Charu Kandpal Final Report on HEP

CHARU KANDPAL

THDC INSTITUTE OF HYDROPOWER

ENGINEERING AND TECHNOLOGY

Summer Training Report

TEHRI HYDRO POWER PLANT

TEHRI HYDRO POWER PLANT Summer Training Report

1 | P a g e Charu Kandpal THDC Institute of Hydropower Engineering and Technology 2014-15

Table of Contents

Serial Number

Topics Page Number

Submission Details 2 Acknowledgement 3 Introduction 4 Energy Scenario In India 5 Types of Power plants 7 Features of Tehri Dam 9 Components of Tehri HEP 11 Power Generation 15 Excitation System 16 Braking System 18 Governor System 19 Gas Insulated Switchyard 21 Computerized Control Room 23 References 25 Epilogue 26



Submission Details

Name of the organization- Tehri Hydro Development Corporation

Location of Power House- Bhagirathi Puram, Tehri Garhwal

Duration of Training- July 23rd, 2014 to august 2nd, 2014

Title of Report- Tehri Hydro Power Plant

Submitted To- Er. S.K. Arya

Name- Charu Kandpal

College- THDC Institute of Hydr0power Engineering and Technology

University- Uttarakhand Technical University

Branch- Electrical Engineering

Roll No. - 110970105019

Guides:

1) Er. D. P. Kothiyal

2) Er. P. C. Pandey

3) Er. Rakesh Panwar

4) Er. Sachin Vyas

5) Er. Arpan Kumar

6) Er. Shrikant Pant

7) Er. Rahul Joshi



Acknowledgement

I would like to sincerely thank Mr. Seemant Pant, Deputy General Manager THDC India Limited, for his immense support that has

made this training possible. I would also like to thank Mr. S.K.Arya, Senior Manager (O&M) for their great supervision as a mentor.

I would like to whole heartedly thank all the guides for their true

effort they put in to make us understand principles behind working

of all sections in brief.

Charu Kandpal

THDC Institute of Hydropower Engineering and Technology

Uttarakhand Technical University



ntroduction

THDC-

TEHRI HYDRO DEVELOPMENT CORPORATION, or THDC, is

a joint venture of the Central Government and Uttar Pradesh State

Government.

Tehri Dam-

The Tehri Dam is a multi-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 phases.

Phase 1. Tehri HEP (4X250MW) was completed in 2006.

Phase 2. Koteshwar HEP (4X100MW) was completed in 2012.

Phase 3. (4X250MW) Pumped storage Plant of hydroelectricity generation is under

construction.

This dam is Asias largest & worlds 3rd. largest rock fill dam. The area of the

reservoir is around 44 km2 and the catchment area expands to over 7511

km2 The complex will afford irrigation to an area of 270,000 hectares

(670,000acres), irrigation stabilization to an area of 600,000 hectares

(1,500,000acres). and a supply of 270 million gallons of drinking water per day

to the industrialized areas of Delhi, Uttar Pradesh and Uttarakhand ,

thereby supplying drinking water to over ten million people

I



nergy Scenario in India

Coal dominates the energy mix in India, contributing to 55% of the total primary energy

production. Over the years, there has been a marked increase in the share of natural gas in

primary energy production from 10% in 1994 to 13% in 1999. There has been a decline in the

share of oil in primary energy production from 20% to 17% during the same period.

Coal Power:

India has huge coal reserves, at least 84,396 million tons of proven recoverable reserves

(at the end of 2003). These amounts to almost 8.6% of the world reserves and it may last for

about 230 years at the current Reserve to Production (R/P) ratio. In contrast, the world's

proven coal reserves are expected to last only for 192 years at the current R/P ratio.

Natural Gas:

Natural gas accounts for about 8.9 per cent of energy consumption in the

country. The current demand for natural gas is about 96 million cubic meters per day (mcmd) as

against availability of 67 mcmd. By 2007, the demand is expected to be around 200 mcmd.

Natural gas reserves are estimated at 660 billion cubic meters.

Hydro Power:

India is endowed with a vast and viable hydro potential for power generation of

which only 15% has been harnessed so far. The share of hydropower in the country's total

generated units has steadily decreased and it presently stands at 25% as on 31st May 2004. It is

assessed that exploitable potential at 60% load factor is 84,000 MW.

E



Nuclear Power:

Nuclear Power contributes to about 2.4 per cent of electricity generated in India.

India has ten nuclear power reactors at five different nuclear power stations. More nuclear

reactors have also been approved for construction.

Figure 1: Energy Production by Different Sectors in India



ypes of Power Plants

Power Plant:

A power plant or a power generating station is basically an industrial location

that is utilized for the generation and distribution of electric power in mass scale. Since for the

purpose of bulk power generation, only thermal, nuclear and hydro power comes handy,

therefore a power generating station can be broadly classified in the 3 below mentioned types.

Thermal Power Station:

It uses coal as the primary fuel to boil the water available to superheated steam for driving the steam turbine. The steam turbine is then mechanically coupled to an alternator rotor, the rotation of which results in the generation of electric power.

Nuclear Power Station:

In nuclear power plant, the radioactive fuels are made to undergo fission reaction within the nuclear reactors. The fission reaction propagates like a controlled chain reaction and is accompanied by unprecedented amount of energy produced, which is manifested in the form of heat. This heat is then transferred to the water present in the heat exchanger tubes. As a result, super-heated steam at very high temperature is produced.

Hydro-Electric Power Station:

In Hydro-electric plants the energy of the falling water is utilized to drive the turbine which in turn runs the generator to produce electricity. Rain falling upon the earths surface has potential energy relative to the oceans towards which it flows. This energy is converted to shaft work where the water falls through an appreciable vertical distance. The hydraulic power is therefore a naturally available renewable energy given by the equation:

Where g = acceleration due to gravity = 9.81 m/sec 2

T



= density of water = 1000 kg/m 3

H = height of fall of water i.e. gross head

This power is utilized for rotating the alternator shaft, to convert it to equivalent electrical

energy.

An important point to be noted is that, the hydro-electric plants are of much lower capacity

compared to their thermal or nuclear counterpart. For this reason hydro plants are generally

used in scheduling with thermal stations, to serve the load during peak hours. They in a way

assist the thermal or the nuclear plant to deliver power efficiently during periods of peak hours.



eatures of Tehri Dam

Reservoir

Full Reservoir Level (F.R.L) EL 830 M

Maximum Level During Design Flood EL 835 M

Dead Storage Level (D.S.L) EL 740 M

Water Spread at F.R.L 42 Sq. KM

Water Spread at D.S.L 18 Sq. KM

Dam

Type Earth and Rock Fill Dam

Top Level 839.5 M

Height 260.5 M

Width at Riverbed 1125 M

Length at Top 592 M

Spillway

Chute Spillway

Crest Level EL 815 M

Waterways 3 bays of 10.5 M each

Type and No. Of Gates Radial Gates, 3 Nos

Right Bank Shaft Spillway

Type and No. of Gates Ungated, 2 Nos

Crest Level 830.2 M

Diameter of Shaft 12 M

Left Bank Shaft Spillway

Type and No. Of Gates Radial Gated, 2 Nos

Crest Level EL 815 M

Diameter of Shaft 12 M

Intermediate Level Outlet

Number One

Size (Diameter) 8.5 M

F



Penstocks

Numbers 4

Size 5.75 M dia. Each

Total Length 1040 M

Power House

Machine Hall

Type Underground

Location Left Bank, Underground

Number & Units 4, 250 MW each

Head Maximum: 231.5 M Minimum: 127.5 M Designed: 188.0 M

Transformer Hall

Type Underground

Size 16118.529 M

Step Up Transformer

Capacity 306 MVA

Number 4

Voltage Ratio 15.75/420 KV

Switchyard

Type Indoor SF-6 Switchgear

Tail Race Works

Number and Size of Tail Race Tunnel 2 Nos, 9.0 M dia. Each

Length of Tunnels 862.5 M, 747.5 M

Insert Level of Outlet EL 598 M

Installed Capacity

Total 2400 MW

Tehri- I 1000 MW

Tehri- II 1000 MW

Koteshwar 400 MW



omponents of Tehri HEP

Earth and Rock Fill Dam:

The dam is earth and rock fill type & its height is 260.5m. The length at the top is 592 m & width is 25.5 m. The elevation of the top of the dam is 842 m.

Figure 2: Tehri Earth and Rock Fill Dam

Head Race Tunnel-

There are 04 Numbers of HRTs on the Right Bank of the reservoir having

circular shape, 8.5 m diameter. The lengths of HRTs are 779 m, 855 m, 997 m &1033 m. It takes

water from reservoir and supplies it to power house machines for generation. HRT-1 and

HRT-2 carry the later to Hydro power plant (HPP). HRT-3 and HRT-4 carry the water to the

pump storage plant (PSP) which is still an ongoing project and is not functional right now.

C



Penstocks:

Water enters through the different penstocks to the different generating units.

Each penstock comprises upper horizontal, vertical & lower horizontal reach including upper &

lower bend. The diameter of penstock is 5.75 m.

Inlet Valves:

One Butterfly Inlet Valve (BIV) at mouth of the each penstock and one machine inlet

valve (MIV) before the spiral casing are installed. The valve remains close in case of unit

shutdown.

When the unit is started then after sensing the starting command, MIV opens first to build up

the pressure in spiral casing and roll the turbine.

Figure 3: Head Race Tunnel

Figure 4: Butterfly Inlet Valve



Turbine:

Four Vertical Francis turbines are installed having net head of 188 meter.

Water from the spiral casing enters through the 28 guide vanes and strikes the 14 blades of the

runner, which is coupled to the main shaft. The shaft is coupled to the rotor of the generator at

the other end. The opening of guide vanes depends upon the generation requirement. Water

strikes the blades of the runner and fall axially in the draft tube. For keeping shaft vertically,

Turbine guide bearing is installed which is of rotating sump self-cooled type.

Generator:

It is 278 MVA, 0.9pf, 50HZ, 3 Phase generator which generates power at a

voltage of 15.75 KV. A generator has two parts, Stator and Rotor. Power generated is

transmitted through isolated phase bus duct to transformer gallery from where it is stepped up

to 400 KV by GSU transformers. Two bearings named as Thrust bearing and upper guide

bearing are installed for sustaining the outward thrust of rotor and keeping shaft verticality.

Both the bearings are of water cooled type. The direction of rotation is anticlockwise when

viewed from the top.

Figure 5: Main Inlet Valve



Transformer Gallery:

Eight in numbers, 306 MVA, 15.75/ 400KV GSU 3 Phase transformers are

installed in transformer gallery (TG) for the four units. Other four set of transformers are

installed for upcoming Pumped Storage Plant (PSP). 15.75 KV is generated from the each unit

and this power is stepped up to 400 KV here and sent to switchyard through oil filled cables.

These generating transformers are provided with makeup valve which is filled with water that

cools the oil that is being used to cool the transformer. These transformers are also equipped

with micro wave detector which detects the microwave that generated In case of some spark

and raises the alarm. Transformer oil conditioner is used to purify the oil which is used to cool

the transformer and eliminates different gases from the oil that got mixed during the cooling

process.

Figure 6: Turbine and Generator in a HPP



ower Generation

Water enters from reservoir through HRT-1 and HRT-2. Each HRT further divides

into two penstocks which are equipped with a butterfly valve. Hence four penstocks

lead to four turbines. This water rotates the turbine blades and turbine rotates the

excited rotor. This leads to change in flux and according to faradays law electricity is

generated.

Water from turbine enters the draft tubes and there after tail race tunnel TRT-1

and TRT-2. These TRTs takes the water to mainstream.

P

Figure 7: Tehri HPP and PSP power generation scheme



xcitation System

The basic principle of power generation is when a magnetic field is moved across a

stationary conductor, voltage is induced in the conductor. Voltage will be induced even if

conductor is rotated and magnetic field is kept stationary, Generators consist of two circuits an

electric circuit and a magnetic circuit; one is rotating with respect to other. The magnetic circuit

of a generator is called exciter.

In modern generators magnetic field is produced by an electromagnet. The

intensity of magnetic field can be varied by varying the amount of DC current

applied to electromagnet. Generator output voltage is affected by the following

factors:

1) Intensity of the flux in the rotating magnetic excitation field. This can be

varied by varying the DC current applied to the electromagnets.

2) Rate at which flux lines cut by the conductor. This is not variable since the

generators operator at the rated constant speed.

3) Length of the conductor (Not variable).

The excitation system is intended for providing the following functions:

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

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

generator.

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

Field forcing at the set voltage response and de excitation at disturbances in the power

grid causing voltage rise or drop in the system.

E



Rotor field suppression by the field circuit breaker at protection operation with

simultaneous inversion of the rectifying unit.

Operation on joint control maintaining even distribution of the reactive load between

machines.

Limiting the ratio of ceiling field current to nominal field current by two (2) per unit

without time delay as well limiting of over load by the time-inverse characteristics.

Limiting minimum field current with set point depending on generator active power in

the mode of VAR load demand from the grid.

Protection of the generator for loss of excitation/asynchronous run.

Protection of generator transformer from damage at frequency drops under no load

conditions by lowering the voltage regulator setting suitably.

Compensation for step-up transformer impedance.

Startup of pumped storage units by back-to-back method and for electrical braking

operation of the units.



raking System

1) To stop the machine, first wicket gates are closed.

2) It is then left in the idle condition, so that the speed reduces to 50%. 3) Dynamic brakes: When the speed is reduced to 50% dynamic brakes are

applied. For this, first the

4) 11KV incomer line is stepped down to 230V which after passing through

circuit breakers followed by field breakers is supplied to the rotor in

opposite direction (opposite to the direction of excitation) and the 3

phase AC is shorted, which applies the force in opposite direction and

helps in reducing the speed.

5) Dynamic brakes are applied until machine reduces to 4 percent.

6) Mechanical brakes are applied when the speed reduces to 4% after application of

Dynamic brakes.

B

Figure 8: Mechanical Brake



overnor and oil pressure System

Governor System:

The main purpose of governor system is to maintain the rotational speed of the

rotor within permissible limits. It consist of Electrohydraulic Transducers, which takes

input from electronic transducers installed in unit control boards and performs desirable

action by sending it to servomotor. It also takes signals from servomotor and in case of

any malfunctioning, it sends signal to electronic transducer to take mandatory action

according to the scenario.

For controlling the speed of a turbine a signal proportional to the speed is to be fed to

the control system. The pressure is maintained constant by a separate unit called as oil

pressure unit.

For achieving automatic control, a portion of the system output is fed back to the

system and this signal is called feedback. The governor then automatically adjusts the

flow to control the prime movers power.

Oil Pressure Unit:

Application of oil pressure system:

1) The heat generated by the moving parts can be carried away

by the oil which can be transmitted to exchanger.

2) Various devices (big or small) like operating server motors for

the wicket gates and opening and closing of the spherical valve of MIV

(Main inlet valve) can be operated using a simple energy source.

3) The oil acts as a lubricant which can increase the component life and hydraulic

actuators have a good response.

G



Figure 10: Oil pumping unit with motor

Figure 9: Oil and air pressure units



as Insulated Switchyard

After generation of power at 15.75 KV it is stepped up to 400 KV by transformers installed at

elevation EL 605 M. Then it is passed through GIS before sending it to power grid. GIS needed

very less space for a switchyard than in comparison of building it in an open space.

a) 3 phase AC wave is first passed through the surge arrestors which arrests the

high peaks in the wave. Basically it is the capacitor which charges and discharges in

order to remove those high peaks.

b) Current transformers are there for the protection. Their rating is 500A/1A. c)

Isolators give option to switch between the bus bars.

d) Circuit breakers are also there, which contains Nitrogen gas to pressurize the

oil. Nitrogen pushes the piston as a result the circuit is completed and the conduction

starts. Circuit breakers here are hydraulic type. The pressure of SF6 in circuit breaker is

6.9MPa.

e) Bus Coupler: - It connects the power generated to the transfer line. B11 is

connected to B12 & B21 is connected to B22.

f) Insulation: - For insulation SF6 is used. AS soon as the line charges, spark is

generated, SF6 quenches the spark. SF6 is used because Fluorine ions have high electro

negativity which quickly recombines to form SF6.

g) L1 line trap is provided for the hotline communication.

h) Here capacitive voltage transformers are used because it works well on high

voltage and are economical.

G



In GIS red cylinder contains Nitrogen whereas blue cylinders contain SF6. Nitrogen is used here

to take vacant space created by motor whenever breaks are applied. As breakers are removed or

applied by a motor and Nitrogen fills it very fast and it is cheap.

Figure 11: Gas Insulated Switchyard



omputerized Control Room

It uses SCADA i.e. Supervisory Control and Data Acquisition system. It has full control on

starting, running and stopping of a machine. Amount of energy produced, Shutdown of a

machine, starting of a machine etc. is ensured by SCADA system of ALSTOM installed in

CCR.

Start Sequence:

C START

1) Check Start Condition

2) Open Start Page

3) TM START

1) MIV open

2) Gen. Cooling Water ON

3) Gen. Space Heaters OFF

4) Field Beaker ON

5) Governor Start



If Speed> 95%

Excitation ON

If Voltage>80%

Spinning Mode

Check

Synchronization

and close circuit

breaker

END



eferences

1) A report on Energy Scenario of India, Bureau of energy efficiency, India

(BEE)

2) Official Site of THDC, www.thdc.gov.in

3) Technical Directories of THDC India Limited

4) Official site of ALSTOM (www.alstom.com)

5) Wikipedia Tehri dam Portal

R



pilogue

This industrial training has helped me in improving my practical knowledge about

electrical machines and electrical apparatus. With state of the art gigantic structure this

is a source of power for the country. I realized how it is easy to waste energy easily and

how difficult and costly it is to make. GIS, SCA Transformers was such an important part

of learning.

The ability of staff to let us understand the working principle of machines and

their familiar behavior was unforgettable. TEHRI HEP was a phenomenal experience for

me to get trained in such a place full of engineering and technology.

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Documents

Charu Kandpal Final Report on HEP