一种利用小波原理防止变压器差动保护误动的新算法

A NEW ALGORITHM TO PREVENT MISOPERATION OF TRANSFORMER DIFFERENTIAL PROTECTION BASED ON PRINCIPLE OF WAVELET TRANSFORM

外部短路时 ,由于电流互感器 (CT)饱和所引起的暂态不平衡电流造成的变压器差动保护误动作 ,一直是变压器差动保护中的一大技术难题。作者从理论上分析和证明了在外部发生短路故障时 ,电流互感器不会立即饱和 ,暂态不平衡电流也不会立即出现的现象 ,并提出了一种应用小波变换原理提取故障暂态特性 ,准确检测故障发生时间 ,利用“时差法”

The misoperation of transformer differential protection caused by transient unbalanced current resulted from saturation of CT is still a difficult technical problem. In this paper, through theoretical analysis it is revealed that under external short circuit the CT will not be saturated immediately and the transient unbalanced current will not appear at once. Applying wavelet transform principle to pick up transient characteristics of the fault and accurately detect the time when the fault occurs, a new algorithm is put forward. It makes use of the time difference which can effectively prevent the misoperation of transformer differential protection caused by transient unbalanced current resulted form external short circuit.