In October 2011, the Illinois General Assembly enacted the Energy Infrastructure Modernization Act (EIMA). One of the main beneficiaries was ComEd, the Chicago-based electric/gas utility. With the passage of the EIMA, ComEd embarked on a 10-year, $2.6 billion program to modernize its power system.


“The EIMA investments have provided an important boost to local manufacturers, suppliers and service providers with the expertise needed to support the electrical upgrade system,” ComEd said in a press release. Some of those service providers to benefit have been electrical contractors in Illinois, including INTREN (Union, Ill.), Aldridge Electric (Libertyville, Ill.) and Meade Electric (McCook, Ill.).


A recent ComEd infrastructure project involved the construction of a new 6-mile-long, 345-kilovolt transmission line in Chicago, from the Burnham substation on the city’s south side to the Taylor substation near the central business district.


At the time, according to studies conducted by ComEd’s transmission planning department and PJM Interconnection, the existing system was in danger of becoming overloaded.


ComEd partnered with a number of organizations, including design firms and contractors, to plan and build the project.


Because the line had to run through dense urban environments, the construction team decided to underground the line. While doing so provided safety, placing the line underground added to the complexity and cost of the project, in that the route consisted of a highly congested subsurface utility environment, and, of course, involved substantial amounts of tunneling, including going under the Chicago River, heavy rail tracks and an expressway.


Specifically, the project included the conversion of two existing single-circuit, high-pressure fluid-filled (HPFF) transmission lines into one double-legged, single-circuit HPFF transmission line.


The project also included new transmission equipment at four substations, including modification and installation of GIS and AIS 345-kV terminations; protection and control modifications for existing circuits; and installation of series conductors, circuit breakers and buses to accommodate the new lines.


The price tag for the project was $148 million. The new line went live in March 2014, and the result is a new transmission line designed to meet the expected load demands in the future as well as improve system reliability during high-load conditions.