以无穷大容量电源、恒阻抗负荷模型的电力系统三相短路为基础,通过三要素法推导冲击电流表达式,分析非周期分量中时间常数Ta为极限值时短路电流的波形,重点分析时间常数Ta递增时的冲击电流及其出现时刻的变化趋势,以及1/4周期内电流的极小值及其出现时刻的变化趋势.指出冲击电流出现时刻的极小值为9.6ms,约为短路后1/2工频周期处;估算冲击电流时可取短路后稳态电流幅值的1.82倍;1/4周期内电流的极小值出现时刻的最大值为2ms,为短路后1/10工频周期处.%It is based on the three-phase short-circuit of power system, in which infinite capacity source, constant impedance model is assumed.Using three-element method, impulse current expression is derived, short-circuit current waveform is studied as time constant Ta in non-periodic part is equal to extreme value, variation tendency of impulse current and its appearance time, current minimum value and its appearance time in one fourth of power cycle are especially analyzed as time constant Ta increased.It is pointed out that the minimum value of appearance time of impulse current is 9.6ms, which is about one half of the power cycle after short-circuit is occurred;the estimation value of impulse current is 1.82 times of steady-state short-circuit current;the maximum value of appearance time of the minimum value in one fourth of power cycle is 2ms, which is one tenth of power cycle after short-circuit is occurred.
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