一起三相不一致保护误动分析及其回路改进

Analysis on a Three-phase Inconsistent Protection Malfunction and a Improvement of the Circuit

某220kV线路进行单相重合闸校验时,故障相跳开后,两正常相随后亦跳开,重合失败。原因为断路器本体三相不一致时间继电器拨片氧化,致使其延时短于重合闸时间,三相不一致先于重合闸出口。对2种三相不一致回路改进方法进行了分析,方法 1不能避免出口继电器接点误动,方法 2需断路器辅助接点完成三相跳闸回路电流灭弧,可能会导致严重故障,且2种方法均增加了拒动风险。提出将可调整型时间继电器更换为固定延时型,简化继电器结构,提高可靠性,可避免因拨片氧化、旋钮振动变位等原因带来时间误差并造成保护误动作。

In a single-phase reclosing check of a 220 k V lines, the reclosing failed with tripping of two normal phase circuit breakers after that of the fault phase, which was triggered by the oxidized time relay gear of the three-phase inconsistent protection that made the time of three-phase inconsistent protection shorter than the reclosing time and three-phase inconsistent protection acted before the reclosing. Two common three-phase inconsistent circuit improvement methods are analyzed： the first method can not avoid lockout relay contact misoperation while in the second method the auxiliary contact of circuit breaker is needed for arc suppression in three-phase tripping circuit, which may lead to serious faults; moreover, both of the methods increase the risk of operation refusal. The paper suggests replacing the adjustable time relay with fixed delay type ones,simplifying the relay structure and improving the reliability to prevent protection misoperation caused by time errors resulting from gear oxidation or knob displacement due to vibration.