Research On Non-contact Measurement Method For Phase Current Of Three-phase Four Core Cables

With the rapid development of smart grids,in order to ensure their safe and effective operation,it is necessary to timely and accurately obtain valuable information,and accurate measurement of current is an important indicator to measure the reliability and condition of cables.In response to the problem of inter phase current interference and magnetic field superposition during operation of multiphase cables,traditional mutual inductance current measurement methods cannot be used for measuring phase current of such cables or require the destruction of insulation layers.Non contact measurement technology can more conveniently reflect the electrical parameters of the cable without damaging the insulation layer.However,currently,a single non-contact measurement element cannot directly measure multiphase current,The array type sensor with multiple measuring elements is a distributed structure,and how to ensure that each sensor can be accurately arranged in the corresponding position is also a challenge.In response to the above issues,this article proposes a non-contact current measurement method for threephase four core cables based on magnetic field decoupling calculation.1.The research background and significance of this topic were elaborated,and the development status and trends of three-phase cable current measurement tech-nology at home and abroad were briefly introduced.The research status of current sen-sors was analyzed,summarized,and analyzed,in order to determine the main research content of this topic.2.By applying the Biot Savart theorem and the measurement principle of flux gate current sensors,the tangential distribution law of magnetic induction inten-sity when a three-phase four wire cable is connected to a linear load is derived.A mag-netic induction intensity voltage output model and a current voltage output model are established,and a method for measuring the phase current of a three-phase four wire cable using a magnetic sensor is proposed.A model based on voltage current transmis-sion theory was constructed to address the issues of imbalance and faults in the connec-tion of threephase four wire cables to star loads in real life.The results showed that re-gardless of the state of the three-phase four wire cable,the output voltage of the sensor is linearly related to the measured three-phase current,and the waveform of the meas-ured current can be restored through the output voltage waveform of the sensor.3.Using COMSOL multi physical field coupling simulation software,the relative position relationship between each wire core and the sensor inside the three-phase four wire system cable was analyzed.The parameterized scanning method was used to analyze the magnetic induction intensity amplitude at 360 degrees around the cable of the sensor and preliminarily determine the deflection angle θ The relation-ship between the ratio of wire core and sensor output is proposed,and a table lookup method is proposed to measure the deflection angle of the wire core and sensor,so that the sensor can be measured at any position;Under normal and multiple fault conditions,the threephase current model has been simulated and decoupled,and the measurement error of this method has been evaluated.4.Through simulation analysis,a flux gate array current sensor was de-signed for detecting the phase current of three-phase four core cables.The sensitivity,linearity,and dynamic measurement range of the designed fluxgate current sensor were tested on the three-phase four wire current carrying straight wire current measurement experimental platform.In addition,current reduction verification was conducted on three-phase four wire cables in balanced current state,unbalanced current state,and several common fault states.The results showed that the error of the three-phase current restored by the fluxgate current sensor was less than 2.8%,proving the feasibility of sensor measurement.Through this study,a non-contact method for measuring the phase current of threephase four wire power cables was proposed.It can accurately measure the phase current of the cables and deeply explore the current detection mechanism and principle under different states,thus providing a new solution for the measurement of three-phase four wire power supply systems.