Design Of Leakage Current Monitoring System For Low Voltage Power Grid Based On NB-IoT

At present,leakage current safety issues such as aging and damage of low-voltage lines in urban and rural areas in my country and short-circuit insulation have not been effectively resolved,resulting in frequent leakage accidents.The traditional leakage current detection device can only achieve single-phase single-channel capture,and in some cases cannot accurately identify the leakage current waveform,it is impossible to make effective judgments on the leakage current fault,and it lacks reliable data support.This paper proposes a new type of leakage current monitoring system for low-voltage power grid based on NB-IoT,which can accurately identify human body electric shock accidents caused by leakage current,and can collect leakage current signals and transmit them to the cloud platform and the mobile terminal through the NB-IoT module for real-time monitoring.Firstly,the types of the most common leakage current fault equivalent loads are studied,and the linear load equivalent circuit model is established.For the low-voltage power grid of the TT grounding system,the model is established in the electromagnetic transient simulation software,the leakage current model that may exist in the TT grounding system is added to the power grid,and the equivalent load circuit model is also connected to the power grid to simulate and analyze the leakage current characteristics.Secondly,the overall scheme of the leakage monitoring system is designed.The appearance of the hardware circuit part is designed,and its application scenarios are explained.Based on the overall scheme of the system,a schematic diagram of the hardware circuit is designed.Based on the analysis of leakage current characteristics,the acquisition module circuit is designed;the STM32l151 single-chip processor is selected and the control module circuit is designed;the transmission module circuit is designed based on the LTE BC28 NB-IoT module of Shanghai Quectel Communication Technology Co.,Ltd..Thirdly,the overall functional flow framework of the software is designed,and it is realized by using Keil software to write C language programs.The setting method and debugging process of NB-IoT’s BC28 module communication are studied,AT commands are sent and returned through serial debugging software for NB communication test,and the solution of BC module and telecom IoT cloud service platform to achieve docking is studied.Finally,experiment and debug in the laboratory and on-site.In the laboratory,the leakage current simulated by the sliding rheostat is collected by sensors and transmitted to the cloud platform to test the most basic software and hardware acquisition and transmission functions of the system.Then combined with the mobile phone We Chat applet to conduct field experiments,the leakage current capture device successfully monitored the leakage current in Fengyang Stone Material Factory and transmitted it to the mobile phone terminal.The experimental results show that the function of the leakage current monitoring system designed in this subject is basically realized,which can effectively reduce the occurrence of leakage accidents and improve the power safety level of the low-voltage power grid.