Question

The current carrying capacity of cables in DC is more than that in AC mainly due to
1. Absence of harmonics
2. Non-existence of any stability limit
3. Smaller dielectric loss
4. Absence of ripple

Answer 1

Correct Answer - Option 3 : Smaller dielectric loss

• Compared with the AC cable, the power (dielectric loss) during the transmission of the DC cable is small.
• The power loss of the DC cable is mainly the DC resistance loss of the conductor, and the insulation loss is small (the size depends on the current fluctuation after rectification).
• The AC resistance of the low-voltage AC cable is slightly larger than the DC resistance, the high-voltage cable is obvious, mainly because the proximity effect and the skin effect, the loss of insulation resistance accounts for a large proportion, mainly the impedance generated by the capacitor and the inductor.
• Therefore, the current carrying capacity of cables in DC is more than that in AC.