电磁干扰导致发电机励磁系统误动的分析

随着发电机单机容量的增大,厂用电配电网络中电缆线路产生的电磁干扰问题愈来愈不容忽视。特别是高压大容量电动机的起动过程,暂态时间长、电流幅值大,如果控制电缆的敷设未按照相关标准进行,将会对机组励磁等某些敏感设备造成电磁兼容性故障,影响发电机的正常运行,进而破坏电力系统稳定。针对一台300MW汽轮发电机在机组电动给水泵起动时励磁系统跳闸的故障现象,从励磁系统灭磁逻辑、设备安装现场的电磁环境方面进行系统分析,认为误动跳闸是电磁干扰引起的。提出并采取将安装于控制室的自动电压调节器(AVR)柜迁移至发电机底部的励磁室、以消除给水泵动力电缆与励磁低压电缆间电感性耦合干扰的改造措施。两年多的运行实践验证了分析的正确性和改造措施可行性。

Analysis of Generator Excitation System Trips Caused by Electromagnetic Interference

Along with the increase in the generator capacity,electromagnetic interference produced by station supply system could not be ignored.Especially if control cables are improperly set,when large capacity motor starts,with it's long transient start-up time and high current,will result in electromagnetic compatibility trouble to some sensitive systems,jeopardize the normal generator operation and power system stability finally.The excitation system of a 300MW generator set tripped coincidently during the period of any one of the three boiler feed water pumps started.Through systematical analysis both from excitation system de-excitation logic and the electromagnetic environment in which the equipment was installed,it is shown that all the mis-operations were caused by electromagnetic interference.To reduce or eliminate the reactive coupling interference from the cable of feed water pump,many disturbance suppressions were provided and carried out accordingly,such as relocating the auto voltage Regulator(AVR) cubicle which once installed in the control room to the excitation system cabinet under the generator.Two years of normal operation testifies the correctness of the analysis and the feasibility of the taken measures.