Transformer Differential Protection And Magnetizing Inrush Current

This paper mainly focuses on the differential protection for transformer. The main contents are as following:(1) We analyse the effects of protection sensitivity from unbalanced current caused by adjusting the transformer On-Load Tap Changer (OLTC).According to the phenomena of dynamic examination, we analyses the vector of the unbalanced differential current caused by adjusting the transformer On-Load Tap Changer (OLTC) and the vector of differential current caused by internal resistance ground fault, then it is pointed out that moving up or down the OLTC will increase the unbalanced differential current, but they have different influence on the sensitivity. Finally an example is given to show the different influence.(2) There are two transformations as delta-star and star-delta. This paper carries out a initial research on the affection of the two transformations to distinguish inrush.