对电力变压器短路承受能力试验标准的理解

标准中认为为了在一个线圈中获得最大的非对称电流,应在该相线圈的电压过零时合闸。通常把线圈看成是纯电感,即认为线圈短路阻抗角为90°,在电感两端电压为零时合闸,可得到最大电流值。但是并不是所有的变压器的实际阻抗角都接近于90°,甚至有的只有37°,通过计算表明,考虑到实际阻抗角对最大电流值的影响后,即在线圈的电压过零时合闸所得到的非对称电流值最大。

IEC60076-5 considers that for acquiring the maximum asymmetry current in a winding, we need to close the power switch the voltage of the winding passes through zero.Generally the winding is regarded as a pure inductance,it means that the impedance angle of the winding is 90°,so we can acquire the maximum current when we close the switch as the voltage of a pure inductance passes through zero.But there are many transformers that their impedance angles are not close to 90°,even only 37°,In this case, when to close the power switch for getting the maximum asymmetry current? The article gives the conclusion that even conclusion that even considering the effect of actual impedance angle to maximum asymmetry current,we still need to close the power switch when the voltage of the winding passes through zero.