CABLES AND WIRES - Novkabel

Table: Single-core cables laid in the air distanced from the wallMethod of cable installationOn perforatedtraysOn perforatedtraysOn touchOn touchAt distanceNo. oftraysNo. of three-phase circuit1 2 31 0,98 0,91 0,872 0,96 0,87 0,813 0,95 0,85 0,781 1,00 0,97 0,962 0,98 0,93 0,893 0,97 0,90 0,861 1,00 0,98 0,962 0,97 0,93 0,893 0,96 0,92 0,86Cable positionThree cables inlineThree cables inlineThree cables – intriangleOn verticalperforatedtraysOn laddersupports,cleatsAt distanceAt distance1 1,00 0,91 0,892 1,00 0,90 0,861 1,00 1,00 1,002 0,97 0,95 0,933 0,96 0,94 0,90The values in the table are given in accordance with IEC 60502 standard and the followingreferences apply to them:- the distance between the tray and wall is at least 20mm,- the distance between two groups of three cables laid in triangle s equal to 2 cable diameters,- the distance between the ends of vertical perforated trays is at least 225mm,- the given values represent the average values for the cable types and refer to the observedcross-sections of cables,- the factors are used for one layer of cables laid in triangle or line and cannot be applied whenmore layers are being laid,- the given values refer to the vertical distance between the trays 300mm; the coefficients arelower for shorter distance.233- for the circuits that have more parallel connected cables per phase, each three-phase groupshould be considered as a circuit in accordance with this table.CalculationsConductor resistanceDC conductor resistance at t temperature different from 20 O should be calculated acc. to thefollowing formula:t – conductor temperature ( O C)R 20 – conductor resistance at 20 O C (Ω/km)R t – conductor resistance at t O C (Ω/km)– temperature resistance coefficient, (Copper - 3,93x10 -3 , Aluminium - 4,03x10 -3 ).