Research On Grounding Fault Diagnosis Of Smart Substation DC System

In the system composed of power plants and substations,the DC system is an important component,which provides DC power for relay protection,control circuits,signal circuits,emergency lighting,etc.Ground faults can cause accidents such as protection malfunction or refusal to operate,relay burnout,fuse blown,equipment failure tripping,and even endanger the safe operation of the entire power grid.Therefore,the study of ground fault detection methods has far-reaching significance to ensure the safe operation of power systems.First of all,this article introduces the composition of the smart substation DC system,the functions of each part and its working methods.Analyzed the methods and principles of DC system fault finding,and explained the classification of DC system ground faults based on examples of ground faults,and explored how the fault occurred and its harm.Secondly,an equivalent model of the DC system during normal and faulty operation is established,and the calculation principles of AC injection method and DC method detection are analyzed.A method combining the improved bridge method and the leakage current sensor method to detect the ground fault of the DC system is proposed.A specific analysis is combined with examples,and an indirect method is used to predict the faults of the branches and buses.The simulation test results prove the effectiveness of the improved method.Thirdly,a ground fault detection system device for DC system is designed.The main functions of the hardware part of the derice are data collection,processing and display;the main functions of the software part are system initialization,monitoring and display functions.The actual application of the device in the DC system of the smart substation verifies that the device can more accurately distinguish the type of ground fault in the DC system,and provides strong support for the subsequent fault point search and treatment.Finally,a fault diagnosis platform for the DC system of a smart substation was established,and field experiments and analysis were conducted.According to the design goals and principles,the overall design of the platform is proposed.The platform adopts a layered structure design,including the acquisition layer,communication layer and monitoring layer.Combined with the existing detection devices of the substation,a specific implementation plan for the fault diagnosis platform of the DC system is proposed.The platform has been tested on site in the 750kV Jingwei substation.The results show that the platform can quickly determine the fault branch,accurately locate the fault point,shorten the troubleshooting time,improve the reliability and safety of the smart substation DC system,and save a lot of The manpower and material resources have certain practical application value.