Practical Law Glossary Item 0-517-7946 (Approx. 3 pages)
Glossary
Transmission
The bulk transfer of electrical energy over long distances from generating stations to electrical substations through high voltage (at least 115 kilovolts (kV)) transmission lines. By contrast, the transport of electricity from substations to customers through low voltage lines (less than 34.5 kV) is known as electricity distribution. Lines that carry power at voltages between 34.5 kV and 115 kV may be classified as transmission or distribution lines depending on whether they move bulk power from power plants to different utilities or within a single utility to retail consumers. Electricity is generated at lower voltages and stepped up through transformers to match the voltage of the transmission lines before it enters the transmission network. This is because transmission lines can carry more power and will experience lower line losses. Transmission lines are generally subject to federal regulation and distribution lines are regulated under state law.
Although transmission is a key component of the electricity delivery system, it has been identified by the US Department of Energy, politicians, and energy industry experts as one of the key barriers to electricity generation in the US. This is because:
There are not enough transmission lines to deliver the energy being produced to where it is most needed. There is a maximum amount of electricity that a transmission line can carry and new lines are often required to meet the increased energy demand.
It is expensive and time consuming to construct transmission lines. These lines often need to travel hundreds of miles across different counties and states. Permitting, siting, and land acquisition rights can have high costs.