Application of the EDS (Energy Dissipation System)
The PRV valve is designed to rapidly divert the water flow away from the turbine into a turbine bypass system when the guide vane apparatus needs to perform a sudden manoeuvre (for example to close suddenly at emergency shutdown, or when the unit is quickly unloaded at sudden load reduction). PRV’s primary operation is short term, only to enable safe turbine manoeuvring and to protect the power plant against subsequent transient loads and possible turbine runaway. The PRV can be utilized for long term operation during discharge regulation at ramping. For optimal performance during the transients, operation of the PRV shall be appropriately synchronized with operation of the turbine’s guide vane
apparatus. Synchronous operation takes the place when the flow through the turbine is quickly reduced and simultaneously the flow through the PRV is increased so that the sum of both flows during the whole transient process is remaining unchanged. It is possible to reduce the water flow through the turbine quickly without any essential alteration of the flow in the penstock and undue pressure rise in the water supply system.