Comprehensive analysis of field inversion, IEC 60287 Standards, finite element modelling, and case studies to optimise HVDC cable ampacity and insulation design.

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.

Charging current in power cables is 10-20 times larger than for overhead lines. The maximum length of cable circuits is determined by their capacitance. This report provides equations and shows how critical cable length depends on voltage level, cable size and frequency.

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.

Most power cables have a design life of between 20 to 30 years. If the cables are not fully loaded, they are expected to last beyond their design life. The insulation is the weakest part of a cable. Montsinger's Rule states: Insulation life is halved by a temperature increase of 8 to 10 ˚C. An example calculation using the Arrhenius equation is provided.