Research On Device And Application For Diagnosis Of Grounding Electrode Corrosion Degree

Grounding electrode is the significant equipment for the safety of transmission line,the condition of which is directly linked to the reliability of power supply.Diagnosing the corrosion degree of grounding electrode regularly is vital for the security of transmission line.The corrosion degree of grounding electrode is mainly judged by the grounding resistance at present,which is limited such as being affected by soil resistivity and simplex classification of corrosion degree.On the foundation of existing theory on corrosion diagnosis of grounding electrode,this paper put forward a method based on relative grounding resistance,which diminished the diagnostic error caused by soil resistivity.By corresponding relative grounding resistance with corrosion degree of grounding electrode,the classification of corrosion degree was refined.Moreover,a device for grounding electrode corrosion diagnosing was developed.The main works are as follows:(1)Calculation based on mean potential method for the grounding resistance was carried out.Conclusion showed that the grounding resistance was related to the corrosion degree,however,the change of grounding resistance in different periods could not completely reflect the change of the corrosion degree of the grounding electrode.The corrosion deformation of the grounding electrode was analyzed.Result showed that the corrosion deformation of the grounding electrode had the characteristic of end effect.But on the whole,the corrosion deformation was relatively uniform.Moreover,the amount of corrosion and dissolution of metals was approximately equal to that of corrosion products.The current discharge distribution on the surface of grounding electrode was analyzed.Result showed that the distribution of current discharge had the characteristic of end effect.But for the whole grounding electrode,the current discharge was relatively even.Besides,with the corrosion process going on,the end effect was suppressed.In addition,the higher the soil resistivity was,the more obvious the end effect was.According to the positive correlation between corrosion rate and current discharge density,the corrosion of grounding electrode was relatively homogeneous as a whole.The resistivity of corrosion products from different areas with the same operating period was measured.The work in this part provided theoretical basis for the establishing of diagnosis method of grounding electrode corrosion degree.(2)Physical calculation model for grounding electrode with corrosion products was established,thus obtaining the correction method of grounding resistance considering the influence of corrosion products.Besides,the correctness of the method was verified by simulation analysis.On this basis,the concept of relative grounding resistance was put forward.By choosing relative soil resistivity,the grounding resistance in different soil resistivity was normalized,thus obtaining the relative grounding resistance under a certain criterion.The relationship between the grounding resistance and the corrosion depth of the grounding electrode was analyzed,thus obtaining the diagnostic criterion.The diagnosis of the corrosion degree of grounding electrode was realized from the method.The change trend of the criterion with the buried size of grounding electrode was analyzed.Moreover,error analysis of the diagnostic method was carried out from the three aspects of the corrosion degree of grounding electrode,the burised depth of grounding electrode and the effective length of grounding electrode,thereby verifying the accuracy and reliability of the diagnostic method.(3)A device based on the theory of relative grounding resistance for the diagnose of grounding electrode corrosion degree was developed.The experiment platform of soil pool was built,and laboratory experiments were carried out to verify the feasibility and reliability of the diagnostic method and the device.In addition,field experiments were carried out on typical towers of transmission line under the jurisdiction of Power Supply Company of Quzhou,Zhejiang.And the specific corroding degree of the experimental grounding electrode was verified by excavation as well.By comparing the device diagnosis result with the excavation result,the correctness and applicability of the diagnostic method and the device were proved.