The closed light path structure and the straight through light path structure are the two primary structures of optical current transformers based on Faraday magnetic-optic glass. The advantages of optical current transformers based on the straight through light path structure are obvious on the machining difficulty and the stability. But the disadvantages are also obvious on the conductor positional sensitivity and the resistance disturbance capability. In this paper, the differential optical current transformer is proposed. The influence of the conductor positional change and the magnetic crosstalk on the measurement precision is analyzed. The results show that the differential optical current transformer used in smart substation with phase spacing more than0.8 m can absolutely achieve the measurement precision of 0.2-level without special shield.%采用光学玻璃的光学电流互感器主要有两种结构:闭合光路结构和直通光路结构.直通光路结构的光学电流互感器在加工难度和稳定性方面具有明显的优势,但存在对测量位置敏感和抗外磁场干扰能力差的缺点.提出了一种差分式结构的光学电流互感器,分析了导体位置变化和相间磁干扰对其测量精度的影响,并设计了相间磁干扰和返回导体对测量精度影响的实验.分析和实验结果表明:采用差分式结构的光学电流互感器应用在相间距离大于0.8m的智能变电站中,不需特别设计屏蔽措施,完全可以满足0.2级的测量准确度要求.
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