Theoretical Analysis of Differential Protection Based on Sampled Vaules

This paper gives out a detail analysis on the fuzzy zone about the differential protection based on sampled values (the sample differential protection in short). At first it gives a brief introduction about the sample differential protection and illuminates some basic rules about the sequential fulfilled zone R and the repeated fulfilled zone S. Based on the relationship among R S and their medially unfulfilled zone, it unprecedentedly decomposes all the combination values of R S and jV into three cases. Then it gives out the mathematics expressions about the boundaries and fuzzy zone of all three cases. For easily unstanding this paper presents the 3-D illustration about the boundaries and the fuzzy zone. After analyzing it gives out some useful conclusions about how to choose R and S. It also makes some comparisons about the reliability and sensitivity between the two differential protections.