Hydro electric

PRESENTATION OUTLINE

• Introduction to Nepal Electricity Authority

• Electrical Power System in Nepal

• Middle-Marsyangdi Hydroelectric Stations.

• Operating Principles of Hydroelectric plants.

• Hydro electric Power components

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INTRODUCTION TO NEPAL ELECTRICITY AUTHORITY (NEA)

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• NEA is a government owned electricity provider.• It works on all the part of electrical system.

GENERATIONTRANSMISSION DISTRIBUTIONCONSUMER PRICING

Electrical Power System in Nepal

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• GENERATION Voltage level: 11 KV, 3 Phase, AC, 50 Hz

• TRANSMISSION (voltage stepped up) Voltage level: 110 and 220 KV, 3 Phase, HVAC,

50 Hz

• DISTRIBUTION (Voltage stepped down) Voltage level: 11KV, 3 Phase, 50 Hz feeder line

220/380 Volts at consumer end

Middle-Marsyangdi Hydroelectric Stations

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Established: The plant was commissioned on 14 December 2008

Features:-One of the large power houses in Nepal.-70 MW generation capacity. Two units of 35 MW.System Voltage of 11 KV.-Connected to the National grid at the voltage level of

132 KV.-The average annual energy output amounts to 398 GWh

(Power x annual operating hours)

Middle-Marsyangdi Hydroelectric Stations

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Middle-Marsyangdi hydro electric power station.

Middle-Marsyangdi organization Chart (Technical)

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Operating Principles of Hydroelectric Stations

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A typical Hydropower Station

Operating Principles of Hydroelectric Stations

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1. Water flowing through Marsyangdi river is dammed so that required water level is maintained to pass the water to the intake gates. Spillways are operated to prevent the flooding.

2. Water then passes through intake gates to trash rack which prevents large debris from entering into the tunnel. The trash racks are cleaned periodically using cranes.

Operating Principles of Hydroelectric Stations

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3. Water then enters the desander where the sand present in water is removed by sedimentation. The collected sand is pumped back into the river through flushing channel.  4. Water almost free from sand then passes through tunnel to surge tank which prevents water hammering in penstock pipe and maintain constant flow through it.

Operating Principles of Hydroelectric Stations

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5. Water then enters the penstock after passing through the valve chamber and in the penstock; the discharge of water is measured. 6. The penstock then bifurcates to supply water for each unit. Each bifurcation is provided with a bypass valve for balancing the pressure during maintenance.

Operating Principles of Hydroelectric Stations

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7. Water then passes through the expansion pipe followed by main inlet valve (MIV) and enters the spiral casing. 8. Water is guided by the adjustable guide vanes which then impact the runner, thus rotating the turbine.

Operating Principles of Hydroelectric Stations

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9. This rotates the turbine shaft which is coupled with the generator which generates electricity based on the principles of electromagnetism. 10. The current so generated is passed to the transformers which step up the voltage to provide supply to the national grid.

Hydropower components

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1. Civil Structures like Dam, Opening etc

2. Some Mechanical Components like Turbine

Governor, valves etc

3. Electrical Components likePower Generator

Power TransformerExcitation System

Switch gear and Protection System etc

Civil Structures

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A typical dam and opening in Hydroelectric

stations at the Middle Marsyangdi MMHPS

Mechanical Equipments (only some are shown)

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1. Francis Runner 2. Butterfly valve Opened

Mechanical Equipments (only some are shown)

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3. Bypass valve 4. Guide Bearing

Electrical Equipments

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1. Power Generator

Generator Specifications at

MMHPS

: Type: 3-Phase, 2 unit, Synchronous

: Power: 35 MW each unit.

: Voltage level: 11 KV

: Frequency: 50 Hz

Electrical Equipments

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1. Generator Principles

1-Phase Three Phase Waveforms

Faraday’s law of electromagnetic induction

Electrical Equipments

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Brushless Excitation System

To provide the excitation field (magnetic fields) needed by

synchronous generator.

11 KV/180 volt excitation system is used at MMHPS

Electrical Equipments

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Power Transformer (Step Up)

Specification:

: 11 KV Primary (generation voltage level)

: 132 KV (Secondary national grid voltage level)

: Delta/Star type

: Power rating 42 MVA

: Purpose: For national grid connection.

Electrical Equipments

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Station and local Transformers (Step down)Specification:

: 132 KV Primary (National Grid level)

: 33 KV (Secondary Station level)

: Star/Delta type

: Power rating 5 MVA

: Purpose: Local Power Supply through Damauli-Udipur 33kv line

Thanks for your attention!

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Questions!

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