直流分量下常规CT和抗直流CT计量性能对比研究

交直流配网的发展及整流型负荷的不断增加,使得交流电网中往往存在直流分量。直流分量致使常规单铁芯CT超差严重。基于直流分量下常规单铁芯CT失准机理的研究,对一种基于高磁导率铁芯与低磁导率铁芯的复合铁芯结构抗直流CT,借助电路及磁路关系,建立抗直流CT的误差传变模型,对其计量性能进行研究。基于比例直流叠加法进行计量性能试验,结果表明双铁芯抗直流CT工频交流测量性能与常规单铁芯CT相当,精度满足0.2级。直流分量占比小于40%的交流电流测量性能明显优于常规单铁芯CT,比差小于3%,角差小于360′,具备良好的抗直流性能。

Research on difference of conventional CT & anti-DC CT

With the development of AC and DC distribution networks and the increasing number of rectifying loads, this paper presents DC components in the AC grid, which causes the error characteristic of conventional Single-core Current Transformer (SCT) to be extremely poor. Based on the study of SCT misalignment mechanism with DC component, a composite dual-core anti-DC Current Transformer (DCT) comprised of high magnetic permeability core and low permeability core is designed to resist DC component. By the analysis of equivalent circuit and magnetic circuit, its error characteristic and measurement performance are studied. The measurement performance test based on proportional DC superposition method shows that the AC measurement performance of DCT is similar to that of SCT, and its accuracy meets the class of 0.2. For AC current with DC component less than 40%, the measurement performance of DCT is obviously better than that of SCT. The ratio difference of DCT is less than 3%, and the phase difference of DCT is less than 360'', which shows DCT has good anti-DC performance. This work is supported by Science and Technology Project of State Grid Corporation of China (No. 52182018000F).