Research On Impulse Resistance Reduction Method And Dispersing Current Optimization Of Grounding Device Under Lightning Impulse

With the continuous expansion of the scale of modern power grid,transmission lines must pass through mountains,farmland,cities and towns.In mountainous and rocky areas with complex soil structure,the grounding resistance of towers is generally too high to meet the requirements of regulations.The conventional method of reducing impulse grounding resistance is no longer applicable.There are fish ponds and paddy fields near the towers.Due to the difference of resistivity,dispersing current will pose a great threat to aquatic organisms and even operators.Solving the problem of high impulse grounding resistance in mountainous areas and the hazards of dispersing current in densely populated areas is still an urgent problem in the field of grounding.Firstly,based on the finite element analysis method of electromagnetic field theory,this paper establishes the finite element analysis model of lightning impulse transient of grounding device,and describes the calculation process of the model through theoretical modeling and software implementation.This method is simple in solving process and takes into account the calculation accuracy.It is actually suitable for the transient current dispersion process in the ground.It provides an effective means for the optimization design of grounding device and the formulation of protection scheme.Impulse test is carried out by choosing a rectangular grounding device as test object.The error between the model and the test is less than 10%.The correctness of the finite element analysis model for lightning impulse transient of grounding device is verified.Secondly,the common impulse resistance reduction measures and their resistance reduction characteristics are studied,and the practical problems of grounding devices in some areas are pointed out.According to the different types of towers and soil environment,the comprehensive impulse resistance reduction schemes under typical geomorphology are studied and designed,and the resistance reduction effect is given.The typical towers are selected to complete the pilot project transformation and evaluation.Finally,the field test scheme of dispersing current is studied.The measurement device of dispersing current is introduced and the current density measurement method in ground is given.The influence of the radius of the return ring electrode on the test of dispersing current is studied.The distortion of current density near the return ring electrode is obvious,and the closer to the return ring electrode,the more serious the distortion is.In order to ensure the validity of the measured data,it is suggested that the radius of the return ring electrode be set at least twice the measurement distance of the farthest target.Three dispersing current optimization schemes are proposed and the effects of each are predicted.The typical tower in Foshan City of Guangdong Province is selected for pilot project application,which shows the effectiveness of the dispersing current optimization schemes.