Cable ampacity calculations iec

F:\Elements\cable programs\cable ampacity calculation IEC.docx

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)


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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



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



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


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


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


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)


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

Cable ampacity calculations iec

Engineering

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