Study On Electromagnetic Transient Characteristics Of EHV/UHV Circuit Breaker

The long-distance and high-capacity transmission in modem power system are needed, the short-circuit current, transient recovery voltage and secondary arc characteristics are analyzed when the current limiting reactors are installed in the concentrated load regional, the series capacitor compensation device are used to improve the transmission distance and UHV transmission system, the electromagnetic transient effection of increase the auxiliary measures in the power system are discussed in this paper.Firstly, the transient electromagnetic characteristics with current limiting reactor in the load concentrated region of power system are analyzed. The short-circuit current is reduced significantly when the current limiting reactors are installed in the power system, but they will make circuit breaker the rate of rise of transient recovery voltage increases, to this problem, the parallel capacitors are used to limiting the rate of rise of transient recovery voltage; The introduction of the current limiting reactors to power system will increase the secondary current amplitude, but not influence the secondary arc extinguished time.Secondly, the transient electromagnetic characteristics with compensation capacitor compensation devices in the transmission lines of power system are analyzed. In the condition of small short-circuit current, the capacitors bypass device may not action, thus will make the rate of rise of transient recovery voltage increase obviously. The different layouts of series capacitor are compared, the simulation results show that the transient recovery voltage amplitude raised about 50%; when the circuit breakers arc extinguished, the over-voltage amplitude of line side is higher, the attenuation is slower and influence the insulating properties; the low frequency oscillation and DC component are included in the secondary current because of the capacity discharging, they have the influence on the secondary arc extinguished seriously. Therefore, for the compensation capacitor transmission line, when the fault occurs, series capacitor compensation device must be reliable bypassed, so it can reduce the effection of transient electromagnetic on the power system. Finally, the short-circuit current, the transient recovery voltage, the secondary arc and the secondary current and resonance overvoltage characteristics of neutral reactor are analyzed for the UHV transmission system. In the initial operation of the UHV power system load flow is lighter, short-circuit current is lesser, at the same time both sides have the simple lines, so have the big transient recovery voltage; At the same time long lines, large interphase capacitance and large secondary current, the shunt reactor and neutral reactor are used to compensate the capacity of interphase and phase to ground, so the secondary current and the resonance overvoltage are restrained, accordingly, neutral reactor to appropriate selection are needed so as to achieve better effect.