When choosing a cable, the customer should consider the following factors:
- Electricquota
- Pressure drop
- Short circuit current
- Installation method
- ambient temperature or soil temperature
Electricquota :
Electric currents in the conduit will produce heat that causes the cable to heat up. When the cable temperature exceeds the allowed level, the cable with the larger conductor cross section must be selected.
The following power ratings and pressure drop tables are based on:
- Maximum allowable working temperature of the conductor.
- Air temperature
- temperature of soil
- heat resistance of soil.
- Installation depth (when burying cables in soil)
- Installation conditions
Pressure drop :
Another important factor to consider when choosing a cable size is the pressure loss due to cable losses.
Pressure drop depends on:
- Load current
- Power factor
- cable length
- Resistance cable
- cable resistance
IEE 522-8 regulates the pressure drop not to exceed 2, 5% of nominal voltage
With single phase 220V, the voltage drop is 5.5V
With three-phase 380V, the voltage drop is 9.5V.
When the pressure drop is greater than the allowable level, the customer must choose a cable with a larger conductor cross section.
Level and pressure drop of CVV copper conductor, PVC insulation, unarmoured PVC sheathed, aerial