Explore the factors affecting cable ampacity in trays, including thermal and electromagnetic effects. Learn calculation methods and best practices for safe power cable installations.

Based on extensive field experience, this article recommends the best materials for cable trays for use in offshore facilities such as offshore wind, solar, and oil rigs.

It's difficult to decide on the thermal resistivity of soil or backfill to use for cable rating studies. The typical thermal resistivities of common native soils and engineered materials used as backfills for buried cables are provided in tables.

The widely accepted maximum operating temperature of XLPE insulated power cables under “normal use” conditions is 90 ˚C. During emergencies, the temperature of a buried cable may be permitted to exceed this temperature. The duration considered for such emergencies ranges from 10 minutes up to 15 days. In many countries, XLPE-insulated cables are allowed to operate up to 100-105 ˚C for short durations.

We performed ampacity calculations for hundreds of industrial and utility power cables from Southwire. The assumptions used for modelling in the software are explained. The calculated ampacities were all within 3 % of the values given in ICEA and NEC standards.