Abstract: The overspeed signal is one of the most important protection signals in the turbine protection system. As an important parameter in DEH (Digital Electro-hydraulic Control) system, the response time of overspeed is always difficult to test. By improving the signal source from the signal generator, the amplitude and the frequency of the signal source can be adjusted, and the frequency change point can be accurately identified in the testing process, therefore the accurate testing results can be obtained.

Key words: steam turbine, ETS, DEH, over-speed response time, test, signal source