This paper presents the structure, work principle and main functions of HP fire-resistant oil DEH digital electrohydraulic control system, and its application to 200MW condensing steam turbine.

To restrain the frequent action of over-speed protection control (OPC) and to prevent secondary acceleration over-speed, it is suggested that OPC acting logic in digital electronic-hydraulic system (DEH) should be optimized and the reheat steam pressure be lowered as soon as possible after load rejection, thus providing reference for load rejecting test on large units.

In order to guarantee the power system security, economy running, simultaneously causes the electrical to conform to the quality index, The current turbine power unit set widely uses digital electro-hydraulic control system (DEH), it already became most important part of power plant automation.