励磁涌流导致330 kV变压器差动保护误动分析

Analysis of 330 kV Transformer Differential Protection Undesirable Tripping Caused by Inrush Current

风电及光伏等分布式电源的接入导致系统故障暂态过程日趋复杂,变压器差动保护的环境愈发恶劣。分析了一起含分布式电源系统变压器空投时差动保护误动的案例,通过调取现场录波数据,发现变压器空投时产生较严重的励磁涌流,由于变压器电流差动保护采用了按相闭锁的涌流识别策略,并且为了提高保护的性能,谐波制动判据采用了随时间变化的浮动定值,变压器主保护误动跳闸,导致空投失败。针对此次误动案例,考虑目前变压器电流差动保护采用的谐波闭锁/制动原理,从差动电流补偿方式、谐波闭锁/制动原理、影响励磁涌流衰减的因素等角度,通过理论分析和仿真验证研究了谐波闭锁/制动策略对变压器主保护性能的影响,并针对可能产生的不正确动作情况,提出了切实可行的建议。

The access of distributed generation such as wind power and photovoltaic leads to the increasingly complex transient process of system fault and the worse environment of transformer differential protection. This paper analyzes a case of mal-operation of differential current protection when the transformer is no-load energizing in the system with distributed generation. The analysis of recording data shows that there is serious inrush current when the transformer is energizing, and the main protection locked by phase is not locked correctly, resulting in the protection mal-operation. In view of the fact that the differential protection based on the second harmonic restraint cannot act correctly in some cases, this paper studies the differences between the two protection methods and the possible incorrect operation through theoretical analysis and simulation verification from the perspectives of current compensation mode, locking mode and inrush current attenuation, and puts forward appropriate suggestions.