光纤直流大电流传感器非线性机理及校准技术

Nonlinear Mechanism and Calibration Technology ofFiber-Optic DC High Current Sensor

非线性误差是干涉型数字闭环光纤电流传感器超大电流测量的主要误差源之一。借助琼斯矩阵方法,推导了光纤1/4波片不理想条件下传感器输出与被测电流的理论关系,确定了1/4波片的方位角和相位延迟误差是造成光纤电流传感器超大电流测量非线性的主要原因之一。仿真结果表明:在5~300 kA范围内,方位角误差小于4.53°,相位延迟误差小于9.05°,可保证传感器的测量误差小于0.2%。搭建了光纤直流大电流传感器校准系统,提出了分段线性插值补偿方法校准光纤电流传感器的非线性误差。测试结果表明:非线性补偿后传感器的测量误差由最大的0.6%降低到0.1%以内,证明了非线性补偿方法的有效性。

Nonlinear error is one of the main error sources for the ultra-large current measurement of the interferometric-type digital closed-loop fiber-optic current sensor(FOCS).Based on the Jones matrix method,the theoretical relationship between the sensor output and the current to be measured is derived under the condition of the imperfect fiber quarter-wave retarder.It is determined that the azimuth mismatch and phase retardation error of the quarter-wave retarder are both the main causes of the measurement non-linearity for the FOCS.The simulation results show that if the azimuth mismatch and the phase retardation error are kept within±4.53°and±9.05°,respectively,the measurement error of the sensor will be less than 0.2%for the current to be measured from 5 kA to 300 kA.The calibration device for the FOCS is built,and the error compensation method based on the linear interpolation is proposed to calibrate the nonlinear error of the FOCS.The test results show that the measurement error of the sensor can be reduced from 0.6%to be within 0.1%by using the mentioned error compensation method,which proves the nonlinear error compensation method is effective.