Research On Optimization Model To Design Grounding Grids In500kV Substations

With the development of electric power industry in our country, more and more security problems of grounding grids appear during operation. However, the grounding grids are still designed in traditional method which makes the contradiction between the design and actual reliable operation much more prominent. It requires introducing a new effective design of grounding systems in electrical substations. In order to ensure the security and stability of substations, a good grounding grid design in substations to improve power supply reliability has become urgent.This paper considers the grounding grid for500kV substation as an example. Two-layer soil model is established through analysis and derivation. Carry on simulation experiments with unrestraint optimization algorithms to provide more accurate soil information for further analysis and design reliable grounding grid. Ignoring some unimportant factors, a new optimization model to design grounding grids in electrical substations is proposed through analysis and assumptions. Then discuss the calculation of the circuit parameters in details. Overturned traditional design fixing the dimension of grounding grid, the size determined in advance serves as a constraint condition of the new model in which the cheapest program is found while security is guaranteed. Two different ideas are applied to solve the multi-objective optimization problem described in the model:weighted combination method and the method based on Pareto optimum theory.According to the importance of security and capital investment, two objectives are combined by linear weighted coefficients into a new objective function. This paper puts forward an adaptive clustering differential evolution algorithm based on traditional differential evolution algorithm which is applied to the optimization model to design grounding grids in electrical substations subsequently. Simulation experiments on the standard test functions verify the superiority of this improved algorithm. The improved algorithm makes it easier to avoid the local optimal and has stronger optimal capacity and higher precision.With the concept of dominance to evaluate and select the solutions, the method based on Pareto optimum theory gets a non-dominated solution set in which the solutions are equal to each other and none of them is better than others. The designer can select one program for implementation on the basis of the experience and user’s requirements. The best reference solution may be obtained from the non-dominated solution set mathematically. In this paper, a fast and elitist non-dominated sorting genetic algorithm, the most representative algorithm for multi-objective optimization problems, is adopted to solve the optimization model to design grounding grids in electrical substations and improvement of the algorithm are provided simultaneously.Based on intensive study, this paper raises a new method for processing constraints in multi-objective optimization problems. Objective converting method converts the constraints into a new objective which does not add any parameter. This paper employs two different methods and constraint processing methods to the new optimization model to design grounding grids in electrical substations and verifies the feasibility and effectiveness of the model by comparing and analyzing the result.At the end, this paper summaries the whole work briefly and analyzes the shortage of the new optimization model to design grounding grids in electrical substations proposed here and gives some advices on further work.