The primary distribution box uses aluminum core cables

Currently, the mainstream practice is to use aluminum alloy cables (such as YJHLV and ZC-YJHLV models) for the main trunk lines from the substation to the building's distribution box, while using copper wire for smaller branch lines inside the building. Aluminum URD (Underground Residential Distribution) cable is the primary "backbone" for modern underground power grids. Designed to carry high-voltage loads from substations to residential and commercial transformers, these cables must be engineered for maximum longevity in harsh, direct-burial. Southwire Company'sPower Cable Installation Guide provides installation information for extruded dielectric power cable systems. This guide covers copper and aluminum conductors from No. 14 AWG though 1000 kcmil, insulated for operation from 600 volts though 35 kilovolts. It acts as a protective enclosure that houses several key components, such as circuit breakers, fuses, and bus bars. These components work together to prevent electrical faults, such. The Unified Facilities Criteria (UFC) system is prescribed by MIL-STD 3007 and provides planning, design, construction, sustainment, restoration, and modernization criteria, and applies to the Military Departments, the Defense Agencies, and the DoD Field Activities in accordance with USD (AT&L). Predominantly used for primary underground distribution in conduit systems suitable for use in wet or dry locations, direct burial, underground duct, and where exposed to sunlight.