A New Approach Of Fault Mode Identification In Power System Based On Fractal Theory

The object of the paper is to fault type recognition in transmission line andsingle phase earth-fault line selection in small current grounded system based onfractal theory.With the development of power system, the quantity of the high voltagetransmission line increases, and they are very important to the safe of power system.There are many single phase reclosing device in transmission system, so effectivephase selector is the base to make reclosing device work correctly. Phase selector isalso the important part of the line protection and influent the function of protectiondevice directly. A new approach of fault type recognition based on fractal theory intransmission line is first proposed and studied, the essence of which is data miningclassification based on fractal theory. The criterion of fault type recognition areextracted and formed based on calculation and analysis of fractal dimension to thefault transient phase and zero sequence current in this paper. It is shown thefeasibility and validity to different fault type recognition based on fractal theory intransmission lines, in respect that this work had made a great number of the ATPsimulations and verifying tests to different fault type and its feature. The criterion isnot influent by fault transition resistance and power system mode. The essence offractal theory is similarity, the principle is to mine from the similarity of the timesequence data. Non-linear principle is better than the linear one, so the accuracyincreased greatly.Small current grounded system are widely used in power distribution system inChina, and the single phase to earth fault happened most frequently in distribution,thus how to detect the fault line quickly and accurately is an important and difficultsubject in power system protective relaying. The reliability and accuracy of existedline selector device is very low. This paper summarizes all the existing theories onthe fault line section systematically and understands the theory of fault. A newapproach of fault line selection for ungrounded neutral system based on fractaltheory is first proposed. The theory can identify the fault line by calculating andcomparing fractal dimension of transient current of fault line and normal line. Thefractal theory have high accuracy and is not influent by the amplitude of current andother uncertain factor, because its principle is to mine the regularity and extract thesimilarity in transient current...