Abstract
Underground cables utilizing utility and industries are concerned about the overload and ampacity selected and temperature as a major cause of outages, and in general, the prevailing stresses producing insulation aging. Also concerned about water penetration of insulated electrical devices and especially plastic insulated multi-conductor cables which can seriously effect the electrical properties of such devices/or "conductors. The problem of water penetration is amplified when the electrical cable is positioned underground or in a high humidity environment. This paper is to investigate the real causes of outages and effects of underground cable rated at 34.5 KV of Saudi Electric Company (SEC), and find out whether these are the main responsible cause of such failures. The 34.5 ICV underground cables are laid in the kingdom for more than 10,000 km of length. Random and haphazard loads planning, digging and installation of more loads on feeders at the distribution level increase the amount of current over cables rating, along with many other non-declared connected apparatus. The study is aimed to analyze previous outage records to develop a trend and clarify the major causes of these outages. Many failures are occurring in the underground cable distribution system (UGS). These failures can affect the power distribution to either industry or customers and Millions of Saudi Riyals can be lost due to the caused outages in a region that has a lot of publication. Outages records were collected from different SEC regions such as, Dammam, Al-Madinah, and Southern region. Only one area will be analyzed to determine the main causes of failure due to number of pages limitation. From the analysis of different outages records of UGS, it is clear that failure causes at different regions are not the same. In Medinah, the most frequent cause of failures was joint problem. However, in southern region, the main factor for the 13.8 kV level failures was burnt cable. In Dammam, the failure cause that repeatedly occurred was equipment problem. This concludes that UGC manufacturer should examine the raw material of insulation to ensure that it has no aging. Skilled joint and termination installation, contractor adherence and implementation of UGS lay, commissioning to all SEC standards.