电气专业外文翻译--抗雷击架空配电线路的可靠性.doc

外文资料翻译 Reliability of Lightning Resistant Overhead Distribution Lines Lighting continues to be the major cause of outages on overhead power distribution lines. Through laboratory testing and field observations and measurements, the properties of a lightning stroke and its effects on electrical distribution system components are well-understood phenomena. This paper presents a compilation of 32 years of historical records for outage causes, duration, and locations for eight distribution feeders at the Oak Ridge National Laboratory (ORNL) . Distribution type lightning arresters are placed at dead-end and angle structures at pole mounted wormer locations and at high points on the overhead line. Station class lightning arresters are used to protect underground cable runs, pad mounted switchgear and unit substation transformers. Resistance to earth of each pole ground is typically 15 ohms or less. At higher elevations in the system, resistance to earth is substantially greater than 15 ohms, especially during the dry summer months. At these high points, ground rods were riven and bonded to the pole grounding systems in the 1960s in an attempt to decrease lightning outages. These attempts were only partially successful in lowering the outage rate. From a surge protection standpoint the variety of pole structures used (in-line, corner, angle, dead end, etc.) and the variety of insulators and hardware used does not allow each 13.8 kV overhead line to be categorized with a uniform impulse flashover rating (170 kV, etc.) or a numerical BIL voltage class (95 kV BIL; etc.). For simplicity purposes in the analysis, each overhead line was categorized with a nominal voltage construction class (15 kV, 34 kV, or 69 KV). Six of the eight overhead lines (feeders 1 through 6) were built with typical REA Standard horizontal wood cross arm construction utilizing single ANSI Class 55-5 porcelain pin insulators (nominal 15 kV insulation). The shield angle of the