Summary of Experimental Study on Switching Impulse Flashover Characteristics of Typical Air Gaps in EHV/UHV Transmission Systems

In the design of EHV/UHV power transmission projects,the selection of air gaps is very important for it impacts on the sizes of transmission towers and distances among various electrified constructional elements within substations or converter stations.Rational design of air gap not only concerns secure and stable operation of power system,but also direcly bears up on construction cost of the project.Generally speaking,the air gap to withstand switching overvotlage needs maximum air gap length than those withstanding power frequency overvoltage,DC overvoltage or lightning surge,thus the switching impulse flashover characterisitics of typical air gaps of transmission tower,and those in substations and converter stations is one of the important factors impacting on security and economy of transmission projects,and is also the main foundation in the design of EHV/UHV AC/DC transmission projects.The discharging characteristic of air gap under switching overvoltage is related to such factors as the form of electrode,distance between electrodes,the waveform of the applied votlage and so on.To provide reference for more in-depth researches in future in this field,the experimental studies on switching impulse flashover characteristics of air gaps home and abroad are summarized,including various switching impulse flashover characteristics and factors impacting the characteristics.