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F:\Elements\cable programs\cable ampacity calculation IEC.docx Page 1
1 SCOPE AND DEFINITIONS The scope of the attached calculations is to determine the required cables sizes based on the project standards and design criteria. Design Criteria.
Following design criteria is used for the settings sheet. Maximum Operating Conductor temperatures with Insulation: 1.1 Thermoplastic (PVC) = 75°C 1.2 Thermoset (XLPE or EPR) = 90°C 1.3 Cable Voltage Rating = 1 kV (Um = 1.2 kV)
F:\Elements\cable programs\cable ampacity calculation IEC.docx Page 2
2 CABLE AMPACITY 2.1 Conductor Ampacity Selection The cable ampacities are based as follows; PVC insulation, copper conductors –Conductor temperature: 70 °C, reference ambient temperature: 30 °C Current-carrying capacities in amperes for installation methods–XLPE or EPR insulation, copper conductors –Conductor temperature: 90 °C, reference ambient temperature: 30 °C
MM2 AIR
PVC XLPE-)
3-1/C (1.5-16MM2)
& (25-400MM2)]
1-3/C
3-1/C (1.5-16MM2)
& (25-400MM2)]
1-3/C
2.5 25 25 32 32 4 34 34 42 42 6 43 43 54 54
10 60 60 75 75 16 80 80 100 100 25 110 101 135 127 35 137 126 169 158 50 167 153 207 192 70 216 196 268 246 95 264 238 328 298
120 308 276 383 346 150 356 319 444 399 185 409 364 510 456 240 485 430 607 538 300 561 497 703 621 400 600 600 823 823
F:\Elements\cable programs\cable ampacity calculation IEC.docx Page 3
Current-carrying capacities in amperes for methods of installation PVC insulation, three loaded conductors/copper or aluminium –Conductor temperature: 70 °C, ambient temperature: 30 °C in air, 20 °C in ground. Current-carrying capacities in amperes for methods of installation XLPE or EPR insulation, three loaded conductors/copper or aluminium – Conductor temperature: 90 °C, ambient temperature: 30 °C in air, 20 °C in ground
MM2 DB PVC-
XLPE-
1-3/C-DB-COND
1-3/C -DB-CABLE
1-3/C-DB-
COND
1-3/C -DB-CABLE
2.5 24 24 28 30 4 30 33 36 39 6 38 41 44 49
10 50 54 58 65 16 64 70 75 84 25 82 92 96 107 35 98 110 115 129 50 116 130 135 153 70 143 162 167 188 95 169 193 197 226
120 192 220 223 257 150 217 246 251 287 185 243 278 281 324 240 280 320 324 375 300 316 359 365 419 400 400 400 400 500
F:\Elements\cable programs\cable ampacity calculation IEC.docx Page 4
2.2 Conductor Ampacity and Temperature de-rating factor (TDF) Correction factor for ambient air temperatures other than 30 °C to be applied to the current-carrying capacities for cables in the air.
AIR AMB TEMP
PVC-AIR-AMB-deg-C-10 1.22 PVC-AIR-AMB-deg-C-15 1.17 PVC-AIR-AMB-deg-C-20 1.12 PVC-AIR-AMB-deg-C-25 1.08 PVC-AIR-AMB-deg-C-30 1 PVC-AIR-AMB-deg-C-35 0.94 PVC-AIR-AMB-deg-C-40 0.87 PVC-AIR-AMB-deg-C-45 0.79 PVC-AIR-AMB-deg-C-50 0.71 PVC-AIR-AMB-deg-C-55 0.61 PVC-AIR-AMB-deg-C-60 0.5 XLPE-AIR-AMB-deg-C-10 1.15 XLPE-AIR-AMB-deg-C-15 1.12 XLPE-AIR-AMB-deg-C-20 1.08 XLPE-AIR-AMB-deg-C-25 1.04 XLPE-AIR-AMB-deg-C-30 1 XLPE-AIR-AMB-deg-C-35 0.96 XLPE-AIR-AMB-deg-C-40 0.91 XLPE-AIR-AMB-deg-C-45 0.87 XLPE-AIR-AMB-deg-C-50 0.82 XLPE-AIR-AMB-deg-C-55 0.76 XLPE-AIR-AMB-deg-C-60 0.71
F:\Elements\cable programs\cable ampacity calculation IEC.docx Page 5
Correction factors for ambient ground temperatures other than 20 °C to be applied to the current-carrying capacities for cables in ducts in the ground.
GR AMB TEMP
PVC-GR-AMB-deg-C-10 1.1 PVC-GR-AMB-deg-C-15 1.05 PVC-GR-AMB-deg-C-20 1 PVC-GR-AMB-deg-C-25 0.95 PVC-GR-AMB-deg-C-30 0.89 PVC-GR-AMB-deg-C-35 0.84 PVC-GR-AMB-deg-C-40 0.77 PVC-GR-AMB-deg-C-45 0.71 PVC-GR-AMB-deg-C-50 0.63 PVC-GR-AMB-deg-C-55 0.55 PVC-GR-AMB-deg-C-60 0.45 XLPE-GR-AMB-deg-C-10 1.07 XLPE-GR-AMB-deg-C-15 1.04 XLPE-GR-AMB-deg-C-20 1 XLPE-GR-AMB-deg-C-25 0.98 XLPE-GR-AMB-deg-C-30 0.93 XLPE-GR-AMB-deg-C-35 0.89 XLPE-GR-AMB-deg-C-40 0.85 XLPE-GR-AMB-deg-C-45 0.8 XLPE-GR-AMB-deg-C-50 0.76 XLPE-GR-AMB-deg-C-55 0.71 XLPE-GR-AMB-deg-C-60 0.65 XLPE-GR-AMB-deg-C-65 0.6 XLPE-GR-AMB-deg-C-70 0.53 XLPE-GR-AMB-deg-C-75 0.46 XLPE-GR-AMB-deg-C-80 0.38
F:\Elements\cable programs\cable ampacity calculation IEC.docx Page 6
Correction factors for cables buried direct in the ground or in buried ducts for soil thermal resistivities other than 2,5 K·m/W to be applied to the current-carrying capacities
soil thermal resistivity Thermal Resistivity-K*m/W-1(DB) 1.5
Thermal Resistivity-K*m/W-1.5(DB) 1.25 Thermal Resistivity-K*m/W-2(DB) 1.12
Thermal Resistivity-K*m/W-2.5(DB) 1 Thermal Resistivity-K*m/W-3(DB) 0.9
Thermal Resistivity-K*m/W-1(DUCT) 1.18 Thermal Resistivity-K*m/W-1.5(DUCT) 1.1 Thermal Resistivity-K*m/W-2(DUCT) 1.05
Thermal Resistivity-K*m/W-2.5(DUCT) 1 Thermal Resistivity-K*m/W-3(DUCT) 0.96
F:\Elements\cable programs\cable ampacity calculation IEC.docx Page 7
Reduction factors for more than one circuit, cables laid directly in the ground – Installation method – Single-core or multi-core cables.
DB-1/C OR 3/C DB-Touching-Circuit-1 1 DB-Touching-Circuit-2 0.75 DB-Touching-Circuit-3 0.65 DB-Touching-Circuit-4 0.6 DB-Touching-Circuit-5 0.55 DB-Touching-Circuit-6 0.5
DB-One Dia apart-Circuit-1 1 DB-One Dia apart-Circuit-2 0.8 DB-One Dia apart-Circuit-3 0.7 DB-One Dia apart-Circuit-4 0.6 DB-One Dia apart-Circuit-5 0.55 DB-One Dia apart-Circuit-6 0.55
DB-0.125-m - apart-Circuit-1 1 DB-0.125-m - apart-Circuit-2 0.85 DB-0.125-m - apart-Circuit-3 0.75 DB-0.125-m - apart-Circuit-4 0.7 DB-0.125-m - apart-Circuit-5 0.65 DB-0.125-m - apart-Circuit-6 0.6 DB-0.25-m - apart-Circuit-1 1 DB-0.25-m - apart-Circuit-2 0.9 DB-0.25-m - apart-Circuit-3 0.8 DB-0.25-m - apart-Circuit-4 0.75 DB-0.25-m - apart-Circuit-5 0.7 DB-0.25-m - apart-Circuit-6 0.7 DB-0.5-m - apart-Circuit-1 1 DB-0.5-m - apart-Circuit-2 0.9 DB-0.5-m - apart-Circuit-3 0.85 DB-0.5-m - apart-Circuit-4 0.8 DB-0.5-m - apart-Circuit-5 0.8 DB-0.5-m - apart-Circuit-6 0.8
F:\Elements\cable programs\cable ampacity calculation IEC.docx Page 8
Reduction factors for group of more than one multi-core cable to be applied to reference current-carrying capacities for multi-core cables in free air –
Reduction factors for group of more than one multi-core cable to be applied to reference current-carrying capacities for multi-core cables in free air –
Ladder Tary-multi-layer-Circuit-1 1 Ladder Tary-multi-layer-Circuit-2 0.8 Ladder Tary-multi-layer-Circuit-3 0.7 Ladder Tary-multi-layer-Circuit-4 0.65 Ladder Tary-multi-layer-Circuit-5 0.6 Ladder Tary-multi-layer-Circuit-6 0.57 Ladder Tary-multi-layer-Circuit-7 0.54 Ladder Tary-multi-layer-Circuit-8 0.52 Ladder Tary-multi-layer-Circuit-9 0.5 Ladder Tary-multi-layer-Circuit-12 0.45 Ladder Tary-multi-layer-Circuit-16 0.41 Ladder Tary-multi-layer-Circuit-20 0.38 Ladder Tary-Single-layer-Circuit-1 1 Ladder Tary-Single-layer-Circuit-2 0.87 Ladder Tary-Single-layer-Circuit-3 0.82 Ladder Tary-Single-layer-Circuit-4 0.8 Ladder Tary-Single-layer-Circuit-5 0.8 Ladder Tary-Single-layer-Circuit-6 0.79 Ladder Tary-Single-layer-Circuit-7 0.79 Ladder Tary-Single-layer-Circuit-8 0.78 Ladder Tary-Single-layer-Circuit-9 0.78
F:\Elements\cable programs\cable ampacity calculation IEC.docx Page 9
3 CABLE IMPEDANCE CALCULATIONS 3.1 Conductor Resistivity
The Resistivity is defined as the electrical resistance of a body of unit length, and unit cross-sectional area or unit weight. Volume Resistivity is commonly expressed in ohms for a theoretical conductor of unit length and cross-sectional area, in inch-pound units in Ω ·cmil / ft and in acceptable metric units in Ω·mm2/m. It may be calculated by the following equation:
Where: = ρ = Volume resistivity, Ω·cmil / ft, A = cross-sectional area, cmil, L = gauge length, used to determine R, ft R = measured resistance. In Accordance with ASTM- B-193, Table 2 Volume resistivity for Copper, Ω·cmil/ft or Ω·mm2/m = 10.371
AL
R
F:\Elements\cable programs\cable ampacity calculation IEC.docx Page 10
3.2 Temperature Correction The measurement is made at any other than a reference temperature; the resistance may be corrected for moderate temperature differences to what it would
be at the reference temperature, as follows:
Where: Rt = resistance at reference temperature T2, R = resistance as measured at temperature T1, Alpha T = known or given temperature coefficient of
resistance of the specimen being measured at reference temperature T, T2 = reference temperature, and T1 = temperature at which measurement is made.
NOTE 1—The parameter AlphaT, in the above equation, varies with conductivity and temperature. For copper of 100 % conductivity and a reference temperature of 20°C, its value is 0.00393.
Rt R 1 T2 T1
F:\Elements\cable programs\cable ampacity calculation IEC.docx Page 11
3.3 Resistance of stranded conductors Correction. 3.3.1 DC RESISTANCE @ 70 DEG C OR 90 DEG C
CALCULATE
CALCULATE STRANDING
FACTOR
CALCULATE CALCULATE Nominal Cross
Section Area
Nominal CONDUCTOR
Diameter
Minimum Number
of Wires in
Conductor
Nominal Stranded
CONDUCTOR Diameter
Maximum Resistance of Conductor at
20 deg C Annealed Copper
Conductor Plain Wires Ώ / km
Resistance at= t Deg C temperature IEC-60228-
Annex B
mm2 d=(4/pi*A)^.5
= mm Circular
Cu d x str-factor =
Mm
Rdc-t= [1+0.00393
(t-20)]* Rdc-20 Ώ/1000
meter =90 0.5 0.798 7 1.134 0.905 36 45.904
0.75 0.977 7 1.134 1.108 24.5 31.240 1 1.128 7 1.134 1.279 18.1 23.079
1.5 1.382 7 1.134 1.567 12.1 15.429 2.5 1.784 7 1.134 2.023 7.41 9.448 4 2.257 7 1.134 2.559 4.61 5.878 6 2.764 7 1.134 3.134 3.08 3.927
10 3.568 7 1.134 4.046 1.83 2.333 16 4.513 7 1.134 5.118 1.15 1.466 25 5.642 7 1.134 6.397 0.727 0.927 35 6.675 7 1.134 7.569 0.524 0.668 50 7.978 19 1.147 9.152 0.387 0.493 70 9.440 19 1.147 10.829 0.268 0.342 95 10.997 19 1.147 12.615 0.193 0.246
120 12.360 37 1.151 14.224 0.153 0.195 150 13.819 37 1.151 15.903 0.124 0.158 185 15.347 37 1.151 17.661 0.0991 0.126 240 17.480 37 1.151 20.115 0.0754 0.096 300 19.543 61 1.152 22.520 0.0601 0.077 400 22.566 61 1.152 26.004 0.047 0.060 500 25.230 61 1.152 29.073 0.0366 0.047 630 28.320 91 1.153 32.656 0.0283 0.036 800 31.913 91 1.153 36.800 0.0221 0.028
1000 35.680 91 1.153 41.143 0.0176 0.022
F:\Elements\cable programs\cable ampacity calculation IEC.docx Page 12
3.3.2 CALCULATE CABLE SPACING BASED ON INSULATION THICKNESS “PVC, XLPE, EPR”.
Nominal Cross
Section Area
Nominal Thickness
of PVC Insulation
Nominal Thickness of XLPE
Insulation
Nominal Thickness
of EPR Insulation
fictitious diameter
Dc of single core PVC cable
fictitious diameter
Dc of single core
XLPE cable
fictitious diameter
Dc of single core EPR cable
Diameter overlaid up
cores Reduced Neutral
Size
mm2
0.6/1 (1.2) kV mm
0.6/1 (1.2) kV mm
0.6/1 (1.2) kV mm
Dc= dL+2 * ti
=mm Dc=
dL+2 * ti=mm
Dc= dL+2 * ti=mm Df=kDc=mm mm 2
0.5 0.6 0.7 1 2.105 2.305 2.905 1 0.5 0.75 0.6 0.7 1 2.308 2.508 3.108 1 0.75
1 0.6 0.7 1 2.479 2.679 3.279 1 1 1.5 0.6 0.7 1 2.767 2.967 3.567 1 1.5 2.5 0.6 0.7 1 3.223 3.423 4.023 1 2.5 4 1 0.7 1 4.559 3.959 4.559 1 4 6 1 0.7 1 5.134 4.534 5.134 1 6
10 1 0.7 1 6.046 5.446 6.046 1 10 16 1 0.7 1 7.118 6.518 7.118 1 16 25 1.2 0.9 1.2 8.797 8.197 8.797 1 16 35 1.2 0.9 1.2 9.969 9.369 9.969 1 16 50 1.4 1 1.4 11.952 11.152 11.952 1 25 70 1.4 1.1 1.4 13.629 13.029 13.629 1 35 95 1.6 1.1 1.6 15.815 14.815 15.815 1 50
120 1.6 1.2 1.6 17.424 16.624 17.424 1 70 150 1.8 1.4 1.8 19.503 18.703 19.503 1 95 185 2 1.6 2 21.661 20.861 21.661 1 95 240 2.2 1.7 2.2 24.515 23.515 24.515 1 120 300 2.4 1.8 2.4 27.320 26.120 27.320 1 150 400 2.6 2 2.6 31.204 30.004 31.204 1 240
F:\Elements\cable programs\cable ampacity calculation IEC.docx Page 13
3.3.3 CALCULATE CABLE SPACING BASED ON INSULATION THICKNESS “PVC, XLPE, EPR”.
CALCULATE CALCULATE CALCULATE CALCULATE Nominal Cross
Section Area
3-cond, k=2.16 PVC
Reduced Neutral Size
PVC 3-1/2-cond,
PVC 4-cond, k=2.42 PVC
Df=kDc Dc=
dL+2 * ti Df=2.42 (3
Dc1+Dc2)/4 Df=kDc mm2 3-cond-PVC mm-PVC
3-1/2-cond-PVC 4-cond-PVC
0.5 4.55 1.00 4.42 5.58 0.75 4.99 1.00 4.79 6.07
1 5.36 1.00 5.11 6.48 1.5 5.98 1.00 5.63 7.18 2.5 6.96 1.00 6.45 8.28 4 9.85 1.00 8.88 9.58 6 11.09 1.00 9.92 10.97
10 13.06 1.00 11.58 13.18 16 15.37 1.00 13.52 15.77 25 19.00 1.00 16.57 19.84 35 21.53 1.00 18.70 22.67 50 25.82 1.20 22.42 26.99 70 29.44 1.20 25.46 31.53 95 34.16 1.40 29.55 35.85
120 37.64 1.40 32.47 40.23 150 42.13 1.60 36.37 45.26 185 46.79 1.60 40.28 50.48 240 52.95 1.60 45.46 56.91 300 59.01 1.80 50.67 63.21 400 67.40 2.20 57.97 72.61
F:\Elements\cable programs\cable ampacity calculation IEC.docx Page 14
3.3.4 CALCULATE CABLE SPACING BASED ON INSULATION THICKNESS “PVC, XLPE, EPR”. CALCULATE CALCULATE CALCULATE CALCULATE
Nominal Cross
Section Area
3-cond, k=2.16 XLPE
Reduced Neutral Size
XLPE 3-1/2-cond,
XLPE 4-cond, k=2.42 XLPE
Df=kDc Dc=
dL+2 * ti Df=2.42 (3
Dc1+Dc2)/4 Df=kDc mm2
3-cond-XLPE mm XLPE
3-1/2-cond-XLPE
4-cond-XLPE
0.5 4.98 2.10 5.46 5.58 0.75 5.42 2.31 5.95 6.07
1 5.79 2.48 6.36 6.48 1.5 6.41 2.77 7.06 7.18 2.5 7.39 3.22 8.16 8.28 4 8.55 4.56 9.94 9.58 6 9.79 5.13 11.33 10.97
10 11.76 6.05 13.54 13.18 16 14.08 7.12 16.14 15.77 25 17.71 7.12 19.18 19.84 35 20.24 7.12 21.31 22.67 50 24.09 8.80 25.56 26.99 70 28.14 9.97 29.68 31.53 95 32.00 11.95 34.12 35.85
120 35.91 13.63 38.42 40.23 150 40.40 15.81 43.51 45.26 185 45.06 15.81 47.43 50.48 240 50.79 17.42 53.22 56.91 300 56.42 19.50 59.21 63.21 400 64.81 24.52 69.29 72.61
F:\Elements\cable programs\cable ampacity calculation IEC.docx Page 15
3.3.5 CALCULATE CABLE SPACING BASED ON INSULATION THICKNESS “PVC, XLPE, EPR”. CALCULATE CALCULATE CALCULATE CALCULATE
Nominal Cross
Section Area
3-cond, k=2.16 EPR
Reduced Neutral Size
EPR 3-1/2-cond,
EPR 4-cond, k=2.42
EPR Df=kDc
Dc= dL+2 * ti
Df=2.42 (3 Dc1+Dc2)/4 Df=kDc
mm2 3-cond-EPR mm EPR 3-1/2-cond-
EPR 4-cond-EPR 0.5 6.27 2.305 6.67 7.029
0.75 6.71 2.508 7.16 7.521 1 7.08 2.679 7.57 7.936
1.5 7.70 2.967 8.27 8.632 2.5 8.69 3.423 9.37 9.735 4 9.85 3.959 10.67 11.032 6 11.09 4.534 12.06 12.424
10 13.06 5.446 14.27 14.631 16 15.37 6.518 16.86 17.224 25 19.00 6.518 19.91 21.288 35 21.53 6.518 22.04 24.125 50 25.82 8.197 26.65 28.923 70 29.44 9.369 30.40 32.981 95 34.16 11.152 35.45 38.272
120 37.64 13.029 39.51 42.166 150 42.13 14.815 44.36 47.196 185 46.79 14.815 48.28 52.419 240 52.95 16.624 54.55 59.327 300 59.01 18.703 60.90 66.114 400 67.40 23.515 70.86 75.513
F:\Elements\cable programs\cable ampacity calculation IEC.docx Page 16
AC-RESISTANCE OF CONDUCTOR
Nominal Cross
Section Area R=R' (1+ys+yp)
ys=xs^4 / (192+0.8 . xs^4) xs^2= 8.pi.f.(10^-7) ks /R'
ks=1 yp=xp^4*(dc/s)^2 0. 2.9/(192+xp^4)
xp^2=8.pi*f.10^-7 .lp /R' kp=1
mm2 xs^2=
ys=xs^4 / (192+0.8 .
xs^4) xp^2=
yp=xp^4*(dc/s)^2.0. 2.9
/(192+xp^4)
R=R' (1+ys+yp)
0.5 2.738E-06 6.510E-03 2.738E-06 2.091E-14 4.620E+01
0.75 4.023E-06 6.510E-03 4.023E-06 5.632E-14 3.144E+01 1 5.445E-06 6.510E-03 5.445E-06 1.192E-13 2.323E+01
1.5 8.145E-06 6.510E-03 8.145E-06 3.213E-13 1.553E+01 2.5 1.330E-05 6.510E-03 1.330E-05 1.053E-12 9.510E+00 4 2.138E-05 6.510E-03 2.138E-05 2.175E-12 5.916E+00 6 3.200E-05 6.510E-03 3.200E-05 5.762E-12 3.953E+00
10 5.385E-05 6.510E-03 5.385E-05 1.962E-11 2.349E+00 16 8.570E-05 6.510E-03 8.570E-05 5.734E-11 1.476E+00 25 1.356E-04 6.510E-03 1.356E-04 1.468E-10 9.330E-01 35 1.881E-04 6.510E-03 1.881E-04 3.080E-10 6.725E-01 50 2.547E-04 6.510E-03 2.547E-04 5.743E-10 4.967E-01 70 3.677E-04 6.510E-03 3.677E-04 1.289E-09 3.440E-01 95 5.106E-04 6.510E-03 5.106E-04 2.506E-09 2.477E-01
120 6.441E-04 6.510E-03 6.441E-04 4.176E-09 1.964E-01 150 7.948E-04 6.510E-03 7.948E-04 6.344E-09 1.591E-01 185 9.945E-04 6.510E-03 9.945E-04 9.930E-09 1.272E-01 240 1.307E-03 6.510E-03 1.307E-03 1.737E-08 9.677E-02 300 1.640E-03 6.510E-03 1.640E-03 2.760E-08 7.713E-02 400 2.097E-03 6.510E-03 2.097E-03 4.612E-08 6.032E-02
F:\Elements\cable programs\cable ampacity calculation IEC.docx Page 17
Inductance Inductance - Inductance -
Nominal Cross
Section Area
PVC Insulated L=K+0.2
Log e (2S /d)
mH/km
PVC Insulated X=2pif*L
Ώ/km
XLPE Insulated L=K+0.2
Log e (2S /d)
mH/km
XLPE Insulated X=2pif*L
Ώ/km
EPR Insulated L=K+0.2
Log e (2S /d) mH/km
EPR Insulated X=2pif*L
Ώ/km
Typical Values for Constant (K) for
different Stranded Conductors (50 Hz)
n=3, K=0.0778 n=7, K=0.0642
n=19, K=0.0554 n=37, K=0.0528 n=61, K=0.0514
Typical Values for Constant (K) for
different Stranded Conductors (50 Hz)
n=3, K=0.0778 n=7, K=0.0642
n=19, K=0.0554 n=37, K=0.0528 n=61, K=0.0514
Typical Values for Constant (K) for
different Stranded Conductors (50 Hz)
n=3, K=0.0778 n=7, K=0.0642
n=19, K=0.0554 n=37, K=0.0528 n=61, K=0.0514 mm2
0.5 0.2330703 0.0732212 0.2512262 0.078925 0.297502883 0.093463287 0.75 0.2109673 0.0662773 0.2275884 0.071499 0.270487529 0.084976163
1 0.1965267 0.0617407 0.2120421 0.066615 0.252455876 0.079311353 1.5 0.177925 0.0558968 0.1918829 0.0602818 0.228718644 0.071854081 2.5 0.1573508 0.0494332 0.1693922 0.0532161 0.201695389 0.063364475 4 0.1797057 0.0564562 0.1514817 0.0475894 0.179705662 0.056456199 6 0.1629193 0.0511826 0.1380623 0.0433736 0.162919334 0.051182618
10 0.1445377 0.0454079 0.1236337 0.0388407 0.144537705 0.045407859 16 0.1301779 0.0408966 0.1125648 0.0353633 0.130177935 0.040896604 25 0.1279172 0.0401864 0.1137885 0.0357477 0.12791723 0.040186383 35 0.1192845 0.0374743 0.1068696 0.0335741 0.119284456 0.037474317 50 0.1175864 0.0369409 0.1037302 0.0325878 0.108786415 0.03417626 70 0.1101962 0.0346192 0.1011915 0.0317902 0.10139625 0.031854571 95 0.109415 0.0343737 0.0963511 0.0302696 0.100614953 0.03160912
120 0.1047842 0.0329189 0.0953838 0.0299657 0.093384173 0.029337503 150 0.1050129 0.0329908 0.0966359 0.0303591 0.1050129 0.032990776 185 0.1050314 0.0329966 0.0975049 0.0306321 0.105031372 0.032996579 240 0.1037631 0.0325981 0.0954339 0.0299814 0.103763075 0.032598131 300 0.1028433 0.0323092 0.0938597 0.0294869 0.10284331 0.032309179 400 0.1006596 0.0316232 0.0928164 0.0291591 0.100659619 0.031623152
F:\Elements\cable programs\cable ampacity calculation IEC.docx Page 18
3.4 Conductor Reactance
D= Spacing between conductors D= diameter of wire (2 x radius) + 2 x insulation thickness r = Radius of conductors.
, the insulation thickness for multiconductor cables with outer coverings is as follows,
XL 2 f L
L 8 1 4 ln D
r
4 10 7 Hm
F:\Elements\cable programs\cable ampacity calculation IEC.docx Page 19
Nominal Cross
Section Area
Nominal Thickness
of PVC Insulation
Nominal Thickness of XLPE
Insulation
Nominal Thickness
of EPR Insulation
fictitious diameter
Dc of single core PVC cable
fictitious diameter
Dc of single core
XLPE cable
fictitious diameter
Dc of single core EPR cable
Dc=
dL+2 * ti Dc=
dL+2 * ti Dc=
dL+2 * ti
mm2
0.6/1 (1.2) kV mm
0.6/1 (1.2) kV mm
0.6/1 (1.2) kV mm mm mm mm
0.5 0.8 0.7 1 2.505 2.305 2.905 0.75 0.8 0.7 1 2.708 2.508 3.108
1 0.8 0.7 1 2.879 2.679 3.279 1.5 0.8 0.7 1 3.167 2.967 3.567 2.5 0.8 0.7 1 3.623 3.423 4.023 4 1 0.7 1 4.559 3.959 4.559 6 1 0.7 1 5.134 4.534 5.134
10 1 0.7 1 6.046 5.446 6.046 16 1 0.7 1 7.118 6.518 7.118 25 1.2 0.9 1.2 8.797 8.197 8.797 35 1.2 0.9 1.2 9.969 9.369 9.969 50 1.4 1 1.4 11.952 11.152 11.952 70 1.4 1.1 1.4 13.629 13.029 13.629 95 1.6 1.1 1.6 15.815 14.815 15.815
120 1.6 1.2 1.6 17.424 16.624 17.424 150 1.8 1.4 1.8 19.503 18.703 19.503 185 2 1.6 2 21.661 20.861 21.661 240 2.2 1.7 2.2 24.515 23.515 24.515 300 2.4 1.8 2.4 27.320 26.120 27.320 400 2.6 2 2.6 31.204 30.004 31.204 500 2.8 2.2 2.8 34.673 33.473 34.673 630 2.8 2.4 2.8 38.256 37.456 38.256 800 2.8 2.6 2.8 42.400 42.000 42.400
1000 3 2.8 3 47.143 46.743 47.143
F:\Elements\cable programs\cable ampacity calculation IEC.docx Page 20
4 CABLE VOLTAGE DROP CALCULATIONS. Permissible Voltage Drop, with respect to Load Power Factor.
Volt drop can be defined as the difference in magnitude of the voltage at the supply compared to the voltage at the load. This voltage drop is based on the loads power factor, the cable's internal resistance and reactance, and the cable length. The three phase voltage drop permitted on the circuit run is calculated using the following equation.
Vd.3 I L R cos ( ) X sin ( )( 3 Where: Vd3p = three phase voltage drop, volts (V) ө = Power factor Angle I = current flowing in cable, amperes (A) L = route length of circuit, meters (m) R = AC resistance of cable, ohm/kilometer (W/km) X = reactance of cable, ohm/kilometer (W/km)
F:\Elements\cable programs\cable ampacity calculation IEC.docx Page 21
5 CABLE SIZING & CURRENT-CARRYING CAPACITY CALCULATION STEPS To calculate the current-carrying capacity requirements of a circuit:
STEP-1 Determine the current requirements, based on 1.25 times the FLA
continuous current, of the Loads. STEP-2 Select the Cable Size based on the De-Rated Ampacity of the
Cable. STEP-3 Calculate Length x Amp factor for each size of the cable based on
% voltage drop and the circuit power factor, as per the following formula.
STEP-4 Calculate the length of the selected cable based on the FLA of the circuit.
STEP-4 If the calculated length L is < than the circuit length D, then calculate Length x Amp FLA x D of the circuit.
STEP-5 Select the cable FLA x D with the matching Length x Amp L X I factor.
STEP-6 Calculate Length x Amp factor for each size of the cable based on % voltage drop and the circuit power factor, as per the above formula.
STEP-7 Calculate the Circuit Voltage drop for the length of the circuit. STEP-8 if the voltage drop exceeds the design criteria then increases the
Cable size to meet the voltage drop. STEP-9 SELECTS THE CALCULATED CABLE SIZE.
IL Vd3R cos ( ) X sin ( )(
L Vd3R cos ( ) X sin ( )( )( I