Conducts Location Of Grounding Grid Based On PCB Hollow Coil Sensor By Magnetic Field Method

As one of the necessary equipment for safety reliable operation in substation,the performance of grounding grid is directly related to the safety of staff and the normal operation of the power equipment.Therefore,there is the rule that the grounding grid must be excavated for corrosion detect to ensure the status of the conduct.But in the actual situation,the design drawing of grounding gird is often lacking or the construction is not standardized in the old substation,which leads to the conducts location unknown.A lot of manpower and material resources have been wasted with the inaccurate position guide.At the meantime,the diagnostic results of the grounding grid base on principle of electrical network is depended on the accurate the position of the conducts.Hence,for some substations whose design drawing is missing or lacking and construction is not standard,the AC(Alternating Current)excitation source and the magnetic field sensor made by multi-layer PCB(Printed Circuit Board)hollow coil have been designed to locate the conducts for accurate guidance for the excavation and fault diagnosis in grounding grid.For the interference of substation magnetic field noise,a specific frequency AC excitation source is used to generate the magnetic field signal,and the magnetic field sensor measurement accuracy can reach to nT level.At the same time,the multi-stage band-pass filters are used for magnetic field signal processing,which can be used to detect the conductors position of the grounding grid according to the distribution of the magnetic field peak.The results of the detection can provide the theory premise for the excavation and corrosion diagnosis of the grounding grid.Here is the main research contents in the paper:(1)Based the calculation in the magnetic field distribution of a current carrying single-conductor with finite length,the characteristics of the magnetic field distribution in the current-carrying grid conductor are obtained.According to the actual situation of the grounding grid,the spatial magnetic field distribution of the grounding grid is simulated.(2)The magnetic field sensor has been made by multi-layer hollow PCB connection to fit on-site environment of the substation and the magnetic properties of the target.The acquired inductive voltage is processed by a multi-stage active band-pass filter amplifier circuit which is validated through the accuracy test and simulation analysis of filter capability.(3)According to the magnetic field method to detect the conductor position of grounding grid,the overall design idea of the system device was made with the principles of portable,modular,and expandable design aimed at the actual environment of the scene.The whole measurement device was divided into excitation source module and magnetic field signal measurement device.The array of the magnetic field sensor was designed for the actual measurement process.(4)The experiments of single-conductor and field-character grid conductors were designed in the laboratory according to the AC excitation source and magnetic field measurement device.At the same time,relevant tests were performed at the substation site.Both of the experiments results can verify the effectiveness of the designed device on conductor position detection.