Medium Voltage Cable Selection

[kcsen]

How do I select 4160V cable for medium voltage feeder using Vacuum Contactor (V-Contact)protection. Is it the same rule like 125% of FLA? Please advise.

 

[busbar]

NEC 430-6 and 430-22 do not seem to exclude medium-voltage motors, but Table 430-150 does not have a 4000-volt column, implying the need to interpolate/extrapolate published values. The 90°C values in Tables 310-76 and 310-80 seem to safely be conservative. It may be desirable to avoid the 105°C column, for termination/splice reliability may become an issue.

For medium voltage motors and controls, skimping on cable sizes and connectors would seem far more suicidal than for low voltages.

 

[aolalde]

In spite of complain with NEC 430, voltage drop at full load and starting should be considered while selecting the conductor size to feed an electric motor.