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常规变电站的智能化改造过程中,可能存在电磁型CT与电子式电流互感器(electronic current transformer,ECT)混合用于变压器差动保护的情况。变压器区外短路时,由于电磁型CT与ECT的传变特性不同,可能引起差动保护误动,为此提出了与ECT混合用于变压器差动保护的电磁型CT的校验方法。该方法需要根据实际系统和电磁型CT的具体参数进行计算,校验过程中综合考虑了铁心剩磁的影响和保护装置抗饱和措施的要求。校验合格的电磁型CT与ECT混合用于变压器差动保护,即使在最严重的外部故障情况下,也能保证差动保护动作的可靠性。EMTDC/PSCAD仿真结果验证了该校验方法的有效性。
Conventional substation intelligent transformation process, there may be electromagnetic CT and electronic current transformer (ECT) mixed for transformer differential protection. Due to the different transfer characteristics of electromagnetic CT and ECT, it may cause differential protection misoperation when the transformer is short-circuited. Therefore, the verification method of electromagnetic CT mixed with ECT for transformer differential protection is proposed. The method needs to be calculated according to the actual system and the specific parameters of the electromagnetic CT. During the verification, the influence of the iron core remanence and the anti-saturation measures of the protection device are taken into consideration. Qualified electromagnetic CTs and ECTs are used for transformer differential protection to ensure the reliability of differential protection even under the most severe external fault conditions. EMTDC / PSCAD simulation results verify the validity of the verification method.