Research On Numerical Calculation And Optimization Design Of Substation Grounding System

The grounding system plays a very important role in the substation system,which can effectively stabilize the voltage of the whole system and ensure the continuous and reliable operation of the substation.The current power grid capacity is increasing and the soil structure of substation site are more complicated,so the traditional empirical formula using standard calculation of grounding parameters error is relatively large which has been difficult to meet current requirements of many substation design.Also simple equidistantly horizontal grounding grid potential gradient,making contact the grounding grid voltage is significantly higher at the apex.Therefore,this paper makes an in-depth discussion on the two aspects of the numerical calculation method and the optimization design method.In this paper,by using the analysis of the constant current field,the Green function expression of the starting current source is set up in the multi-layer layered soil.At the same time,by using the complex image method,four kinds of Green functions in the horizontal double layer soil can be obtained.The grounding model considering the mutual inductance between the inner and outer conductor impedance inductance itself and two conductors,using node voltage method,direct calculation of grounding potential at each point,and the unequal potential model is built,and analyzed the influence factors of horizontal grounding net potential difference.When the same amount of steel is used,the more the number of grounding conductors is laid,the smaller the equivalent radius of the conductor is,the smaller the maximum potential difference of the rectangular ground network.In homogeneous soil,this paper uses the method of adding vertical grounding electrode to reduce the grounding impedance and contact voltage of grounding grid,and analyze the related factors that affect the value of these grounding parameters.According to the national standard and method given in uniform soil unequally spaced horizontal grounding conductor,conductor arrangement fitting more simple calculation formula,while the difference between the maximum touch voltage minimum mesh is set as a target,when the horizontal rectangular grounding grid according to this arrangement of conductors,conductor number ratio using cross the longitudinal direction of the.In the horizontal stratified double layer soil,the complex image method is adopted to establish the simulation model.The rectangular grounding grid is optimized by adding vertical grounding pole and unequal spacing of horizontal conductor.Some factors that affect the grounding impedance of composite grounding grid are analyzed after adding vertical grounding electrode.The maximum contact voltage of the whole grounding network is minimized and the optimization target is set up.The optimal compression ratio is obtained based on the improved adaptive genetic algorithm.The horizontal conductor is laid according to the exponential law.Finally,the grounding grid of 110kV substation in horizontal double layer soil is simulated,and the specific values of ground impedance,the surface potential and the contact voltage 'are obtained.Through the above two ways to implement the optimization of rectangular grounding grid,the horizontal conductor found unequal spacing laying cannot reduce the grounding impedance,but effectively refine the contact grounding net voltage.However,the vertical grounding electrode added to the horizontal grounding network can reduce the contact voltage and the grounding impedance.