For predicting accurately the trip risk of overhead transmission lines under the condition of mountain fire and improve safe operation level of power grid

the breakdown voltage characteristics of conductor-plane gap under the condition of typical high-risk vegetation fire of Southern Power Grid are studied. The fire combustion characteristics simulation test platform and mountain fire gap breakdown simulation test platform are set up for the study of flame combustion characteristics and gap breakdown characteristic of such five vegetations as the pinus yunnanensis

metasequoia

eucalyptus

shrubs

and thatch

and the replationship between the flame temperature of different vegetation

flame height

ash content

and fuel heating value and breakdown characteristic of conductor-plane gap is studied. The study results show that the relationship between the above factors and the average gap breakdown voltage gradient is approximately linear and its multiple linear regression formula is obtained by curve fitting. It is found by using the entropy-weight method that flame temperature has the highest weight in vegetation combustion characteristics

and pinus yunnanensis has the highest risk of fire trip among the five vegetations. The study results can provide a reference for predicting risk assessment of mountain fire trips of overhead transmission lines.