断路器合闸输电线路单相接地短路故障线路两侧短路电流计算与分析

输电线路发生单相接地故障,当短路故障不能及时消除时,线路两侧的断路器在重合闸操作过程中可能存在合闸短路故障的工况。运行经验表明,线路两侧断路器在合闸短路故障时,流过断路器的短路电流存在延迟过零的现象,从而导致断路器开断失败。文中通过建立单相等值电路模型,理论分析了在不同的合闸短路工况下故障线路两侧断路器流过的短路电流表达式,结论表明,由于后合闸断路器对电路拓扑的改变,使得先合闸断路器中流过的短路电流可能会出现延迟过零。又进一步分析与讨论了合闸初始相角α、间隔时间Δt、幅值比K对短路电流的影响规律。最后,通过在PSCAD/EMTDC软件中搭建仿真模型,以实际电网中电厂送出联络线上故障线路两侧断路器合闸短路故障为例,计算与讨论了故障线路两侧断路器流过的短路电流波形及其延迟过零现象。

Calculation and Analysis of Short Circuit Current on Two Sides of Single-phase Grounding Fault Line of Circuit-breakers Closing Transmission Line

As single-phase grounding fault occurs in transmission line, the short circuit fault cannot be eliminated in time, the circuit breakers on both sides may close short circuit fault during reclosing operation. Operating experience shows that the short circuit current flowing through the breaker has the phenomenon of delayed zero -crossing when the breakers on both sides close the short circuit fault, which cause circuit breaker to interrupt the fault. By establishing a single-phase equivalent circuit model, this paper theoretically analyses the expression of short circuit current flowing through the breakers on both sides of the fault line under different closed conditions. The conclusion shows that due to the change of circuit topology caused by the later closed circuit breaker, the short circuit current flowing through the first closed circuit breaker may delay zero-crossing. Furthermore, the effects of initial phase angleα, interval time Δt and amplitude ratio K on short circuit current are analyzed and discussed. Finally, taking the closing short circuit faults of circuit breakers on both sides of power plant output transmission line as an example, building a simulation model in PSCAD/EMTDC software, the short circuit current waveforms and delay zero-crossing phenomena of circuit breakers are calculated and discussed.