发电机机端电压互感器匝间短路引起的过励磁保护动作分析

针对发电机机端电压互感器（TV）一次绕组匝间短路过程产生的电流引起熔丝缓慢熔化的情况，推导了TV一次绕组匝间短路和熔丝熔断过程TV二次绕组电压计算公式，得出故障后二次绕组电压降低的结论。在此基础上分析了ABB Unitrol F型励磁调节器内TV断线逻辑存在的缺陷，同时研究了熔丝缓慢熔化引起该类型励磁调节器强励和过激磁保护的机理，并结合一起现场事故案例对理论进行验证。最后，通过搭建Matlab/Simulink仿真对理论进行验证，仿真结果证明了理论的正确性。

Operation Analysis of Over-Excitation Protection due to Voltage Transformer Inter-turn Short-Circuit at Generator Terminal

A number of inter-turn short-circuit accidents have occurred in recent years in the primary winding of voltage transformer (TV) at generator terminal, which often causes slow fuse melting due to the large short-circuit current. In this paper, a calculation formula of TV secondary winding voltage is derived respectively for TV's primary winding inter-turn short-circuit and slow fuse melting, and it is concluded that the secondary winding voltage will decrease after a fault occurs. An analysis is made on the bugs in the TV disconnection logic in ABB Unitrol F excitation regulator, and a study is conducted on the mechanism of over-excitation protection and strong excitation of the excitation regulator caused by slow fuse melting. The theory is verified through a case study of an accident. Finally, the Matlab/Simulink simulation is used to verify the theory, and the simulation result proves the correctness of the theory.