变压器差动保护的P级电流互感器“同型”匹配方法

Type-matching of P-class CTs for differential protection of power transformer

为有效防止变压器区外故障时因各侧电流互感器饱和程度不一致引起的差动保护误动,基于电路、磁路分析,以变压器发生区外故障时各侧电流互感器同时进入饱和为原则,提出变压器差动保护中各侧P级电流互感器的"同型"匹配方案。该"同型"匹配方案可消除由变压器各侧电流互感器饱和程度不一致引起的不平衡电流,防止变压器发生区外故障时因电流互感器饱和引起的误动。利用所提方案得到了影响电流互感器"同型匹配"的因素。利用PSCAD/EMTDC进行了大量的仿真分析,验证了所提"同型"匹配方案的有效性。基于研究结果给出了变压器差动保护用电流互感器的选型建议。

Aiming at the misoperation of power transformer differential protection due to the saturation difference among the CTs（Current Transformers） of different sides during out-zone faults,a type-matching scheme is proposed for the P-class CTs at different sides of power-transformer differential protection,which,based on the analysis of electric and magnetic circuits,considers that the CTs at different sides enter saturation simultaneously as a principle to eliminate the unbalanced current caused by the saturation difference among the CTs of different sides and thus avoid the misoperation of power transformer differential protection during out-zone faults. The influencing factors of CT type-matching are attained. Numerous PSCAD/EMTDC simulations are carried out to verify the effectiveness of the proposed scheme and suggestions about CT type selection for power transformer differential protection are given based on the research results.