New Line-selection Method for Single Phase Grounding Fault in Distribution Networks with Two Phase's Current Transformers

摘要

In China,current transformers (TAs) are just installed at A-phase and C-phase in most distribution networks with neutral indirectly grounding.It is a very difficult problem to select single-phase grounding line using the currents of A phase and B phase.After analyzing the currents of A-phase and C-phase when B-phase grounding fault occurs,the fault line detection algorithm applying the transient characters of the sum of A-phase mutational current and C-phase mutational current is proposed.For A-phase to ground fault or C-phase to ground fault,the algorithm of constructing B-phase transient current and furthermore constructing the exact zero-sequence current is founded out through the analysis in frequency domain and time domain,and the fault line-detection method can be actualized according to zero-sequence current's transient characters.Based on them,a new method used to identify single phase to ground fault line using transient characteristics in two TAs distribution networks is formed.The proposed line-selection method is not affected by the mode whether the Petersen coil exists at neutral and the unbalanced current under normal operation condition.