【導(dǎo)讀】進行的分析實現(xiàn)在網(wǎng)絡(luò)中顯示存在相關(guān)典型頻率的連續(xù)小波變換轉(zhuǎn)換信號和特殊路徑代替轉(zhuǎn)換小波引起的故障。在MV離散系統(tǒng)中利用以上所提到的相關(guān)性確定MV配電系統(tǒng)故障定位的步驟。型為代表，以及研究各種故障類型和網(wǎng)絡(luò)特點。近年來中壓配電網(wǎng)絡(luò)的故障定位是一個日益受到重視研究話題，由于既要最嚴的質(zhì)量的要求并要提供改進測量和監(jiān)測系。眾所周知，相對于DWT的算法，CWT是一種讓表現(xiàn)出該故障暫態(tài)更詳細持。這些頻率可用于推斷的故障位置，在網(wǎng)絡(luò)的拓撲結(jié)。構(gòu)小波沿線傳播速度和已知故障類型?；贑WT故障定位的程序是與測量系統(tǒng)旨在獲得雙方的起始時間的瞬態(tài)及有關(guān)波形設(shè)想結(jié)合起來。3部分介紹了擬訂對連續(xù)小波變換的分析和具體的路徑沿網(wǎng)絡(luò)所涵蓋的行波源故障的相互關(guān)系。第4部分提出申請離散系統(tǒng)對稱。在連續(xù)小波變換為基礎(chǔ)的分析方面，目前已分開進

　　

【正文】 c tively), as the traveling wave is re?ected at the line terminations. Fig. 3 presents the results of the CWTanalysis of the voltage transient of Fig. 2 at the observation point (bus 4). Table 1 pares the results inferred theoretically by assuming, in a ?rst approximation, the traveling wave Phase voltage (kV) Phase voltage (kV) CWT signal energy (.) 使用連續(xù)小波變換在配電系統(tǒng)中故障定位 612 Table 1 A. Bhetti et al. / Electrical Power and Energy Systems 28 (20xx) 608–617 modify signi?cantly the re?ection coe?cients at the line Frequency values theoretically associated to the paths covered by the traveling waves originated by a balanced fault at bus 1 observed at bus 4, and values identi?ed by the CWTanalysis Path Length Theoretical CWTidenti?ed termination. . Nonsymmetrical faults (km) L1 + L2 + L3 4 10 L1 + L2 + L4 2 7 frequency value (traveling wave at light speed) (kHz) frequency value (kHz) For the case of nonsymmetrical faults, the di?erent propagation velocities of the various modes of the traveling waves must be taken into account [15]. Considering the line con?guration shown in the Appendix, as a ?rst approxima L1 + L5 2 3 50 tion, the Clark transformation is applied to the voltage transients at the observation point (bus 4) of the distribu tion work of Fig. 1, for di?erent types of unbalanced faults at various locations, also with nonzero fault velocity equal to the speed of light with those identi?ed from the peaks in Fig. 3. If the CWTanalysis is applied to the voltage transients recorded in a di?erent observation point, in other words we are considering a measurement system with distributed architecture (see Section 5), it is possible to increase the information relevant to the fault location. Fig. 4 and Table 2 show the results of the CWTanalysis at bus 2 for the previous case of a zeroimpedance threephase fault at bus 1. For this observation point three paths are of interest: L3 + L4, with opposite sign re?ections at the fault location and at the bus 2, L1 + L2 + L4, with re?ection at the line terminations having the same sign, and L2 + L4 + L5 with re?ection at the line terminations having the same sign. As it can be seen, by joining the information provided by this observation point with those of bus 4, two fault locations can be obtained and an increase of the reliability of the procedure therefore achieved. Fig. 5 and Table 3 show the results for the case of a bal anced fault at bus 5. In this case only two paths are of interest: L1 + L2, with opposite sign re?ections at the fault location and at the main feeder sending end and L1 + L5, with re?ection coe?cient of the same sign at the line terminations. Fig. 6 and Table 4 show the results for the case of a bal anced fault at bus 2, which is the termination of a lateral. In this case three paths are of interest: (a) L1 + L2 + L4, with opposite sign re?ections at the fault location (bus 2) and at the main feeder sending end (bus 4), (b) L1 + L2 + L3 and (c) L1 + L5, with re?ections at the line terminations. The CWTanalysis, performed by using the Morlet motherwavelet, is able to detect only the frequencies asso ciated with two paths, namely the ?rst and the third ones, while the frequency peak associated with the second path appears to be hidden by the ?rst peak due to the large ?lter amplitude related to the adopted motherwavelet. The in?uence of the presence of distributed generation has been also investigated. The analysis is repeated for bal anced faults at bus 1 and bus 5 in presence of a generator connected at bus 2 through a transformer. The CWTiden ti?ed frequency values are very similar to those of Tables 1–3, showing that the presence of the generator does not impedances. Fig. 7 illustrates the results of the CWTanalysis of the voltage transients due to a phasetoground fault at bus 1, both for the case of a grounded and ungrounded neutral. Also in this case, the considered paths are those illus trated in Fig. 1. The phase velocity of mode 0 is however signi?cantly lower than speed of light (as shown in Table 9 of Appendix). This velocity is used to evaluate the theo retical frequency values, which, in Table 5, are pared with those identi?ed by the CWTanalysis. For the same system in Fig. 1 and Table 6 shows the results for a phasetoground fault at bus 5. The simulations and the analysis are repeated also by taking into account a fault resistance equal to 10 X, and quite the same results as those shown in Tables 5 and 6 have been obtained. Also the presence of unbalanced loads does not appear to have evident impacts on the results. Table 7 shows the results for the case of a phaseto phase fault, and Table 8 shows the results obtained for a two phasetoground fault. For both cases, two fault loca tions are examined: bus 1 and bus 5. The neutral is consid ered ungrounded. Although some of the results show some limits of the adoption of the Morletwavelet, namely those relevant to fault at the laterals of the work in Fig. 1 (., balanced fault at bus 2), overall a reasonably good match between the theoretical values and the CWTidenti?ed frequencies has been achieved. Such a match encourages the develop ment of a fault location system exploiting this information. Section 4 is devoted to this subject. 4. Measurement system with distributed architecture The described CWTbased algorithm is conceived to be bined with a distributed measurement system. Each unit, located at some suitable busses of the distribution work, is equipped with a GPS synchronization device and is able to acquire both the starting instant of the transient and the relevant waveform. A measurement unit of the faultlocation distributed