The rapid development of smart grid requires a more stable and reliable power supply.Transmission line faults caused by meteorological disasters,tower tilt,traverse temperature,traverse ice,traverse sag and other factors seriously threaten the safe operation of the power system.Therefore,it is vital to carry out online monitoring of the surrounding environment and the condition of the transmission line.In recent years,a variety of new monitoring methods have emerged in an endless stream.However,the existing energy harvesting power supply is low,which is difficult to meet the power demand of the online monitoring device of the transmission line.It is necessary to design a stable and reliable power supply for its power supply.The power supply technology based on electric field induction is a new power supply mode for the on-line monitoring device of transmission lines,but the power supply of this technology is not ideal at present.To solve this problem,this paper designs a variety of energy acquisition methods based on AC electric field induction,which can effectively improve the output power of electric field induction power supply and provide sensing channels for the monitoring of lightning overvoltage.Firstly,the existing electric field energy extraction methods are classified,which can be divided into direct energy extraction,high potential energy extraction and low potential energy extraction according to the load connection mode.Based on the classification,five kinds of energy extraction schemes for overhead insulated wires,namely direct energy extraction,unequal potential energy extraction of high potential internal electrode,equal potential energy extraction of high potential internal electrode,high potential internal electrode decomposition energy extraction and high potential external electrode decomposition energy extraction,were proposed.The equivalent circuit models were constructed,the formulas were derived,and the key factors affecting the energy extraction effect were analyzed.Secondly,on the basis of theoretical analysis,simulation modeling was carried out to discuss the influencing factors of the energy taking power from four aspects:electrode shape,longitudinal distance of the outer electrode,influence of the measurement part on the energy taking side and impedance matching of the back-end energy taking circuit.The high-potential energy taking structure was modeled by COMSOL,and the energy taking effect of cylindrical and plate outer electrodes was simulated and compared.It was found that the average surface area of plate outer electrode was higher to the ground,and the energy taking effect was better,which was in line with the theoretical law.The longitudinal distance of the outer electrode was changed,and the influence of the displacement distance on the energy taking side was discussed.It was concluded that 7-8 cm displacement distance could be maintained to obtain higher power.Then using MATLAB to calculate the formula,to judge the voltage measurement part of the influence on the energy side,the measurement part and the energy part of the basic decoupling conclusion;The working principle of impedance matching and capacitance compensation of energy taking circuit is introduced and analyzed in detail,and the optimized design of energy taking device is carried out based on the above conclusions.Finally,the effectiveness of impedance matching and capacitance compensation and the correctness of theoretical analysis of each scheme are verified by experiments.The experimental results show that 140.9 mW power can be obtained by direct energy taking method when the power supply voltage to earth is 6 kV.The power of 4.1 mW can be obtained by the unequal potential internal electrode.30.7 mW power can be obtained by equipotential energy taking method of high potential internal electrode.The high potential internal electrode decomposition method can obtain 36.2 mW power.The high potential external electrode decomposition method can obtain 31.5 mW power.It can be seen that the power of direct energy harvesting is significantly higher than that of high potential energy harvesting,but this method is threatened by lightning and not practical.At high potential energy extraction,the power obtained by internal electrode equipotential is significantly increased compared with that of internal electrode equipotential.Due to the high precision capacitance compensation of internal electrode decomposition scheme,the internal electrode decomposition scheme has higher energy extraction power than that of external electrode decomposition scheme,but the lightning voltage wave measurement effect of internal electrode decomposition is slightly worse than that of external electrode decomposition scheme.Integrated chip rectifier and bridge full wave rectifier are respectively used for high potential energy take-up schemes.The conversion effect of bridge full wave rectifier is obviously better,and the rectifier power of 23.7 mW is finally obtained. |