三相短路冲击电流出现时刻的分析

Discussion on the Instant of Short Circuit Maximum Peak Current’s Occurrence

对于无穷大电源供电的50 Hz感性电路而言,冲击电流约出现在突然短路后的0.01 s。但不同时间常数的电路所对应的冲击电流出现时刻会有所差异。为此有必要分析实际电路中冲击电流出现时刻与0.01 s的最大差异,即最不利的情况。经过分析认为:冲击电流出现在短路发生后的(0.0096,0.01)s,即其与0.01 s的最小比值大于96%。另外,冲击电流出现时刻与电路时间常数的关系是非单调变化的。

As far as a RL series circuit supplied by constant voltage source is concerned,roughly speaking,the maximum peak current occurs nearly at 0.01s after the short circuit suddenly occurs.Because the circuits with different time constant affect the instants of short circuit maximum peak current’s occurrence differently.It is necessary to consider the worst case,namely,the maximum discrepancy with 0.01s when maximum peak current appears.The conclusion is that the time interval when maximum peak current appears is(0.0096 s,0.01s)after the short circuit suddenly occurs,i.e.,the minimum ratio compared with 0.01 s is larger than 96%.In addition,the relation between the instants of short circuit maximum peak current’s occurrence and the time constants of circuits are neither monotonically increasing nor monotonically decreasing.