Analysis on the malfunction of zero sequence protection in 35kV ungrounded system of wind farm

Due to the wind farm 35kV system single-phase grounding fault capacitance current is relatively large, Therefore, the wind farm 35kV system adopts the bus configuration Z-type grounding transformer and the neutral point is grounded by small resistance, Zero sequence protection are used to quickly remove the single phase ground fault.In this paper, the single-phase ground fault of wind power plant collection wire in Eastern Inner Mongoliais is taken as an example. introduces the working principle of zero sequence current transformer,Clarify the setting and matching principles of zero sequence protection,,Comparing the different wiring modes of several cable shielding layers will be cause how Influence on the secondary measurement current of zero-sequence transformer, Analyze the zero sequence protection rejection of the set wire,The cause of the grounding tripping event. Summarizes the cable shield connection mode correctly,And propose rectification measures on site.