Research On Dynamic Model Of Polluted Insulators Under AC Voltage Based On The Electro-Thermal Characteristics

In recent years,China's economic level has developed rapidly,and new requirements have been put forward for power grid development planning and safety and stability.It is necessary to accelerate the development of power construction,and ensure that power systems can operate safely,reliably and stably under various geographical and meteorological conditions.Due to the special nature of environmental conditions,power system construction projects in some remote areas have become the bottleneck for the development of domestic power technology.The pollution flashover of insulators is one of the main factors threatening the safe operation of the power systems.Since the pollution flashover process involves multiple fields such as light,heat and electricity,the mechanism of pollution flashover is complicated.Although domestic and foreign scholars have done a lot of research on the insulator flashover characteristics.However,the research on pollution flashover prediction under real environmental conditions made slow progress.During the operation in the outdoor environment,Conductive contamination will gradually accumulate on the surface of the insulator.With moist air,the surface will be dissolved by moisture,and the wet layer will be gradually dried by the action of leakage current Joule heat.The electric field distribution on the insulator surface will be non-uniform,which lead to descend of the electricsal performance of the insulator.And under certain conditions,the electric arc can be come along the surface,and even flashover.At present,the mechanism of contamination flashover on the surface of insulators has been scholars' argument focal point,until now not yetachieves consistently.There is still a big controversial for the key points in the development of localized arc.And with the economic development,the atmospheric environment of modern society is deteriorating,and the operating environment of power systems is becoming more and more severe.Scholars have inadequate knowledge about the pollution flashover phenomenon under the current environmental conditions.In order to reveal the surface discharge characteristics of insulators,more research is needed.Using the pollution flash circuit model to simulate the pollution flashover process is one of the most effective research methods for studying the mechanism of insulator flashover.Based on the research of the pollution flashover model,this thesis proposes an insulator flashover dynamic model based on electro-thermal characteristics under AC voltage.The main work is as follows:The static circuit model cannot reflect the problem of arc development time characteristics.To solve this problem,the AC pollution flashover dynamic model isestablished.Based on the AC pollution flashover static circuit model,the time-dependent degeneration of the resistance of the unabridged part of the pollution layer and other circuit parameters during the local arc development process is considered,and the arc development speed and arc development criteria are introduced.In the calculation of the circuit parameters of the dynamic model,the arc characteristic parameters are dynamic parameters rather than constant constant values.The characteristics of the arc characteristic are affected by the arc combustion environment,and the characteristics of the arc characteristic parameters changing with time and environmental conditions,which are analyzed.The calculation formula of the characteristic parameters and the arc temperature is introduced to replace the static parameters,and the accuracy of the dynamic model to predict the pollution flash voltage is improved.In order to solve the problem of the influence of ambient temperature on AC pollution flashover,the influence of temperature on the residual fouling conductivity of the insulator surface and the re-ignition of the AC arc is analyzed and calculated.The function of the conductivity of the fouling layer on tiome and the salt density is calculated,and the relationship between the voltage gradient value of the AC arc reignition voltage and the temperature is obtained.The parameter calculation in the arc dynamic model is corrected,and the influence of the ambient temperature can be modeled.Finally,on the basis of the above analysis,the simulation calculation of the development of the local arc is carried out by Maple mathematical calculation software.The simulation results are compared with other AC pollution flashover models,experimental data and theory.The critical flashover voltage prediction proved by the improved dynamic model provides is more accurate,to a certain extent.And the effect of ambient temperature on pollution flash can be reflected.The study of AC pollution flashover model based on electro-thermal characteristics is helpful to analyze the insulator flashover characteristics more deeply,and has important research value for predicting and preventing pollution flashover accidents,guiding insulator design and selection,which will provide a new concept for the study of the mechanism of pollution flashover.