Research On Electric Field Of Electrical Railway Catenary Insulator Influenced By Bird Streamer

Catenary is the power supply circuit of the electrical railway and along all over the electrical railway. The space for birds is large, thus, the bird related problems caused by bird habits has significant impact on the safe operation of the catenary. Among bird related problems, the bird streamer has the biggest impact on the insulator. The work environment of insulator is changed when the bird streamer dropping around the insulator or polluted on the insulator. Once the work environment of insulator is changed, electric field distribution of insulator is distorted. Flashover accident could happen when the electric field along the surface of insulator is greater than field strength of air breakdown. Therefore, the analysis of electric field distribution along the surface of polluted catenary insulator under the threat of bird streamer can provide a reference for the study on insulator flashover mechanism.Currently the autotransformer feeder wire insulators used in autotransformer-feeding scheme are more vulnerable to bird streamer. Thus the catenary rod-column ceramic insulator of QBJX-25/70 Q being used is selected as the analysis object. The model clean insulator is established in the electrostatic field. The model bird streamer dropping around the insulator and the model polluted on the insulator is established in the quasi-static electric field. The closed area is set reasonably by the artificial truncation method, in order to satisfy the condition for finite element analysis to calculate the electric field distribution of insulator. Due to the complex condition of bird streamer, ordinary computer’s memory is difficult to meet the computational demand, therefore rational simplified models based on the structural characteristics are established. So the goal that satisfying the accuracy of the results and saving computing time can be achieved simultaneously. In this thesis, the software COMSOL Multiphysics based on the finite element is used to analyze distortion of electric field along the insulator surface, under two kinds of condition that bird streamer dropping around and polluted on the surface.The results of simulation show that different distances between bird streamer and insulator distort the electric field along the surface of insulator differently. Electric field strength is increased with decreasing of distances, and the biggest increase happens at the big shed near the high voltage terminal and low voltage terminal of the insulator. Different lengths of bird streamer distort electric field along the surface of insulator differently. With the stretching of bird streamer, the distortion of electric field happens at the big shed of the insulator near the head of bird streamer, the strength of electric field increases at the big shed near the low voltage terminal of the insulator near the end of bird streamer. When bird streamer evenly spread on the shed surface of insulator, the influence on electric field distribution of whole insulator was rarely existed. When uniform dry band caused by bird streamer appeared on the shed of insulator, the distortion of electric field distribution was at the shed which uniform dry band appeared. When dropping of the bird streamer along the shed surface of insulator happened, the distortion of electric field distribution was at the shed which bird streamer appeared. When bridge connection caused by dropping of the bird streamer along the shed surface of insulator happened, the big distortion of electric field distribution was at two sheds which bird streamer bridged.