| Summary: | 碩士 === 中原大學 === 電機工程研究所 === 92 === The electrical field distribution in the breaker of gas insulated substation (GIS) during interrupting the short-circuit current and switching surge are analyzed based on finite element method for investigating the ability of interrupting and insulation strength of breaker. The standard current and transient recovery voltage of short-circuit test will be as analyzing basis and consider different arcing time and interrupting speed to analyze the maximum electrical field distribution. The electrical field distribution is caused by both of transient switching surge voltage of interrupting and system voltage and it can be judged if the interrupting characteristics, including re-strike, will happen or not and if insulated safety rage is sufficient or not by electrical field analysis. When breaker closes (making), the switching surge will influence insulated safety rage. The voltages appeared between the enclosure and the contacts includes switching surge voltage transferred from the grounding system and system transient voltage. Whether the electrical field distribution resulted from these voltages influence the insulation strength or not will be investigated in the thesis. Moreover, the switching surge transferred from grounding system has close relation with the closing operation modes of breaker and the disposal conditions of GIS grounding wire. The electrical field distributions in the breaker due to switching surges with respect to various closing operation modes of breaker and disposal conditions of grounding wire are analyzed for investigating the insulation strength in the breaker. The analysis result indicates that whether breaker opens or closes transiently, the safety factors of the internal insulation range will reduce. If the interrupting speed too slow and arcing time too short ,the electrical field may cause re-strike to fail interruption and decrease the safety factors of insulation strength. Moreover, the closing operation time difference between three phase contacts of breaker and the inductance of grounding wires too large will also cause to decline the safety factors of insulation strength. Therefore, to maintain the breaker with normal interrupting speed and arcing time and improve grounding system are very important for the interrupting ability and insulation strength of breaker. The analysis results in this thesis can be used for finding the weak points of breaker and for improvements.
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