| Power system operation experience has shown that, grounding technique has important influence to the safe and stable operation of the power system. Power grid in China is moving toward the direction of greater, higher power, more intelligent, the development put forward higher challenge to reliable, safe and effective operation of the present stage grid, the impulse grounding resistance of transmission line tower grounding electrode directly affect lightning protection effect of transmission line, and the lightning protection performance of transmission line tower grounding system is closely related to the impulse current dispersing characteristics. The impulse current dispersing characteristics of the transmission line tower grounding system is studied in this paper, the influence factor and influence rule of impulse current dispersing characteristics of grounding system is analyzed, it will provide technical support for the grounding system in practical engineering design.Firstly, the research status for impulse properties of transmission line tower and grounding system is summarized in this paper, then introduce several typical simulation model of transmission tower, analyze current transient calculation model of grounding system, experimental method and application range. The typical lightning wave spectrum is calculated, current dispersing mechanism of grounding electrode under impulse current and the influence rule of grounding electrode influenced by soil resistivity is revealed.Secondly, impulse current dispersing model of transmission line tower grounding system is established by using electromagnetic simulation software CDEGS, and studied the influence factors of impulse current diffuser of grounding system, found that the longer impulse, current front time, the higher tower, the larger cross arm width, the lower soil resistivity and the longer grounding electrode will lead to lower impulse voltage peak of tower top and grounding electrode, the longer impulse half wave time, the higher soil resistivity and the shorter transmission tower span will lead to more shunt of lightning conductor and litter shunt of tower which is struck by lighting.Finally, this paper establish distribution parameter circuit model of grounding electrode by using the ATP-EMTP which consider spark discharge, and the electrical parameters and the mutual inductance between grounding electrode of this model is calculated. Base on this model the impulse transient response of the single horizontal grounding electrode, the two parallel grounding electrodes and the Y type grounding electrode is analyzed. Impulse test platform is established and discharge test is carried on horizontal grounding electrode, by analyzing the test results and simulation results, the impulse current dispersing of grounding electrode under spark discharge is revealed. |
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