Central Maine Power Company began work this week on a new electric transmission line between Portland and Westbrook. The $3 million project will replace an existing 3 Â½-mile line between substations near Morrill’s Corner in Portland and near Prides Corner in Westbrook. The work is part of CMP’s plan to spend nearly $400 million in 2013 to expand and modernize its system. CMP’s John Carroll says some of the equipment being replaced dates back to the 1920s. He says the new line will ensure continued reliability. The new line will be put up in the existing corridor, using slightly taller wood poles and higher capacity conductors. The line will continue to operate at 34,500 volts, but it’s designed to operate at higher voltage if more capacity is needed later.