ELECTRICAL FORMULAS FOR POWER CABLE

Power Cable Capacitance (C) Formula
Single Conductor Shielded Cable
        C = 0.024113 x e/ [log (d2/d1)]   microfarad/ kilometer
where:
e = dielectric constant for XLPE = 2.3, PVC = 5.0-7.0
d2 = diameter under insulation
d1 = diameter over the insulation

Power Cable Insulation Resistance (IR) Formula
According to ICEA Specification
IR @ 15.6 degrees C = K log (d2/d1)    Megaohm - 1000ft

According to JIS Specification
IR @ 20.0 degrees C = 3.665 x 10^-12 x p x log (d2/d1)    Megaohm - km

where:
d2 = diameter under insulation
d1 = diameter over the insulation
K = constant (XLPE = 20,000; PVC = 500)
p = volume density (ohm-cm) ; XLPE = 2.5 x 10^15, PVC = 1 x 10^13

Power Cable Inductance (L) Formula
Multiple conductor cable or single conductor cable arranged in parallel and three single conductor arranged in triangular
          L = 0.46 log (S/d) + 0.19    mH/km
where: 
d = diameter of conductor
S = distance between conductor

Power Cable Charging Current (Ic) Formula
          Ic = 2 x pi x fC x v/ 1.73    Amp/km
where: 
C = capacitance (F/km)
V = rated line to line voltage (Volt)
f = frequency (Hz)

Power Cable Potential Gradient Formula
         E = (v/1.73)/ X ln (d2/d1)    kV/mm
where:
X = distance from center of the conductor (mm)
V = rated line to line voltage
d2 = diameter under insulation
d1 = diameter over the insulation

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1 comment:

Anonymous said...

Il semble que vous soyez un expert dans ce domaine, vos remarques sont tres interessantes, merci.

- Daniel