一种高准确度有源光学电流互感器的研制与校验

Development and Calibration of an Active Optical Current Transformer With High Accuracy

和传统的电磁式电流互感器(CT)相比,本文研制的高准确度有源光学电流互感器(AOCT)具有绝缘简单可靠、体积小、重量轻等优点。高压线路的待测电流经小型高准确度 CT 和精密电阻变为弱电压信号,再经调制电路和发光二极管转换为光脉冲信号,通过光纤传输到低压端进行信号解调和处理。地面的大功率激光器发出的光能经能量光纤传送到高压端,由光电池转换为电能作为高压端的工作电源。高压端和低压端靠光纤连接和绝缘。基于误差分析理论,提出校验通道的误差应不大于被试通道误差限的五分之一。据此构造了 AOCT 的测试系统,对本文研制的 AOCT进行了线性度和温度特性测试。分析了温度对 AOCT 测量结果的影响,提出了相应的温度补偿方法:求出 AOCT 在多项式回归模型下的温度响应函数,进而修正测量结果。在?40℃～60℃的工作温度范围内,本文研制的 AOCT 满足国际标准 IEC60044?8 对 0.2 级计量用电流互感器的准确度要求。

Compared with traditional current transformer (CT), the active optical current transformer (AOCT) with high accuracy, which is developed in this paper, has many advantages such as simple 'and reliable insulation, small size, light weight and so on. The accuracy CT and precision resistor convert the current flowing in the power line into the voltage signal. The voltage signal is modulated and transferred to the optical pulse, which is transmitted to the low potential area through optical fiber and demodulated by signal processing unit. The optical energy from the large power laser in low potential area is transmitted to the photoelectric cell to energize the circuit in high potential. The reliable insulation between the high potential and low potential is achieved by optical fibers. Based on error analysis theory, it is deduced that the error of calibrating channel should be no more than one fifth of the tested channel error limitation. The calibration channel is designed to test the linearity and temperature performance. The effect to AOCT of temperature is analyzed, and the compensation method is presented. In the temperature range from -40°C to 60°C, the accuracy of the AOCT satisfies IEC60044-8 class 0.2, and fits for metering purpose.