| Grounding grid provides reliable grounding for electric power system operation.And it’s a hugely important part of relay protection system.The corrosion or fracture faults of grounding grid can affect the dependability of electric power system,so it’s obbligato to detect the corrosion or fracture of grounding grid,which insures the dependability of electric power system.The emerging of issues that the conventional way is a time-consuming and arduous,thereby the non-excavation detection way is used to effectively find the grounding grid breakpoints,to undertake the secure work.At present,there is no reliable,long-distance and capable detection method at home and abroad,so it’s very important to put forward a new detection approach.This paper studies the detection approach of based on magnetic resonance in case of grounding grid breakpoints,proposes the difference of circuit topology when grounding grid loop is disconnected and closed,and establishes a detection method of grounding grid loop breakpoints based on the difference of input impedance of the two on the primary side.The method specifically solves problems of remote transmission and anti-interference.The specific content is as follows:(1)It is analyzed that the transceiver coil system and the state of grounding grid.The equivalent circuit modeling is carried out and visualize the grounding grid.The circuit model is proposed and analyzed when the grounding grid is intact or there is a fracture.According to the principle of magnetic resonance and the principle of frequency bifurcation,the existing conditions of the resonant features of grounding grid are analyzed to find out the characteristic region reflecting the resonant frequency information of target coil,and the detection method based on resonant is proposed.What’s more,its correctness is verified by simulation.(2)In order to meet the requirements of long-distance detection,the coil optimization standard is proposed.Based on mutual inductance,different transmitter of detecting system are presented.For the transmitting coil and rectangular transmitting coil,mutual inductance is analyzed respectively for the grounding grid.According to mutual inductance and coupling degree,the standard of optimized transmitting coil is proposed to meet the requirements of long-distance detection.The type,size,size and winding method of transmitting coil are analyzed,and the optimized transmitting coil is designed for the grounding grid detection system,which is used in the research of grounding grid breakpoints detection.And the optimized transmitting coil is used for simulation analysis to verify the effectiveness of the optimized coil.(3)The experimental platform of grounding grid system is built.In the case of single mesh of grounding grid,the condition of single mesh is verified by using the optimized transmitting coil.In the case of grounding grid net,a variety of different fracture types are proposed,and a detection method of grounding grid net is proposed by inducting and analyzing the lattice structure mesh.In the case of known or missing topological information,the detection method is verified to find out the fracture of the grounding grid.(4)For analyzing the anti-interference of detecting system,the influence of receiving-transmitting system with or without the metal obstacle at different positions is researched.Considering the influence of the metal obstacle,a circuit model with metal obstacles receiving and receiving coil system is proposed,and the circuit topology extraction and calculation method of metal obstacles are proposed based on the change of input impedance,and the theoretical model is verified by experiments.Finally,the anti-jamming ability of this method is explored for metal obstacles of different thickness,different size and different materials. |
