近年來電力公司在市區的配電系統慢慢改為地下化的方式傳送，地下電纜中最容易發生故障的地方為電纜直線接頭，主要因素大多是在施工所造成的人為瑕疵，因此探討地下電纜直線接頭絕緣狀態是目前最重要的課題。
本文使用直線接頭當作被試物進行局部放電試驗，並在接頭續接處故意製作一個人為瑕疵，施加高電壓直到絕緣擊穿為止，在試驗期間以固定時間擷取局部放電資料，透過濾波、化簡、轉換，並萃取出所需的特徵參數和相位解析圖，最後透過分形的計算求出每張相位解析圖之維度值，並和其他的特徵參數互相比較，可發現透過分形計算後的結果與放電總和以及放電次數有相類似的演進趨勢，並且可將分形維度限制在2與3之間。最後再計算一階擬合的誤差，並計算誤差的平均值乘上不同的條件當門檻，取出各個試驗較精確的維度值，當維度值接近2.25或超過時，已進入絕緣狀態的末期，若能在此時提出適當的警告，將能夠有效降低事故的發生。

In the recent years, the transmission way is changed from overhead line circuit to underground for power companies in the urban distribution systems. In the underground cables, the cable joints may be weak points for breakdown as a result of the construction of the artificial defection. Therefore, exploring the underground cable joint insulation state is the most important issue.
In this thesis, the cable joint is used as the test material in the partial discharge test and the artificial defect is produced in joints deliberately, and then applying high voltage to the test material until the insulation breakdown, during the trial term, the partial discharged data is retrieved by data captured card in the fixed time and by using filtering, simplification, conversion to extract the characteristic parameters and phase resolve pattern. Finally, the fractal dimension value is obtained by calculation of the phase resolve pattern for each pattern, and compared to each other characteristic parameters, by the calculation of the result mentioned above. The discharge sum and discharge number are the similar diameter trend, furthermore, the fractal dimension is limited to between 2 and 3. Finally, the first-order fitting error is calculated, and the differential thresholds are computed by the differential rates of the averaged error. Furthermore, the more precise dimension values among those tests in each condition are taken out. When dimension values are close to 2.25 or exceed, it will end in the insulating deterioration. Therefore, the appropriate warning can effectively reduce the accident occurance at this time.

[1]張瑞村，「數位局部放電量測應用於高壓電纜終端接頭絕緣狀態之評估」，碩士論文，國立台灣科技大學，民國九十四年。
[2]侯朝傑，「地下電纜接頭瑕疵之絕緣劣化分析」，碩士論文，國立台灣科技大學，民國九十七年。
[3]K. Uchida, S. Kobayashi, T. Kawashima, H. Tanaka, S. Sakuma, K. Hirotsu and H. Inoue, “Study on Detection for The Defects of XLPE Cable Lines,” IEEE Transactions on Power Delivery, Vol. 11, No. 2, pp. 663-668, Apr. 1996.
[4]台灣電力公司業務處，「配電技術手冊(四)地下配電線路設計」，民國八十五年。
[5]張建國，「地下電纜接頭局部放電線上監控系統之研製」，碩士論文，國立台灣科技大學，民國九十五年。
[6]F. Guastavino and B. Cerutti, “Tree Growth Monitoring by Means of Digital Partial Discharge Measurement,” IEEE Transactions on Dielectrics and Electrical Insulation, Vol. 10, No. 1, pp. 65-72, February 2003.
[7]B. H. Ward, “Digital Techniques for Partial Discharge Measurement,” IEEE Transactions on Power Delivery, Vol. 7, No. 2, pp. 469-479, April 1992.
[8]E. Gulski, “Computer-Aided Measurement of Partial Discharge in HV Equipment,” IEEE Transactions on Dielectrics and Electrical Insulation, Vol. 28, No. 6, pp. 969-983, December 1993.
[9]Ruay-Nan Wu and Chien-Kuo Chang, “The Use of Partial Discharges as an Online Monitoring System for Underground Cable Joints,” IEEE Transactions on Power Delivery, Vol. 26, No. 3, July 2011.
[10]何俊彥，「高電壓地下電纜接頭絕緣狀態即時性評估之研究」，碩士論文，國立台灣科技大學，民國一百年。
[11]R. Bozzo, G. Coletti, and F. Guastavino, “Studies About the Electrical Treeing Growth based on the Evolution of the PD Patterns,” IEEE Symposium on Electrical Insulation, Vol. 2, pp. 415-419, June 1998.
[12]M. S. Mashikian and A. Szatkowski, “Medium Voltage Cable Defects Revealed by Off-Line Partial Discharge Testing at Power Frequency,” IEEE Electrical Insulation Magazine, Vol. 22, No. 4, pp. 24-32, July/August 2006.
[13]P. F. Gale, “Cable-Fault Location by Impulse-Current Method,” Proc. IEE, Vol. 122, No.4, pp. 403-408, 1975.
[14]Barry Clegg, “Underground Cable Fault Location,” McGraw-Hill, 1993.
[15]N. Sarkar and B. B. Chaudhuri, “An Efficient Differential Box-Counting Approach to Compute Fractal Dimension of Image,” IEEE Transaction on Systems, Man and Cybernetics, Vol. 24, No. 1, pp. 115-120, January 1944.
[16]G. J. Paoletti and A. Golubev, “Partial Discharge Theory and Technologies Related to Medium-Voltage Electrical Equipment,” IEEE Transactions on Inductry Applications, Vol. 37, No. 1, pp. 90-103, January/February 2001.
[17]“High-Voltage Test Techniques Partial Discharge Measurement,” IEC60270, 2000.
[18]陳振銘，「地下電纜絕緣樹枝現象之劣化趨勢研究」，碩士論文，國立台灣科技大學，民國九十六年。
[19]D. A. Nattrass, “Partial Discharge Measurement and Interpretation,” IEEE Electrical Insulation Magazine, Vol. 4, No. 3, pp. 10-23, May. 1988.
[20]F. H. Kreuger, Partial Discharge Detection in High-Voltage Equipment, Butterworths & co Ltd, London, 1989.
[21]王宗鏗，「配電」，中國電機工程學會，1992年11月。
[22]台灣電力公司，材料標準規範A043(95-04)，「高壓單芯交連PE電纜」，民國九十五年。
[23]台灣祥登股份有限公司，25kV 200A #1AWG直線接頭施工說明書。
[24]QT-II(QT151/152/251/252)冷縮式屋內型電纜終端處理頭施工說明書。
[25]許肇棠，「電纜終端因施工不當造成之絕緣缺陷的改善方法」，碩士論文，國立清華大學，民國九十六年。
[26]台灣電力公司，材料標準規範E056(95-08)，「預張式高壓電纜終端接頭」，民國九十五年。
[27]張濟忠，「分形」，北京，清華大學出版社，1995年。
[28]B. B. Mandelbort, “How Long Is the Coast of Britain? Statistical Self-Similarity and Fractional Dimension,” Science, New Series, Vol. 156, No. 3775, pp. 636-638, May 5, 1967.
[29]Carl Bovill, Fractal Geometry in Architecture and Design, 1996.
[30]古峰昌，「XLPE電力電纜局部放電量測與瑕疵模式辨識」，碩士論文，國立勤益科技大學，民國九十八年。
[31]K. Falconer, FRACTAL GEOMETRY: Mathematical Foundations and Application, Wiley, 1990.
[32]Chen Li-Jung, Lin Whei-Min, Tsao Ta-Peng and Lin Yu-Hsun, “Study of Partial Discharge Measurement in Power Equipment Using Acoustic Technique and Wavelet Transform,” IEEE Transactions on Power Delivery, Vol. 22, No. 3, pp. 1575-1580, July 2007.