Сельскохозяйственные машины и технологии (Aug 2017)
PERATION PECULIARITIES OF SINGLE-WIRE HIGH FREQUENCY POWER TRANSMISSION LINES
Abstract
Increasing efficiency of power transmission lines is an important factor for providing agricultural objects with electric power. During the development power transmission systems, lines direct current, lines alternating voltage of industrial frequency and lines of alternating voltage high frequency have appeared. The author considers some features of operation power transmission systems over single-wire transmission lines operating at high frequency in range of 5-20 kHz. The system allows to transmit electrical energy on one wire with return through low-conductivity grounds due to the high frequency. To operate a single-wire power transmission system, it is necessary to arrange grounding. A distinctive feature work of grounding at a high frequency is that in addition to conductivity of soil, dielectric permittivity of soil layers also works. This makes it possible to reduce size of switches earthing or to transmit electrical energy through low-conductivity grounds with small losses. Calculations of efficiency of electric energy transfer are given. Efficiency of transmission electric power of 10 kW at a frequency 10 kHz through dry silica can be 96.5 percent. When the frequency is 50 Hz, so efficiency of transmission electric power will tend toward zero. Corrosion damages of the steel electrodes placed in an electrolyte on currents of various frequency were estimated. Effect of high frequency on circuit of grounding switches was studied. If the high frequency equals 2.6 and 100 kHz, so the corrosion of electrodes decreases by 15-20 percent compared to the frequency of 50 Hz, and by 60 times in comparison with a constant current. Therefore as grounding conductors of a single-wire power line it is possible to use not only special electrodes, but also agricultural objects.
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