IEC_60287-1-1_2001_PARTE_2.pdf

60287-1-11EC:1994+A1:1995-41-+A2:20012.3.5 Effect of large segmental type conductorsWhere the conductors are subject to a reduced proximity effect,as with large conductors ofinsulated segmental construction,the sheath loss factor of 2.3.1,2.3.2 and 2.3.3 cannotbe ignored,but shall be obtained by multiplying the value of obtained from 2.3.6 for thesame cable configuration,by the factor F given by the formula:F=4M22+M+N24(M2+1)(N2+1)whoreM=N=Rs for cables in tretoil formationandM=RsX+XmFor cables in flat formation with equidistant spacingN=RsX-Xm3Where the spacing along a section is not constant the value of X shall be calculated asin2.3.4a).2.3.6 Single-core cables,with sheaths bonded at a single point or cross-bonded2.3.6.1Eddy-current lossesFor single-core cables with sheaths bonded at a single point or cross-bonded the eddy-current loss factor is given by:R9s01+41+42)+B121012where1,74gs=1+(1Ds103-1,6)Ds40B=107PsPs is the electrical resistivity of sheath material at operating temperature(see table 1)(2.m);Ds is the external diameter of cable sheath(mm);NOTE For coresath ma outsld diametershall busd.2fs is the thickness of sheath(mm):0=2NOTE For lead-sheathed cables.gs can be taken as unity and-(B)12xcab noglected.For aluminium-sheathed cables both terms may need to be evaluated when sheath diameter is greater thanabout 70 mm or the sheath is thicker than usual.Copyright por International Electrotechnical CommissionTue Sep0915:14:412003