Calculation Analysis of Dynamic Properties of Impulse Lines of Steam Turbine Protection System with Electronic Safety Governor

The article examines the advantages and disadvantages of the failure of the mechanical and electronic safety governors in the protection systems steam turbines from unacceptable overclocking. The justification for using an electronic safety circuit breaker to increase the reliability of protection systems is given. A computational analysis of the dynamics of the operation of two types of schemes for connecting the valves of the electronic safety governor to the impulse line of the protection system has been carried out. In the first scheme, the valves is connected in parallel with the protective devices. The pulse protection line is powered through a choke washer. The valves of the electronic safety governor and protective devices drain from the impulse line. In the second scheme, the valves of the electronic safety governor is connected in series with the protective devices. In this scheme, the devise of the electronic safety governor simultaneously controls the supply and drain of working fluid from the impulse protection line. For each scheme, mathematical models have been developed, which represent systems of nonlinear differential and algebraic equations. The calculation was carried out for the case of protection tripping of the PT-25-90/10 steam turbine, which has an electro-hydraulic control system. The results of the calculations show that installing the valves of the electronic safety governor in series with the protective devices allows to have the higher pressure relief speed in the impulse protection line. It is concluded that the dynamics of the process is largely determined by the number of spring switches of the servomotors included in the impulse protection line. The results obtained can be used to modernize protection systems of steam turbines by introducing an electronic safety governor.