Reliability Analysis Of Power Line And Secondary Equipment Under Mulitiple Uncertainties

As an important component of supply system in power system,power line is responsible for transmission and distribution of electrical energy.Years of operating experience in power systems show that due to long-term exposure to harsh environments,power lines and other equipment are susceptible various uncertainties such as internal factors,external environmental factors and operation factors.In addition,the secondary equipment,which operate at the same time and undertake the tasks of monitoring,controlling,measuring and protecting the running status of the power line,is also an important part of the power system.As the first defense line of the power grid safety,the relay protection device is the important device in the secondary equipment;its fast and reliable action can effectively curb cascading failure of power system.Therefore,reliability analysis of power lines and their secondary equipment while considering the influence of multiple uncertainties is an essential part in the performance evaluation of power systems.This thesis focuses on uncertainty quantification based on evidence theory,competitive failure of shock process and degradation process in the system,and reliability analysis of relay protection based on GO method.The main work and contributions of this thesis are as follows:(1)Uncertainties acting on the power system include aleatory and epistemic uncertainties.The uncertainty quantification method based on the evidence theory can effectively deal with these two types of uncertainties.In consideration of the above,this thesis introduces a unified expression method of aleatory-epistemic mixed uncertainties based on evidence theory.In this method,aleatory uncertainties and other uncertainties are divided into intervals,and a basic probability is assigned to each interval.On this basis,mixed uncertainties are quantified and modeled by evidence theory in a unified manner.(2)In most engineering systems,there are two kinds of deterioration mechanisms:natural deterioration and shock deterioration,which usually have competing relationship.Therefore,it is necessary to consider the impact of two types of competing failures on the system performance degradation and reliability.In this thesis,the Gamma function is used to model the natural deterioration process of the system.The Poisson process is used to model the shock process.The Gaussian distribution is used to model the shock effect.At the same time,the shock effect is divided into three categories to be considered separately:the shock having no impact on the system,the shock leading to an increase in the system performance degradation,and the shock directly leading to the system failure.On this basis,models of natural degradation and recoverable degradation are considered when the system is under cumulative shocks and the mixture of cumulative shocks and ?-shocks respectively.The reliability analysis model of the power line under multiple factors is also constructed.(3)As the important one of the relay protection methods,the directional blocking pilot protection is widely used in the power system.In this thesis,the GO method is used to analyze the reliability of the directional blocking pilot protection.Based on the working principle of the directional blocking pilot protection,the GO chart is established,and the qualitative and quantitative GO calculations are then carried out based on it.According to the results,the reliability analysis is carried out for the directional blocking pilot protection.