IEEE 399 Standard

IEEE 399

IEEE 399 Standard

The IEEE 399 standard applies to underground (U/G) cables.

Cable Raceway Installations

ETAP's high-performance ampacity software for underground cables offers the following installation types:

  • U/G Directly Buried
  • U/G Duct Bank
Duct Bank Cable InstallationUnderground Directly Buried Raceway

Temperature Correction

Calculate the derated ampacity based on the ambient and conductor temperatures.

  • Base Ambient Temperature
  • Base Conductor Temperature
  • Operating Ambient Temperature
  • Operating Conductor Temperature


Grouping Factors

Grouped cables operate at higher temperatures than isolated cables. To derate the ampacity, the number of rows and columns of the duct bank must be specified to determine a cable grouping adjustment factor. ETAP’s ampacity evaluation software provides the following grouping options:

  • Number of Rows
  • Number of Columns

Alert for Allowable Ampacity

ETAP provides alerts when a critical situation occurs such as overloading which may deteriorate the cable and reduce its lifetime. The alerts can be set based on the following options:

  • Based on the calculated Derated Ampacity
  • User-Defined value
  • Based on thermal analysis results of underground raceway systems module

Soil Resistivity Correction

One of the important parameters affecting the cable ampacity is the soil resistivity. The cable ampacity calculator allows defining soil resistivity.

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