Research On A Draw-Out Power Supply For On-Line Monitoring Of Transmission-Line State Parameters And System Design

The continual increment of transmission-line voltage grade and capacity necessarily calls for higher security in transmission-line operation. It is discovered through exhaustive theoretical analysis and vast experiments that the transmission-line operating mode has affinitive relations with some meteorological, mechanical and electrical parameters which are called"state parameters". Therefore, the research interest is advanced to develop a measuring and controlling system that can comprehensively monitor real-time transmission-line state parameters and provide them for the operation sectors.The power supply strategy is among the key problems in monitoring the transmission-line state parameters. As each powering scheme has its shortcoming at present, this paper researches and develops a sort of powering pattern ("Draw-Out Power Supply") in which the electric power is obtained from the transmission line. A novel scheme of the draw-out coil is proposed, aiming at the ubiquity of problems in existing literatures that the draw-out coils are prone to deep saturation and high heat consumption, and the circuits are complex. The problems in the current technology are resolved via introducing an air-gap magnetic resistance to the draw-out coil, as well as properly matching the parameters such as the configuration of the coil, the material of the magnetic core, number of winding turns, and air-gap length. Then a power supply equipment is developed based on this draw-out coil. Integral test results illustrate that the power supply provides stable outputs with no saturation and low heat consumption throughout the variational range of the transmission-line currents. Besides, this paper analyses the influence to the power supply's reliability caused by abnormal large current through the conductor. Detail measures to enhance the reliability are presented. Short circuit and impulse current tests show that the adopted measures are capable of restraining the demolishment from the electrodynamic force and overvoltage imputed to abnormal large current. How to improve the output power is also explored to meet the future requirement of draw-out power supplies to possess heavy-load endurance. The functional relationship among output power, winding turn number and initial current is deduced by establishing the equivalent circuit model for the draw-out coil.Also, an on-line monitoring system for state parameters on transmission lines is developed based on the draw-out power supply. State parameters such as the leakage current through insulators, transmission-line temperature, ambient temperature, ambient relative humidity, conductor tension, and so forth, are monitored via hardware and software design. In addition, a real-time clock module is employed for adding calendar and time info to the parameters, and they are packed in an external memory. Ultimately the data are transmitted to the ground host monitoring computer by GPRS communication. A mass of test results prove that the system succeeds in remotely monitoring the transmission-line state parameters and transferring data in an effective way, which gains a phasic achievement in the research process of on-line monitoring system for comprehensive state parameters on transmission lines.