Different insulating materials can withstand different maximum operating temperatures. For instance, Cross-Linked Polyethylene (XLPE) can typically withstand 90°C, whereas Polyvinyl Chloride (PVC) is often limited to 70°C. A higher temperature limit allows the cable to dissipate more heat, thereby increasing its ampacity.
Assuming a 3-core, 185 mm² XLPE-insulated cable, buried in soil with a thermal resistivity of 1.2 TΩm, and an ambient temperature of 20°C. cable rating calculation