【導(dǎo)讀】由于過去幾年在瑞典大范圍停電，因此電力公司采用地下電纜大大取代他們的。由于采用了很多地下電纜，在未來利用地下電纜線診斷測量結(jié)果可能會很重要。中壓交聯(lián)聚乙烯絕緣電纜可能會水樹退化。水樹退化是指水穿透絕緣層，但他沒有統(tǒng)一。水樹退化可能是局部或均勻分布在不同的電線電纜之間。現(xiàn)象在年底檢測到電纜故障。經(jīng)常出現(xiàn)的故障是暫態(tài)過電壓的情況，例如當(dāng)電纜重新連接后，它已退出服務(wù)電纜。其中一項評估是為了試。對不同水樹定性的模型，以及對它們的開發(fā)，來表明這些水樹行為?，F(xiàn)場使用的測量儀。在中，該技術(shù)有用于交聯(lián)聚乙烯電纜和電纜故障定位診斷。分析報告中，這是為了決定是否分別檢測復(fù)達(dá)欣電纜故障的問題。其中至少有一個是電纜周圍的粘土對電纜的壓迫造成的損害。來自斯德哥爾摩的統(tǒng)計表明，電網(wǎng)故障的主設(shè)備是相連的地下電纜。目前已進(jìn)入到達(dá)爾文的統(tǒng)計報告，EkeröEnergi. 水樹嚴(yán)重惡化之前，較好的檢測可能最大限度地減少電纜故障發(fā)生的頻率。

　　

【正文】 he dissipation factor tanδ at a variable frequency sweep between Hz. Bauer’s PHG 70 and PHG 80 and sebaKMT’s VLF and HV diagnostics HVA 30, 30,5 and 60 measures the dissipation factor tanδ at a fixed very low frequency, VLF. Tettex Midas, 2820 and 2877 measures the dissipation factor tanδ at powerline frequency. Omicron’s CPC 100 with CP TD1 also measures the dissipation factor tanδ , however, at a frequency sweep between 1570 Hz. sebaKMT’s CDS measures the losses with the isothermal relaxation current, IRC method. The measurement techniques used in these instruments are considered to be nondestructive at a voltage level up to 0 V . The fault location instruments found in the literature study are all based on the same technology, the time domain reflectometry. SebaKMT provides four instruments the Surgeflex 15, 25, 32 and the Teleflex T30E. Surgeflex 15 and 25 and Teleflex T30E are batterypowered and portable instruments. PFL401500/2020 is supplied by Megger and is a batterypowered portable instrument. The 5150 first response cable fault locator by Hipotronics is also portable and batterypowered. The failure statistics from the Stockholm grid shows that the major number of faults is connected to underground cables. The largest fault category for high voltage, low voltage and service cables are lack of maintenance or worn out cables. The second large category for all threevoltage levels is unknown. A more extensive investigation of the failure statistics from the Eker246。 grid was made. The statistics reported to Darwin, Eker246。 Energi’s own statistics and the failure reports that the statistics are based on was investigated. Extra information in some faults was also available. The fault frequency in Eker246?！痵 XLPEcable grid connected to insulation failures was faults per 100 km cable and year, which is considered to be low. The fault frequency of total number of faults was 1,99, which is considered to be a low failure frequency pared to Stockholm and G246。teborg. Eker246?！痵 total fault frequency is also lower than the total fault frequency reported to Darwin, which is 2,41. However, Eker246。’s fault frequency is a bit misleading due to the fact that digging, customer fault and a flood in the station cause five of 17 faults. If the fault frequency is recalculated only with faults related to the cable or cable accessories the fault frequency per 100 km cable and year would be . Darwin is a national database to which the energy panies report their failure statistics. During this period seven faults were reported as material or fabrication faults to Darwin. When the information was examined one step down in the chain at Eker246。 Energi’s failure reports. It showed that these seven faults, which were reported under one category in Darwin, could be divided into five different fault categories. Even more fault information was available at internal notes at Eker246。 Energi. This notes showed that two of the fault categories reported in Eker246。 Energi’s failure reports could be divided into four different faults. These examples show that a lot of information is lost during the report procedure. To be able to get reliable information and to get an efficient use 8 of Darwin there has to be more categories inserted. Today it is impossible to separate for example treeing from a joint fault or a termination fault due to the fact that they are reported under the same category. Today the failures are reported on paper sheets and saved in paper form at Eker246。 Energi. The quality of the report is very much dependent on the writer. To write down not just the effect of a fault but also the cause gives valuable information for future investigations. It would be easier to study failures in a later period of time if the failure reports were written directly into a database. Another thing that would increase the knowledge about the condition of the medium/high voltage grid, would be if there was established a protocol or a journal of each medium/high voltage cable. This protocol or journal should give essential information about the cable. Such as manufacturer, type and which year the cable was manufactured. The protocol or journal should give information about type and manufacturer of the terminations and any joints. There should also be information about failures cause and effect. If there had been any diagnostic measurements there should be information about these.