Study On The Bird Streamer Flashover Characteristics And Mechanism Of DC Overhead Transmission Line

With the improvement of power grid construction and ecological environment,the number of transmission line faults caused by bird activities has increased significantly,which the transmission line flashover caused by bird excretion is the main reason.In order to ensure the safe and stable operation of the power system,it is necessary to study the characteristics and mechanism of bird streamer flashover and put forward measures.This paper studies on bird streamer flashover of DC transmission lines as following:This paper analyzes three types dropping modes of bird excretion which may cause flashovers.The characteristics of air gap discharge are studied with a cotton strip under DC voltage and this paper gets the law of air gap breakdown voltage initiated by simulate bird excretion channel.The electric field distortion and electric potential distribution are simulated and analyzed by COMSOL Multiphysics software.The experiment and simulation results show that the position of bird excretion is the main reason of changes of electric filed and it has an important effect of air gap breakdown voltage.In order to study the discharge process of bird streamer flashover,the falling bird excretion droppings channel is regarded as a floating conductor,and the air gap of"conductor-bird streamer-cross arm" is equivalent to the model of "rod-rod-plane" and"rod-rod-rod" air gap.The relationship between the the breakdown voltage of air gap and the position of floating conductor is studied.Based on the experimental results and space charge simulation of corona discharge,the combined air gap discharge process is analyzed.The results show that the combined air gap discharge develops in stages,and the space charge generated by corona discharge is the main reason for the change of breakdown voltage with the space position of floating conductor.The discharge development process of rod-rod-plane air gap under positive impulse voltage is studied by optical-electrical signal synchronous observation system,and the suppose of the development process of combined air gap discharge is verified.On this basis,based on the potential gradient of streamer discharge,a calculation method for breakdown voltage of combined air gap is proposed.Based on the study of this paper,the operation experience and the maximum length of excretion channel of birds along ±400kV Chai-La DC transmission Line,the recommended value of air gap insulation distance and the relevant bird damage prevention measures are given.At last,the anti-bird streamer flashover measures are used in Chai-La DC transmission line and the operation proved the measures,which given by this paper and projects of China Electric Power Research Institute are effective.