Error Calculating and Compensating Method of All-Optical Fiber Current Transformer in ± 10 kV DC Distribution Network

Abstract

Current transformer is one of the main equipment in ±10 kV DC distribution network. Traditional electromagnetic current transformer has poor anti-jamming capacity and poor insulation, so it cannot realize transient protection. The emergence of all-optical fiber current transformer brings solutions to these problems, which has attracted more and more attention. In this study, aiming at the problem of error and compensation of λ/4 waveform of all-fiber current transformer, the fabrication method of λ/4 waveform is studied, the mathematical model of the waveform is established, the influence of the waveform error on the scale factor is analyzed, and a calculating device of angle difference and ratio difference to compare the error is designed. The device adopts the principle of traceability of quantities to collect the state data of the wave plate. At the same time, in order to collect data for errors, database technology and network technology are used to realize remote transmission of monitoring data. The error of the λ/4 wave plate is compensated, the bidirectional principle generated by the birefringence in the fiber ring is analyzed, and the data logic description of the transformer sensitive ring is performed. The phase delay and the angle of the shaft are selected as the main factors causing the error. Compensation is performed by means of peak segmentation and variable cancellation. In the experimental process, compared with the error sampling of the traditional transformer, the error calculated by the current amplitude and phase angle parameters obtained by the all-fiber current transformer is more accurate, and the compensation scheme can suppress the size of the birefringence and improve sensing accuracy of fiber optic current transformers. This study provides a powerful reference for the error analysis of all-fiber current transformer λ/4 wave plates, which is beneficial to promote the better application of such current transformers.

Online measurement of birefringence of sensing fibers in the AFOCT system

“…Therefore, in practical use, the AFOCT system should be calibrated. 2,3 However, the aging of the sensing fiber is an important issue in the longterm operation of AFOCT, because the aging will cause the variation of the birefringence of the sensing fiber. 4 Particularly, the variation of the birefringence is not linearly related to the measurement error, and there exists a nonlinear residual measurement error between the calibration processes.…”

“…The reliability and measurement accuracy of the AFOCT system plays a pivotal role in the stable and safe operation of power systems. Therefore, in practical use, the AFOCT system should be calibrated 2,3 . However, the aging of the sensing fiber is an important issue in the long‐term operation of AFOCT, because the aging will cause the variation of the birefringence of the sensing fiber 4 .…”