The Detection Principle Of Bi-Semiring Leakage Current Sensor And Experimental Research

The DC operation power supply system(DC system) provides uninterrupted power source for protection, measurement, automation and control equipments, its reliability directly affects the security and stable operation of power plants and substations. Branch grounding fault is the most common failure in the DC system, Therefore, the insulation monitoring is of great significance. Because of simple installation and flexible configuration the DC leakage current detection method has been in-depth studied, Due to the lack of sensitivity and accuracy, the ordinary DC current sensor cannot be used in this method. Therefore we designed new Bi-Semiring leakage current sensors, the performance is well according to test, designed insulation monitoring device for DC system of 8 channel using this sensors and completed system test.The main research works of this paper include:① Studied the detection principle of DC current, mainly based on Hall Effect and magnetic modulation. Firstly compared the open-loop and closed-loop operating principle and advantages and disadvantages based on Hall Effect, secondly described the magnetic modulation in detail combining curve graph. then analyzed problems encountered in application of the dual core differential modulation and phase modulation, at last the single core single coil magnetic modulation was chose as the most appropriate plan.② Specific designed the new current sensor. Proposed the Bi-Semiring laminated design scheme, simulated the air gap magnetic flux leakage in different joint structure, selected the cross joint ones in order to minimize the magnetic flux leakage. Designed hardware circuit to process sensor signal, described the key functional modules such as signal amplifier, power frequency interference suppression circuit, etc. At last made some sample sensors.③ Tested the performance of the sensors. Setted up platform for testing sensors, all the test is at room temperature, calculated the important index of the sample sensor such as linearity, precision, uncertainty, the results meet the design requirements.④ Put forward the design scheme of DC system insulation monitoring device, completed the design of hardware and software of the system, the system can detect multiple branch leakage current information,give sound and light alarm when branch leakage current overrun, at the same time upload the leakage current to control center to realize remote monitoring, test the system on the simulation platform of leakage current, the detection error is 0.2m A, which can meet the practical requirements of DC system insulation monitoring.