The Design Of Risk Evaluation System Of Lightning Disaster Based On IEC62305

When the potential between clouds or the potential between ground and cloud orthe potential between cloud and air reaches a point 25~30kv/cm, fierce discharge thatleads to destruction will happen. With the development of society, the destruction oflightning disaster becomes one of the worst natural disasters which blocks theprogress of the world and endangers human being's safety. Statistically, every oneminute, there are two thousand times of lightning disaster; Every year, more than tenthousand people are killed or wounded by lightning disaster.Also,lightning disasterfrequently result in fire, explosion, ect.IEC and ITU promulgate a series of standardsand specifications of lightning disaster protection, which formed a integrated anduseful evaluation system of lightning disaster. However, most of these standardsbased on experience. In different application situations, the effect different. Thestandards that evaluate lightning disaster's destruction is somewhat simple, it can notsatisfy the needs that evaluate the risk carefully and exactly.IEC62305 risk evaluation standard takes the destructions of different lightningstrikes into consideration. It gives a specific and effective partion to the source ofdifferent lightning strikes and the direct and indirect results of damage. It calculatesthe risk ponderances respectively, then adds the ponderances of the same type whichmake up the overall risk of the type. Finally, it compares the loss of use protectionplus protection cost with the loss of not use protection. According to the result, we candecide whether need to take protection. Next, I will introduce what have done in thepaper in details.(1) Create risk evaluation model of lightning disasterThe risk evaluation of lightning disaster commonly divided into three steps:①Determine the type of damage and type of loss. The type of damage divided into:casualties caused by contact and step voltage(D1), Damage of buildings or otherobjects(D2), Electrical and electronic systems failure caused by surges(D3). Thetype of loss divided into: Loss of life(L1), Loss of electricity and communicationequipments that service to public (L2), Loss of cultural heritage(L3),Economiclosses caused by building and its internal installations, public facilities and itsfunctional failure(L4).②Determine the composition of every risk ponderance inthe total risk. For different types of loss L(from L1 to L4), its corresponding risk R(from R1 to R4) is the sum of different risk ponderances RX(RA,RB,RM…).③Evaluate the risk of building, evaluate the risk of public facility and evaluate the economics of protective measures. Constitute the risk evaluation model of building,constitute the risk evaluation model of public facility and constitute the evaluationmodel of economics of protective measures in the paper.One of the main formula the risk evaluation of lightning disaster used isR=N·P·L, R represent the risk of damage , N represent annual time of lightning strikesevery year,P represent the probability of damage after lightning,L represent relativedamage caused by lightning strikes. The deduction process of the formula is:,After multi-step transformation ,we canget R ? N?P?L.(2)The design and implementation of the systemThe system mainly implements three functions, evaluate the risk of building,evaluate the risk of public facility and evaluate the economics of protective measures.Evaluate the risk of building,first,we need to calculate the equivalent cross-sectionalarea of building and household lines, annual time of lightning strikes of building, theprobability damage of building after lightning, relative damage of building, the risk ofdamage of building. Evaluate the risk of public facility,we need to calculate theequivalent cross-sectional area of building and household lines, annual time oflightning strikes of building, the probability damage of public facility after lightning,relative damage of public facility, the risk of damage of public facility.Evaluate theeconomics of protective measures, calculate the total cost(CL) of losses withoutprotective measures; calculate the total cost(CRL) of the remaining with protectivemeasures; calculate annual cost(CPM) of the selected protective measures.If CL