A Research About Electric Field Energy Scavenging Technique In The Ac Transmission Line Tower Side

Recently, on-line condition monitoring device(CMD) has been widely used in transmission line to enhance the stability and reliability of transmission facility. However, a large amount of application practices show that the currently adopted power technique utilizing photovoltaic cell and battery cannot entirely satisfy the requirement of on-line CMD in the circumstance of transmission line, thereby seriously deteriorating the stability and reliability of on-line CMD and limiting its fulfillment.To solve this problem, this dissertation studies on the electric-field-based energy scavenging technique in AC transmission tower. Specifically, the following works are carried out.(1) Taking parallel-plane capacitor for example, a simulation model is established by using the commercial finite-element software COMSOL. The energy scavenging process is studied under the conditions of no-load, on-load and pulse switch. The output voltage of the plane and the stored energy of the capacitor are considered as two assessment indexes with regard to energy scavenging. Through simulation, the impact of plane parameters(spacing width, area and dielectric permittivity) on energy scavenging has been investigated. The optimization goal of energy storing for the parallel-plane capacitor is also presented. The electric field around a 500 kV straight tower with double-circuit transmission line is calculated by using COMSOL, and the maximal electic field intensity as well as its location is evaluated.(2) The charging and discharging processes of the plane are simulated by the software COMSOL and PSPICE, respectively. The simulation results are compared and analyzed. The equivalent circuit of the energy scavenging converter can be considered as an ac voltage source in series with three capacitors(pF class). The accelerating feature of pulse switch is validated via PSPICE simulations. Results show that the largest stored energy of the capacitor can be obtained in the peak and valley of the applied voltage at the switching frequency of 100 Hz, about four times of that in traditional power conditioning circuit.(3) Based on the traditional power conditioning circuit and pulse switch. surge protection circuit, voltage control circuit and DC/DC converter circuit are designed and included to improve the overall design of power conditioning circuit.(4) The experimental setup is established to test the electric-field-based energy scavenging system. Three different planes with radius of 7.5mm, 15 mm and 20 mm, are used in the experimental study. The impacts of plane spacing width, plane area, the applied electric field and pulse switch on the output voltage of the plane are experimentally verified.