Research On State Detection Technology Of Distribution Network Grounding Wires And Its Device Development

All the time,connecting grounding wires to the earth is always a very important link in the maintenance and reconstruction of power systems.However,the power system accidents caused by the misoperation of grounding wire switches are still frequent in recent years,and these accidents are very serious.At present,during the inspection and repair operations,it mainly relies on the operating ticket system and the degree of personnel's execution of the operating procedures.Moreover,the number of 10 kV distribution lines,which usually cover a wide range,is very large,and the maintenance locations are also not fixed.Therefore,the probability of a ground-line leakage removal events in distribution networks is far greater than those in high-voltage transmission networks.According to statistics,in recent years,the accidents that delivering power energy with grounding wires have still occurred frequently in the distribution networks below 110 kV,which accounting for about 25% of all the misoperation accidents in China.Obviously,if we only rely on the operating ticket system,not only can we not completely eliminate such accidents,but with the rapid increase in the size of distribution networks,such accidents will continue to increase.Consequently,developments of a grounding detection device that is suitable for distribution network lines are particularly important for improving the safe operation of the power grid and for ensuring the safety of the maintenance personnel.For this reason,this paper has carried out the following research work for the state detection technology of distribution network grounding wires.In view of the practical application of grounding wires and the interference factors that affect grounding wire detection,the principle of the ground wires in actual projects was introduced based on the site investigation.According to the actual parameters of a 10 kV distribution network,a simulation model considering the grounding line was built on power simulation platform EMTDC/PSCAD,so as to simulate the physical environment of the grounding lines when distribution lines are inspected.Based on this model,the effects of different frequency signal injection,multi-branching lines,no-load transformer operating,parallel connection of the same rod,and equivalent resistance of ground coupled ground on the state de-tection of ground wires were analyzed in detail.For grounding state detection technology,a detection method based on “frequency conversion injection-scavenging detection” principle was proposed,and both the redundancy criterion method and comprehensive criterion method were also introduced.The detection principle is to inject a plurality of frequency conversion detection voltage signals into a circuit that is to be measured,and then make comprehensive judgments by using the redundant criterion method and the comprehensive criterion method.Moreover,for three different types of grounding,namely single-phase grounding,two-phase grounding and three-phase grounding,the corresponding ground wire detection schemes were respectively proposed.For the development and implementation of a grounding state detection device,a detection prototype based on the “frequency conversion injection-scavenging detection” principle was developed.The hardware design schemes of the developed device,the development principle of the prototype,and the prototype test based on an actual distribution network were introduced in detail.The test results verify the validity of the proposed detection principle and the practicality of the developed prototype.