外文文献及翻译----中压电缆网络绝缘诊断和故障统计的状态评估(编辑修改稿)

外文文献及翻译----中压电缆网络绝缘诊断和故障统计的状态评估(编辑修改稿)内容摘要：

round. It is difficult to say if the measurements made in 1998 were trustworthy or not. What could be said on the other hand, is that even though three of them were judged as old and four of them judged as critical for nine years ago they are all still operating. The mercial cable diagnostic instrument for XLPEcables available on the market right 5 now are all offline instruments. All instruments except one measure the dissipation factor tanδ , at either a fixed low frequency or at a low frequency sweep or at powerline frequency. The other technique used, is to measure the isothermal relaxation current. The techniques used in these instruments are considered to be nondestructive for a voltage level up to 0 U . All fault location instruments in this report are based on time domain reflectometry, TDR. The prelocation are made with two different methods, Time Domain Reflectometry TDR and Arc Reflection Method ARM. The Arc Reflection Method is used to prelocate high resistance fault and the Time Domain Reflectometry is used to prelocate low resistance faults. The instruments are suited for low and medium voltage distribution cables. The statistic 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 the category lack of maintenance or worn out cables. The second large category for all three voltage levels is the category unknown. The largest damages on the high voltage system caused by failures in these two categories are connected to the XLPEcables. However, reading the statistic it is not possible to say if the XLPEcable failures are connected to insulation problems or something else. The fault frequency in Stockholm’s XLPEcables was 3,34 in 2020 and 3,76 in 2020 faults per 100 km cable and year. The total fault frequency in Stockholm was 3,55, which is in the same size as the total fault frequency in G246。 teborg, which was 3,58. The fault frequency in Stockholm’s PILCcables was 1,15 in 2020 and 0,92 in 2020 faults per 100 km cable and year, which is slightly lower than G246。 teborg’s failure frequency on PILCcables. The statistics from Eker246。 Energi’s grid is more extensive. There has been access to statistics reported to Darwin, Eker246。 Energi’s own statistics and the failure reports, which the statistics are based on. Extra information has also been available in some cases. The two largest fault categories reported to Darwin was fabrication or material faults and unknown. When the failure reports were examined, it showed that the seven faults reported under fabrication or material fault could be divided into five different categories. Of these seven faults only three were connected to insulation faults. The total fault frequency in Eker246。 ’s XLPEcable grid is 1,99 faults per 100 km cable and year, which can be pared with the failure frequency reported to Darwin, which is 2,41 faults per 100 km cable and year. However, the fault frequency connected to insulation fault on Eker246。 ’s XLPEcables is 0,4 faults per 100 km cable and year. Both statistics from the Stockholm and Eker246。 grid shows that there is a need of more categories inserted in the report system. The aim with inserting more categories is to refine the statistic in order to get a more exact evaluation of what causes the interruptions. This evaluation can then be used to direct the measure right, improve the failure statistic and reduce the interruptions. Today is the demand of electrical power crucial for a well functioning society,the consumption in Sweden the last ten years has varied between 143150 TWh. The last years problems with blown down overhead lines and power cuts caused by storms, has hasten the replacement of overhead lines in favour of underground cables. It has been showed that medium voltage XLPEinsulated cables with insulation shields made of graphite paint and paint, known as the first generation XLPEcables, are suffering of severe water tree deterioration. Water tree deterioration is water that has perated the semiconductor shield, which could be locally or evenly distributed along the cable. While the water tree growth, 6 the voltage breakdown strength decreases and will at the end lead to a cable breakdown. The most mon factor that leads to a cable breakdown is when a cable with low voltage breakdown strength is energized in a reconnection。