Research On The Energy-Taking Device Based On OPGW Induced Current

The construction practice of the Internet of things in power systems and smart grids proves that online-monitoring equipment plays an important role in detecting the power grid status and resisting natural disasters,but its working reliability is restricted by the power supply problem of transmission line online-monitoring equipment.To address the issue that the current online-monitoring device for transmission lines of 220kV and above lacks an easy-installation and weatherproof energy-taking device,the energy-taking device based on the induced current of OPGW ground wire was studied.Firstly,the mainstream energy-taking devices in the market were investigated and compared in the aspects of application scenarios,advantages and disadvantages in this paper,and the design route of the energy-taking devices was proposed.In general,transmission lines of 220kV and above are equipped with more than one overhead grounding wire that is grounded at each tower and has induced current as a channel for information transmission.The key part of this paper is to convert the induced current into the required stable DC power.Secondly,the formation process and influencing factors of induced current in transmission lines were analyzed.The model of the overhead transmission line and the equivalent energy-taking circuit was established,and the influence of overhead line parameter variations on the distribution of equivalent energy-taking parameters along the overhead transmission line was examined.The results showed that the load impedance introduced by the energy-taking device was far less than the equivalent impedance of the overhead grounding wire along the line,so induced current of the grounding wire could be regarded as the current source.The equivalent energy-taking parameters along the line tended to stabilize after passing through several spans.In other words,equivalent energy-taking parameters in the middle span were approximately equal,which contributed to the unified design of the energy-taking device for the whole overhead transmission line.Special attention should be paid to some factors such as conductor transposition,which had a great influence on the energy-taking effect.The comparison of the field measurement data and the simulation data verified the effectiveness of the model.In this paper,the main circuit of the energy-taking device based on the current transformer was modelled and simulated.The research results indicated that the energy-taking effect mainly depended on the impedance matching of the device.The maximum power output of the current transformer was primarily related to the number of the secondary winding turns,the equivalent impedance of the load,the induced current flowing through the overhead grounding wire,the geometric parameters and materials of the magnetic core.Subsequently,based on the above simulation analysis and research,the main circuit of the energy-taking device was designed,and the type selection and winding of the iron core of the transformer was carries out.To satisfy the actual working conditions of the transmission line,auxiliary modules such as the voltage stabilizing circuit and the protection circuit were added to the main circuit,which perfected the overall design of the energy-taking device.Finally,a laboratory level simulation test circuit of the energy-taking device was constructed,and the principle prototype of the device was tested.The results suggested that the energy-taking device designed had an output voltage of 12V±10%and an output power of no less than 3.5W when the induced current of the simulated overhead grounding wire ranged from 30A-150A.