Research on Zero-sequence Fault Sequence Analysis Strategy for Grounded Systems With Ground Loss Condition

The 220kV effective grounding system occasionally experiences a loss of ground point, leading to the formation of a ground loss condition due to tripping order issues during faults. Consequently, the original effective grounding system transforms into an ineffective grounding system. The zero sequence protection behavior of the transformer grounded through the gap will correspondingly vary with changes in operational mode. An analysis of resulting protective action behavior necessitates a series of grounding mode transitions. The presence of a secondary circuit fault, particularly in the case of multi-point grounding in the TA circuit, can pose challenges for fault analysis. This paper mean to address the main issue of converting from a non-effectively grounded system to an effectively grounded system by analyzing two-port cut-points and transitioning from primary fault transient analysis to secondary TA loop analysis. The analysis method enables effective switching of the analysis perspective based on a relatively fixed process and the selection of analysis ports. This allows for shielding interference information during the analysis, highlighting the focus of the problem, and ultimately pinpointing the essence of the fault to be analyzed from a clear and effective perspective.