Research On Self-supply Technology Based On Electromagnetic Field Of AC Transmission Line

In order to monitor the environmental conditions around the transmission line,wireless sensors need to be installed to feedback environmental data around the line in real time to prevent accidents.Since the monitoring location is not fixed,the power supply of wireless sensors has become the main restricting factor for development.Self-powered technology is a technology that converts environmental energy into electrical energy.This technology can provide wireless sensors with stable and unlimited life electrical energy.There is a wealth of electromagnetic field energy near AC transmission lines,so it is more suitable for powering wireless sensors than other energy-based self-powered technologies based on electromagnetic fields,which is a current research hotspot.Aiming at the magnetic energy harvester,the equivalent mathematical model of the harvesting coil is established,and the factors affecting the harvesting effect are studied.The effective permeability of the magnetic core of the independent harvester is analyzed and simulated,the relationship between the effective permeability and the output of the harvester is obtained,which shows the importance of the optimization of the magnetic core shape for the output.For the electric field energy harvester,the equivalent circuit model of electric field harvesting is established,the relationship between output power and load is deduced,and the method to improve the load capacity of electric field harvesting is analyzed.Taking 220 k V and 600 A double circuit drum tower as the analysis object,the space magnetic field and electric field models of AC transmission line tower are established,the distribution of electromagnetic field on the tower is obtained,which provides a theoretical basis for the selection of electromagnetic field harvesting location.For the magnetic field harvester,two new types of core shapes,dumbbell type and split type,are designed.According to the analysis method of effective permeability,the equivalent mathematical models of the two shapes are established respectively,and the correctness of the mathematical models is verified by Maxwell simulation.The power density of two kinds of magnetic cores corresponding to the harvester is calculated by mathematical model.Through comparison,it is found that the split magnetic core is the optimal shape of magnetic energy harvester.The copper loss and iron loss of magnetic field energy harvester are analyzed,the mathematical model of copper loss of coil is established,and the accurate copper loss expression with coil parameters is given.The existing basic model of iron loss is studied.Considering the core parameters and economy,manganese zinc soft ferrite is selected as the optimal core material.The electromagnetic field combination harvester is designed,the electromagnetic field simulation verifies that the magnetic field and electric field harvesting have no influence on each other.According to the change of magnetic field,the magnetic field management circuit is designed to improve the output characteristics of the harvester.Aiming at the problem of weak load capacity of electric field harvesting,the auxiliary electric field management circuit is designed,and the load capacity of electric field harvesting is improved by voltage comparison circuit.The designed management circuit system does not need external power supply,and the correctness of the circuit design is verified by simulation.The experimental platform of magnetic field harvesting is built.Firstly,the working characteristics of the magnetic field harvester are tested by using different magnetic cores,and the experimental results verify the correctness of the theoretical analysis and simulation research.Secondly,the magnetic field management circuit experiment is carried out,and a complete magnetic field self energy supply system is built.The temperature experimental data of the sensor is obtained successfully,and the minimum working magnetic induction of the coil is calculated.Finally,the electric field self energy supply experiment is simulated,and the electric field management circuit is successfully used to power the wireless sensor intermittently,so that the magnetic field and electric field can power the wireless sensor together.