This document summarizes information about the 70 MW Middle Marsyangdi Hydropower Project located in Nepal. Key details include: - The powerhouse and headworks are located 14 km before Besisahar at an elevation of 760m. The dam site is 4 km before Besisahar. - Construction began in 2001 and was completed in 2007 with financial and technical support from Germany. - It has a run-of-river design with 5 hours of daily pondage. Installed capacity is 70MW from two 35MW turbines, with an annual average energy generation of 398 GWh. - The dam type is a combined concrete gravity and rockfill dam that is 34.5

3. 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 Marsyangdi
Hydropower Plant.

4. Construction
 Project Initiation: 2001
 Project Completed: 2007
 Project was financially and technically supported by
Germany.

5. 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

7. Dam, Spillway and Intake
Structures
 Type of dam: combined concrete gravity and rockfill
dam.
 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)

9.  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.

13. Turbine being shut

14. Surge Tank & Penstock
 Vertical, circular surge tank with net diameter 20m.
 Height 45 m
 1 concrete cased steel pipe Penstock.
 Length: 212-218m (between discharge
measurement chamber
and turbine inlet valve)

15.  Guide vanes are designed
to:
 Allow the water to enter
the runner without
shock. Entire vane is not
open initially and only
certain water is flowed
and when the turbine is
run for sometime, entire
vane is open.
 Allow the water to flow
over them without
forming eddies.
 Allow required quantity
of water to enter the
turbine.

16. Turbine Details
 2 Francis, vertical shaft
 40 m3/s rated discharge
 Gross head: 110m
 Rated Output: 35.9 MW
 Rated Speed: 333.33 rpm

17.  Erosion in turbines are many due to cavitation.
 Cavitation is the formation of bubbles filled with
vapours within the body of moving liquid. It causes:
 Noise and vibration of various parts.
 Causes pitting (erosion of material) making the surface
rough.
 Reduction in discharge which causes suddent drop in
power output and efficiency.

18. 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)

19. Excitation System
 Consists of autonomic voltage regulator (AVR), exciter,
measuring elements, power system stabilizer (PSS) and
limitation and protection unit.
 Exciter is required to provide necessary field current to the
rotor winding of a sync. machine.
 Exciter has its field winding in the stator, and armature
winding in the rotor.
 Exciter is controlled by the AVR, which is very effective
during steady-state operation, but, in case of sudden
disturbances it may have negative influence on the damping
of power swings, because then it forces field current changes
in the generator.
 This may be eliminated by introducing the power system
stabilizer (PSS).

20.  Here, STATIC excitation (self-excited) DC system is
used.
 It consists of thyristor or transistor bridge and
transformer.
 Energy needed for excitation is brought to generator
field winding via slip-rings with carbon brushes.
 The main disadvantage is that excitation supply
voltage, and thereby excitation current, depends
directly on generator output voltage.
 Another problem: large time constant (about 3 sec)
and commutation difficulties.

22. 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.

23.  Buchholz Relay protects
transformers from all kinds of
faults.
 It is equipped with an external
overhead oil reservoir called
a conservator.
 Function of Conservator: To allow
room for oil expansion and
contraction.
 The conservator acts as a
reservoir of oil that can then flow
back into the tank so that no air
enters it.

24.  Breather are used to absorb
the moisture content from
the sucked air, while the
transformer oil gets
expanded due to heating.
 Breathers make use of
silica gel coloured with
brown used extensively in
power transformers.

25. 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

26.  From right to left:
 Switches, SF6 Circuit Breaker, Current Transformer,
Switches, Potential Transformer, 132 KV NEA TL

28. Potential Transformer
 Primary Voltage: 132000/ √3
 Secondary Voltage: 110/ √3
 50 VA

29. Monthly Generation Report from
Commissioning till date
Generation (MWh)
2068/69
S.N Month
Designed 67/68 % inc/dec with respect to
Target Generation
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

30. Fault Sheet and Log

31. Presented by:
Bhavin Pradhan
Bishnu Dawadi
Kalyan Shrestha
Kishwor Karki
Umesh Gurung
Roshan Gurung
DEPARTMENT OF ELECTRICAL
ENGINEERING
Kathmandu Engineering College