A faulty line detection method for single phase-to-ground fault in resonant grounding system with CTs reversely connected

Abstract

Single-phase grounding (SPG) faults often occur in distribution systems but are not well resolved in resonant grounding systems due to their complexity, particularly when zero-sequence current transformers (CTs) are connected in the reverse direction. This paper presents a faulty line detection method that is adapted to the reversal of current transformers. First, the zero-sequence equivalent model of a single-phase grounding fault is analyzed, and according to the healthy line equation, it can be deduced that the zero-crossing time of the transient zero-sequence current of the line is the same. Second, the transient zero-sequence current zero-crossing time difference between the faulty line and the healthy line is analyzed using Monte-Carlo simulation, and it is concluded that the absolute value of this difference is less than 1 ms in fewer cases. Finally, the zero-crossing time difference between the lines is used to construct the total timing sequence coefficient (TTSC). When all TTSC is less than 1 ms, the bus is faulty; otherwise, the line with the largest TTSC value is the faulty line. The test of the method is completed on the radial distribution network, laboratory data, field test data, and arc wave recording data. The results of extensive validation show that the proposed method has good performance and can detect faulty lines when the current transformer is reversed.