator Over-voltage Protection:

There are two different ways to provide this protection. One is to have this protection on all the 3 phases and the other is to have it only between these two phases. In both the cases there are instantaneous as well as delayed protection. Considering that an over voltage is generally a 3-phase phenomenon, it is sufficient to provide this protection between any 2 phases.

B. GENERATOR-TRANSFORMER PROTECTION:

i) Generator-Transformer Overall Differential Protection:

The type of relay used is preferred to be of low-impedance type because of its advantage when both sides of any transformer have different CTs. However an independent differential protection for the generator-transformer is not provided in addition to the overall differential protection. The overall differential protection operates for any phase-to-phase fault in the protected

zone or any inter-turn fault in the winding and these faults always give rise to arcing in the oil, thus causing the Bucholoz Protection to operate. For earth faults the Bucholoz relay again operates because of the arcing involved and the E/F Protection operates. The back-up protection takes care of the generator transformer also.

ii) Unit Auxiliary & Excitation Transformers:

The unit auxiliary transformers and excitation transformers are always connected to the units without any isolation on the HV side, as units do not run without them.

By providing CTs on the HV side of the above transformers and connecting them in the overall differential scheme, it is possible to obtain operation of this protection for phase faults on the protected zone but no operation will occur for faults in the auxiliary and excitation transformers. Though the earth faults on the HV side are still covered by the stator E/F relay, phase faults not involving earth and earth faults on the LV side need to protect against by an independent O/C protection with a high set element. This O/C protection draws its operating current from the HV side of CT.The auxiliary and excitation transformers are protected by a low voltage O/C protection.

C) BUCHOLOZ PROTECTION FOR TRANSFORMERS:

It is a gas detector relay and the only relay that anticipates and also prevents the faults. Whenever a fault occurs in the transformer, the oil of the transformer gets overheated and gases are formed. The generation of gases is violent for the major faults while it is very slow for minor faults. It is the generation rate of the gases that is used as the means for fault detection.

SWITCHYARD

Switchyard is one of the most important and the last section of the power project from where power is supplied to the grid for the distribution. The power comes from the generating transformers of the unit. The 220 KV equipments consist of the following:

1. LINK LINE:

It is that portion of the transmission line, which connects the Generator transformer to the switchyard.

2. CIRCUIT BREAKERS:

To enable the power plants and the transmission lines-when these become faulty-to be rapidly and safely isolated, the circuit breakers are used. A CB consists essentially of current carrying contacts called electrodes. The basic construction of any CB requires the separation of these contacts in an insulating fluid, which serves two functions. One, it extinguishes the arc drawn between the contacts when the CB opens, and two, it provides the adequate insulation between the contacts and between each contact and earth.The fluid chosen for arc extinction depends upon the rating and type of the CB.The commonly used insulating fluids are:

a. Air at tam. Pressure.b. Compressed airc. Oil which produces hydrogen for arc extinctiond. Ultra high vacuum e. Sulphur hex fluoride (SF6)

The gases, which have been considered for CB, are (i) simple gases-air, oxygen, nitrogen, carbon dioxide and (ii) electro-negative gases, sulphur hex fluoride, arcton. The gases used should have high dielectric strength, thermal and chemical stability, non-inflammability, high thermal conductivity and good arc extinguishing ability.

In this project the Air Blast CB (ABCB) are used in the switchyard. ABCB has two types-axial blast type and cross blast type. The former type is used here in this ABCB the fixed and the moving contacts are held in closed positions by spring pressure. When the air enters the arc chamber, which moves with sonic velocity near the nozzle, exerts a pressure greater than the spring pressure(15 kg/cm-cm here) on the moving contacts, the contact opens.

3. SURGE DIVERTORS OR LIGHTNING ARRESTORS:It is used to protect the various equipments from the over voltage

wave reaching there by diverting these waves to earth. It is connected between the earth and the line at the substations and stations. When a voltage wave reaches the divertor, it sparks over a certain prefixed voltage and provides a conducting path of relatively low impedance between the line and the earth. This flow of current to the earth limits the amplitude of the line-to-earth over

voltage known as the residual or discharge voltage, to a safe value of insulation of the equipments. It should be noted that this surge impedance is low only for the instant of the over voltage and otherwise it remains at its normal value i.e. it is a non-linear type resistor which works as an insulator at normal voltage but acts as a low resistance at over voltage. The used diverter is of rod-gap type in which there is a plain air gap between 1” sq. rods cut at right angles at the ends, connected between the line and the earth. The gap may be in the form of horns or arcing rings.

To avoid ascending across the insulator surface of very steep fronted waves, the rods gap should be set to breakdown at about 20% below the impulse spark over voltage of the insulation at the point where it is installed. The distance between the insulator and the gap should not be less than about one-third the arc gap length in order to prevent the arc from being blown on the insulator.

4. BUS BARS:

The bus bars are either of the rigid type or of the strain type. Here strain type bus bars are used. These are an overhead system of wires strung between two supporting structures and supported by strain type insulators.Material used for these bus bars is ACSR (Aluminum-Core-Steel-Reinforced). Here the double bus bar system is used so that-Each load may be fed from either bus.

a. The in-feed and the load circuits may be divided into two separate groups if needed.

b. Either bus bar may be taken out for the maintenance and cleaning of insulators.

A bus coupler is also provided as it enables on-load changeover from one bus bar to another.

5. ISOLATOR AND EARTHING SWITCH:

There are many isolator and earthing switches used for each phase. Isolators are used on no-load condition and when the CB is normally open. Horizontal-arm center connected isolator is also used. Earth switch at each isolator is provided to earth the leakage current at the time of maintenace. Each pole of this high speed-earthing switch is equipped with spring snap action mechanism for high speed opening and closing.

6. CURRENT TRANSFORMERS AND POTENTIAL TRANSFORMERS:

(CTs AND PTs):

A large no. of CTs & PTs are provided in the switchyard for the purpose of measurement and protection. The CT convert a high current to a value within the range of 5 A and the PT converts a high voltage within a range of 110 V .This transformed signal is also used to initiate the various relays used.

The primary winding of the CT is connected in series with the sensing circuit while the secondary is connected to the operating coil of the relay. The primary current is independent of the secondary. On the other hand the secondary current of the PT is equal to the magnetizing current, independent of the load. The errors introduced by the PTs are less as compared to that by CTs.Whenever two or more parallel lines are running from a common bus, a single PT is connected to the bus because it is capable to supply the protective relaying equipment of all the lines.

7. WAVE TRAP AND CAPACITIVE VOLTAGE TRANSFORMERS:

Whenever there is a desire of the carrier communication through the power lines, CVT is used. If the voltage on the secondary side is adequate, as in general, only coupling capacitors for carrier communication is used. Here two new CVT systems are used while the old two are in spare. It uses capacitor circuits enclosed by an inductive cylinder. The wave trap is also used when the carrier communication through the power lines is desired.

8. DOUBLE-CIRCUIT TRANSMISSION LINE:

To supply the power from the switchyard to the grid a double circuit line is used which has the advantage that in case of failure of supply through one of the lines the supply could remain continuous through other lines.

OPERATION PROCEDURE

The systematic order in which a particular unit runs is as follows:

1. GENERAL CHECKS:

a. Ensure that no work permit is pending against the m/cb. Draft tube and pressure release valve of the m/c should be open.c. Disc valve of the m/c should be opened.d. Penstock should be in fully charged conditione. Spherical valve should be in closed position

2. CONTROL ROOM:

a. Machine is free from all faults and no alarm triggers on annunciation at control room

b. AC and DC supply is in on position. DC supply to thrust bearing pumps is available.

c.220 KV air blast pump breaker is in open positiond. DC thrust bearing pump breaker should be in on positione. Unit ready for start relay (7AY) signal appears on the control desk.f. The closing and opening operation of 220 KV bus isolators of

generators and feeders should be done from control room.

3. EL 845(MACHINE HALL AND TRANSFORMER GALLERY):

a. Switch on the AC/DC supply of the UCB b. No fault alarm appears on the board.c. Unit ready for start signal appears on the UCBd. Oil level and proper air pressure is available on the OPU of the

turbine. Oil level in the sump should be normal.e. Oil pressure of governor should be normal and mode of operation

should be kept in auto.f. In the mechanical governor cabinet, frequencychanger knob

should be kept at the nearly 50% position and output changer knob should be kept in minimum position.

g. The air pressure air brake system of generator should be around 5.5 kg/cm-cm. This pressure reading can be seen in the gauge on brake panel near UCB, checks whether brakes can be applied manually. The brakes should be in the release condition before starting the m/c

h. Water flow and oil circulation in transformer is checked.i. Oil level and silica gel condition of generator transformer and UAT

should be checked.j. Air pressure and glass bulbs of emulsifier system should be

checked

4. EL 838(SWITCHGEAR ROOM):

a. Supply to UAB should be available and all the outgoing MCCB feeders should be switched on

b. Power supply for transformer oil circulating pump should be switched on from UAB.In no case the water supplied to the transformer oil cooling system should be opened without the oil circulation pumps in operation.

c. Air pressure and oil level should be normal in OPU of sph. valve.d. If the m/c is static for more than 24 hours than the m/c should be

jacked. After the completion of jacking operation the knob should be turned to break position

e. Brake pads should be checked and it should be in released position.

f. Both HP & LP compressors should be checked and ensured that air pressure in receivers is normal.

g. Supply of carbon dioxide control panel should be on and should be kept on auto

5. EL 834(TURBINE FLOOR):

a. Cooling water pumps should be running with appropriate valve openings. Water pressure should be normal (in the range of 4-5 kg/cm-cm). If there is a difference of pressure more than 1.5 kg/cm-cm in pressure gauge of before and after strainer, maintenance staff should be informed

b. After checking the operation of both thrust bearing pumps on manual control of one pump should be kept on working position and second pump on reverse position.

c. Manual operation of DC thrust bearing pump should be checked and then its control should be kept in auto position.

d. Shaft seal pressure should be around 2 kg/cm-cme. Spherical valve oil supply valve should be in open position and

bypass valve, seal valve and other valves should be in close positionf. OLU pumps of turbine and spherical valve should be checked

manually and put on auto position.g. Dewatering pumps should be in healthy conditions and kept in

working and reserve position.h. Drainage pumps should be in healthy condition and kept in

working and reserve positioni. Mulsifyre pumps should be in healthy condition and its tank should

be full of water.

6. SYNCHRONIZING AND LOADING OF MACHINE:

Once the m/c is building up the required voltage and if frequency is 50 Hz, approx it can be synchronized with the grid system. This is to be done with the help of synchronizing switch having three positions, namely; manual, auto and off. Procedure for manual synchronization:

a. Keep the Synchronizing switch SS on the control panel to manual position.

b. Adjust the generation voltage and match it with system voltage bcs/6cs on control desk. The m/c voltage should be higher than the system voltage.

c. Turn synchroscope switch on the synchronizing panel ON. It will bring synchroscope in circuit. The clockwise or the anticlockwise movement of the synchroscope needle will indicate whether the m/c is slower or faster than the system.

d. Increase or decrease the speed of the m/c by switch 12KY(Speed control) to match the speed for frequency matching. Ensure that the needle is moving very slowly in the clockwise direction.

e. Flip the switch BCS (Breaker control switch) towards trip side.f. During the clockwise movement of the needle, with very slow and

smooth speed at the position of 12 o’clock of the needle flip BCS to close position. This operation will synchronize the m/c with the grid.

g. Switch off the synchroscope. Change synchronizing switch SS to OFF position and take out the key from the switch.

h. MVAR sharing by the m/c on bar can be varied through switch and rheostat provided on the vertical face of the control desk in the compounding circuit of exciter. Try to keep the compounding circuit current minimum. Power factor is also kept above 0.9.

i. When m/c is synchronized shift the auxiliary load of the m/c from SST to UAT.The 175 HP cooling water pump of the respective machines are restarted as soon as the supply is changed from SST to UAT.

7. STOPPING OF THE MACHINE:

a. The operator at EL 845,EL 838 & EL 834 are informed for the operation concerning the stopping of the machine. At EL 834 operator is ready to restart the 175 HP cooling water pump after changeover of auxiliary supply of m/c SST from EL 838.Operator at EL 845 should watch the speed of m/c and be ready to apply the brake at 25% speed.

b. Change the load of auxiliaries from UAT TO SST.Reduce the load of the m/c in steps and when the load is about 5 MW, open the CB by turning the knob of BGS to TRIP position.

CONCLUSION

India is endowed with enormous economically exploitable and viable hydro potential assessed to be about 84044 MW at 60% load factor (148700 MW installed capacity).Total annual energy potential of 600 billion unit has been accessed and so far only 15% of the potential has been exploited.

Over one billion people in SAARC are amongst the poorest in the world and lack even the basic social amenities including electricity. Per capita demand of electricity in Asia is only 1250 KWhr, which is half of the world average. A certain study indicates that the need of consumption of minimum 1500 KWH of electricity to maintain even marginal standard of living. Against this, the per capita consumption of electricity in India is only 350 KWH, which speaks of immediate and urgent need of planning and undertaking accelerated hydro development in the country.

India, with no large known oil and gas reserves, is independent on indigeneous coal as the main in feed for electricity production. This is leading to depletion of non-renewable source of energy on one hand and environmental degradation as well. Switching to clear fuels, wherever available is therefore to be taken on top priority. In India vast potential exists for Hydro-development from white coal i.e. water. Over the years due to paucity of funds, the regional power development had led to imbalance in the hydrothermal mix to 25:75 as against desired ratio of 40:60.It is well known that hydropower can give excellent peaking support and prevent sub-optimum level of operation of thermal plants i.e. burning expensive oil off peak hours. As per CEA 15 th Electric Power survey, the present peak demand is 63853 MW and projected peak demand is 95757 MW for the Year 2001-02.

The recent R & D innovations in the field of hydro-dynamics make it possible to derive higher outputs from the existing hydraulic space in turbines by employing higher specific speed and better efficiency profiles on one hand and use of better class epoxy insulation on the other which makes it possible to use higher conductor size in the existing stator slots for higher outputs. The older plants hold substantial potential of up rating at the time of renovation thereby making up rating proposals cost effective. Besides enhancement of peaking capacity, there would be extra energy benefit in the case of run-off-the-river scheme. The other good thing about run-off-the-river scheme is that it creates lesser impact on the environment and lesser no. of people are distributed in the area.

The regional grids in India suffer from problems of wide frequency and voltage fluctuations, frequent grid failure, uneconomic operation, problems in evacuation of power etc. Hydropower can give relief from most of these problems.