What are the two most common types of underground secondary cables?

The selection of three and four conductor aluminum cables as the most common types of underground secondary cables is based on their wide usage in electrical distribution systems. These types of cables are favored for several reasons.

Aluminum conductors are lightweight yet strong, making them easier to handle and install compared to heavier materials. They also provide a good balance between performance and cost. The use of three and four conductors allows for effective distribution of electrical power while accommodating multiple phases, which is critical in a three-phase system commonly found in commercial and industrial applications.

Furthermore, aluminum conductors, particularly when insulated properly, have good resistance to environmental factors, making them suitable for underground installations where moisture and soil conditions can affect performance.

Thus, the choice of three and four conductor aluminum cables reflects the industry's preference for materials and configurations that optimize efficiency, installation feasibility, and durability in underground wiring systems.