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How does a Pelton turbine control water flow when electricity demand changes?
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To maintain a constant generator speed when electricity demand changes, a Pelton turbine must adjust its power output by modifying the water flow rate. This process is managed through the following mechanisms:
- Needle Control: The flow rate through each nozzle is regulated by a centrally located spear or needle. This component slides forward or backward, controlled by a hydraulic servomotor, to adjust the opening while maintaining consistent water velocity.1
- Preventing Pressure Surges: Because sudden flow reductions can cause destructive pressure surges (water hammer) in the supply pipeline, the system avoids rapid needle closure. Instead, it employs a governor to manage the transition.12
- Deflector Plates: To safely manage load decreases, a deflector plate is often partially inserted between the jet and the runner. This diverts and dissipates a portion of the water's energy immediately, allowing the needle to close slowly and safely without causing pressure spikes in the penstock.1