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Components of a run-of-river plant

Short answer

A run-of-river plant diverts river flow without significant storage. Components: diversion weir, intake, gravel trap, desander (critical for sediment removal), headrace canal/tunnel, forebay or surge tank, penstock, turbine, generator, tailrace. Output varies with river flow.

Discuss the functions and importance of various components of hydropower plant with proper schematic diagram of ROR hydropower plant.

A run-of-river (ROR) plant diverts part of the river flow through a waterway to a powerhouse without any significant storage, so its output follows the natural river flow. Each component has one job: take water in, clean it, carry it with little head loss, convert its energy, and return it to the river.

Schematic of an ROR plant

 River
 ==|==  Diversion weir + intake (trash rack, gate)
   |
 [Gravel trap] -> [Desander / settling basin]
   |
   |  Headrace canal / tunnel (low slope)
   v
 [Forebay] or [Surge tank]
   |
   |  Penstock (steel pipe, steep)
   v
 [Valve]-[Turbine]-[Generator]  POWERHOUSE
   |              |
 Tailrace        GSU transformer -> Switchyard
   |              -> Transmission line
   v
 Back to river

Components, functions and importance

ComponentFunctionImportance
Diversion weir / barrageRaises water level and diverts flow into intakeGives a steady water level at intake
Intake with trash rack and gateAdmits the design discharge, stops floating debrisProtects the waterway; gate closes for floods and maintenance
Gravel trapRemoves coarse gravel just after intakePrevents canal choking
Desander (settling basin)Settles fine sediment (usually particles above 0.2 mm)Protects turbine runners from abrasion, very important in Himalayan rivers
Headrace canal / tunnelCarries water at low slope to the forebay or surge tankMost of the head is gained here, so head loss must be small
Forebay (canal system)Small pond before the penstock; final settling and spillProvides submergence and absorbs small load changes
Surge tank (tunnel system)Open shaft at end of pressure tunnelAbsorbs water hammer and supplies water on sudden load increase
PenstockPressure pipe from forebay/surge tank to turbineConverts elevation to pressure head; designed for water hammer
Main inlet valveButterfly or spherical valve before turbineIsolates the turbine for shutdown and emergency
TurbineConverts hydraulic energy to mechanical energyType chosen from head and discharge
GeneratorConverts mechanical energy to electrical energyUsually a synchronous machine, run in step with the grid
Governor and excitationControl speed (frequency) and voltageKeep the unit stable and in step with the grid
Transformer and switchyardStep up voltage, switching and protectionConnect plant to the grid
TailraceReturns water to the riverMust avoid backwater that reduces net head

Key points

  • ROR plants are cheap and have small environmental impact, but output drops sharply in the dry season.
  • Because Nepalese rivers carry heavy sediment, the desander and good intake design decide the life of the turbines.
  • A riparian release (environmental flow) is always let past the weir for downstream life.

✓ Answer checked by Claude Opus 5.5 (high effort)

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