Ice-melting Flashover Pre-warning Method and Criterion of Composite Insulators on 110 kV Transmission Lines Based on Utlraviolet Imaging Technology

To reduce the possibility of ice-melting flashover on transmission lines,we experimentally study the ice-melting flashover of ice-covered composite insulators on 110 kV transmission lines.The discharging phenomenon is observed by using utlraviolet(UV) imaging technology,and is compared with the leakage current during the test gained by the online monitoring devices.The results show that the leakage current and the UV image have a periodical corresponding relation during the icing flashover.The number of UV photons is regarded as the characteristic quantity to detect discharging,and the three-segment method of UV warning for the discharging process of ice-covered insulators is put forward.The method and criterion about flashover pre-warning of composite insulators on 110 kV transmission lines are given.When the monitoring distance is 6.5 m,it is considered to enter the warning zone if the high-potential side has a sudden change in the number of the intermittent photon,and a warning would be given or not according to the discharge situation under the different gains.