一起因导线电动力造成的保护越级动作分析

Analysis of skip action of protection caused by electrodynamic force between conductors

分析了大庆油田电网35 kV喇四线延时电流速断保护越级动作的原因,阐述了喇四变电所35 kV喇四十线继自装置的事故调查过程,通过35 kV喇四线电动力分析及计算,得到了导线电动力、导线短路最大电流、导线最大偏角、导线最低点处放电的弧垂边界值。分析结果表明,萨北变电所35 kV喇四线保护误动事故是由于35 kV喇四线最低点处的弧垂长度过长(应小于2.5 m)、短路电流产生的电动力使A、C两相放电造成的。

This paper analyzes the reasons for the skip action of instantaneous delay current protection in 35 kV Lasi conductor of Daqing Oilfield power network and presents the accident investigation of the relay protection and automation device in 35 kV Lasishi conductor of Lasi substation.Through the analysis and calculation of the electrodynamic force of 35 kV Lasi line,the electrodynamic force,the maximum current while short circuit,the maximum declination and the sag boundary value of discharge at the lowest point of conductors are worked out.The analysis shows that the protection maloperation in 35 kV Lasi conductor of Sabei substation results in the over length（which should short than 2.5 m） of the sag at the lowest point and discharge from two phases A and C by the electrodynamic force generated by short-circuit current.