Location Powerhouse and headworks is located at Suindibar (14

km before Besisahar).

Dam Site: Besisahar (4 km before Besisahar).

Elevation: 760m (2,490 ft)

40 km upstream of the existing Lower MarsyangdiHydropower Plant.

Construction

Project Initiation: 2001

Project Completed: 2007

Project was financially and technically supported by Germany.

General Info

Run-of-river type with daily pondage of 5 hours peaking.

Second largest hydro-electric project.

Max. gross head: 110m

Net head: 98m

Installed Capacity: 70MW(two 35MW turbines)

Annual average energy: 398 GWh

Dam, Spillway and Intake Structures

Type of dam: combined concrete gravity and rockfilldam.

34.5m height above foundation.

Power tunnel length

Low pressure: 5,230m(between desander outlet and surge tank)

High pressure: 225m (between surge tank and discharge measurement chamber)

Spillway: 3 radial gates

W x H = 12 x 19.54 m

Spillway capacity: 4,270 m3/s

at headwater level of 626 masl

Leakage of certain amount of water due to rocks or minerals settling.

Turbine being shut

Surge Tank & Penstock Vertical, circular surge tank with net diameter 20m.

Height 45 m

1 concrete cased steel pipe Penstock.

Length: 212-218m (between dischargemeasurement chamberand turbine inlet valve)

Guide vanes are designed to: Allow the water to enter

the runner withoutshock. Entire vane is notopen initially and onlycertain water is flowedand when the turbine isrun for sometime, entirevane is open.

Allow the water to flowover them withoutforming eddies.

Allow required quantityof water to enter theturbine.

Turbine Details

2 Francis, vertical shaft

40 m3/s rated discharge

Gross head: 110m

Rated Output: 35.9 MW

Rated Speed: 333.33 rpm

Erosion in turbines are many due to cavitation.

Cavitation is the formation of bubbles filled withvapours within the body of moving liquid. It causes:

Noise and vibration of various parts.

Causes pitting (erosion of material) making the surfacerough.

Reduction in discharge which causes suddent drop inpower output and efficiency.

Generators Two 3-phase synchoronous

generators.

Rated output: 39 MVA

Rated voltage: 11 KV ± 7.5%

Rated frequency: 50 Hz

Power factor: 0.85-0.9

Rated speed: 333.33 rpm (18 poles)

Excitation System Consists of autonomic voltage regulator (AVR), exciter,

measuring elements, power system stabilizer (PSS) andlimitation and protection unit.

Exciter is required to provide necessary field current to therotor winding of a sync. machine.

Exciter has its field winding in the stator, and armaturewinding in the rotor.

Exciter is controlled by the AVR, which is very effectiveduring steady-state operation, but, in case of suddendisturbances it may have negative influence on the dampingof power swings, because then it forces field current changesin the generator.

This may be eliminated by introducing the power systemstabilizer (PSS).

Here, STATIC excitation (self-excited) DC system is used.

It consists of thyristor or transistor bridge andtransformer.

Energy needed for excitation is brought to generatorfield winding via slip-rings with carbon brushes.

The main disadvantage is that excitation supplyvoltage, and thereby excitation current, dependsdirectly on generator output voltage.

Another problem: large time constant (about 3 sec)and commutation difficulties.

Transformers Ratio : 132 ∕ √3 : 11 KV

Total of 5 tr. used: four 3-phase and one 1-phase.

Rated Power: 14.5 MVA

Forced oil type transformers. Oil is circulated by pump from the top of the transformer tank to a cooling plant.

For regulating the voltage, load tap changers are provided.

Oil/air heat exchanger used.

Buchholz Relay protectstransformers from all kinds offaults.

It is equipped with an externaloverhead oil reservoir calleda conservator.

Function of Conservator: To allowroom for oil expansion andcontraction.

The conservator acts as areservoir of oil that can then flowback into the tank so that no airenters it.

Breather are used to absorbthe moisture content fromthe sucked air, while thetransformer oil getsexpanded due to heating.

Breathers make use ofsilica gel coloured withbrown used extensively inpower transformers.

Circuit Breaker SF-6 CB used.

Rated voltage: 145 KV

Rated lightning withstand voltage: 650 KV

Rated normal current: 3150 A

Rated out-of-phase breaking current: 10 KA

From right to left:

Switches, SF6 Circuit Breaker, Current Transformer, Switches, Potential Transformer, 132 KV NEA TL

Potential Transformer

Primary Voltage: 132000/ √3

Secondary Voltage: 110/ √3

50 VA

Monthly Generation Report from Commissioning till date

S.N Month

Generation (MWh)

Designed 67/68

2068/69

Target Generation% inc/dec with respect to

Design 66/67 67/68 Target

1 Shrawan 47,840.00 38,821.40 38,683.14 44,085.60 -9.9% 13.4% 11.0% 11.4%

2 Bhadra 47,110.00 34,967.10 37,766.30 46,977.90 -1.6% 14.3% 32.6% 22.8%

3 Ashwin 46,980.00 38,460.50 37,763.22 42,807.70 -8.9% 24.9% 11.3% 13.4%

4 Kartik 42,225.00 37,942.20 37,906.55 43,003.00 1.8% 14.0% 13.3% 13.4%

5 Mangsir 30,805.00 20,057.90 36,810.44 36,903.30 19.8% 0.3% 84.0% 0.3%

6 Poush 21,410.00 27,531.70 27,459.97 27,596.25 28.9% 1.8% 0.2% 0.5%

7 Magh 15,990.00 21,542.80 21,509.72 12,596.75 -21.2% -41.0% -41.5% -41.4%

8 Falgun 14,610.00 19,874.80 22,509.63

9 Chaitra 17,565.00 20,831.30 22,371.43

10 Baisakh 26,305.00 28,733.20 30,483.50

11 Jestha 39,615.00 44,877.40 43,439.36

12 Asadh 47,135.00 43,511.40 42,603.22

Annual Gen.(GWh) 397.59 377.14 399.31

Fault Sheet and Log

Presented by:Bhavin PradhanBishnu DawadiKalyan ShresthaKishwor Karki

Umesh GurungRoshan Gurung

DEPARTMENT OF ELECTRICAL ENGINEERING

Kathmandu Engineering College