Cable Parameters: Insulation Resistance,Charging Current, Dielectric Losses

Cable Parameters: Insulation Resistance,Charging Current, Dielectric Losses

Before we formulated cable basic parameters resistance, inductance and capacitance, now we will try to 3 more parameters like Insulation Resistance, Charging Current  and Dielectric Losses.

Insulation Resistance:
Using the following formula you can calculate insulation resistance in mega-ohm per kilo-meter of cable, to do this you consider the insulation material, diameter of cable including semiconductor layer, diameter of insulated core.

R =K In (D/d )  MΩ/km

Where
R = Insulation resistance in MΩ/km;
K = Constant depends on the insulation material;
d = Diameter of the conductor in mm including the semiconducting layer;
D = Diameter in mm of the insulated core;
- mega ohm, km- kilo meter, mm- mili meter.



Charging Current:
The charging current is the capacitive current which flows when AC voltage is applied to the cables as a result of the capacitance between the conductor and earth, and for a multi-core cable in which cores are not screened, between conductors. The value can be calculated from the following equation.

IC = Uo ω10-6   A/km

Where
IC = Charging current in Ampear/km;
Uo =Voltage in volt between phase and earth;
ω= 2 π f (π=22/7, f= frequency in hertz) Hz;
C= Capacitance in micro-farad per kilo-meter to neutral;



Dielectric Losses:
To calculate the dielectric losses of an AC cable are proportional to the Capacitance, the frequency, the phase voltage and the power factor. The value in watt per kilo-meter per phase can be calculated from the following equation.

WD = 2 π f C Uo2 tanδ 10-6   watt/km/phase

Where 
WD = Dielectric losses in watt/km/phase;
f = Frequency in hertz;
C = Capacitance in micro-farad per kilo-meter to neutral;
Uo = Voltage in volt between phase and earth;
tanδ=Dielectric power factor.



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