基于数学形态梯度的变压器转换性故障识别新判据

转换性故障的准确识别是变压器差动保护亟待解决的难题之一。该文利用TA饱和的变化特征对变压器转换性故障进行识别。当TA饱和后，在一次电流过零点附近总会存在一定的线性传变区，在区外故障期间表现为差流波形中含有间断，而区内故障时不存在间断。通过对相邻2个极值点之间的差流波形进行形态梯度处理，将形态梯度处理后的波形进行3等分，根据3段波形面积的相对大小来判断差流波形中是否存在间断，从而实现对变压器转换性故障的正确识别。仿真结果表明，该方法能在TA饱和情况下正确识别变压器区内、外故障，并对变压器发生转换性故障(区外转区内)做出正确判断。

A New Algorithm to Distinguish the Transferring Fault of Transformer Protection Based on Morphological Gradient

Distinguishing the transferring fault is one of difficulties for transformer differential protection. According to CT (current transformer) saturation characteristic, a new algorithm of distinguishing the transferring fault is put forward. As the primary current of CT crosses zero, a small linear transmission part of CT would appear, no matter how CT saturated. Based on this characteristic, the waveform of the differential current would expose discontinuous parts when an external fault occurred; in contrast, this phenomenon would not appear for an internal fault. The morphological gradient is adopted to deal with the waveform between two adjacent extremal points of the differential current. By dividing the gradient waveform into three parts and calculating each part's area, the discontinuous in the differential current could be detected according to the relative size of three above areas. By judging whether the discontinuous parts are existed in the differential current, the transferring faults could be easily distinguished. Simulation results show that this algorithm can distinguish the internal fault, external fault and the fault transferred from the external to the internal under the condition of CT saturation.