Designation And Research On The Methods Of On-line Monitoring Divider Of Overhead Transmission Line

On-line monitoring and signal transmission technology privide a foundation for intelligent development of power system. In substations, lightning monitoring technology has been more and more widely used. However, for transmission lines, this kind of technology is still in the initial research stage. The research of lightning in power field is mature. Lightning seriously threatens the stable operation of overhead lines. The probability of lightning strikes on lines will increase with the increasing of voltage grade. Therefore, it is meaningful to adopt effective on-line monitoring research for overhead lines. At present, the lightning monitoring for overhead lines lacks relatively accurate voltage-divided device. In order to solve this problem, this paper has made deep research and analysis for online monitoring voltage divider of overvoltage. This paper proposes a kind of voltage divider which uses Zinc oxide Varister valve plates as voltage-divided device for line overvoltage monitoring system.This paper first introduces the main types of lightning overvoltage in overhead lines and analyzes the characteristics of lightning overvoltage. Secondly, this paper illustrates the voltage-divided methods of overvoltage at the present stage. For the problems and shortcomings of current voltage-divided methods, this paper proposes Zinc oxide Varistor voltage divider as the new equipment of voltage-divided device. This paper carries on the discussion and research about Zinc oxide Varistor voltage divider from the following several aspects:1) Firstly, we study the micro-structure characteristics of the Zinc oxidevaristor valve plates by theory. According to the principle of structure analysis the ratio requirement which to meet the demands of voltage divider. Meanwhile describing and analyzing the zinc oxide varistor valve plates at different current on the equivalent circuit to to grasp its electrical properties, and get the proportion that meet certain ratio characteristics of zinc oxide varistor voltage divider.2) Proposing the used principle of zinc oxide varistor divider, proving only its thickness and properties associated with the proportional property of zinc oxide varistordivider. Concluding that the voltage divider with fixed proportional property, and through the Fourier expansion, conclude that its frequency characteristic and determine its meet the setting requirements of sample.3) Through the simulation software of EMTP- ATP and Origin 8.0, we can further determine the rationality of the amplitude and frequency characteristics, and can maintain the unity with theoretical analysis. It demonstrates that no matter shocked by what kind of over voltage striking, the partial pressure ratio of the zinc oxide varistordividerdoes not vary with the change of waveform, It is only with its own thickness ratio.4) Using simulation to analyze the advantage and disadvantage of different low pressure divider element. From both amplitude and frequency characteristics to demonstrate that no matter in any case, connecting the same type of zinc oxide varistor valve plates can satisfy the requirement of voltage divider.5) Finally, according to the zinc oxide varistor voltage experiment test, demonstrate that it has a good ratio of partial pressure, and the introduction of proportional characteristic matching resistor and a voltage follower can obtain more precise voltage divider, meanwhile, it can demonstrate the important role of matching resistance and voltage follower.In this paper, through the explanation of the theory, simulation analysis and the process of experimental verification, it analyzes the micro structure principle of zinc oxide varistor valve plates, and it demonstrates the zinc oxidevaristor bleeder which as new partial pressure monitoring device meet the requirements. Getting lightning over voltage signals at a time in the line, can avoid the resonance error introduced by using of the capacitor voltage transformer(CVT); And the equipment is security and stability, it won’t happen such transformer bushing at the end of the screen with the discharge problem;At the same time, the divider which reformed based on the line arrester,can save cost, and not easily interfered by electromagnetic interference and so on.