System for responding to a partial loss of load of a turbine power plant

Abstract

An electrohydraulic system for rapidly reducing the steam flow through the high pressure and lower pressure stages of a turbine power plant in response to a partial loss of electrical load, is disclosed. In response to the detection of a partial loss of load, the system provides for controlling a portion of the governor valves and all of the interceptor valves to close rapidly and independently of the turbine control system; also to operate the turbine control system to cause the remaining governor valves to operate to a predetermined partially closed condition independent of the normal governor valve reference demand signal by applying a signal for changing the open limit position of the governor valves; and to eliminate the affect of the impulse pressure loop from the turbine control system. The upper valve position limit signal and the slower rate of change reference demand signal is matched to the applied signal. Restoration of a predetermined total steam flow to the lower stage of the turbine is provided through a combination of a rapid opening of the interceptor valves followed by a slower opening where such rapid to slower opening is governed by a signal representative of the additive position of all the interceptor valves. After an adjustable time delay all the governor valves are controlled in accordance with the reduced valve position limit signal, then can be controlled by the total reference demand signal under normal control at a sustained reduced load.