基于电压相量差的发电机GCB失灵保护新原理

大型发电厂普遍安装发电机出口断路器(GCB),当发电机出现内部故障或异常工况时,依照相关规定对应的保护需通过GCB切除发电机,并同时启动GCB失灵保护.由于此时发电机电气量的特殊性及切机方式的多样性,目前工程中采用基于电流判据(相电流、负序电流判据)的GCB失灵保护无法有效检测部分GCB失灵故障.为提高GCB失灵保护动...

Novel principle of generator circuit breaker failure protection based on voltage phasor difference

GCB(Generator Circuit Breaker) is generally installed in large power plants. When the generator has internal faults or abnormal working conditions, the corresponding protection trips the generator by GCB according to relevant regulations, and the GCB failure protection is started at the same time. Due to the particularity of generator electrical quantity and the diversity of generator tripping modes, GCB failure protection based on current criterion(phase current and negative-sequence current criterion) used in current engineering cannot effectively detect some GCB failure faults. To improve the performance of the GCB failure protection, the electrical quantity characteristics of different GCB failure faults are analyzed by constructing fault composite sequence network using symmetrical component method. Considering the de-excitation process of generator, the conclusion is get that the fundamental voltage phasor difference between the two sides of GCB in the correct operation phase is large, while the fundamental voltage phasor difference between the two sides of GCB in the phase which fails to operate is nearly zero. Based on the difference of fundamental voltage phasor between two sides of GCB, the GCB failure protection criterion based on the fundamental voltage phasor difference is constructed. In order to improve the reliability of GCB failure protection under light load, the auxiliary criterion of third harmonic voltage phasor difference is introduced. Simulative results show that the proposed protection principle has high sensitivity under different GCB failure conditions.