Sét đạt tới nhiệt độ °C ( °F) gấp 20 lần nhiệt độ cần thiết để biến cát silica thành thủy tinh (chỉ cần 1330 °C để làm nóng chảy SiO2), những viên đá được tạo ra bởi sét đánh vào cát gọi là fulgurite (thường nó có dạng hình ống do sét di chuyển vào lòng đất). | íùrse Each primary risk can also be expressed with reference to the source of damage. See page 13 Source of damage. Thus Rn can be split into two basic components for each loss. Rn RD RI Where RD direct relates to risk components attributable to flashes to the structure S1 . RI indirect relates to risk components attributable to flashes near the structure to the services connected to the structure and near the services connected to the structure S2 S3 and S4 . These direct and indirect risk components can be further expressed by their own individual risk components viz. RD Ra 2 RB RC i R Rm i Ru Rv Rw i Rz i 1 Only for structures with risk of explosion and for hospitals with life-saving electrical equipment or other structures when failure of internal systems immediately endangers human life. 2 Only for properties where animals may be lost. The generic equation for evaluating each risk component is RX NX X PX X LX Where NX is the annual number of dangerous events PX is the probability of damage to a structure LX is the amount of loss to a structure Thus RA ND X PA X La RB ND X PB X LB RC ND X PC X LC Rm Nm X Pm X Lm Ru nl NDa x pu X Lu RV NL NDa x PV X LV Rw Nl NDa x Pw X Lw RZ NI -Nl xPz XLZ The values of NX PX and LX are determined from parameters formulae contained with BS EN 62305-2. Annex A provides information on how to assess the annual number of dangerous events NX . Annex NB provides the necessary detail to assess the probability of damage to a structure PX . Annex NC helps to assess the amount of loss to a structure LX . Number of dangerous events NX The number of dangerous events experienced by a structure or service line s is a function of their collection areas and the lightning activity in the vicinity. Collection area The physical dimensions of the structure are used to determine the effective collection area of the structure. The collection area is based on a ratio of 1 3 height of structure .
