【正文】 1，d2，d3級中即時相位變換現(xiàn)象尤其明顯。在更高級的分解中，如d4，d5，d6中，相位變換現(xiàn)象就不那么明顯了（非故障線路）或者成為主要成分了（故障線路）。這種現(xiàn)象可以作為區(qū)別故障線路和非故障線路的依據(jù)。信號中斷時的尖形突出將會導(dǎo)致信號平均值遠(yuǎn)低于信號的峰值。在d4，d5，d6級中包含高頻成分，平均值絕對值（）的執(zhí)行比例和在寬度N的數(shù)據(jù)窗中計算得的第K個值滿足如下關(guān)系：； （10）間歇性接地故障中短路線路的描述通過比較C和起始值實(shí)現(xiàn)，C代表瞬時電流絕對值與平均值的比值。； （11）當(dāng)保護(hù)滿足式（11）條件時，斷路器會斷開，零序電壓分量（OS1=1）證實(shí)接地故障仍然存在，任何切斷保護(hù)導(dǎo)納部分（OS2=0）脈沖（OS）均不發(fā)出。圖16中，表示了一種自適應(yīng)接地故障保護(hù)的方案框圖，它是對傳統(tǒng)導(dǎo)納保護(hù)（見圖2）的延伸?；镜难a(bǔ)充模塊有：測量信號多級分解模塊WD模塊，實(shí)現(xiàn)線路描述算法的PAC比較器（峰值均值比較器）（見圖15）。鑒于傳統(tǒng)保護(hù)判據(jù)的不可靠性，上述保護(hù)的邏輯結(jié)構(gòu)中，WD模塊和PAC模塊增強(qiáng)了保護(hù)運(yùn)行過程中故障消除的能力和可靠性。結(jié)語本文間歇性接地故障實(shí)驗中測得信號和表明，傳統(tǒng)保護(hù)設(shè)備在確定這類故障和鑒別故障線路方面存在一些問題。如果故障間中斷時間超過10ms，檢測困難也會增加。因為這種中斷也會在不平衡配網(wǎng)中出現(xiàn)，一些接地故障時保護(hù)不動作情況自然也會出現(xiàn)。因此，基于消除此類問題的新的保護(hù)判據(jù)也正在研究當(dāng)中。經(jīng)過分析間歇性接地故障實(shí)驗，我們很容易得出，多級小波分解能夠甄別被保護(hù)線路的信號特征。本文所有例子表明，故障線路和非故障線路原始信號在初級分解（d1，d2，d3）中干擾比較明顯。而在高級分解之中，故障和非故障線路的譜圖明顯不同，這也促進(jìn)了分辨故障線路，排除故障。參考文獻(xiàn)[1] , A Theory for multiresolution signal deposition: the wavelet representation, IEEE Trans. On Pattern Analysis and Machine Intelligence, Vol 11, No 7, 1989, .[2] ShyhJier Huang, ChengTao Hsieh, ChingLien Huang, Application of wavelets to classify power system disturbances Electrical Power and Energy System, 47, 1998, .[3] O. Chilard., L. Morel., D. Renon., Compensated grounded medium voltage network protection against resistive phase to ground faults,CIRED, Nice 1999[4] Abur A., Magnano ., Use of time delays between modal ponents in wavelet based fault location, Electrical Power and Energy System,22, 2000, [5] Lobos T., Rezmer J., Wavelet transforms for realtime estimation of transmission line impedance under transient conditions, Electrical Engineering, 84, 2002, .[6] , . Kishora, . Sinha, A wavelet multiresolution analysis for location of faults on transmission lines, Electrical Power and Energy System, 25, 2003, 69.作者簡介J243。zef Loren，生于1949年，波蘭的小鎮(zhèn)Jarocin，獲得波茲南科技大學(xué)電氣工程專業(yè)的碩士和博士學(xué)位。目前，職稱為副教授，擔(dān)任電氣電力工程學(xué)會主任。從事電力系統(tǒng)繼電保護(hù)領(lǐng)域工作，主要研究電網(wǎng)保護(hù)判據(jù)、無功補(bǔ)償、中壓配網(wǎng)中性點(diǎn)運(yùn)行、接地保護(hù)、電流沖擊保護(hù)等方面。Kazimierz Musierowicz，生于1943年，于1969年畢業(yè)于弗羅茨瓦夫科技大學(xué)電氣工程專業(yè)，獲得Wroc?aw波茲南科技大學(xué)碩士學(xué)位，現(xiàn)為該校講師和研究員。從事電力系統(tǒng)繼電保護(hù)和數(shù)字信號處理領(lǐng)域的研究工作。Andrzej Kwapisz，生于1971年，波蘭的小鎮(zhèn)Szczecinek,獲得波茲南科技大學(xué)碩士學(xué)位。目前為該校研究員。主要從事電力系統(tǒng)數(shù)字技術(shù)，計算機(jī)輔助電力系統(tǒng)分析，暫態(tài)和穩(wěn)態(tài)電力系統(tǒng)仿真，繼電器開發(fā)標(biāo)準(zhǔn)等領(lǐng)域研究工作。英文原文Detection of the Intermittent Earth Faultsin Compensated MV NetworkJozef Lorenc*/, Kazimierz Musierowicz*/, Andrzej Kwapisz*/Abstract – The experience acquired from the Polish medium voltage power distribution networks shows the unreliability of the localization criterions applied to the intermittent earth faults. It results from the lack of stability and low power level of the measuring signals falling often down below the protection’s startup level. In the paper, a new adaptive algorithm based on the wavelet analysis enabling detection of specific dynamics of the measuring signal during intermittent earth faults is presented. The algorithm was analyzed utilizing the signals generated in the EMTP program package.I. INTRODUCTIONIn general, the MV distribution networks in Poland operate with the neutral point grounded through the coil to pensate the capacitive short circuit current to the earth. It refers mainly to the rural area networks where the lines are the overhead ones. Such networks are characterized by large number of the earth faults exceeding 90% of all recorded faults. Due to the relatively high cross resistance at the defect’s location (RF) as well as to the effects of the weather phenomena such asdischarges, gusts of wind, high and low temperatures resulting in the rupture of the line conductors continuity, the earth faults occur. Characteristics of these faults makes impossible the detection and localization of such disturbance [3].The following fault types can be encountered to the discussed faults group: resistance faults of high cross resistance , , break in the live wire short circuit on the receiver side, faults being broken cyclically and noncyclically.An actual fault can show either one or all of the listed features. In the paper, the analysis is limited to the automatic protective units operation during intermittent faults. To assess the protection’s operability, the levels and features of measuring signals which can occur during the fault are to beidentified.The most important signal indicating occurrence of the intermittent earth fault in the network is a zerovoltage ponent the values of which is often found by adding the instant values of phase voltages. The criterion value of the fault localization can be: zero current ponent, power of the zero current ponent, , and zero voltage ponent, , phase shift angle between the zero current and voltage ponents, zero admittance ponent, , or its ponents: active or reactive. However, the criterion values as listed above are often unreliable when the intermittent earth fault occurs.II. MODEL OF NETWORKFor modeling and studies of the earth fault phenomena acpanying the intermittent earth faults, a typical medium voltage balanced network has been chosen. The scheme of modeled network is shown in .The faults were modeled and simulated using the EMTP/ATP program package. Chosen parameters of network assumed for simulation purposes are shown in Table 1.TABLE 1MODELLED 15 KV NETWORK PARAMETERSNetwork capacity current 101,3AFault line capacity current 10,6ADepensation level +15%Cross resistance 2 WIn the model the assumption was made that the faults occur in a line with togroundcapacitive current of A and a moderated power load of 150 kW.The following fault types have been considered:A type continuous fault, B – type intermittent fault of tsc=10ms duration time,tp=10ms pause time, C type intermittent fault of tsc=10ms duration time,tp=100ms pause time, D type intermittent fault of tsc=50ms duration time, tp=50ms pause time.All faults have been modelled at the beginning of the line 1,adjacent to the bus bars. The following magnitudes h