Regular pattern of power grid continuous icing days is important for anti-icing design of transmission line

deployment of anti-icing measures

and emergency strategy. Based on glaze or rime observation data

we established a continuous icing day identification model and calculated the maximum continuous ice-covering days of Hunan power grid from 1951 to 2015. By using the Person-Ⅲ probability function

we analyzed the spatial patterns of continuous ice-covering days for recurrence of 15

30

50

and 100 years. The results show that the high-value center of ice-covering days locates on north

southwest and southeast of Hunan. With increasing of recurrence

the growing rate of maximum continuous icing days shows the pattern of "northeast>north>southeast>others". In addition

the recurrence of extra serious ice-covering period is 11.8 years by calculation

which provides an important reference for anti-icing design of power grid.