【作者】 张帆；

【导师】 段雄英；

【作者基本信息】 大连理工大学 ， 电机与电器， 2020， 博士

【摘要】 随着我国特高压系统的发展,北方的太阳能和风能及南方的水力资源能够顺利输送到东南沿海城市。为了能够更安全、更高效地输送能源,特高压系统的绝缘水平成为研究的重中之重,而决定绝缘水平的主要因素之一就是操作过电压。为了解决系统的安全性以及技术经济问题,采用选相投切技术(也称相控技术)可有效地抑制操作过电压,从而降低系统的绝缘水平。但目前六氟化硫(SF6)断路器预击穿特性及机械分散性、线路耦合效应对最佳合闸时刻的影响尚缺乏深入细致的研究,另外相控技术对合闸线路故障率影响的定量分析以及特高压线路选相重合闸策略方面研究也较少。本文旨在研究特高压断路器绝缘下降率的非线性对最佳合闸时间和预击穿时间的影响,以及相控开关的预击穿特性、机械分散性与特高压线路故障率的定量映射关系,解决选相投切技术应用于特高压系统的技术障碍。本文提出一种基于SF6气体流注理论击穿判据的合闸预击穿电压曲线计算方法,针对特高压断路器灭弧室内电场强度不均匀问题,将断路器合闸时的绝缘下降率作非线性处理,确定不同关合系数k下的预击穿时间,在此基础上结合机械分散性确定选相合闸不同负载的最佳合闸时刻。为验证选相合闸抑制过电压的效果,搭建了 1000 kV晋东南—南阳—荆门特高压交流试验示范工程的仿真模型,该模型基于ATP-EMTP进行仿真计算。仿真结果表明:对于合闸空载输电线路,预击穿时间对过电压的影响比机械分散性的影响更大,合闸过程应该更多地关注预击穿过程。对于特高压变压器的不同剩磁分别采取三种合闸相控策略:快速、延时及同步合闸,仿真结果表明三种合闸策略相结合可抑制过电压和励磁涌流。由此可得,选相投切技术可以明显地降低特高压系统的操作过电压,进而降低系统的操作冲击绝缘水平。由于输电线路相位之间的耦合效应,在首相合闸之后,会在第二相和第三相上产生感应电压,如果仍在电压零点处相控合闸会导致过电压的产生。因此,基于行波的模量分析和拉普拉斯变换理论,提出了各相断路器最佳合闸时刻的计算方法,并通过ATP软件建立了不同拓扑结构的线路模型,仿真计算的结果表明优化的相控策略对于无换位和完全换位的传输线均有效,且对双回线路的效果更明显。从原理上来说,选相投切技术能从根本上减小决定特高压系统绝缘水平的合闸操作过电压,但这一定性的认识过于宏观和模糊,相控开关技术要在特高压输电系统应用,需要将这一过程放大化,清晰给出各环节的细节,进行量化定标。因此,为了定量分析断路器关合性能、线路拓扑结构与合闸线路故障率的映射关系,基于自适应神经模糊推理系统(adaptive-network-based fuzzy inference systerm,ANFIS)建立了特高压输电线路合闸故障率模型,该模型解决了某一项参数发生较小变化即需要进行重复仿真及处理大量结果的问题。根据此模型,可以对选相关合特高压线路的故障率实现预测,即用户可以在断路器关合特性参数和线路参数确定的前提下,预测评估相控合闸的线路故障率。反之,当系统对线路故障率有一定的要求时,断路器制造商可根据其要求值调整开关性能参数,以满足系统用户需求。随着特高压系统覆盖范围的不断扩大,人们越来越重视系统能否安全、可靠性地持续运行。当系统突然发生故障时,工厂的生产和人们的生活都会受到严重的影响。因此,以特高压系统的重合闸为研究对象,针对重合于永久故障时会产生大电流的问题,根据双端电源系统模型计算正常运行电流和故障电流,进而提出特高压相控重合闸的最佳重合角度为0°或180°,最后通过仿真结果证明相控重合闸策略可行,即当线路重合于电压0°或180°时能够有效地将重合电流的峰值降至最严重情况时电流峰值的33%以下。通过本文的理论分析与建模仿真研究了相控断路器的关合特性及线路拓扑结构对最佳合闸时刻的影响,建立了断路器关合性能、线路拓扑结构与线路故障率之间的映射模型,提出了特高压相控重合闸策略,实现了选相投切对特高压系统绝缘影响的量化分析,为选相投切技术在特高压系统实际应用提供了一定的参考。更多还原

【Abstract】 With the development of Ultra High Voltage(UHV)system in China,the solar energy and wind energy in the north and the water resources in the south can be smoothly transported to the southeast coastal cities.In order to transport energy more safely and efficiently,the insulation level of UHV system has become the most important research.One of the main factors affecting the insulation level is the switching overvoltage.In consideration of safety,technology and economy,controlled switching can be taken to limit the switching overvoltage of UHV system.Then controlled switching can decrease the insulation level of UHV system.However,the influence of pre-breakdown characteristics and mechanical dispersion of SF6 circuit breaker,line coupling effect on the optimal closing time is still lack of detailed research at present.In addition,there are few researches on the quantitative analysis of the influence of controlled switching on line risk of failure and controlled reclosing strategy of UHV line.The purpose of this dissertation is to study the influence of the nonlinearity of rate of decrease of dielectric strength(RDDS)of UHV circuit breaker on the optimal closing time and pre-breakdown time,the quantitative mapping relationship between the pre breakdown characteristics and mechanical dispersion of the phasing controlled circuit breaker and the risk of failure of UHV line,so as to solve the technical problems of the application of controlled switching technology in the UHV system.This dissertation proposes a calculation method of pre-breakdown voltage curve based on SF6 gas breakdown criterion of the steamer theory.Aiming at the problem of the uneven electric field strength in the arc extinguishing chamber of UHV circuit breaker during the closing process,RDDS is nonlinear when the circuit breaker is closed.Then the pre-breakdown time under different relative value k is calculated.Combined with mechanical dispersion,the optimal closing instants of controlled closing different load are determined.In order to verify the suppressing effect of controlled closing on overvoltage,the 1000 kV Changzhi-Nanyang-Jingmen demonstration project of China is simulated.The model is based on ATP-EMTP for simulation calculation.The simulation results show that for no-load transmission line,the influence of pre-breakdown instants on overvoltage is greater than that of mechanical dispersion,and more attention should be paid to the pre-breakdown process.For different residual magnetism of UHV transformer,three controlled closing strategies are adopted:rapid,delay and simultaneous closing.Simulation results show that the combination of the three closing strategies can suppress overvoltage and inrush current.The technology of controlled switching can obviously reduce the overvoltage of UHV system,and then reduce the switching impulse insulation level.Due to the coupling effect between the phases of the transmission line,induced voltage will be generated on the second phase and the third phase after the first phase is closed.Controlled closing at the voltage zero point will generate overvoltage.Therefore,based on the modal analysis of traveling waves and Laplace transform theory,the calculation method of the optimal closing instants of each phase breaker is proposed.The line models of different topological structures are established by ATP.The simulation results verify that the optimized controlled switching strategy is effective for untransposed and transposed transmission lines,and the effect is more obvious for double-circuit lines.In principle,controlled switching can reduce the switching overvoltage that determines the insulation level of UHV system.However,this qualitative understanding is too macro and fuzzy.In order to apply controlled switching in UHV transmission system,it is necessary to enlarge this process,clearly give the details of each link,and carry out quantitative calibration.Therefore,the model of risk of failure of closing UHV transmission line is established.The model represents the mapping relationship between closing performance of circuit breaker,line topology and risk of failure,and solves the problem that a small parameter change requires to repeat simulation and deal with a large number of results.According to this model,the risk of failure of closing UHV line can be forecasted.In other words,the user can predict the risk of failureof line with controlled switching on the premise that the closing performance of circuit breaker and line parameters are known.On the contrary,when the risk of failure of line need be considered,the circuit breaker manufacturer can adjust the closing performance parameters according to the user requirements.With the continuous development of UHV system,the safety and reliability of system operation become more and more important.Once a fault occurs,it will have a significant impact.When UHV system is reclosed in permanent fault,large current will be generated.The normal operation current and fault current are calculated according to the two-source system model.Then the optimal reclosing angle of UHV is 0° or 180°.Finally,the simulation results show that the controlled reclosing strategy is feasible when reclosing angle is 0° or 180° of voltage.The method can reduce the peak value of reclosing current to less than 33%of the maximum current that may occur in random reclosing.Based on the theoretical analysis and simulation in this dissertation,the influence of the closing performance of circuit breakers and line topological structure on the optimal closing time is studied.The mapping model between the closing performance of circuit breakers,line topological structure and risk of failure of line is established.The strategy of UHV controlled reclosing is put forward.The quantitative analysis of the influence of controlled switching on the insulation of UHV system is realized.The results provide a certain reference of application of controlled switching in UHV system.更多还原