Detection And Experiment Study Of Low Voltage Fault Arc On Characteristic Signal

In recent years,the electrical fire events caused by the fault arc has increased.The diagnosis and protection of the fault arc are very important.Fault arc can be divided into parallel arc,grounding arc,series arc.Parallel arc and grounding arc can be effectively protected by the existing protection devices because the loop current is large.But the arc current of series arc is generally less than normal current,so it is difficult to detect the arc.The effective detection and prevention of series arc fault are more difficult and important.The reason and the development process of the low voltage series fault arc are explored by the microscopic theory.The characteristics of the arc signal are summarized.Based on the analysis and comparison of the physical quantities of arc combustion,the arc current and arc voltage are determined as the characteristic signal of arc.In this paper,the advantages and disadvantages of the existing arc model are analyzed.According to the circuit theory,a mathematical model of arc is presented,which takes arc resistance and load parameters as variables.The arc is equivalent to a variable resistance.The arc resistance is regarded as a periodic function of time.The arc resistance is processed in the domain.The mathematical expressions of the arc resistance are given.The arc current of different loads is calculated by the model.The calculation results are compared with the Cassie arc model and the Stokes arc model.The comparison results show that the arc model is correct and practical.The research can provide theoretical bases for the diagnosis of low voltage series fault arc.Based on the analysis and comparison of current sensors,the electromagnetic current sensor and the closed loop Holzer current sensor are selected.They can be used for the arc current detection.The magnetic field of the sensor core is analyzed.The magnetic field simulations of the magnetic core are analyzed using COMSOL Multiphysics software.The effects of magnetic core size on the output characteristics of the sensor are studied.The static and dynamic magnetic properties of the magnetic core are analyzed in detail.The effects of the air gap width on the output signal are discussed.What's more,the Holzer arc current sensor is improved by the way of turn compensation.The two kinds of arc current sensors are designed and fabricated,and the test and error analysis are carried out.The experiment platform of series arc generator is set up,and a variety of experiments are carried out.Data are collected for two kinds of improved arc current sensor.Comparing with The fault signals and normal signals,the characteristics of arc fault under different load conditions are analyzed.The experimental results are compared with the model calculation results,which verify the correctness and practicability of the model.This researches have important significances for the accurately detections and diagnoses of the series arc.