The design,standard installation and maintenance of high voltage transmission line and substation grounding network is to ensure the safe operation of the system,the requirement for grounding network performance is more and more strict.But the grounding network is independent concealed device buried underground,and in the construction of grounding network,there are phenomenona not comply with the design,as well as the bad grounding conductor performance variation caused by running environment,forming the potential safety hazard.Therefore,the accurate detection method for grounding network physical state of transmission line and substation,is of great significance to ensure the integrity and compliance of the ground net.At present,for the ground net,the primitive,traditional measurement method by excavation or indirect measurement,are concluded the disadvantages of blindness,and large workload,slow speed,inaccuracy.Ground penetrating radar(GPR)detection system using Ultra-wideband radar signal to detect the underground targets,through the collection and processing of grounding network location,shape,material,physical structure and other detail information,realizes the electric power grounding network without excavation,nondestructive and continuous detection with high precision.This paper relies on the National Natural Science Fund Project "The Research on UWB Random Noise Radar Polarization Imaging Method Used in the Power Grounding Grid Corrosion Diagnosis ",based on the digital image processing technology in radar image processing.The paper puts forward to complete processing flow for the needs of online testing process in power grounding grid construction site.The main research is the propagation characteristics of electromagnetic signal,the pretreatment process of radar image,the extraction process of the target echo and the accurate estimation of the depth of the target and the velocity of electromagnetic wave traveling in the earth.And optimize the model parameters based on the construction practice.Firstly,the paper has a discussion on the existing power ground grid specifications,through the analysis of GPR imaging principle,design of grounding grids in radar imaging probe in B-SCAN data,based on the GprMax(GPR forward simulation software)modeling on the grounding grid in substation and transmission line,providing parameters for the estimation of electromagnetic wave velocity;Secondly,combined with digital image processing technology,in the field of target detection for ground penetrating radar B-SCAN image process,the paper proposes a technological process,considering electric grounding grid detection characteristics.Combined with threshold segmentation and edge detection of the radar image pre-processing process,the paper proposes a method to search image symmetry point suitable for automated processing.The method illustrated with the transmission line and the grounding body and compared with the existing means is proved that the method possesses better applicability.Lastly,paper proposes a method for actual demand in estimating the velocity of electromagnetic wave for fast online detection in power grid construction site,by comparing the existing velocity calculation method,the paper proposes using the point on approximate fitting curve instead of original data,and by using the weighted curve offset the region of velocity larger distortion,put forward a method based on curve fitting to realize velocity estimation based on the weighted.Compared with the theoretical value and the original method,the method can be found to be advanced.Finally,the algorithm is verified by engineering practice measurement data processing of progressiveness and rationality. |