Analysis on Bird Damage Accident of Overhead Transmission Lines in Ningxia Region and Optimization Design of Insulating Grading Ring

Bird damage is one of the main reasons for transmission line tripping or even outage. In order to analyze the characteristics and causes of bird damage faults, the bird damage faults of 110 kV and above transmission lines in Ningxia Power Grid from 2015 to 2020 are statistically analyzed. The results show that most of the bird faults in Ningxia power grid occur in plain and farmland, and most of them occur from July to October. The main cause of the fault is bird manure flashover, and all of them are short air gap flashover. In view of this phenomenon, the electric field distribution of composite insulator with grading ring is studied. The results show that the installation of grading ring greatly reduces the electric field along the insulator surface. At the same time, the pipe diameter and diameter of grading ring are selected as $R=\mathrm{30}$ mm and $D=\mathrm{260}$ mm, respectively. The application of insulation grading ring reduces the electric field along the surface of composite insulator, and different insulation layers and their thicknesses should be determined according to different voltage levels.