voltage drop?

[shocker9]

how do you calculate the voltage drop on an hv cable, as we use the Amtech software to find the correct cable required for LV, there is no facility on the software to calculate the voltage drop in a HV cable.

 

[davidbeach]

Current through the cable times cable impedance equals voltage drop across the cable.

 

[jghrist]

Remember that both current and impedance are complex quantities. The voltage drop will be a complex quantity and the difference in voltage magnitude from the voltage at the start to the end is not the magnitude of the voltage across the cable.

In terms of magnitude, the voltage drop is approximately:

VD = I·(R·cosØ + X·sinØ)

where R and X are the cable resistance and reactance. Ø is the current angle with respect to the voltage (pf = cosØ). I is the current.

 

[pashwuee]

For cable sizing following factors to be taken into consideration :

(a) Voltage drop in cable during starting of equipment(cable manufacturers provide voltage drop of cable in per ampere /per km basis so drop can easily calculated by just multiplying load in amperes )
(b) Short circuit capacity of cable.
(c) derating of cable current carrying capacity due to various reasons like cable arrangement , laying , ambient temperature , etc