Research Of Transient Recovery Voltage Of Circuit Breaker In Small Capacity Generator Terminal

In recent years, our country vigorously advocate and develop new energy technology, a large number of distributed energy power station is builded, the small capacity generator(≤30MW)have been widely used. Scholars have demonstrated the necessity of installing generator circuit breaker(GCB) in the large capacity generator terminal, but they did not make in depth study on whether GCB should be installed in small capacity generator terminal.So in this paper, transient recovery voltage(TRV) of circuit breaker in small capacity generator terminal is researched with the electromagnetic transient program PSCAD/EMTDC as generator circuit occurs three-phase short circuit fault or out-of-step fault, to determine whether distribution circuit breaker can replace GCB to be installed at the generator terminal. To meet the needs of practical engineering, this paper researchs measures to reduce the rate of rise of TRVand derives expressions of calculating the value of TRV as generator circuit occurs three-phase short circuit fault. In addition, the transient recovery voltage of circuit breaker in feeder line in the distributed energy power station is also researched in this paper. The main achievements are as follows:① If three-phase short circuit fault occurs in generator terminal, the transient recovery voltage of circuit breaker in small capacity generator terminal is caused by the RLC series or parallel circuits of 110 k V system source and step-up transformer, and the rate of rise of TRV is highest of first-pole-to-clear circuit breaker. With the increase of generator capacity, the rate of rise of TRV of circuit breaker in generator terminal also increase.If the capacity of generator is 12~24MW, the rate of rise of TRV is no more than 0.34 k V/μs, thus distribution circuit breaker can replace GCB to be installed at the generator terminal, however GCB must be installed at the generator terminal if the capacity of generator is 24~30MW. The calculation results show that the capacitor which is installed in the terminal(which is near step-up transformer) of circuit breaker can effectively reduces the rate of rise of TRV. If the capacitor is greater than 0.2μF, the rate of rise of TRV is less than 0.34 k V / μs.② If three-phase short circuit fault occurs in low voltage terminal of transformer, the transient recovery voltage of circuit breaker in small capacity generator terminal is caused by the RLC series or parallel circuits of generator, and distribution circuit breaker can replace GCB to be installed at the generator terminal if the capacity of generator is 12~30MW. If generator circuit occurs three-phase short circuit fault, the short circuit fault occurrence time random and the circuit breaker disconnected time random has no influence on simulation results, the conclusion has universal applicability. The error of the value which is calculated by expressions of TRV and the simulation value is less than 3%, thus can meet the needs of practical engineering.③ The author explain the rule of how to value the out-of-step angle if distributed energy power station occurs out-of-step fault, analyse transient recovery voltage of circuit breaker in generator terminal as the generator capacity is different and the out-of-step angle is different. The calculation results show that when installed 0.2μF, 0.3μF, 0.4μF, 0.5μF, 0.6μF, 0.8μF capacitor in the terminal(which is near step-up transformer) of circuit breaker if the capacity of generator is 12~30MW, respectively, can effectively reduces the rate of rise of TRV to less than 0.34 k V / μs, thus distribution circuit breaker can replace GCB to be installed at the generator terminal.