三相变压器励磁涌流及保护方案

Analysis of Magnetic Inrush Current of Three-phase Transformer and the Differential Protection Scheme

针对近期基于波形对称原理的变压器差动保护频繁误动的现状,从三相变压器励磁涌流的产生机理入手,分析了波形对称原理与2次谐波制动原理的内在联系,结合目前流行的2种相位补偿方式,指出了传统采用相间差动的保护方案误动的根本原因。针对220 kV以上D侧套管内装设电流互感器的变压器,提出了一种采用相电流差动接线的保护方案。该方案在理论上克服了传统方案的全部弊端,并可实现真正的分相制动;缺点在于保护范围有所减小,需要其他保护来配合。

In consideration of the frequent mal-operation of transformer differential protection based on the principle of waveform symmetry, this paper analyzes the internal relationship of the waveform symmetry principle and the secondary harmonic restraint principle based on the generating mechanism of the magnetic inrush current of the three-phase transformer. The root cause of the real-operation with the conventionally adopted differential protection is pointed out by considering the two phase compensating methods in current use. For the 220 kV and above transformer with current transformer equipped on the delta side, this paper provides a new approach based on the phase current differential relay. This approach has made it possible to overcome all the disadvantages of the conventional scheme in theory, and is capable of implementing genuine phase constraint. The drawback of the proposed method is that the protective zone is reduced and needs other relays for coordination.