| As the producer and transport hub of electric energy,power plant and substation are of vital significance in power system.In daily production,power plant,as well as substation,is vulnerable to various kinds of overvoltage,among which lightning overvoltage takes a large proportion,so the safety and stable operation of power system are greatly threatened.What's more,the equipment in the power facilities cannot be self-restored or replaced quickly after the fault occurs,so it is particularly important to protect them from over-voltage fault.Since Arrester is a critical part of lightning protection design for electrical equipment,its insulation coordination and configuration scheme directly affect lightning impulse level acting on electrical equipment and selection of safe distance between equipments.To ensure the normal operation of power system,the arrester parameters must be correctly selected,the installation location and amount of arresters should be reasonably allocated,in order that the overvoltage distribution level under fault condition can be reduced to the allowable range of electrical devices insulation strength.The main work of this paper is as follows:In order to further verify the effectiveness of arrester installation on the power plant and its auxiliary substation operation stability under the influence of lightning overvoltage,after analyzing and summarizing the characteristics of electrical equipment equivalent mathematical models in power plant and substation,an electromagnetic transient simulation program is used to establish the simulation model accorded with the actual situation on site.Based on the calculation results of simulation program,the overvoltage levels of each important electrical equipment in the power plant caused by lightning,with or without arrester,are compared to verify the arrester protection effect.From changing the arrester installation location and counting the node voltage peak-value of important electrical components,the influence of arrester installation position on the overvoltage distribution is verified.According to the influence trend of arrester installation locations on the overvoltage level at different nodes,the installation location of arrester is preliminarily optimized,and its insulation margin is checked,the optimized arrester installation plan provides guidance to insulation coordination design.From the simulation of power plant and substation operation under overvoltage,especially the discussion about the influence of arrester installation location on the overvoltage distribution,an optimization objective of arrester installation scheme considering both economic and security factors is proposed,that is,to set the proportion of each node in power plant and substation with reference to the replacement price of power equipment and to minimize power plant overall failure risk,which calculated from the weighted average calculation of each node failure risk.The optimization method is on the basis of the established power plant simulation model,after enumerating the arrester installation schemes and taking a certain installation distance as the step,the overall failure risk of each installation scheme is obtained through simulation calculation,so is the minimum value.As a result,the arrester installation location optimization is realized.Due to the complexity structure of the power plant and substation,it is quite difficult to calculate the node voltage even all the parameters of each component of the electrical facility are given.Based on the overall failure risk of the power plant corresponding to different arrester installation location mentioned above,this paper uses the neural network algorithm to fit the functional relationship between the arrester installation location and the failure risk of the power plant.For this case,several neural networks are compared on the basis of network structure,calculation velocity and fitting accuracy,and the generalized regression neural network is finally selected.After establishing the corresponding neural network structure,the genetic algorithm,suitable for multi-objective,is applied to find the optimized arrester installation scheme.The optimized scheme gives a result with higher accuracy than the one from former calculation,and the workload of simulation calculation is partly reduced.Based on above-mentioned procedures,a unified process is applied in arrester type,and a quantitative optimization scheme is demonstrated to realize the complete optimization of arrester configuration plan.In this paper,the protection effect of arrester installation on the stable operation of power plants is further verified,and a complete optimization scheme of arrester configuration,which considering both safety and economic factors,is proposed under the effect of lightning overvoltage.This optimization scheme and arrester configuration plan provide a reference for arrester configuration and electrical facility structural design in the future. |
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