工廠多部中壓發電機併聯運轉之
各種系統接地之特性研究

本文探討工廠多部中壓發電機併聯運轉之各種系統接地方式之特性，所謂中壓發電機主要是指4.16KV或3.45KV之發電機，此種發電機之輸出被昇壓至22.8KV或11.4KV高壓，再併聯至工廠高壓配電系統，而系統接地則是指發電機繞組中性點及昇壓變壓器高壓側繞組中性點之接地，所探討的特性包括單相接地故障、開關突波、及負載不平衡三種特性。本文所考慮的接地方式包括：發電機中性點直接接地、發電機中性點電阻接地、發電機中性點不接地、變壓器中性點直接接地、變壓器中性點電阻接地、及變壓器中性點不接地。前述三種特性的內容則包括：單相接地故障電流、健全相及故障相電壓及電流變化、負載端電壓、變壓器中性點電壓電流、及發電機中性點電壓電流。文中首先建立針對分析單相接地故障、開關突波、及負載不平衡之電路模型，並將各種接地方式考慮進去。然後應用這些模型逐項進行各項特性的分析，最後將各種分析結果加以比較，以評估各種系統接地的優缺點。研究結果顯示：直接接地方式對保護協調、中性點的電位穩定、及開關突波的消除較為有利，但單相接地故障電流太大可能燒毀發電機及變壓器，亦需較大短路容量的斷路器。因此，目前中壓發電機及其昇壓變壓器之中性點均採取電阻接地。

關鍵字

系統接地；開關突波；負載不平衡；單相接地故障

並列摘要

In the thesis, the characteristics of various types of system grounding in the plant with multiple medium voltage generators parallel operations are studied. The medium voltage generators are mainly the 4.16KV or 3.45KV generators, their output voltage will be upgraded to high voltages which are mainly 22.8KV or 11.4KV. So, the generators are parallel connected on the high voltage distribution system. The system grounding includes the neutral grounding of generator armature winding and transformer high voltage winding. The characteristics to be studied include the voltages and current variations on phases and neutral buses of transformer and generator during single line-to-ground fault, switching surges and unbalanced load with respect to various types of system grounding. The types of system grounding include solid grounding, resistance grounding, and ungrounding neutral point of generator armature winding and transformer high voltage winding. The circuit models with respect to single line-to-ground fault, switching surges, and unbalanced load are first constructed. In these models the types of system grounding are considered. Then, the characteristics of each system grounding are analyzed by these circuit models. Finally, base on the analysis results, the benefits and defects of various system grounding are compared and assessed. The comparisons and assessments results have shown that the solid grounding can getting better performances on protection coordination, stabilizing neutral potential and eliminating the switching surges, but very large fault current will lead to high risk to generator, transformer and breaker. Thus the conventional resistance grounding for neutral is widely used.

並列關鍵字

System Grounding ； Unbalanced Load ； Single line-to-ground Fault ； Switching Surges

參考文獻

[18] 黃鈺倫,“捷運系統主變電站接地系統之開關突波特性分析”,中原大學電機系碩士論文,民國91年6月。

[2] ANSI/IEEE Std 446-1987, “IEEE Recommended Practice for Emergency and Standby Power System for Industrial and Commercial Applications,” IEEE Society, New York 1986.

[3] Rene Castenschiold , Gordon S. Johnson , “Proper grounding of On-Site electrical Power System,” IEEE Industry Applications Magazine, pp. 54-62, March/April 2001.

[4] Rene Castenschiold , “Ground Control for Alternate Power,” IEEE Power & energy Magazine, pp. 49-55, May/June 2003.

[5] Larry Bey, “Grounding and Ground Fault Protection Consideration Specific to Emergency/Standby Generator Sets.” Telecommunications Energy Conference, 1994. INTELEC '94., 16th International, pp.392 – 399, 30 Oct.-3 Nov. 1994.

國際替代計量

工廠多部中壓發電機併聯運轉之各種系統接地之特性研究

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