Research On Detecting Method And Equipment Of Grounding Grids Structure Using Combined Pulse Source Electromagnetic Method

In recent years,with the rapid explosion of China’s power grid,numerous substations built and put into operation.Owing to the construction specification in those days and influenced by corrosion,the properties of grounding grid has declined and it is difficult to meet the needs of safe running.Therefore,there is an impendency need for the appraisal of grounding grid corrosion.The existing grounding grid corrosion diagnosis methods asks that the grounding grid topology is known.So the research and development of grounding grid topology detection device possess important engineering value and significant relevance.In view of the defect of the existing frequency domain electromagnetic detection methods for grounding grid structure,a combined pulse source electromagnetic detection method was proposed in this paper.Rotating ipolar steep pulse current was injected via multiple points,and then the induced voltage of surface pulsed magnetic field was measured.At last,the grounding grid topology got extracted according to the distribution characteristics of magnetic field data.Based on the proposed method,the combined pulse source electromagnetic transmitter and two-component magnetic field receiver were designed and developed,and the topology imaging algorithm is developed.In this paper,the equivalent circuit of current carrying grounding grid was constructed,and the current distribution law of grounding grid was obtained.The time-domain and spatial distribution characteristics of surface magnetic field signal were studied,based on which the advantages of multi-point rotating injection pulse current in response signal strength,superposition denoising and construction efficiency were analyzed.The electromagnetic field simulation model of grounding grid structure detection by combined pulse source electromagnetic method was established,which comfired that the method was verified.In order to meet the needs of detection methods,a combined pulse source transmitter,a two-component magnetic field receiving coil and a receiver were developed.Based on the proposed four leg constant voltage clamp circuit,the transmitter realized the 4-electrode rotation output of linear turn-off bipolar pulse current.The orthogonal receiving coil could collect two components of the magnetic field,and the ultra wideband positioning technology and gyroscope were used to record the coil position and attitude.Meanwhile,GPSDO was used to design the receiving and transmitting pulse synchronization scheme,which realized the pulse magnetic field extraction and Superposition denoising.For the improvment of anti-jamming level,a topological structure acquirement algorithm was developed.Which was based on mathematical morphology.The magnetic field data were processed by morphological filtering and boundary extraction,afterwhat the topological map of grounding grid was obtained directly,withing out missing or misjudging grounding conductor.Based on the above methods,the detection process of grounding grid topology structure was established.The grounding grid topology detection experiment was carried out in the grounding grid test field and substation.The experimental results show that the proposed method is correct,the device is reliable and efficient,and the imaging algorithm is robust.