Troublesome problems existing in oil injecting test device of overspeed protective systems for four extraction steam turbines with unit capacity of 50MW put into operation in 1970s at Beijing Thermal Power Plant No.2 have been systematically described

the causes of device failure are analysed

and corresponding retrofit measures are put forward

having more thoroughly solved the problems of miss operation and failures in the oil injecting test devices for four said turbines

obtaining better benefits of safe and economic operation.