Cable Ampacity Software - IEEE Standard
The IEEE 399 standard applies to underground cables. The cable ampacity calculation software tool derates the ampacity using the following parameters:
Cable Raceway Installations
ETAP’s high-performance ampacity calculator software for underground (buried) cables offers the following installation options:
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 tool provides the following grouping options:
- Number of Rows
- Number of Columns
The cable ampacity simulation application calculates the derated ampacity based on the ambient and conductor temperatures. In addition, the user can either select the base temperature provided by the manufacturer or the operating temperature of the cable.
- Base Ambient Temperature
- Base Conductor Temperature
- Operating Ambient Temperature
- Operating Conductor Temperature
Soil Resistivity Correction
One of the important parameters affecting the cable ampacity is the soil resistivity. The cable ampacity calculator part of the ETAP software allows defining soil resistivity based on:
Alert for Allowable Ampacity
ETAP provides alerts to the user when a critical situation occurs such as overloading. A critical situation may deteriorate the cable and tremendously reduce its lifetime. The alerts in ETAP can be based on the options listed below.
- Based on the calculated Derated Ampacity
- User-Defined value
- Based on thermal analysis results of underground raceway systems module
This cable ampacity analysis method is computing cable ampacity according to the IEEE Std 399, IEEE Recommended Practice for Industrial and Commercial Power Systems Analysis. This cable ampacity analysis program covers installation types of underground duct and directly buried. The cable ampacity calculation is based on ampacity at a base condition and adjustment factors derived from detailed calculations using the Neher-McGrath method.
These factors establish a maximum feasible load capacity, which results in no reduction of the cable expected lifetime.