What is the acceptable voltage drop limit for a cable?

Voltage drop is the voltage lost along a cable as current flows through the conductor's resistance. Left unchecked it under-supplies the load at the far end. Indian practice, following IS 732 and IEC 60364-5-52, keeps the total drop from the origin of the installation to any load point within roughly 3 per cent for lighting and about 5 per cent for power, with tighter figures for sensitive electronic loads. On short indoor circuits the drop is negligible. On long feeders it often decides the conductor size ahead of the current rating. The drop is estimated from the cable's mV/A/m figure, the design current and the run length. Where a long run breaches the limit, the fix is a larger conductor. APAR recommends checking both current rating and voltage drop, then sizing on whichever needs the bigger conductor. See APAR LV XLPE power cables.