电力变压器励磁涌流和内部故障识别新方法

区分励磁涌流和内部故障时的短路电流,是变压器差动保护的难点技术之一,虽然目前已有多种方法,但每种方法都或多或少地存在着一些问题,空载合闸误动或内部故障时拒动(或延时动作)的情况还时有发生。在引入瞬时无功功率理论的基础上,提出了一种依据变压器两侧三相差瞬时有功功率和瞬时无功功率直流分量比值的变化关系来识别变压器励磁涌流和内部故障电流的新方法。该方法不仅简便易行,而且从平均有功和平均无功的关系出发,进一步揭示了变压器励磁涌流与内部故障本质上的不同。RTDS仿真实验结果表明:该方法简单可靠,识别效果显著。

A new approach to the discrimination between inrush-current and internal fault current of transformers

The discrimination between internal fault current and inrush current in transformer is very difficult in transformer protection.This paper proposes a new algorithm based on the theory of instantaneous reactive power for the discrimination between internal fault current and inrush current of transformer protection.This algorithm is mainly based on the relationship of DC component between the instantaneous active power and the instantaneous reactive power.There are not only the advantages of simpleness and convenience,but also the advantages,due to considering the relationship between active power and reactive power,of revealing the differences between inrush currents and internal fault currents more deeply in nature.The results of RTDS simulation show that a valid discrimination between internal fault currents and inrush currents in transformer can be made by this algorithm,which is simple and reliable.