基礎(chǔ)防雷外文資料翻譯-閱讀頁(yè)
2025-06-06 12:35本頁(yè)面
【正文】 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 magic behavior. Lightning prevention or protection (in an absolute sense) is impossible. A diminution of its consequences, together with incremental safety improvements, can be obtained by the use of a holistic or systematic hazard mitigation approach, described below in generic terms. Lightning Rods In Franklin39。s typical impulse reveals both a high and a low frequency content. The high frequency is associated with an extremely fast rising front on the order of 10 microseconds to peak current. The lower frequency ponent resides in the long, high energy tail or followon current in the impulse. The grounding system appears to the lightning impulse as a transmission line where wave propagation theory applies. A single point grounding system is achieved when all equipment within the structure(s) are connected to a master bus bar which in turn is bonded to the external grounding system at one point only. Earth loops and differential rise times must be avoided. The grounding system should be designed to reduce ac impedance and dc resistance. The shape and dimension of the earth termination system is more important a specific value of the earth electrode. The use of counterpoise or crow39。 protect all relevant secondary distribution panels。 SCADA equipment, etc. Further, protect ining and outgoing data and signal lines. Protect electric devices which serve the primary asset such as well heads, remote security alarms, CCTV cameras, high mast lighting, etc. HVAC vents which perate one structure from another should not be ignored as possible troublesome electrical pathways. Surge suppressors should be installed with minimum lead lengths to their respective panels. Under fast rise time conditions, cable inductance bees important and high transient voltages can be developed across long leads. In all instances, use high quality, high speed, selfdiagnosing protective ponents. Transient limiting devices may use a bination of arc gap divertersmetal oxide varistorsilicon avalanche diode technologies. Hybrid devices, using a bination of these technologies, are preferred. Know your clamping voltage requirements. Confirm that your vendor39。 avoid water and all metal objects。 avoid solitary trees。s distance is easy. Use the Flash/Bang (F/B) technique. For every count of five from the time of seeing the lightning stroke to hearing the associated thunder, lightning is one mile away. A F/B of 10 = 2 miles。s earnest hope. With such techniques, lightning paths can be forecast reliably. Codes
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