the succes story on r m

8/22/2019 The Succes Story on R M

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SUCCESS STORY ON R, M & U WORKS OF UMIAM STAGE II HEPP

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SUCCESS STORY

ON R, M & U WORKS OF UMIAM STAGE II HEPP,

Meghalaya Power Generation Corporation Limited, UMSUMER

Umiam Stage II Hydroelectric Power Plant is located at Umsumer in Meghalaya State of India,

which is 36-km from Shillong, the capital of the State. The project site is at an elevation of 729-meters above

mean sea level at around latitude 25.6 N, longitude 91.5E and is surrounded by hills. The maximum

ambient temperature experienced has been 32.5C and the minimum temperature has been 5C outdoors and

9C indoors, respectively.

MeECL has been controlling following five hydro electric power plants in the Umiam-Umtru

river basin.

(a) Umiam Stage I Hydroelectric Power Plant, (4 x 9 MW) Commissioned in 1965

(b) Umiam Stage II Hydroelectric Power Plant, (2 x 9 MW) Commissioned in 1970

(c) Umiam Stage III Hydroelectric Power Plant, (2 x 30 MW) Commissioned in 1980

(d) Umiam Stage IV Hydroelectric Power Plant, (2 x 30 MW) Commissioned in 1992

(e) Umtru Hydroelectric Power Plant (4 x 2.8 MW), Commissioned in 1957 & 1970

The total installed capacity of the system in the basin is 185.2 MW.


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Fig. 1

The Umiam Stage II Hydroelectric Power Plant was commissioned in 1970. Both the hydro

turbines and generators of the power plant were manufactured by Toshiba Corporation, Japan. After

operation of approximately 40 years, some problems have occurred on the generating units. Because of the

importance of Umiam Stage II Hydroelectric Power Plant for coordinated economic operation of the above

mentioned Power Stations of MeECL located at the downstream cannot be ignored in the context of draw

down water from Umiam reservoir for running the downstream power stations. If this power station ceases to

operate, all other stations will starve because of a cascade generation system. As such, Renovation of Umiam

Stage II Hydroelectric Power Plant was necessitated.

In the month of May 2003, Meghalaya State Electricity Board (MeSEB), now Meghalaya

Energy Corporation Limited (MeECL) approached Japan Bank for International Cooperation (JBIC) for

financial assistance for the complete R&M works of the Umiam Stage-II Power Plant. In response, the

JBIC arranged the technical team TERI (The Energy & Resource Institute) to conduct a survey about themachine condition for R&M. Soon after, JBIC entrusted a consultant firm, TEPSCO (Tokyo Electric

Power Services Company, Japan) which carried out a feasibility study under the team (SAPROF) Special

Assistance for Project Formation) after which a report was submitted on September 2003. The report

recommended for the renovation and modernization work on the generating Units for Umiam Stage-II

Power Plant including 132 kV Switchyard Equipments and Generator Transformers.

In 2005, Joint Venture of Tokyo Electric Power Services Company (TEPSCO) Limited and

the Tokyo Electric Power Company (TEPCO) signed contract for the consultancy services for the RM&U

works of Umiam Stage-II HEPP with MeECL.

In 2009, after the bidding, MeECL contracted RM&U works for the project with the

following company on December 4, 2009:-

Toshiba Corporation, Japan (Toshiba)(for design & supply of hydro turbine, generator & control/protection system).

Toshiba Plant System Corporation, India (TPSC)(for design & supply of BOP and installation & commissioning works).

Toshiba Technical Services International Corporation, Japan (TTSI)(for dispatching installation & pre-commissioning technical supervisors).

The work for Renovation and Modernisation started in May 2011 with the disassembling,

replacement and repair works for the existing equipment/parts and continued until October 2011. Later,

pre-commissioning test and commissioning tests were performed by the contractors. The project was

finally commissioned on January 6, 2012 (25 monthly form the commencement date of the contract).

The following were the major works carried out.

1.1.Hydraulic Turbine1.1.1. General


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Prior to R,M and U work the turbine in Umiam Stage II HEPP had a capability of unit output of

10.5MW. However, the turbine could not output 10.5MW due to the limitation of the generator

capacity of 10.6MVA with a power factor of 0.85. The project had the total capacity of 2 x 9MW

only since the original commissioning. In this R, M & U Works, in order to enable the turbine to

output 10.5MW, the generator is designed to have as capacity of 12MVA with a power factor of

0.9.

The major parts of turbine except the existing turbine shaft, guide vanes and embedded parts (draft

tube liner, stay ring, bottom ring) are replaced with the new ones based on the latest design. The

main inlet valves, governor system and the related mechanical equipment also are replaced with

the new ones.

1.1.2. Hydraulic Turbine1.1.2.1.Type and Rating

(1) Number installed : Two (2)

(2) Type of Turbine : Vertical Shaft Francis Type

(3) Elevation

a) Reservoir water level

- Maximum : EL. 804.02 m (2,638 ft.)

- Minimum : EL. 801.58 m (2,630 ft.)

b) Tail water level

- Maximum : EL. 725.08 m (2,379 ft.)

- Minimum : EL. 722.34 m (2,370 ft.)

c) Centerline of turbine distributer : EL. 722.16 m(4) Net Head

- Maximum : 78.50 m

- Design : 77.67 m

- Minimum : 75.00 m

(5) Turbine Output

- at Maximum net head : 10,500 kW

- at Design net head : 10,500 kW

- at Minimum net head : 9,980 kW

(6) Rated Turbine Discharge : 15.47 m3/s (per unit)

(7) Rated Speed : 428.5 min-1

1.1.3. Pressure Relief Valve (PRV)All reused parts of Pressure Relief Valve such as the valve body, cylinder, cylinder cover, valve,

piston were repaired and/or machined in shop and the embedded part (lower body) were

repaired at site. All other parts for PRV were replaced with the new ones and self-lubricated

bearings were applied to all bearing portions for PRV.

1.1.4. Governor System including Oil Pressure & Compressed Air Supply Systems(1) Type and Rating


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a)Number of Governor : Two (2)b)Type of Governor : Digital PID electro-hydraulic type

(2) System Description

The existing governor actuators were replaced with the latest designed ones, and oil pumping

sets and oil pressure tanks, air compressors, air tank, oil & air piping, electrical cables and their

accessories were replaced with the new ones except the existing oil sump tanks. The existing

governor regulators were removed. In the Contractors governor design, the governor regulator

functions were accommodated in the unit control cubicle. The oil pressure supply system for

each unit is commonly used for operation of the guide vane, PRV and MIV.

The oil pumps and air compressors for the system are automatically controlled by the new

Motor Control Center (MCC), which was installed on the Generator Floor.

Compressed Air Supply System:

The Compressed air supply system is commonly used for generator brake operation, governor

system of both units.

1.1.5. MIV and By-pass Valve

(1) Type and Rating

a) Number of MIV : Two (2)b) Type of MIV : Thru-flow typec) Nominal diameter : 1,700 mmd) Maximum flow : 15.47 m3/se) Operation of MIV :Oil pressure (2 servomotors for each MIV)

(2) Description of MIV

The existing MIVs were removed and the new MIVs were designed, manufactured by

FOURESS ENGINEERING (INDIA) LIMITED. Each new MIV is operated by two (2) oil

operated servomotors mounted on the top of MIV. The oil pressure of MIV servomotors is

supplied from the oil pressure supply system commonly used for the governor & MIV.

1.1.6. Cooling Water Supply System & Drainage/Dewatering System(1) System Description

The existing equipment, parts, devices and piping (excluding embedded piping) for the

cooling water supply system and drainage/dewatering system were removed and all new

system were installed. Cooling water for the generating units is taken from the penstock and

cooling water is filtered through the strainer mounted on the line between the penstock and

water head tank and, after that, cooling water is filtered again through the strainer mounted

on the line between the head tank. The automatic water strainers and their sand discharge

valves are controlled by the new Motor Control Center (MCC) with detecting a differential

pressure between the outlet and inlet of strainer and/or timer. The drainage pumps for the


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drainage/dewatering system are controlled by the new Motor Control Center (MCC) with

detecting the water level in the drainage pit.

(2) Construction of Cooling Water Supply System

a) Water head tank (existing one) : One (1)b) Automatic motor-operated water strainer

- between the penstock and water head tank : Two (2)

- between the water head tank and generating unit : Two (2)

c) Shaft seal strainer : Two (2)d) Automatic motor-operated valve : Two (2)

3) Construction of Drainage/dewatering Systema) Drainage pump (submergible type) : Two (2)b) Water level switch (float type) : One (1)

1.1.7. Motor Control Center (MCC)The new Motor Control Center (MCC) is installed on the Generator floor. The MCC controls

the following auxiliary equipment of the generating units.

(1) Oil Pumps for Governor SystemTwo (2) oil pumps (one for normal use and other for stand-by) for each unit are installed on

the turbine floor. The oil pumps are controlled by detecting oil pressures and oil levels in the

oil pressure tank.

(2) Generator Space HeatersThree (3) Generator Space Heaters were installed in the generator air housing and they arecontrolled by detecting temperature inside the generator air housing.

(3) Air Compressors for Compressed Air Supply SystemTwo (2) oil pumps (one for normal use and other for stand-by) for each unit are installed on

the turbine floor. The oil pumps are controlled by detecting oil pressures in the oil pressure

tank.

(4) Drainage Pumps for Drainage/Dewatering SystemTwo (2) submergible drainage pumps are installed in the drainage pit. The drainage pumps

are controlled by detecting water levels in the drainage pit.

(5) Automatic Motor-operated Water Strainers and Sand Discharge ValveTwo (2) automatic strainers (one for normal use and other for stand-by) is installed on the

line between the penstock and water head tank and other two (2) automatic strainers (one for

normal use and other for stand-by) are installed on the line between the water head tank and

generating units. The automatic strainers are controlled by detecting a differential pressure

between the inlet & outlet of strainer and/or timer. Each strainer is equipped with an

automatic sand discharge valve and water after filtering in the strainer is discharged to the

tailrace through the sand discharge valve.

(6) Automatic Motor-operated Valves


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Two (2) automatic valves (inlet from the penstock to water head tank and outlet from the

water head tank to the generating units) are installed on the line of cooling water supply

system. The automatic valves are opened before starting the generating unit and closed after

stopping the generating unit.

1.2.Generator1.2.1. General

The existing generator in Umiam Stage II HEPP with capacity of 10.6MVA at a power factor

of 0.85 (lagging) was upgraded to a capacity of 12MVA at power factor of 0.9 (lagging) so

that turbine could deliver maximum output of 10.5MW in this R, M & U Works.

The major parts of generator except the existing generator main shaft, rotor rim, stator frame,

bearing brackets, and base block for stator, are replaced with the new ones based on the latest

design. The air cooler, oil cooler, excitation system and the related mechanical and electrical

equipment also are replaced with the new ones.

1.2.2. Generator1.2.2.1.Type and Rating


(2) Type of generator : Vertical shaft, Francis Turbine driven, and

alternating current synchronous generator

(3) Rated output : 12.0 MVA

(4) Rated power factor : 0.9 lagging

(5) Rated frequency : 50 Hz(6) No. of phases : Three (3)

(7) Rated voltage : 11.0 kV

(8) Rated speed : 428.5 min-1

(9) Direction of rotation : Clockwise viewed from top

(10) Runaway speed : 780 min-1

(12) Stator winding connection : Star (Y)

(15) Maximum cooling water temperature : 25

(16) The value of I22t capacity of the generator : not less than 20

(17) Required flywheel effect : not less than 123 t-m2

(18) Excitation system

- Excitation ceiling voltage : 110 %- Ratio of ceiling voltage to rated excitation voltage : 211.8 %- Excitation system nominal response : 0.06 sec-1

(19) Type and Cooling method

- Type of generator : Suspended Type

-Cooling method : By air

1.3. Excitation System


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1.3.1. Type and Rating(1) Applied standard : IEC

(2) Ratings of excitation system

a) Type of excitation system : Brushless excitation system

b) Rated capacity : 69.5 kW

c) Rated voltage : 151 V

d) Rated speed of AC exciter and rotating rectifier : 428.5 min-1

e) Rated frequency

- Input and output of excitation transformer : 42.9 Hz

- Output of AC exciter : 42.9 Hz

(3) Parameters and performances of excitation system

a) Ceiling voltage : 225 V

b) Ratio of ceiling voltage to rated excitation voltage : 200 %

c) Flashing current and duration period for excitation system : 6 A15 sec.

d) Voltage setting range

- for AVR setter (90R) : 80 % - 110% rated voltage

- for Manual voltage setter (70E) : 30 % - 110% rated voltage

e) Excitation system nominal response : less than 0.06 sec-1

f) Excitation system voltage response time : less than 1.0 sec

g) Excitation control accuracy : 2 %

h) Maximum generator voltage rise at full load rejection : 30 % rated voltage

i) Power frequency withstand voltage for 1 minute- Circuits electrically connected with generator rotor winding : 1500 V

- Circuits not connected with generator rotor winding : 1500 V

- Control and detection circuits : 1500 V

(4) AC exciter

a) Type : Three phase, rotating armature type

b) Number of poles : 12

c) Rating of AC exciter

- Rated capacity : 74 kVA

- Rated voltage : 114 V

- Rated speed : 428.5 min-1

- Rated frequency : 42.9Hz

- Insulation class (armature and field winding) : Class F

- Temperature rise (armature and field winding) : 80 K

- Power frequency withstand voltage for 1 minute : 2 kV

Existing DC exciter was completely replaced by brushless AC excitation system as shown in

Fig. 2 Outline of AC Excitation System. In the drawing collector ring is for resistance

measurement during site commissioning test.


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Fig. 2 Outline of AC Excitation System


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1.4. Main Transformer1.4.1. General

The existing main transformers in Umiam Stage II HEPP were replaced by new main

transformer with rating of 3-phase step-up oil immersed with external heat exchangers

suitable for outdoor services in the climate conditions at site as given in Special Conditions

of Contract, and ONAF rating , and ONAN rating when the transformer is operated with the

power less than 80 % of the rated capacity.

1.4.2. Main transformer1.4.2.1.Type and Rating


(2) Type of transformer : Three (3) phase, outdoor, two (2)

winding, natural-air-cooled, step-up,

oil-immersed-type, generator transformer

(3) Ratings

a) Operating duty : Continuous

b) Rated capacity

- High-voltage winding : 9600/12000 kVA

(ONAN/ONAF)

- Low voltage winding : 9600/12000 kVA

(ONAN/ONAF)

c) Rated frequency : 50 Hz

d) Rated voltage- High-voltage winding : 132 kV

- Low voltage winding : 11 kV

f) Tapped winding capacity : 12,000 kVA

i) Maximum temperature rise

- Windings (Resistance method) : 55 K

- Top oil (Thermometer) : 50 K

j) Connection of windings

- High voltage side : Grounded Y

- Low voltage side : Delta

- Phase displacement : YNd11

(4) Temperature rises at rated operating conditions- Windings (average) : 55 K- Oil (top) : 50 K

(5) Temperature at rated operating conditions- Thrust bearing : 70- Upper guide bearing : 70- Lower guide bearing : 70


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1.4.2.2.Technical Data of Main Transformer(1) Applied standard : IS 2026

(2) Type and cooling method

- Type of main transformer : 3-phase oil immersed outdoor type

- Cooling method of main transformer : ONAN/ONAF

(3) Ratings

a) Operating duty : Continuous

b) Number of phases : 3

c) Rated capacity

- High voltage winding : 12,000 kVA

- Low voltage winding : 12,000 kVA

d) Rated frequency : 50 Hz

e) Rated voltage

- High voltage winding : 132 kV

- Low voltage winding : 11 kV

f) Connection and phase displacement : YNd11

1.5. 11 KV Metal-enclosed Switchgear and Service Transformers1.5.1. General

11kV Metal Enclosed Switchgears are composed of 11kV Generator incoming cubicle, 11kV

Link cubicle, 11kV VCB cubicle, 11kV Station service transformer cubicle and NGR cubicle.

The existing 11kV Metal Enclosed Switchgears and Service Transformers were replaced withnew ones. New 11kV Metal Enclosed Switchgears and Service Transformers were

manufactured by C&S EFACEC MV INDIA PVT.LTD in India. The 11kV Metal Enclosed

Switchgears were transported inland with all accessories including supporting structures,

spares, and all other equipment making the 11kV system.

1.6. Station Power Supply Facilities1.6.1. General

Station Power Supply Facilities are composed of Battery, Battery Charger, AC & DC power

supply boards. The existing Station Power Supply Facilities were replaced with new ones.

Battery, Battery Charger, DC power supply board were manufactured by Statcon Power

Controls Ltd. in India. AC power supply boards were manufactured by Larsen & Toubro

Limited. The Station Power Supply Facilities were transported inland with all accessories

including supporting structures, spares, and all other equipment making the Station Power

Supply Facilities.

1.7. Control and Protection Boards1.7.1. General


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The existing generator-transformer boards were replaced with new designed Control and

Protection boards. Control and Protection Boards are composed of two Unit Control Board,

one 132kV Switchyard Control Board and Recording Board. The Control and Protection

Boards are integrated type. Unit Control Board has sequence controller, automatic

synchronizer and HMI (Human Machine Interface). Each unit can connect in parallel with

power system automatically by using automatic synchronizer. The Control and Protection

Boards were manufactured by Toshiba in Japan. The Control and Protection Boards were

transported from Japan with all accessories including supporting structures, spares, and all

other equipment making the Control and Protection Boards.

1.7.2. Unit Control Boards(1) Components in board

a) HMIb) Metersc) Status indicatorsd) Fault indicatorse) Control switchesf) Mimic busg) Test terminalsh) Protection relays for Turbine and Generator

A compact list of the items replaced or repaired during the Renovation is given in Annexure I.

andphotos showing before and after R&M is given in Annexure II.

Pre-commissioning Tests.

Prior to commissioning of the Units in January 2012, all tests as per contract

were performed. Besides other tests, Generator Efficiency Test were performed on Unit #2

and Turbine Index Tests for comparison/confirmation with CFD analysis were performed on

both Unit #1 and Unit #2.

Final Acceptance Tests

All the tests for final acceptance as per contract were performed in for 10th

December up to

5th

December 2012. The tests include the following:

1. PRV operation check of Unit #1.2. Load Rejection Test of both Unit #1 and Unit #2.3. Output Test of both Unit #1 and Unit #2.4. Heat Run of both Unit #1 and Unit #2.

The following excerpt from the IEEMAJournal Volume 3-No.9. May 2012, page 112

During the Annual review meeting held in CEA during March-April 2012 with various utilities, 4 schemes


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which were earlier scheduled to be completed during XI plan have been shifted to XII plan. However, R&M

of one scheme namely Umiam Stage II (2X9 MW) of MeECL which was scheduled for XII plan, was

completed in 2011- 12, Thus, during XII Plan a total of 43 hydro R&M schemes (5 in Central Sector and

38 in State Sector) having an installed capacity of about 6663 MW at an estimated cost of about Rs. 4433

Crs. which will accrue benefit of about 3773 MW through uprating, life extension and restoration are

planned for implementation. One scheme of MeECL namely Umiam St. III (Kyrdemkulai) shall be taken up

in XII plan and will accrue benefit of 66 MW (6 MW uprating & 60 MW-LE) during plan

A comparison of Energy generated of Umiam Stage II with reference to Umiam Stage I,

before and after RM&U of the station is given below:

Generation of Stage I and Stage II in KWH for the last five years before RM&U of Stage II

Year Stage I(a)

Stage II(b)

% Generation of Stage II w.r.t. Stage I(b/a)x100

Average

2006-2007 61642800 27660080 44.87%

45.37%

2007-2008 150633800 67267000 44.66%

2008-2009 107800680 48667500 45.15%

2009-2010 110320850 51176900 46.39%

2010-2011 103803640 47519700 45.78%

Generation of Stage I and Stage II in KWH After RM&U of Stage II

MonthStage I

(a)

Stage II

(b)

Average % Generation of Stage II w.r.t. Stage I

(b/a)x100

Feb 2012

toJan 2013

99022800 48251300 49.57%

As a result of the R,M&U works on the Umiam Stage-II HEPP, it is observed that the

percentage generation of Umiam Stage-II with respect to Umiam Stage-I Power Station, shows an

upliftment by about 4.20 % as compared to the generation before the R,M&U work.


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ANNEXURE- I

The outline of R, M & U Works done for Umiam Stage II HEPP is described in table below.

Table 2.1-1 Works done for Equipment and Parts

R: Replacement item with new one O: Overhauling and repairing item X: Removal

Items Unit 1 Unit 2 Descriptions

1. Mechanical Equipment

(1) Turbine and Its Auxiliary

a) Runner R R

The runners were replaced with the newly designed

ones made of 13Cr-high Ni stainless steel material

based on CFD analysis.

b) Spiral case & stay ring O OThe hydraulic surfaces of spiral case and stay ring were

cleaned, repaired and painted.

c) Guide vanes O O

The hydraulic surfaces of guide vanes were cleaned

and painted for both units. The spindles of guide vane

were machined in shop for applying self-lubricated

bearing.

d) Head cover R R

The head covers were replaced with the newly

designed ones having self-lubricated bearing and

separated construction from the bearing housing in

consideration of ease of maintenance for the shaft seal

and applying the new type (segment type) guide

bearing.

e) Bottom ring O O

The guide vane bearing portions of bottom ring for

both units were bored/machined at site for applying

self-lubricated bearing.

f) Facing plates and wearing rings R RThe facing plates and wearing rings on the head cover

and bottom ring were replaced with the new ones.

g)Guide vane servomotors and

gate operating mechanismR R

The guide vane servomotors were replaced with the

new ones excluding the cylinders and cylinder covers.

The gate operating mechanisms including guide ring

were replaced with the newly designed ones having

self-lubricated bushings.

h)Guide bearing, cooler and

bearing housingR R

The guide bearing and the bearing housing were

replaced with the newly designed ones (Guide bearing:

segment type/Housing: separated construction from

head cover).

i) Shaft seal and sealing box R R

The shaft seals were replaced with new designed one

(Carbon seal type) and also the sealing boxes were

replaced with the newly designed ones.


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j)Upper draft tube and draft tube

linerO O

The air injection pipes were replaced with the new ones

and the inner surfaces of upper draft tube liner were

repaired and painted.

k)Thru-flow type inlet valve and

its servomotorR R

MIVs with its servomotors were replaced with the

newly designed thru-flow type MIV with servomotor.

Each MIV has two (2) servomotors.

l) By-pass valve R RThe by-pass valves were replaced with the newly

designed ones.

m) Pressure relief valve (PRV) O O

The PRVs were overhauled. The existing parts for

applying self-lubricated bushings were machined in

shop and some parts were replaced with the new ones.

The PRV liners were repaired and especially the outlets

of liners were patched with steel liners.


n)

Drain valves and pipes for

spiral case, draft tube and

penstock

R RThe drain valves and pipes for spiral case, draft tube

and penstock were replaced with the new ones.

o)Instruments, devices, cables

and pipingR R

All existing instruments, device, cables and pipes

except the embedded pipes were replaced with the new

ones.

(2) Governor and Turbine Control

System

a) Governor actuator R R The governor systems were replaced with the new type

governor system with the latest technology, which is

the digital PID electro-hydraulic type governor.

The governor regulator functions were accommodated

in the Main Control Boards.

b) Governor regulator R R

c) Turbine control panelR R

d) Speed Signal Generator (SSG) R R

(3) Oil Pressure Supply System

a) Oil pump with motor R R The oil pumps with motors were replaced with the new

ones and the oil pump motors are controlled by Motor

Control Center (MCC). All oil pressure tanks with

accessories, oil pipes and valves were replaced with the

new ones.

b)Oil pressure tank, oil piping and

valvesR R

(4) Air Compressed Supply System

a) Air compressor with motor R

Two (2) sets of air compressor with motor were

replaced with the new ones and the motors are

controlled by Motor Control Center (MCC).

(5) Cooling Water Supply System

a) Water head tank O The water head tank were cleaned and repaired.


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b) Water piping and valves R R

The exposed pipes and valves were replaced with the

new ones. The strainers were replaced with a motor

operated automatic strainer controlled by Motor

Control Center (MCC). Four (4) sets of automatic

strainers were supplied for the cooling water supply

system. Two (2) strainers were installed on the line

between the penstock and the water head tank and

others were on the line between the water head tank

and the generating units.

c) Water flow relays R R

The water flow relays were replaced with the new

magnetic flow meters installed at drainage side of

bearing coolers & generator air coolers

(6) Dewatering & Drainage System

a)Submersible water pump with

motorR Two (2) submersible pumps were installed for

dewatering and drainage and their operation is

controlled automatically by Motor Control Center

(MCC) through detecting the water level.

b)Water level switches with

accessoriesR

c) Necessary piping and valves R

(7) Auxiliary Machine Control

a) Motor Control Center (MCC) R R Including auxiliary control

b) Necessary wiring and cables R R

(8) Water Depression System

a)All devices, equipment, pipes

and valvesX X

All existing devices, equipment, pipes and valves for

the system were removed.

(9) Other Items for Mechanical

Equipment

a)Level monitoring devices

for intake & tailrace water levelR R

The float type level monitoring devices were installed

on the intake and tailrace and all level data is

transmitted to the powerhouse.

b) Spare parts and special tools R



2. Electrical Equipment(1) Generator and Its Auxiliary

a) Stator core R R The stator core and the stator winding were replaced

with new ones for both units. The existing stator frame

was reused because it is fixed on the concrete

foundation.

b) Stator winding with accessories R R

c)Stator winding main and neutral

leadsR R

d)Rotor winding and excitation

leadsR R

The following parts were replaced with new ones:

a) Rotor winding and excitation leads for both units

b) Rotor pole pieces with damper winding for both

unitse)

Rotor pole piece with damper

windingR R


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f)

Brake ring & brake /jack

system R R

The brake ring was replaced with new one for both

units.

All the brakes and jacks were replaced with doublecylinder type brake/jack system that used as brake by

compressed air injection and as jack by pressurized oil

for both units.

g) Upper bearing bracket O OThe upper bearing bracket was overhauled for both

units.

h) Thrust bearing pads R RThe thrust bearings were replaced with new ones for

both units.

i)Segment type upper guide

bearing and oil cooler

R R

The guide bearings were replaced with segment type

bearings and the oil coolers were also replaced with

new one for both units.

j) Lower bearing bracket O OThe lower bearing bracket was overhauled for both

units.

k)Segment type lower guide

bearing and oil coolerR R

The guide bearings were replaced with segment type

bearings and the oil coolers were also replaced with

new one for both units.

l) Collector ring X XThe collector ring was removed because of application

of brush-less type excitation system

m) Brush and brush holder X XThe brush and brush holder were removed because of

application of brush-less type excitation system

n) Air coolers R RAll air coolers for both units were replaced with

vertical flow type air coolers.

o) Pipes and valves R R

p) Instruments and relays R R

q) Operation lamp R R

r) Generator housing O O Painting

s) Terminal boxes R R For instrument, control & alarm cables

(2) Excitation System

a) Brush-less type AC exciter R R The existing exciters were replaced with brush-less

type excitation system for both units.b) Rotating rectifier R R

c)Protection relays for brush-less

exciterR R

d)Automatic voltage regulator

and excitation cubicleR R

e)

Epoxy resin molded self-cooled

excitation transformer equipped

with thermometer with alarm

contacts and adjustable wheels

R R

(3) Main Control Boards


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a) Main control board R R The generator-transformer panels for both units were

replaced with new designed ones.

New main control boards have sequence controller,

automatic synchronizer and HMI (Human MachineInterface).

b) Automatic control, recorder and

protection relay boardsR R

c) Supervisory control boards X XThe supervisory control panel was removed, because it

was not used.

d) 132kV control boards RThe 132kV control boards were replaced with new

ones.

e) Synchronizer & Synchroscope RThe synchronizer & synchro-scope were replaced with

new ones.

(4) 11kV Metal-Enclosed Cubicles

a) 11kV Metal-enclosed cubicles

with accessoriesR R

The existing 11kV cubicles were replaced with new

designed 11kV cubicle equipped with vacuum circuit

breakers for generators.

(5) Main Transformer

a)Outdoor-use three phase ON

transformer with accessoriesR R

The main transformers were replaced with new

designed ones.

b) Terminal boxes R R For instrument, control & alarm cables

(6) Station Transformer

a)

Epoxy resin molded self-cooled

station transformer with

accessories

R R

The transformers were replaced with new designed dry

type or resin molded type ones and those were installed

in the new 11kV cubicle.

b)Vacuum circuit breaker for

station service transformersR R

The vacuum circuit breakers were installed on station

service transformers circuit instead of existing

isolators.

(7) Station Service Low Voltage AC &

DC Circuit Boards

a)Station service low voltage AC

Circuit BoardsR Common use

b)Station service low voltage DC

Circuit BoardsR Common use

(8) Electrical Cable

a) 11kV power cables R R

b) Power cables for low voltage R R Including common cables

c) Control cables R R Including common cables

(9) Station Battery

a) Station battery with accessories RThe station battery was replaced with new one.

(Common use)

b)Battery charger with

accessories

R

The battery charger was replaced with new one and it

was equipped with auto changeover function that DC

supplies to emergency light at AC power failure.


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(10) Other Items for Electrical

Equipment

a)

All paints, sealing materials,

bolts and nuts necessary for

overhauling works

R R Including common use

b) Spare parts and special tools R Including common use

Annexure II


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After R&MDuring R&M


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After R&MDuring R&M

before after


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before after

before after


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before after

before after


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before after

before after


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before after

Digital typeMechanical type

afterbefore


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11KV, 12MVA

after

11KV,10.6 MVA

before

before after


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before after

before after


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before after

before after


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before after

Before After


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before after

before after


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before after

before after


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before after

before after


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before after

before after


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before after

Before repair After repair


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before after

afterbefore


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before after

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before after

before after


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before after

11/132KV, 10.6 MVA 11/132KV, 12 MVA

before after

the succes story on r m

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