Electric power transmission is the bulk movement of electrical energy from a generating site, such as a power plant, to an electrical substation. The interconnected lines which facilitate this movement are known as a transmission network. This is distinct from the local wiring between high-voltage substations and customers, which is typically referred to as electric power distribution. The combined transmission and distribution network is known as the “power grid” in North America, or just “the grid”. In the United Kingdom, India, Malaysia and New Zealand, the network is known as the “National Grid”.

Most transmission lines are high-voltage three-phase alternating current (AC), although single phase AC is sometimes used in railway electrification systems. High-voltage direct-current (HVDC) technology is used for greater efficiency over very long distances (typically hundreds of miles). HVDC technology is also used in submarine power cables (typically longer than 30 miles (50 km)), and in the interchange of power between grids that are not mutually synchronized. HVDC links are used to stabilize large power distribution networks where sudden new loads, or blackouts, in one part of a network can result in synchronization problems and cascading failures.

Transmission towers and poles are among an electric utility’s largest and most important commercial assets. Unfortunately, as the need to generate profits and shareholder dividends has intensified, regular investment in tower and pole maintenance has often been reduced or eliminated to cut costs. Ironically, such cost-saving measures have the potential to double or triple long-term maintenance costs while increasing the risk for power outages and public safety problems.

Transmission lines
Carry electricity across the state
Transport bulk electricity at high voltages ranging from 60 kV-500 kV
Are usually supported on tall metal towers, but sometimes on wooden poles
Have different vegetation standards than distribution lines due to the high voltages they carry
Are managed using the utility industry’s best-management practice of Wire Zone Border Zone
Require only low-growing vegetation underneath—typically nothing taller than 10 feet at maturity
Our goal is to achieve a sustainable landscape that supports native plants and natural habitats. Trees near these lines can’t be managed by pruning and often must be removed.