转移点温度计算(举例)

DocDoc.No. :LGA04-C6-219AIssued :November19,2004Page :PAGE7ofNUMPAGES7technicaldataforCurrentcarryingcapacity&Sag-TensionProperties允许电流及弧垂-张力特性的技术规范书导线名称Cabledesignation:STACIR/AW180㎟TACSR110㎟STACIR/AW130㎟(ALTERNATIVE)投标单位技术资料号码Tender/BidderSpec.No.:0673-NCIP2004/15业主Client&Customer:Preparedby j.s.gilCheckedby s.y.parkApprovedby h.h.parkManagerOverheadTransmissionProjectDept.ElectricPowerDivisionRev.DateDescription

超耐热铝合金镀铝殷钢导线的允许电流CurrentCarryingCapacityforSTACIR/AW若提供允许的导线温度，架空铝导线的允许电流，气候条件和导线特性可依照IEEEStd.738“计算空架空导线的电流-温度关系”算出。Thecurrentcarryingcapacityofoverheadaluminumconductorgivenaallowableconductortemperature,weatherconditionsandconductorcharacteristicscanbecalculatedinaccordancewithIEEEStd.738"CalculatingtheCurrent-TemperatureRelationshipofBareOverheadConductors".线路详细资料和气候条件GivenLineDetailsandWeatherCondition;周围环境空气温度Ambientairtemperature,Ta35℃与导线垂直的海平面风速Windvelocityatsealevelperpendiculartotheconductor,Vw0.5m/s发射率Emissivity,ε0.9太阳吸收率Solarabsorptibity,α0.5太阳和天空辐射的总热流量Totalsolarandskyradiatedheatflux,Qs0.1W/cm2频率Frequency50Hz线路方向ThelinedirectionEast-West纬度Latitude35˚N空气条件AtmosphereconditionClear平均太阳高度Averagesunaltitude,Hc10:00amto12:00noon计算允许电流Calculatingthecurrebtcarryingcapacity对流热损失Convectionheatloss(qc):自然对流（风俗=0）：不应用于本案例Naturalconvection(windspeed=zero):Notapplicableinthiscase

b.强制对流Forcedconvection(windspeed≠zero)在任何风速，Atanywindspeeds,thelagerofthetwocalculatedconvectionheatlossesisused.辐射热损失Radiatedheatloss(qr):获取的太阳热Solarheatgain(qs):稳定情形的热平衡Steady-stateheatbalance:允许电流的计算结果CalculationResultsforCurrentCarryingCapacity超耐热铝合金镀铝殷钢导线的弧垂和张力计算SagandTensionCalculationforSTACIR/AW超耐热铝合金铝包殷钢导线的弧垂和张力计算方法不同于传统的铝包钢芯。因为用于超耐热铝合金铝包殷钢导线芯的铝包殷钢合金具有极小的线性膨胀系数，导线的线性膨胀合成系数很小。在普通条件下将导线安装在架空输电线时，应考虑这种线性膨胀合成系数。另外，在某个温度以上，殷钢芯使超耐热铝合金铝包殷钢导线的所有机械张力保持不变，因为镀铝殷钢丝的热膨胀远小于铝合金丝的热膨胀，导致铝部分的负荷等于零。上述温度被叫做：“转移点温度”因此，在转移点温度以上的温度，导线的热膨胀和弹性延伸取决于殷钢芯，且弧垂增加的百分比极小，由此获取极好的弧垂特性。这种做法存在于传统的铝包导线，但是不被考虑，因为它的温度通常高于持续运行温度ThecalculationmethodofthesagandtensionforSTACIR/AWisdifferentfromthatoftheconventionalACSR.Becausethealuminum-cladinvaralloyusedforcoreofSTACIR/AWhasaextremelysmallcoefficientoflinearexpansion,thecompositecoefficientoflinearexpansionoftheconductorissmall.Undernormalconditionsforstringtheconductoronoverheadtransmission,thiscompositecoefficientoflinearexpansioncanbeconsidered.Inaddition,allthemechanicaltensionintheSTACIR/AWwillbesustainedbytheinvarcoreaboveacertainconductortemperatureatwhichthestressofthealuminumpartcomestozerobecausethethermalexpansionofanaluminum-cladinvarwiresismuchsmallerthanthatofanaluminumalloywires.Thiscertaintemperatureiscalled'transitionpointtemperature'.Thethermalexpansionandelasticelongationoftheconductorthusdependsonthoseoftheinvarcoreabovethetransitionpointtemperatureandthepercentageofincreaseinthesagisextremelysmallsothatexcellentsagpropertiesareobtained.ThisbehaviorexistsintheconventionalACSRbutneednottobeconsideredbecauseitstemperatureisusuallyhigherthanthecontinuousoperatingtemperature.1)公式中符号的定义DefinitionofsymbolsintheformulasS:跨度距离Spanlength(m)Wc:导线重量Conductorweight(kg/m)Ww:导线的风力载荷Windloadonconductor(kg/m)WI:导线的冰负荷Iceloadonconductor(kg/m)A:导线截面的计算区域Calculationareaofsectionofconductor(Aa+As)Aa:超耐热铝合金丝截面的计算区域CalculationareaofsectionofSTALwireAs:殷钢丝截面的计算区域CalculationareaofsectionofInvarwireE:导线的弹性系数ThecoefficientofelasticityofconductorEs:殷钢丝的弹性系数ThecoefficientofelasticityofInvarwireEa:超耐热铝合金丝的弹性系数ThecoefficientofelasticityofSTALwireα:导线的线性膨胀系数Coefficientoflinearexpansionofconductorαa:超耐热铝合金丝的线性膨胀系数CoefficientoflinearexpansionofSTALwireαs:殷钢丝的线性膨胀系数CoefficientoflinearexpansionofInvarwiret0:初始条件下的温度（在此温度下，超耐热铝合金丝和殷钢丝在无张力时长度相同）Temperatureofinitialcondition(inthetemperature,thelengthofSTALwireandInvarwireissameundernotension)t1:最差条件下的温度Temperatureintheworstconditiont2:可选择条件下的温度Temperatureintheoptionalconditiontc:转移点条件下的温度（无风，无雪）Temperatureattransitionpoint(nowind,nosnow)q1:最差条件下的负荷系数Loadcoefficientinworstconditionl0:无张力时的实际长度ReallengthinnotensionT1:最差条件下的张力TensionintheworstconditionT2:可选择条件下的张力TensionintheoptionalconditionTc:转移点张力（无风，无雪）Tensionattransitionpoint(nowind,nosnow)Cr:蠕变Creep2)转移点温度的计算ThecalculationoftransitionpointtemperatureAsfortheinitialconditionthatprescribestherelationofthedividedtensionoftheINVARwireandtheSTALwire,wecanregardthatbothofthemareundernotensiononthetemperatureconditionoft0(℃),usually,t0=15℃,withaconductorlengthofl0rightafterbeingmanufactured.Inthemeantime,afterstringingatsitewithchangeoftemperaturetot(℃)andoftensiontoT(kg),ifwewouldassumethedividedtensionofbothSTALwireandInvarwireasTa(kg)andTs(kg),thefollowingequation,therefore,wouldbeeffective;等式1.1Equation1.1排除l0并忽略小的项目Removingl0andignoringsmallitems等式1.2Equation1.2另一方面,Ontheotherhand,等式1.3Equation1.3由1.2和1.3排除TsEliminatingTsbyequation1.2&1.3等式1.4Equation1.4等式1.4表示在温度t(℃)时超耐热铝合金丝承担的张力T(kg)。其次，我们考虑转移点的条件,此时，铝合金丝不承担导线的任何张力。Equation1.4showsthedividedtensionofSTALwirewhentensionisT(kg)intemperaturet(℃).Next,weconsidertheconditionofthetransitionpoint.Atthattime,Aluminumalloywiredoesnotsharethetensionofconductoranymore.因此，Thus,Ta=0.由此从等式1.4Sofromequation1.4,等式1.5Equation1.5另一方面，由温度和张力关系得出弧垂曲线后的实际长度（在最差条件）。Ontheotherhand,bytherelationshipofreallengthbythesag-curveandthatshowncalculatedbyrelationoftemperatureandtension(intheworstcondition)等式1.6Equation1.6在转移点温度Intransitionpointtemperature,等式1.7Equation1.7由1.6和1.7，排除l0忽略小项目Removingl0by1.6&1.7,ignoringsmallitems等式1.8Equation1.8同时，我们由等式1.5和1.8得TC&tC。WecangetTC&tCbyequation1.5&1.8,simultaneously.3)经计算，我们假设Tc并将其应用在1.5和1.8重复地计算。然而这需要较长时间，所以我们将其简化为实际计算式。现在，我们计算温度t0(℃)无风无雪条件下的张力T01(kg)。我们称其为第一条件。Bycomputing,weassumeTcandapplyit1.5&1.8forcalculationrepeatedly.Butitwilltakelongtime.Sowecanmakeitsimpleasthepracticalcalculatingexpression.Now,wecalculatetensionT01(kg)int0(℃)andnowind,nosnowcondition.WecallitNo.1conditiont1=t0,q1=1.0andT1=T01其次将其应用于1.5和1.8。Nextapplyitto1.5&1.8,等式1.10Equation1.10这里，Here,等式1.10equation1.10因而，我们计算等式得出可变的。Accordingly,wecalculateequationhavinga