電壓驟降，為發生在電力系統中短時間內的電壓降低，是電力品質問題中，最主要的關心議題之一，電壓驟降事故所引起的損失很高而不容忽視，是近來受到關注的主要原因。
以可靠度指標來量化電力系統長時間斷電的影響，已經使用多年；而電力品質指標是反映不同電力品質問題的嚴重性，諸如電壓閃爍、諧波、電壓驟升/驟降、功率因數、損失、電磁干擾及其他現象等等，則仍在持續發展中，尤其近來許多設定國際標準的組織，已經在研究電壓驟降的表示及分類。
為了要在服務品質、設備使用及可能解決電力品質問題的最低成本方案中取得匹配，在IEC 61000-3-7中提到系統擾動準位及設備免疫準位的概念，但並無清楚的定義。本論文提出一個以模糊邏輯技巧為基礎的新電壓驟降指標，可以量化系統擾動準位及設備免疫準位，這個方法考慮到網路弱點、設備敏感性及電壓驟降量測時的不確定性，藉以提供電力公司及用戶有意義的資訊，利用所提出的方法，可以由所有事故紀錄得到的單一事故指標，獲得系統擾動的機率分布，同時可由元件的電壓忍受曲線，評估設備電壓驟降忍受能力的機率分布。
本論文利用擾動與免疫準位的概念，提出預測設備因電壓驟降受影響次數的新架構，在所提出的方法中，是利用不可靠度的概念，來計算受影響的次數；在現場擾動準位分布與設備免疫準位分布間的重疊區域，代表可能受影響的次數，而以干擾理論與可靠度計算為基礎，可以計算出該重疊區域。
本研究方法可為量化系統擾動與設備敏感程度的規劃工具，及做設備與電力系統間匹配度的成本分析，為使電壓驟降的成本最小化，在設備免疫準位與現場擾動準位間，保持最小的重疊區域，將是一個好的策略，讓設備有較適當的運轉條件，可以利用在本研究所完成的工具，執行上述的分析。

Voltage sag (dip), a sudden reduction of the voltage magnitude within a short duration in power system, is one of major concerns of power quality problems. The main reason of the increased concerns for voltage sag problems is that the losses caused by voltage sag events are high and not negligible.
Reliability indices have been used for many years to quantify the effect of sustained interruptions on the electric power system. Power quality indices reflecting the severity of various power quality problems, such as flicker, harmonics, voltage swell and sag conditions, power factor, losses, electromagnetic interference, and other phenomena, are still under development. The representation and classification of voltage sags have been studied recently by standard-setting organizations.
In order to find compatibility between service quality and the equipment adopted and a least cost solution for possible power quality problems, the concept of system disturbance level and equipment immunity level was proposed in IEC 61000-3-7 but without clear definitions. A novel voltage sag index based on fuzzy logic technique to quantify system disturbance and equipment immunity levels is proposed in this dissertation. This approach takes network vulnerability, equipment sensitivity and uncertainties in measuring voltage sags into account, thereby, providing meaningful information for both the utility and customers. Using the proposed method, the probabilistic distribution of system disturbances can be obtained from the single event indices of all events recorded and the probabilistic distribution of equipment sag immunity capability can be evaluated based on the device voltage sag tolerance curve.
This dissertation also presents a novel framework for predicting the number of equipment disruptions due to voltage sags in a unit of time by using the disturbance and immunity levels concepts. In the proposed approach, the number of disruptions is computed by using the unreliability concept. The area of overlapping between the distributions of site disturbance and equipment immunity levels, which indicates the number of possible disruptions, is calculated based on interference theory and reliability computations.
The presented methodology can be used as a planning tool to quantify the system disturbances and equipment sensitivity. It can also be used to perform cost analysis of the compatibility of equipment with an electric power system. To minimize the costs due to voltage sags, it is always a good strategy to maintain a minimum overlap between the equipment immunity level and site disturbance level to have satisfactory operation of the equipment. The tool achieved in this work can be used to perform such analyses.

中文論文審定書 --------------------------------------------------------------------------- I
英文論文審定書 --------------------------------------------------------------------------- II
謝詞 ------------------------------------------------------------------------------------------ III
中文摘要 ------------------------------------------------------------------------------------ IV
Abstract -------------------------------------------------------------------------------------- VI
Contents -------------------------------------------------------------------------------------- VIII
List of Tables -------------------------------------------------------------------------------- XI
List of Figures ------------------------------------------------------------------------------- XII

Chapter 1 Introduction -------------------------------------------------------------------- 1
1.1 Objectives of the Study -------------------------------------------------------------- 3
1.2 Previous Works ----------------------------------------------------------------------- 5
1.3 Contributions of the Work ---------------------------------------------------------- 9
1.4 Structure of the Dissertation -------------------------------------------------------- 10
Chapter 2 Voltage Sag Indices and Standards ---------------------------------------- 11
2.1 Definition of Voltage Sag ----------------------------------------------------------- 11
2.2 Measurement of Voltage Sag ------------------------------------------------------- 12
2.3 Voltage Sag Standards --------------------------------------------------------------- 13
2.3.1 Standards Applied to Utility Supply System ------------------------------- 13
2.3.2 Standards Applied to Equipment --------------------------------------------- 15
2.3.3 Standards Applied to Monitoring and Testing ----------------------------- 17
2.4 Equipment Voltage Sag Tolerance Curve ----------------------------------------- 18
2.5 Representation of Voltage Sag Events --------------------------------------------- 20
2.5.1 Scatter Diagram ---------------------------------------------------------------- 20
2.5.2 Sag Density Table -------------------------------------------------------------- 21
2.5.3 Cumulative Table -------------------------------------------------------------- 22
2.5.4 Voltage Sag Coordination Chart --------------------------------------------- 22
2.6 Voltage Sag Index and Performance Assessment -------------------------------- 26
2.6.1 Single Event Index ------------------------------------------------------------- 28
2.6.1.1 Voltage Sag Energy Index ---------------------------------------------- 28
2.6.1.2 Voltage Sag -Lost Energy Index -------------------------------------- 28
2.6.1.3 Voltage Sag Severity Index -------------------------------------------- 28
2.6.1.4 Loss of Voltage Index --------------------------------------------------- 29
2.6.2 Site Service Performance Assessment -------------------------------------- 29
2.6.2.1 SARFI-%V & SARFI-CURVE --------------------------------------- 29
2.6.2.2 Voltage-Sag Energy Index --------------------------------------------- 30
2.6.2.3 Average Sag Energy Index --------------------------------------------- 30
2.7 Voltage Sag Table -------------------------------------------------------------------- 30
Chapter 3 Quantification of System Disturbance and Equipment Immunity Levels -------------------------------------------------------------------------- 34
3.1 Fuzzy Logic Based Disturbance Level Quantification -------------------------- 35
3.1.1 Membership Functions of the Input Variables Fuzzy Sets --------------- 36
3.1.2 Fuzzy Reasoning Process ----------------------------------------------------- 38
3.1.3 Membership Functions of the Output Variable Fuzzy Sets --------------- 42
3.2 Site Disturbance Level Analysis Using Recorded Data ------------------------- 47
3.3 Fuzzy Logic Based Equipment Immunity Level Quantification -------------- 49
3.4 Discussions --------------------------------------------------------------------------- 50
Chapter 4 Stochastic Prediction of Equipment Disruptions ----------------------- 53
4.1 Unreliability of Interference Concept --------------------------------------------- 53
4.2 Prediction of Equipment Disruption ----------------------------------------------- 58
4.3 Numerical Examples ----------------------------------------------------------------- 59
4.4 Discussions --------------------------------------------------------------------------- 61
Chapter 5 Conclusions and Future Works -------------------------------------------- 70
5.1 Conclusions --------------------------------------------------------------------------- 70
5.2 Suggested Future Works ------------------------------------------------------------ 71

Reference ------------------------------------------------------------------------------------- 73
Vita -------------------------------------------------------------------------------------------- 79

[1] M. H. J. Bollen, Understanding Power Quality Problems— Voltage Sags and Interruptions, Piscataway, NJ: IEEE Press, 2000.
[2] Roger C. Dugan, Mark F. McGranaghan, Surya Santoso, and H. Wayne Beaty, Electrical Power Systems Quality, New York, McGraw Hill, 2002.
[3] Assessment of Emission Limit of Fluctuating Load in MV and HV Power System, IEC 61000-3-7, 1996.
[4] M. H. J. Bollen, “Voltage sags in three-phase systems,” IEEE Power Engineering Review, vol. 21, no. 9, pp. 8–11, Sep. 2001.
[5] M. H. J. Bollen, “Characterisation of voltage sags experienced by three-phase adjustable-speed drives,” IEEE Trans. Power Del., vol. 12, no. 4, pp. 1666– 1671, Oct. 1997.
[6] Lidong Zhan and M.H.J. Bollen, ” Characteristic of voltage dips (sags) in power systems,” IEEE Trans. Power Del., vol. 15, no. 2, pp. 827–832, Apr. 2000.
[7] G. Yaleinkaya, M. H. J. Bollen, and P.A. Crossley, Characterization of voltage sags in industrial distribution systems,” IEEE Trans. Ind. Applicat., vol. 34, no. 4, pp. 682– 688, Jul.-Aug. 1998.
[8] M. H. J. Bollen, “Fast assessment methods for voltage sags in distribution systems,” IEEE Trans. Ind. Applicat., vol. 32, no. 6, pp. 1414–1423, Nov.-Dec. 1996.
[9] IEEE Guide for Electric Power Distribution Reliability Indices, IEEE Standard 1366 – 2003, Dec. 2003.
[10] Testing and Measurement Techniques—Power Quality Measurement Methods, IEC 61000-4-30, 2003.
[11] IEEE Recommended Practice for Monitoring Electric Power Quality, IEEE Standard 1159-1995, Nov. 1995.
[12] M. H. J. Bollen, D. D. Sabin, and R. S. Thallam, “Voltage-sag indices—Recent developments in IEEE P1564 task force,” in Proc. Quality and Security of Electric Power Delivery Systems, CIGRE/IEEE Power Eng. Soc. Int. Symp., Oct. 8–10, 2003, pp. 34–41.
[13] Power Quality Indices and Objectives Jan. 2004, Final Working Group Report, Joint Working Group CIGRE C4.07/CIRED.
[14] IEEE Recommended Practice for the Design of Reliable Industrial and Commercial Power Systems, IEEE Standard 493-1997, Dec. 1997.
[15] Testing and Measurement Techniques—Voltage Dips, Short Interruptions and Voltage Variations Immunity Tests, IEC 61000-4-11, 2004.
[16] Environment - Voltage Dips and Short Interruptions on Public Electric Power Supply Systems with Statistical Measurement Results, IEC 61000-2-8, 2002.
[17] M. H. J. Bollen and D. D. Sabin, “International Coordination for Voltage Sag Indices,” PES TD 2005/2006, May 21-24, 2006, pp. 229 – 234.
[18] IEEE Recommended Practice for Powering and Grounding Electronic Equipment, IEEE Standard 1100-1999, Mar. 1999.
[19] ITI (CBEMA) Curve Application Note, Published by: Information Technology Industry Council (ITI), 1250 Eye Street NW Suite 200 Washington DC 20005, 202-737-8888, Available at http://www.itic.org.
[20] “SEMI F47-0200 Specifications for semiconductor processing equipment voltage sags immunity,” Semiconductor Equipment and Materials International, Mountain View, CA, 2000.
[21] J. Kyei, R. Ayyanar, G. T. Heydt, R. Thallam, and J. Blevins, “The design of power acceptability curves”, IEEE Trans. Power Del., vol. 17, no. 3, pp. 828–833, Jul. 2002.
[22] R. S. Thallam and G. T. Heydt, “Power acceptability and voltage sag indices in the three phase sense,” in Proc. IEEE Power Eng. Soc. Summer Meeting, Seattle, WA, Jul. 2000, paper presented at the Panel Session on Power Quality: Voltage sag indices in the three phase sense.
[23] G. T. Heydt, R. Ayyanar, and R. Thallam, “Power acceptability,” IEEE Power Engineering Review, vol. 21, no. 9, pp. 12 – 15, Sep. 2001
[24] L. E. Conrad and M. H. J. Bollen, ”Voltage sag coordination for reliable plant operation,” IEEE Trans. Ind. Applicat., vol. 33, no. 6, pp. 1459–1464, Nov.-Dec. 1997.
[25] D. L. Brooks, R. C. Dugan, M. Waclawiak, and A. Sundaram, “Indices for assessing utility distribution system RMS variation performance,” IEEE Trans. Power Del., vol. 13, no. 1, pp. 254–259, Jan. 1998.
[26] G. J. Lee, M. M. Albu, and G. T. Heydt, “A power quality index based on equipment sensitivity, cost and network vulnerability,” IEEE Trans. Power Del., vol. 19, no. 3, pp. 1504–1510, Jul. 2004.
[27] N. Kagan, E. L. Forrari, N. M. Matsuo, S. X. Duarte, J. T. Cavaretti, A. Tenorio and L. R. Souza, “A methodology for the assessment of short duration voltage variations in electric power distribution systems,” in Proc. 10th Int. Conf. Harmonics and Quality of Power, Oct. 2002, vol. 2, pp. 6–9.
[28] E. Liu, Management and improvement of voltage sags at high-tech companies Taiwan Power Company, Dec. 2004, Final Report.
[29] D. J. Won, S. J. Ahn, I. Y. Chung, J. M. Kim, and S. I. Moon, “A new definition of voltage sag duration considering the voltage tolerance curve,” in Proc. IEEE Bologna Power Tech Conf., Jun. 2003, vol. 3.
[30] G. J. Klir and T. A. Folger, Fuzzy Sets, Uncertainty and Information. Englewood Cliffs, NJ: Prentice-Hall, 1988.
[31] M. F.Alves, and T. N. Ribeiro, “Voltage sag: an overview of IEC and IEEE standards and application criteria,” in Proc. 1999 IEEE Transmission and Distribution Conference, 11-16 April 1999, vol. 2, pp. 585 - 589.
[32] IEEE Recommended Practice for Evaluating Electric Power System Compatibility with Electronic Process, IEEE Standard 1346-1998, May 1998.
[33] Environment – Compatibility Levels for Low-frequency Conducted Disturbances and Signalling in Public Low-voltage Power Ssupply Systems, IEC 61000-2-2 2002.
[34] IEEE Guide for Service to Equipment Sensitive to Momentary Voltage Disturbances, IEEE Standard 1250-1995, Mar 1995.
[35] IEEE Recommended Practice for Emergency and Standby Power Systems for Industrial and Commercial Applications, IEEE Standard 446-1995, Dec 1995.
[36] Environment – Compatibility Levels in Industrial Plants for Low-frequency Conducted Disturbances, IEC 61000-2-4 2002.
[37] Zhi-Qiang Chen, 2005, “Effect of Voltage Sags on Sensitive Equipment,” Published master thesis, National Sun Yat-sen University, Kaohsiung.
[38] Tao-Ping Tseng, 2006, “Effect of Voltage Sags on Adjustable-Speed AC Drives,” Published master thesis, National Sun Yat-sen University, Kaohsiung.
[39] G. T. Heydt, Electric Power Quality. Scottsdale, AZ: Stars in a Circle, 2002.
[40] G. T. Heydt, and W. T. Jewell, “Pitfalls of electric power quality indices,” IEEE Trans. Power Del., vol. 13, no. 2, pp. 570–578, Apr. 1998.
[41] G. T. Heydt, “Power quality engineering,” IEEE Power Engineering Review, vol. 21, no. 9, pp. 5–7, Sep. 2001.
[42] IEEE Recommended Practices and Requirements for Harmonic Control in Electrical Power Systems, IEEE Std 519-1992, April 1993.
[43] R. S. Thallam, “Power quality indices based on voltage sag energy values,” in Proc. Power Quality Conf. Expo., Chicago, IL, Sep. 2001.
[44] A. Robert and E. De Jaeger, Final Report Round table on power quality at the interface T&D CIRED 2003, May. 14, 2003.
[45] B. D. Bonatto, T. Niimura, and H. W. Dommel, “A fuzzy logic application to represent load sensitivity to voltage sag,” in Proc. 8th Int. Conf. Harmonics and Quality of Power, 1998, vol. 1, pp. 60–64.
[46] Tutorial on Fuzzy Logic Application in Power Systems. Piscataway, NJ: IEEE Power Eng. Soc. Publ., Jan. 2000, No, TP140-0.
[47] C. C. Shen, A. C. Wang, R. F. Chang, and C. N. Lu, “Quantifying disturbance level of voltage sag events,” in Proc. IEEE Power Eng. Soc. General Meeting, Jun. 2005, vol. 3, pp. 2314–2318.
[48] C. N. Lu and C. C. Shen, “Voltage sag immunity factor considering severity and duration,” in Proc. IEEE Power Eng. Soc. General Meeting, Jun. 2004, vol. 1, pp. 626–630.
[49] Cheng-Chieh Shen and Chan-Nan Lu, “A Voltage Sag Index Considering Compatibility Between Equipment and Supply,” IEEE Trans. Power Del., vol. 22, no. 2, pp. 996-1002, Apr. 2007.
[50] K. C. Kapur and L. R. Lamberson, Reliability in Engineering Design. New York: Wiley, 1977, pp. 122–136.
[51] R. L. Burden and J. D. Faires, Numerical Analysis. Boston, MA: PWS-Kent, 1989.
[52] Chan-Nan Lu and Cheng-Chieh Shen, “Estimation of Sensitive Equipment Disruptions Due to Voltage Sags,” IEEE Trans. Power Del., vol. 22, no. 2, pp. 1132 – 1137, Apr. 2007.
[53] M. P. Wand and M. C. Jones, Kernel Smoothing, Chapman and Hall, New York, 1990.
[54] T. J. Hastie and R. J. Tibshirani, Generalized Additive Models, Chapman and Hall, New York, 1990.