An approach based on Joint Probability Density Function（JPDF） of extreme wind speed and direction

combined with the characteristic parameters of lines and geographical environment factors

is proposed in order to evaluate the risk of transmission lines trip-out caused by floaters.Firstly

the JPDF of extreme wind speed and direction is calculated by two variables

namely the extreme wind speed and its wind direction angle.Secondly

the fault sensitivity parameters are calculated according to the characteristic parameters of lines

the angle between line and wind direction

and the local environment of the transmission corridor.Finally

based on the distribution of floater density in the area

the probability of the trip-out caused by floaters is calculated in different months and line segments

and the evaluation of space-time risk for line trip-out caused by floaters is realized.Based on the proposed method

the probability of line trip-out caused by floaters is calculated and the risk grade is determined according to the probability by the example of one of the power grids in a south city.The results show that the risk grade is basically consistent with the operation data

and the effectiveness of the proposed method is proved.