用模糊集贴近度法识别变压器的故障电流和励磁涌流

根据电力变压器差动保护中故障电流和励磁涌流波形的对称情况，提出了用波形对称及模糊集贴近度原理来辨别故障电流和励磁涌流的新方法。数字仿真结果表明，本方法可准确识别故障电流和励磁涌流，即使在空载合闸于内部故障时，保护继电器也能迅速可靠动作，避免了采用二次谐波制动导致的误动问题。

Identifying Fault Current and Energizing Inrush Current of a Transformer Using Fuzzy Degree of Nearness

According to the symmetry of the waveforms of fault current and energizing inrush current from the differential protection of power transformer,a new algorithm of identifying fault current and energizing inrush current using the theory of the symmetry of wave forms and the fuzzy degree of nearness is presented in this paper.The results of the digital simulation show that the method can identify fault current and energizing inrush current precisely and makes it rapid and reliable for the protective relay to trip even if switching on under no-load conditions with occurrence of a internal fault and then the misoperation led to by second harmonic restraint is avoided.