Research And Application Of Current Sensor Based On Reflective Magneto-optical Crystal

As an important means of judging the condition of cable insulation,partial discharge detection is of great significance for preventing power accidents and ensuring the safe and stable operation of power systems.Traditional pulse current measurement methods have shortcomings such as weak anti-interference ability and sensitive sensitivity.The optical current sensor has been paid more and more attention because of its strong anti-electromagnetic interference ability and good insulation performance,and it has a good development prospect.Compared with optical fiber,magneto-optical crystal as a sensing element has the advantages of small size,large Verdet constant and high sensitivity.This article mainly focuses on reflective magneto-optical crystal probes.This article first derives and analyzes the optical characteristics of the magneto-optical crystal fiber current sensor through Jones matrix.An optical fiber sensing measurement system based on a magneto-optical crystal probe was built,and the AC and DC measurement characteristics of the system were tested.The sensing system has high sensitivity,the AC signal measurement resolution is lower than 5m A_rms,and the DC signal measurement resolution is higher than 10m A.In order to overcome the problem of small partial discharge current and high frequency,a magnetic ring is added to make it possible to measure the high-frequency pulse current generated by the partial discharge of the cable.Use nickel-zinc ferrite with high permeability,high measuring frequency,and low coercivity as the core material.At the same time,in order to optimize the performance of the sensing system,the COMSOL Multiphysics finite element analysis software was used to simulate the magnetic field distribution at the magneto-optical crystal when the magnetic ring was added,and the factors affecting the performance of the magnetic ring were analyzed.Determine the size of the magnetic ring and the best placement of the magneto-optical crystal probe.Finally,the selection of the magnetic ring air gap length is 60mm,which improves the measurement sensitivity and enhances the anti-interference ability.A magneto-optical crystal pulse current sensor system based on magneto-optical crystal and magnetic ring was built,and the linearity and sensitivity of the sensor system were tested.The test results show that the linearity is good,and the sensitivity can reach102.1mrad/A;adding an amplifier to further improve the signal-to-noise ratio,the AC signal measurement resolution is less than 0.2m Arms,and the DC signal measurement resolution is also less than 0.2m A;The laboratory has measured high-frequency pulse signals,which can measure pulse current signals up to 120MHz and 0.1m Apk.The discharge defect model of the needle board of the power cable is tested,and the discharge characteristics of the needle board discharge model at different discharge levels are obtained.The experimental results show that the response of the sensor system to different discharge levels of the needle plate discharge model has a linear relationship,and the linearity is good.