There is much more to putting transmission lines underground than just burying them. Overhead and underground lines make use of very different technologies.

Underground lines typically cost more, but can more easily be routed through highly developed urban areas, ideally within tunnels beneath city streets. They also offer aesthetic or other environmental advantages to overhead transmission lines, especially to those who live along the planned overhead transmission route. But a disadvantage to underground installations is that their construction requirements, unlike an overhead line, necessitate access to every foot of the route, increasing construction impacts on roadways, traffic, wetlands, and wildlife habitats. Also, some types of transmission cables are contained in pipes filled with a mineral oil under pressure that can leak if the pipe is ruptured. Unlike an overhead system, these pressurized oil cable systems often require new substations with equipment to pressurize the oil, contain any spills, and manage the electricity flows.

Electric power system engineers recognize that when it comes to working with higher transmission voltages, underground lines have important differences from overhead lines. For instance, because the heat created by resistive losses moves more slowly away from underground cables, underground transmission lines commonly require more or bigger conductors to deliver the same amount of power. Because of the thick insulation around underground cables, installed cable lengths are shorter and many more splices (made in large underground vaults) are necessary. While a failure may happen less frequently on an underground line, when it does its location and repair typically take a couple of weeks to complete, during which time the remaining transmission system must operate reliably without the cable. Also, the substations at the ends of an underground cable will often need to have large shunt reactors installed to compensate for the high charging currents associated with these cables.

Right-of-Way Acquisition

Understanding Rights-of-Way and Easements

To provide electrical service to its customers, Northeast Utilities’ electric companies, The Connecticut Light and Power Company and Western Massachusetts Electric Company (referred to collectively as the “company”) own and maintain transmission lines throughout Connecticut and western Massachusetts. These transmission lines are primarily located on land that is owned by third parties (homeowners and businesses) over which the company has acquired a property interest that is referred to as a “right-of-way” or “easement.”

Most of the company’s transmission lines are located on rights-of-way that were acquired decades ago. At the time these easements were acquired, the company compensated the owner of the land crossed by the right-of-way and acquired permanent easement rights, which remain intact even upon a sale of the land. Therefore, anyone who purchases land that is crossed by a company right-of-way acquires that land subject to the company’s permanent easement rights. Potential land owners have advance notice of the company’s owned rights-of-way because easement documents are filed on the appropriate land records for each town, and can be identified as part of a routine title search.

The Company’s Rights within the Right-of-Way

The easement documents recorded on the land records outline certain of the company’s rights within the right-of-way, which usually includes, among other things, the ability to trim or remove any trees. In addition to those rights specified in the easement document, the company has all rights necessary to implement those rights. For example, a typical company easement states that the company has the right to construct transmission facilities. Since the construction of those facilities requires the use of equipment, the company can operate construction equipment within its right-of-way, even though this activity is not specifically referenced in the easement document.

The Rights of Property Owners within the Right-of-Way

As a general rule, the owner of a property crossed by a right-of-way can still use the property for his/her own personal use as long as such usage does not interfere with the company’s use of its easement.

A property owner may plant grass in the right-of-way if he/she so chooses. However, a property owner cannot construct or place anything within the right-of-way that might interfere with the company’s facilities or with the company’s right and ability to pass freely over the right-of-way in the course of maintaining its existing lines or constructing new lines. For instance, a property owner could not construct a wall or fence that blocks passage along the right-of-way.

For More Information

To learn more, contact ROWinquiry@nu.com.