Research And Calculation Of Relay Protection In Low-resistance Grounding System

The project about relay protection in Tianji Group's network of 6kV isdesigned in the paper, followed the agreement of "Technique Consultation forRun Fashion, Protection Project, Automatization and Power Supply Layout ofTianji Group's Power System".With the increasing of the number of power cables and loads in mediumvoltage systems, low-resistance grounding and arc suppression coil groundinghave been the primary grounding methods of the neutral. The paper comparesall grounding methods' characteristics, studies short current's distribution ofsingle phase grounding fault in low-resistance grounding systems, and putsforward a protection project.The research of relay protection's cooperation between the superior andinferior lines of Tianji Group's network is described in details, and a projectis concluded in the end, which can be perfected with the optimization ofpower supply layout.An equivalent circuit model of three phase power cables is discussedhere, and it is used to do transient-state analysis of low-resistance groundingsystems, in which the single phase grounding fault occurs.The paper uses matlab6.5/simulink to assist to set up circuit models andcalculate short currents, and uses Microsoft Visual Studio to make up aproject for computing the values of relay protection. These methods are veryconvenient, they are valued to be used for reference in the future researchwork.