模拟小信号电子式互感器现场应用抗干扰分析

电子式互感器是智能变电站技术的热点和难点，其中小信号模拟输出的罗氏线圈或LPCT方案的抗干扰问题一直困扰着设备研发和现场应用。文章针对某110kV变电站在拉合10kV电容器组时的主变保护动作问题，试验分析了低压侧LPCT接入保护装置的回路，发现现有关于小信号互感器和二次设备配合的相关电磁兼容标准还不够完善，但保护装置不应因为输入信号幅度的减小而降低隔离和抗共模干扰的要求。同时，由于模拟小信号互感器的额定输出很小，开关柜处的场干扰也成为影响信号质量的重要因素，现场应用时必须采用屏蔽双绞线传输并有效接地。另外，由于增量差动保护对小信号互感器的短时干扰波形敏感，建议在110kV主变保护中不要采用。鉴于现阶段模拟小信号电子互感器应用中的这些问题，应进行更多的试点研究后方能在智能变电站建设中大面积推广。

Anti-jamming Analysis of Simulation Small Signal Electronic Transformer Field Application

Electronic transformer is the hotspot and difficulty of smart substation technology, the anti-jam- ming problem in Roche coil or LPCT scheme of the small signal analog output has plagued equipment re- search and development and the field application. According to the main transformer protection operation problem when closing 10kV capacitor bank in a 110kV substation, the paper experimentally analyzes the circuit of low voltage side LPCT accessing protection device, finds that the existing electro-magnetic com- patibility standard about the coordinate of small signal transformer and secondary equipments is not perfect enough, the protection device should not reduce the demand of isolation and preventing common mode jamming because of the decrease of the input signal amplitude. At the same time, because the rating out- put of the simulation small signal transformer is very small, the field jamming of switchgear also is an im- portant factor to affect the signal quality, and must use shielded twisted pair to transmit and effectively ground when field application. In addition, due to the increment differential protection is sensitive to short-term interference waveform of small signal transformer, it is suggested not to use in the 1 lOkV main transformer protection. In view of these problems in the present application of simulation small signal e- lectronic transformer, behind more pilot study it can be promoted in large range in the construction of smart substation.