Medium Voltage electrical conductor

[mathan1987]

Hi,

For the medium voltage cables in the underground duct banks how do we calculate the derating of the conductor capacity for the soil resistivity?
what are the softwares I can use to calculate the soil resistivity adjustments.

 

[Julius Right]

See IEEE 835 or IEC 60364-5-52

 

[Julius Right]

Sorry. According to IEC 60364-1:
circuits supplied at nominal voltages up to and including 1 000 V a.c. or 1 500 V d.c.;
For medium voltage it is IEC 60502-2.

 

[David Castor]

For software, check out AmpCalc. It does a Neher-McGrath calculation for duct bank derating that should be consistent with the NEC. It's been around a long time. If this is a one-off, you can also just ask cable suppliers to do the calculation for you - Okonite or Southwire have been willing to do this - at least in the past.

 

[Julius Right]

See IEC 60502-2 Table B17