| With the continuous development of electricity industry,the scale of transmission lines is expanding day by day,and the reliability requirements of power grid are constantly improving.It is necessary to enhance the efficiency of fault identification and refined inspection of transmission line.In recent years,unmanned aerial vehicle(UAV)inspection has been widely used in transmission lines inspection because of its small detection blind zone,high efficiency of patrol line,and flexible remote control.Although the application of the UAV has brought great convenience to the transmission line inspection,there are still safety problems such as the collision lines of the UAV,and it is urgent to develop a reliable and efficient collision avoidance method that is suitable for the inspection UAVs.Existing UAV obstacle avoidance methods mostly use non-electrical signals such as images,lasers,and ultrasonic waves as information sources.However,these methods have defects such as limited measurement distance,poor environmental adaptability,and inaccurate identification of obstacles,which cannot meet the security needs of avoidance.Considering that the power frequency electric field generated by the overhead transmission lines is lines' intrinsic property,there is a qualitative and quantitative relationship between the electric field strength and the field-source distance.Besides,the electric field measurement can not be affected by light and meteorological conditions,which means the electric field measurement has good environmental adaptability.In order to ensure the reliability of the UAV and the safety of the transmission lines,this paper takes the electric field of the transmission lines as the source of obstacle avoidance information and proposes a new scheme for the UAV to avoid transmission lines.The main research contents of this paper are as follows:(1)The three-dimensional calculation model of the power frequency electric field of the overhead transmission line with tower is established and the electric field distribution in the adjacent space of the lines is studied.Besides,the influence of the occupancy of the UAV on the electric field distribution is analyzed and the installation position advice of the airborne electric field sensor and electric field correction scheme.are proposed.(2)Combining the factors of electrical insulation safety,corona radio interference and UAV motion performance of high-voltage transmission lines,the theoretical method for determining the safety distance between UAV and transmission line is formed,and the multi-directional direction of the UAV is summarized.The electric field distribution characteristics on the flight path when approaching the line are proposed.The strategy of UAV-transmission line distance safety evaluation based on the electric field loop ratio change rate and the safety distance limit is proposed.(3)An intelligent evaluation algorithm based on dynamic programming and statistical learning for deviation from the obstacle avoidance path is proposed.The dynamic programming and hidden markov model are combined to track the small sample data of dynamic electric field measurement with error,which meets the real-time,accuracy and robustness requirements of the UAV flight direction deviation evaluation.(4)The simulation experiment platform is built to verify the feasibility and accuracy of the distance safety evaluation method of the UAV and transmission line and the deviation of the UAV from the obstacle avoidance path evaluation algorithm are verified by simulation experiments. |
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