## 20/01/2020

### Dielectric Loss in the Cable

The following losses take place in the Cable.
Heating of cable
Copper Loss
Inter sheath loss
Dielectric loss
• The capacitor is formed between core and sheath.
• There is no dielectric loss if the capacitor is pure but this is not possible.
• The capacitor is represented by parallel combination of resistance and capacitor.
• The Phasor diagram is shown in the Figure.
• The current in the cable leads voltage by an angle less than 90 degree due to presence of resistance.
• The losses occur in the capacitor because the cable is not perfect dielectric.

The capacitor current IC flows
IC = V / XC
= ωVC
tan δ = IR / IC
= ( V / R ) / ωVC
= V / ωVC R
= 1 / ωCR
R = 1 / ωC tan δ
The dielectric loss P = V2 / R
= V2 ωC tan δ
Where δ = Dielectric Loss angle
• As the dielectric loss angle is very small, it is considered as tan δ ≈ δ       The dielectric loss P = V2 ωC  δ
Parameters affecting Dielectric Loss
• The dielectric loss is directly proportional to square of applied voltage and directly proportional to frequency.
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