Maine Power

About the Program

Regional Electric System

How Does the Electric System Work?

Maine's electric grid consists of high-voltage transmission lines and low-voltage distribution lines that transport electricity from power generation plants to areas that need electricity throughout the state.

New England's Electric System

Maine's grid connects with the electric systems in Eastern Canada and the rest of New England, allowing power to be imported and exported as needed. This connection allows local electricity providers like CMP to partner with the other utilities in New England to bring strength and reliability to Maine's electric system.

Many of the electricity providers in New England, including CMP, are members of the Independent System Operator for New England (ISO-NE), which is a Non-Profit Regional Transmission Organization composed of electric utilities serving Maine, New Hampshire, Vermont, Massachusetts, Rhode Island and Connecticut.

ISO-NE and its members operate and manage New England's bulk electric power system and are responsible for the reliability of the region's electricity supply, including meeting reliability standards.

Regional benefit upgrades, which include reliability and economic upgrades that benefit the entire region, are paid for with a cost-sharing program by the customers of the participating electric transmission utilities. Electricity customers in Maine pay 8% of the costs for regional benefit upgrades, including the Maine Power Reliability Program, while customers in the rest of New England pay the remaining 92%. This partnership makes large-scale upgrades affordable for all the states in New England, which results in a stronger, more reliable electric grid.

Central Maine Power's Electric System

Central Maine Power's electric system includes transmission lines, substations, switching stations and distribution circuits that deliver electricity from power plants to the businesses and residents of central and southern Maine.

The transmission system in CMP's service territory operates at two voltage levels: 345,000 volts (345 kV) and115,000 volts (115 kV).

The 345 kV system is the backbone of the bulk power transmission system. The 345 kV transmission lines carry more power than any other lines in the entire system and are the connecting lines to Canada and the rest of New England.

The high voltage electricity carried by the 345 kV lines enter step-down substations to lower voltages for use in the transmission and distribution of electricity to commercial and residential areas. There are currently nine 345 kV substations in Maine:

The 115 kV transmission system is the workhorse of the transmission system. It is responsible for transmitting power from intermediate-sized generation facilities and 345 kV substations throughout the entire service territory.

CMP currently operates over 1,000 miles of 115 kV transmission lines, connecting over 60 substations where they are stepped down to 34.5 kV lines for distribution to smaller commercial and residential areas. There are also five 115 kV lines that connect CMP to neighboring utilities to the north (Bangor Hydro Electric Company) and south (Public Service Company of New Hampshire).

CMP annually invests many millions of dollars to maintain its bulk power transmission system and ensure a reliable and stable supply of electric power to its customers. These investments require careful planning to ensure adequate capacity to meet the increasing demand for electric power and to replace or upgrade major capital equipment as it becomes obsolete or reaches its expected lifespan in service.

Looking for more information on electric systems? The Edison Electric Institute website provides detailed information about electric systems and the energy industry.

What's HappeningIn Your Town

Looking for project information about the Maine Power Reliability Program in your community? Select your town or city from the drop-down list to find construction updates, permits, maps and more.

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