主变压器中性点间隙击穿零序保护误动分析与建议

某地区电网110kV系统发生单相接地故障时,引起升压站110kV出线零序Ⅰ段保护越级误动作。通过故障录波图和现场勘查,发现升压站不接地变压器中性点保护间隙击穿放电是事故起因,变电站保护装置定值配合及主变压器中性点保护间隙布置方面也存在问题。对此,提出了有针对性的防误动改进措施,现场应用效果良好。

Mal-operation Analysis and Suggestion on Zero-sequence Relay Caused by Transforms Neutral Point Gap Breakdown

A mal-operation of line No.Ⅰ zero-sequence protection of 110 kV wind farm booster station is resulted from a out-area single-phase ground fault occurring on 110 kV regional power grid grounding system.The unearthed transformer neutral point protection gap strike and discharged in booster station is the fault cause,which is found by the recorded fault waveforms and scene investigation.In addition,it also points out the existing problems due to relay settings improper coordination in substation and problem of neutral point protection gap arrangement for main transformer.Through detailed theoretical analysis on the mal-operation according to the area power system situation,an improving measure to avoid protection malfunction is put forward.The application results on site of substation are verified effective.