Types of Power Lines

Power lines are a necessary part of life in most communities. Without power lines, there would be no electricity running to homes and businesses. It takes a lot of voltage running through those lines to power a community, but not all power lines are the same.

EHV Transmission Power Lines

• Power plants create electrical energy and move that power through extra high voltage (EHV) power lines. Many times the electrical energy travels long distances to reach its destination. EHV lines work like an interstate. Cars move along interstates to reach specific destinations, and extra high voltage energy moves along the EHV lines to reach specific destinations. EHV lines can run from 345 kilovolts to 765 kilovolts.

High-voltage Lines

• A substation directs electricity’s flow and changes the voltage to different levels. The substation decreases EHV voltage down to a high-voltage level. High-voltage lines move electrical power a shorter distance than EHV lines. These lines usually run around 138 kilovolts. A high-voltage line is similar to a four-lane road that has limited access. These power lines generally run to different areas of a city or county.

Distribution Lines

• A substation is also used to decrease voltage from 138 kilovolts (or a high-voltage line) to distribution levels. A distribution power line can run anywhere from 34.5 kilovolts to 7.2 kilovolts. Distribution lines can be compared to a two-lane road that connects the community. There are primary distribution lines (which are the main lines) that connect the larger parts of the community to a substation. Lateral distribution lines are the power lines that connect a neighborhood to electricity. Smaller distribution lines connect the individual residence to electricity.

Power Line Service

• Service can be provided underground or overhead. Underground service buries the power lines in a conduit, while overhead service provides support by use of poles. The most common reason underground electrical service is used is due to the overall appearance. Underground service typically undergoes fewer outages due to wind or lightning. Trees do not have to be trimmed because of power lines when the service is underground. Overhead electric service tends to be more cost-effective in terms of equipment and labor. Visual inspection of an underground fault on a power line is not possible, so specialized equipment must be purchased. Repairs on overhead service do not take as much time and are not as costly as underground service. Trees should not be planted near underground service, as the roots interfere with the operation of the power lines. Underground service uses transformers and switches that are installed on concrete pads. These need easements to provide enough clearance to maintain the equipment.