Study On Typhoon Disaster Risk Assessment Model Of Power Distribution System In Fujian Region

Typhoon is a type of disastrous weather phenomenon with great damage,and it could cause significant threats to human life and property security.Fujian province locates in the southeast coast and borders on the northwest Pacific Ocean,so it is frequently affected by tropical cyclone.Typhoon can cause severe damage to distribution network in Fujian region,and then threaten the safe and stable operation of electric power system.In this paper,firstly,risk assessmentresearches on typical natural disasters are reviewed,those ontyphoon are analyzed,and those on power grid in typhoon weather are reviewed.Secondly,effects of a representative typhoon “Morakot” on distribution network in Fujian province areanalyzed,and solutions and countermeasure suggestions are proposed according to the field situation.Then,the wind velocity theory of typhoon wind fieldis introduced,and materials,loads,strength and reliability are analyzed.Finally,risk assessment of distribution lines is performed based on the degree of reliability.The main conclusions in this paper are as follows.(1)Line breakage,pole collapse and pole breakage are the main failure modes of distribution network in typhoon weather.More attention should be paid to the differences in micro-landform and micro-climate in design and reconstruction of electric lines.Strengthening wind protection in priority areas,performing related standards strictly and studying typhoon information in coastal areas carefully should be done to improve security and reliability of distribution lines.(2)The tensile strength of wires and the bending strength of concrete poles are normally distributed,and the reliability of them is determined by the section stress of their suspension point and the bending moment of their root.For wires,the section stress of suspension point increases with the wind speed increasing.(3)When concrete poles are subjected to wind loads,the stress valuesof poles on the leeward side are greater than those on the windward side in the constraint section,and they are distributed on the surface of the poles.On the centerline of windward side of poles,the maximum stress appears in the constraint section,and it changes insignificantly with the wind speed.Although the maximum stress also appears in the constraint section for the leeward side,it increases significantly with the wind speed increasing.(4)The degree of reliability of wires decreases with the wind speed increasing,in which the wire with the smallest diameter,LGJ-70/10,has the fastest decreaserate,and the one with the largest diameter,LGJ-240/30,has the slowest decrease rate.Overall,the degree of reliability for concrete poles falls more rapidly than that for wires with the wind speed increasing,and it falls faster if the wire diameter is larger.In distribution network,the relation of wires and poles in the same line is in series,so the reliability of the line is the product of the reliability of the line components,which means that the reliability is low when the line is long.Based on the calculation results of line reliability,risk assessment of power distribution can be implemented by combining the requirements of the operation department.