10kv配电线路防雷外文文献.doc

西安科技大学 毕业设计(论文) 英文翻译 题 目 柠条塔煤矿10kV配电线路防雷研究 院、系(部) 电气与控制工程学院 专业及班级 电气工程及其自动化0802班 姓 名 关斌斌（0806060209） 指 导 教 师 李 忠 日 期 2012年6月10日_ 英文资料（一） Fundamentals of Lightning Protection Introduction Lightning is a capricious, random and unpredictable event. Its physical characteristics include current levels sometimes in excess of 400 kA, temperatures to 50,000 degrees F., and speeds approaching one third the speed of light. Globally, some 2000 on-going thunderstorms cause about 100 lightning strikes to earth each second. USA insurance company information shows one homeowners damage claim for every 57 lightning strikes. Data about commercial, government, and industrial lightning-caused losses is not available. Annually in the USA lightning causes more than 26,000 fires with damage to property (NLSI estimates) in excess of $5-6 billion. The phenomenology of lightning strikes to earth, as presently understood, follows an approximate behavior: 1. The downward Leaders from a thundercloud pulse towards earth seeking out active electrical ground targets. 2. Ground-based objects (fences, trees, blades of grass, corners of buildings, people, lightning rods, etc., etc.) emit varying degrees of electric activity during this event. Upward Streamers are launched from some of these objects. A few tens of meters off the ground, a collection zone is established according to the intensified local electrical field. 3. Some Leader(s) likely will connect with some Streamer(s). Then, the switch is closed and the current flows. We see lightning. Lightning effects can be direct and/or indirect. Direct effects are from resistive (ohmic) heating, arcing and burning. Indirect effects are more probable. They include capacitive, inductive and magnetic behavior. Lightning prevention or protection (in an absolute sense) is impossible. A diminution of its consequences, together wit