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随着城市配电网中电缆线路比例的逐年上升,系统对地电容值显著增大,电磁式电压互感器饱和过电压将由通常的工频位移过电压转化为分频(通常是1/2次)谐振过电压,互感器的励磁电流甚至可达额定励磁电流的百倍以上,易烧断互感器高压熔丝,或使互感器严重过热,进而烧损、爆炸。此外,在单相接地消失后,还可能在互感器中形成低频(约2～5Hz)饱和电流,这种电流
As the proportion of cable lines in urban distribution network increases year by year, the capacitance value of the system to ground increases significantly, and the saturation voltage of electromagnetic voltage transformer will be converted from the usual power frequency displacement overvoltage to frequency division (usually 1/2 ) Resonance overvoltage, the excitation current transformer even up to a hundred times the rated excitation current, easy to blow high voltage fuse transformer, or serious overheating transformer, and then burn, explosion. In addition, the disappearance of single-phase ground, it is also possible to form a low-frequency (about 2 ~ 5Hz) saturation current transformer, this current