This guide establishes maximum conductor operating temperatures for underground installations of shielded extruded dielectric cable systems rated 5 kV through 345 kVac. This guide outlines definitions, assumptions, principles and special considerations which apply to the use of the maximum allowable conductor temperatures for normal, emergency, and short-circuit operation of extruded dielectric cables. This guide focuses on precautions and limiting factors which should be considered when operating extruded dielectric cables at high temperatures. This guide applies to the following types of extruded dielectric insulated cables which were manufactured in accordance with AEIC specifications and are installed and operated in accordance with current practices: 1. Cross-linked polyethylene (XLPE) with thermosetting insulation shield 2. Tree-retardant cross-linked polyethylene (TRXLPE) with thermosetting insulation shield 3. Ethylene-propylene rubber (EPR) with thermosetting insulation shield 4. Ethylene-propylene rubber (EPR) with thermoplastic insulation shield 5. XLPE with thermoplastic insulation shield* 6. High-molecular weight polyethylene (HMWPE) with thermoplastic insulation shield* * Designs no longer covered by AEIC specifications and considered obsolete.