基于最值差别和归一化面积识别励磁涌流方法研究

New Method for Discriminating Inrush Current Based on the Difference between the Maximum and Minimum and Unitary Area in Cycle

变压器空载合闸或外部故障切除时会产生励磁涌流,而运行中匝间或匝地短路时会产生内部故障电流。变压器主保护选择差动在原理上存在不足,带来的问题就是如何准确鉴别励磁涌流和故障电流。在大量仿真和试验的基础上,综合两种电流的特点,提出了一种鉴别励磁涌流的新方法。该方法基于励磁涌流偏于时间轴一侧和故障电流接近正弦波的特点,以周波内最值差别和归一化面积作为综合判据。仿真和试验验证了方法的正确性和可行性。

When connecting a transformer to the system without load or remove its exterior fault, it will bring mag- netic inrush current. But when there is short fault happened in the coil-to-coil or coil-to-earth, it will bring internal fault current. Because the differential protection has some theory deficiency as transformer main protection, it needs to discriminate the two kinds of current correctly. After doing a lot of simulations and tests, we put forward a new method for discriminating the inrush current based on integrating the characteristics of the two kinds of cur- rent. Because of the character that the magnetic inrush current leans to the one side of the time axis and the inter- nal fault current is similar to the sine wave, so we use the difference between the maximum and minimum and the unitary area in cycle as a general criterion to discriminate the inrush current. The validity and feasibility of the new method is tested according to simulating and testing.