The Identification Method For Topological Structure Of Grounding Grid Based On Electromagnetic Coupling Theory

The grounding grids is a kind of net structure made of metallic conductors buried under the ground.They offer the transformer substation a relative ground potential through the connection of the grounding electrode and the equipment above the earth.When the system is stricken by the lightening or shortcut error occurs,the grounding grid can direct the current into the ground ensuring the stability of the transformer substation.In China,most of the grounding grids are made by steel.If they are buried under the ground for a long time,they will be corroded to pieces,which will cause vital safety accident.Therefore,grounding grids must be always detected and repaired.The contact method is the most widely used grounding grid detecting method.It rely on the grounding lead.Recently,researchers present the grounding grid detecting method of non-contact transient electromagnetic resistivity figuring.However,the result of the method is not intuitive.In this paper,we diagnose grounding grids using induced voltage slice picture and present the diagnose method based on differentiation method of induced voltage.The research are committed as follows:1.Based on the electromagnetic coupling theory,we use induced voltage to recognize the structure of grounding grids.In addition,we discuss the possibility of detecting the topological structure and breakpoints of grounding grids using induced voltage theoretically.2.We deduce the mutual inductance calculating formula of two parallel planes.Based on the superposition principle,we deduce the mutual inductance calculating formula between two plane combination.In this way,we deduce the mutual inductance calculating formula between the grounding grids and the coils,which offers the theoretical way to calculate the electromagnetic response of grounding grids.3.Based on the simulations,we study the influence on grounding grid topological structure recognition caused by the size and height of coils.What’s more,we offer the method on how to choose the coils of the grounding grid testing.For the usual grounding grid size and burial depth,we calculate the common-use coil size that may face the detecting command.4.We present the grounding grid topological structure diagnose method based on differentiation method of induced voltage.We achieve the simulation result of different type of breakpoints,small-size breakpoints and multi-breakpoints.According to the simulation result,we do the even order differential treatment.By analyzing the even order differential result,we diagnose the topological structure and the breakpoint locations accurately.5.By adopting the scaled-down TEM model,lots of laboratory experiments are committed to verify the feasibility of grounding grid detection using the common-use coil.The affect of different parameters are also verified.When detecting models with different type of breakpoints and local breakpoints,we verify that the differentiation method of induced voltage is feasible for the detection of grounding grid topological structure and recognition of breakpoint location.The results of the experiments show that topological structure and breakpoint location can be clearly detected from the second order differential slice of induced voltage.Different breakpoints show the same principle.This research present a new method for grounding grid topological structure detection.