Investigation on Ampacity for Direct Burial Low-Voltage Power Cables

Generally, cable ampacity is the physically allowable continuous current that a cable can carry under real installation conditions. Allowable continuous current is the current in a conductor limited by the temperature rise in the insulation. Cable ampacity for low-voltage systems is defined by various standards. In addition, most manufacturers provide their own user guides. Today, cable ampacity analyses are commonly performed using different software tools. Although cable ampacity results should be unique, variations may occur that can significantly affect cable health and service life. These differences arise from variations in the current calculations. Software analysis is numerical, and calculations using standards are analytical. The objective of this paper is to compare real cable ampacity values obtained through software modeling with those calculated using standards and manufacturers' guidelines. The paper deals with direct-buried cables. The differences in cable ampacity are calculated and presented. Multiple case studies were analyzed. For direct-buried cables, the ampacity values derived from the reviewed standards, manufacturers' user guides, and software models are similar across the case studies, with deviations of no more than 4%. Furthermore, numerical cable ampacity analysis accounting for load factors (dynamic loading) and soil thermal resistivity was performed for direct-buried cable systems. It is concluded that these two factors significantly influence cable ampacity. KeyWords: Power Cable, Cable Ampacity, Correction Factor, Load Factor, Soil Thermal Resistivity.