基于模糊逻辑的变压器励磁涌流二次谐波闭锁方案

Scheme for Second Harmonic Block of Magnetizing Inrush Current in Transformers Based on Fuzzy Logic

分析了变压器空投时差动保护中3种不同电流相位补偿方式识别涌流的效果,表明3种电流相位补偿方式识别涌流效果相当,可相互补充。引入模糊识别原理,提出了综合利用3种电流相位补偿方式的思想,适当选取二次谐波隶属度函数,分别求取不同电流相位补偿方式下A,B,C三相的二次谐波隶属度,进而得到各相的综合隶属度。在此基础上,提出基于综合隶属度的三取二原则方式来识别涌流,提高了变压器差动保护励磁涌流闭锁的可靠性。动模实验数据和现场实例的仿真分析验证了新方法的有效性和可行性。

This paper analyzes three different current phase compensation methods used in transformer differential protections for identifying inrush current when transformer is energized on no-load. It shows that these three current compensation methods have similar effect on identifying inrush current. According to this, a new algorithm for integrating these three current compensation methods based on fuzzy logic is proposed. By appropriately selecting the membership function of the second harmonic in three-phase differential current, the membership grades in case of different current compensation methods are obtained, then the integrated membership grade are acquired. Using the two-out-of-three principle which is based on the integrated membership grade, this new algorithm improves the reliability of transformer protection in blocking inrush current. Results of dynamic simulation and the analysis of field case show that the scheme for second harmonic blocking is effective and proper.