Design and Performance Study of a Temperature Compensated ±1100-kV UHVdc All Fiber Current Transformer

Abstract

The inherent advantages of fiber optical current transformer (FOCT) are very attractive for high-voltage applications when compared with conventional transformers. However, the accuracy and long-term reliability of FOCT can be greatly affected by temperature. Fiber temperature sensors are suitable for FOCT temperature compensation, especially in ultrahigh voltage (UHV) applications. As a result, a fiber temperature-sensing scheme based on the temperature birefringence effect of polarization maintaining fiber (PMF-TS) was proposed. A high integration real-time temperature correction FOCT based on PMF-TS (PMFTS-FOCT) was designed, and a prototype with rated current of 5000 A and rated voltage of 1100 kV was developed. The accuracy, temperature, frequency response, step response, and transient response of the system was tested. The results showed that within the temperature range of -40 °C to 70 °C, the ratio error (RE) of 500-5500 A was less than ±0.2% after temperature correction, and in the frequency range of 50-1200 Hz, RE and phase error (PE) were less than ±0.75% and 110 μs, respectively. The step response time was less than 125 μs, the overshoot was less than 1.5%, and the composite error was 0.807% for the 50 000-A transient current. We proved that PMFTS-FOCT had good steady-state and transient performance and the possibility for measuring dc and ac harmonics, whose performance meets the error limit requirements specified in GB/T 26216.1-2010.