Research On The Adaptability Of Residual Current Protection In Low-voltage Distribution Network Under Different Grounding Patterns

With the improvement of living standards,people’s demand for electricity continuously increases.The resulting electrical safety risks are also increasing,and electrical fires and personal electric shocks are the main safety risks.Currently,the operation of residual current protection suffers from a low efficiency in installation and service of the general protectors,so that the prevention of fire disasters and personal electric shock is still unsatisfactory.To address this issue,this paper studies the adaptability of different grounding types of residual current protection based on 0.4k V low-voltage distribution network.The main research results of this paper are as follows:First,this paper investigates the grounding patterns of low-voltage power distribution networks in Fujian area and the operating status of residual current protection devices in some distribution stations,as well as the on-site low-voltage grounding patterns.The survey results show that TN-C and TN-C-S grounding systems are widely used in low-voltage distribution networks in some regions of Fujian province.General protectors cannot be installed at the distribution transformers in the TN-C and TN-C-S grounding systems,which cannot protect the leakage current of the distribution network and personal electric shock.Such a system shows a poor safety.Currently,there are still no feasible solutions to the problem that the general protectors of TN-C and TN-C-S grounding systems cannot be operated.Second,this paper analyzes the potential safety hazards in single-phase grounding faults,phase-line collision faults,and zero-break faults of TN-C and TN-C-S grounding systems.Since the general protectors cannot be put into operation,there are different degrees of safety hazards in the actual operation process.This paper focuses on the problem that the general protectors cannot be put into operation in these two grounding systems.The error operation of the general protectors is studied,and a method is proposed that all of the repeated grounding shunt currents of all PEN lines are connected to the current measured at the original general protectors to eliminate the effects of repeated grounding shunts.Thus the general protector can be put into operation theoretically.The power distribution Internet of Things technology is used to synthesize multi-terminal data,and the architecture of entire system is designed based on the low-power wide-area network technology(LPWAN)and security protection technology used in the field of power distribution Internet of Things.The addition of vector sum of six currents is realized through the functions and relationship of the three-tier structure of the Internet of Things,which theoretically eliminates the influence of the repeated grounding of the PEN line.As a result,the general protectors can be put into operation in the TN-C,TN-C-S grounding system.Besides,this paper establishes an online monitoring platform of the residual current to monitor the general protectors in real-time.Finally,this paper studies the feasibility of conclusions and proposal mentioned above,with the TN-C grounding system as an example.The Matlab/Simulink simulation software is used to build a simulation model of TN-C grounding system distribution network,based on which the misoperation of the general protectors under a three-phase load imbalance in normal operation is analyzed and verified.Subsequently,this paper verifies the method of realizing the operation of the general protectors with the assistance of the power distribution Internet of Things technology.On the basis of the operation of the general protectors,this paper verifies that the general protectors can detect the leakage current to the ground during the single-phase ground fault and then successfully trip to protect the safety of equipment and human bodies.This paper investigates the theoretical feasibility of the operation of general protectors in TN-C and TN-C-S grounding systems,which has a good practical value for improving the reliability and security of power supply in the low-voltage distribution network.