主变间隙保护的思考

Thinking of main transformer gap protection

220 kV分级绝缘变压器一般装有间隙保护,传统间隙保护的间隙零序电流和零序电压共用一个延时元件。通过一起雷击线路造成的主变间隙保护动作事故,分析了这起间隙保护动作的原因,得出零序电压作为变压器在不接地系统中运行时的接地保护,间隙零序电流作为变压器由不接地系统变为经过间隙接地运行时的接地保护,两者是变压器在不同运行方式下的不同保护,不应该通过相同的延时跳闸。提出了传统间隙保护的改进方案,并对其中的延时时间提出了整定意见。

Generally,220 kV graded insulation transformer has protection gap device.The zero-sequence current and the zero-sequence voltage sharing a delay element.Through a protection gap action accident of main transformer caused by lightning strike on transmission line,this paper concludes that zero-sequence voltage acts as the protection of a transformer in the non-grounded system,zero-sequence current acting as the protection of a transformer in the non-grounded system is changed to a ground protection in the grounded system through the gap.They are different operating modes protection,so they should not trip by the same delay.Finally,this paper proposes the improvement program and the set method of the delay time.