基于采样值相关原理的变压器保护方案

Study of a transformer protective scheme based on the correlation theory of sampled current values

为提高变压器微机保护性能,提出一种基于采样值相关度的变压器差动保护新方案,利用变压器两侧电流的采样值波形的相关度来有效识别变压器内部故障和外部故障,利用相关原理提取等效瞬时电感变化规律来区分励磁涌流和匝间短路故障。动模实验表明新判据能够快速、可靠地判别变压器内外部故障和励磁涌流。由于借鉴了常规比率差动的定值整定思想,使得新判据定值的整定简单易行,同时基于这种方法的判据对频率偏移和谐波的影响也有一定的抵御能力,在工程中具有良好的实际应用价值。

To improve the performance of transformerg microcomputer-based protections,this paper presents a new transformer differ- ential protection scheme. The new scheme uses correlation coefficients of sampled current values at transformer to distinguish internal faults and external faults, adopts the theory of correlation to extract the variation characteristic of instantaneous excitation inductance for distinguishing magnetizing inrush current and internal faults. Dynamic simulation results show that the new criterion can distinguish in- ternal fault from external faults and magnetizing inrush current very fast and reliably. Based on setting scheme of transformer percentage differential protection, the setting scheme of the new criterion is simple and feasible. Besides, the new criterion can effectively restrain the interference of harmonics and frequency variation, it has good application value in engineering.