- 學位論文
以有限元素法分析GIS斷路器之啟斷特性及開關突波特性
Analysis of the Characteristics of Interrupting and Switching Surge of Breaker in the GIS Based on Finite Element Method
摘要
本文以有限元素法分析氣封絕緣變電站(GIS)之斷路器在啟斷短路電流及承受開關突波時其內部電場分佈，並據此探討斷路器的特性包括啟斷能力及絕緣耐力，其中將以短路試驗標準的電流及暫態回復電壓做為分析的依據，並考慮不同的燃弧時間及啟斷速度進行分析最大的電場分佈，此電場分佈基本上是在啟斷瞬間的開關突波電壓與系統電壓共同造成的，由電場分析可判斷斷路器的啟斷特性包括再襲現象是否發生及絕緣安全裕度是否足夠。至於斷路器投入(閉合)時，開關突波的影響是絕緣安全裕度的問題，在投入瞬間出現在外殼與接觸子之間的電壓包括由接地系統轉移來的突波電壓與系統暫態電壓，這些電壓造成的斷路器內電場分佈是否會影響絕緣耐力是本文探討的另一個重點，其中由接地系統轉移來的開關突波與斷路器投入操作模式及GIS接地線的佈設條件有密切的關係，本文將針對不同斷路器操作模式及不同接地線佈設條件所造成的開關突波進行斷路器電場分佈之分析，以探討對絕緣耐力的影響，分析結果顯示無論斷路器啟斷或投入瞬間，其內部絕緣裕度的安全係數都會降低，其中啟斷速度太慢、燃弧時間太短都可能造成再襲現象而導致啟斷失敗，並使絕緣安全係數降低，三相接觸子的投入操作時差及接地線的電感太大也將造成投入時絕緣安全係數降低，故維護斷路器有正常的啟斷速度及燃弧時間及接地系統的改善對斷路器的啟斷能力及絕緣耐力都非常重要，本文分析的結果可提供斷路器弱點所在及改善之參考。
並列摘要
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.