What feature distinguishes primary lines in electrical distribution?

The distinguishing feature of primary lines in electrical distribution is the higher voltage they carry. Primary lines are responsible for transporting electricity from substations to distribution transformers, where the voltage is then reduced for safe delivery to residential and commercial consumers. These lines typically operate at voltages ranging from about 4 kV to 35 kV or higher, which is significantly more than what is typically found in secondary distribution lines that service end users.

This characteristic of higher voltage is crucial for efficient long-distance electricity transmission, as it reduces energy losses that occur as heat in the conductors. Higher voltages allow for a lower current to deliver the same amount of power, which is vital in minimizing resistance losses in the lines over long distances. In contrast, options such as underground installations, direct connections to residential consumers, or specific insulation types may be relevant in certain contexts but do not specifically categorize primary lines as effectively as the aspect of voltage does.