For the line-type terminal arresters on transmission line

the theory of lightning wave steepness is adopted to deduct a calculation formula of the overvoltage induced by intruding lightning wave on the circuit breaker gap when terminal zinc oxide arrester is used on the 35～500 kV transmission line. The calculation result of the formula shows that the line-type terminal arrester does not meet the requirement of insulation coordination

so it cannot protect the circuit breaker effectively. While the substation-type terminal arrester meets the requirement of insulation coordination and can effectively protect the gap of the circuit breaker. This is the reason why gap breakdown accidents of the circuit breakers on different voltage-level transmission lines still happen occasionally in China after installing a large number of line-type terminalarresters

and this is also the basis for the authors to suggest the industry association to correct its relevant files and technical specifications concerning the anti-accident measures as soon as possible.