How do deflector plates help prevent water hammer in Pelton turbines?

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Rows of white wind turbines with spinning blades stand on a dry, grassy landscape at a wind farm near Tehachapi, California. — turbine Wind turbines near Tehachapi, California.

To prevent the destructive pressure surge known as water hammer, it is necessary to avoid sudden reductions in water flow within the supply pipeline, or penstock.

In Pelton turbines, deflector plates are used to manage load decreases safely. When the power output must be adjusted, a deflector plate is partially inserted between the water jet and the turbine runner. This action diverts and dissipates a portion of the jet's energy, allowing the flow to be reduced gradually by the needle valve without causing a dangerous pressure spike in the system.1