三相V/V牵引变压器励磁涌流的识别

摘要

The key issue of traction transformer differential protection is to distinguish magnetizing inrush from internal fault current. The algorithm based on the equivalent instantaneous inductance can reflect the essential characteristic of the traction transformer operating conditions and distinguish magnetizing inrush from internal fault current correctly. For the three-phase V/V traction transformer, the connection is different and the operating circumstance is much worse than power transformers, and the second harmonic restraint scheme can not restrain effectively. At present, the equivalent instantaneous inductance based algorithm is still not applied to the three-phase V/V traction transformer to recognize magnetizing inrush from fault current, even though it is popular in application to the power transformers. This paper improved the applied conditions and the arithmetic elements to calculate the average equivalent instantaneous inductance in the none-saturation zone of differential currents, and applied the improved algorithm to distinguish magnetizing inrush from fault current. Dynamic experiments verified that the algorithm can distinguish the magnetizing inrush current and turn-to-turn fault current reliably and be immune to saturation of current transformers.%牵引变压器差动保护的关键问题是如何有效识别励磁涌流与故障电流.等效瞬时电感算法能从本质上反映变压器的运行状态,能够准确识别励磁涌流与故障电流.对于三相V/V牵引变压器,其接线形式特殊,运行环境恶劣,二次谐波制动判据往往不能有效闭锁.目前,等效瞬时电感算法已经很普遍地应用于电力变压器,但该算法还没有应用于三相V/V牵引变压器识别励磁涌流和故障电流.本文对现有的等效瞬时电感算法的计算条件和运算单元进行修正,通过计算非饱和区等效瞬时电感的平均值识别三相V/V牵引变压器的励磁涌流与故障电流.通过动模实验验证算法的有效性,实现对励磁涌流与匝间短路的可靠识别,并具有抗电流互感器饱和的特性.