ComEd Finds Unique Way to Boost Power into Substations

ComEd Finds Unique Way to Boost Power into Substations

By Pam Boschee, Associate Editor, Electric Light & Power magazine

As the mercury rises in the thermometer, carrying with it the playful, light-hearted spirits of those struck by spring fever, electric utility planners recognize its pragmatic significance–here comes the cooling season.

Last summer sizzled–in temperature and market prices–with several major utilities facing unprecedented emergency situations. FERC, NERC, Congress and industry experts all tried to make sense out of a tangled web of accusations, domino effects of power contract defaults, transmission procedural snafus, etc. No positive identification of a single perpetrator is universally accepted, and blame remains contested.

Finding itself in the Midwest hotbed of demand last summer, Commonwealth Edison (ComEd) needed additional generating capacity with quick availability. Joe Svachula, ComEd`s transmission and distribution department project manager, said, “We had a think tank at ComEd to get new generation out there.” Out of that process came a unique idea to use a temporary power system at the Elmhurst substation.

The magnitude of the newly added generating capacity is notable–a total of 100 MW. Aggreko and Caterpillar diesel generators were installed within about a month and boosted the power moving into the substation bus. Svachula said quick installation was a key factor, precluding other options such as barges, locomotives, or ComEd`s building of its own new power plant.

Twenty 1-MW Aggreko GreenPower units and 50 1.6-MW Caterpillar utility grade power module units (model XQ1750) were used “about 12 days,” said Svachula. “They served in more of a peaking role on the hottest days.”

Svachula said the Illinois Environmental Protection Agency approved the use of these generators, which were reliable and resulted in no power quality problems. The changing of relay settings soon after installation prevented further tripping out after a single occurrence. The generators were installed with separate trips, which also allowed for compensation of output between generators. He said regulation of voltage was easily achieved via load-tap-changing and regulators.

Breck Breaux, Aggreko`s technical director of power, said, “Ambient conditions determined the need for additional power, and ComEd essentially bought an insurance policy. It just couldn`t afford for power to go out (brownout).” He added that in the United States, the power supply problem is not always due to an overall lack of capacity, but lies instead in “getting it to the right place when it`s needed.”

Caterpillar`s Mike Wuebben, Cat rental power manager, said other utility substations in west Texas and in the Southeast last summer identified this same need and installed Cat units. He pointed to utilities` continued concerns about deregulation, defaulted power agreements and Y2K readiness as catalysts spurring consideration of substation installations. “The Y2K issue tipped them off the fence. They thought, `I better get more serious about this.`” This resulted in “a growing trend in terms of inquiries, but a little hesitancy in actually jumping into it.” Wuebben said, “Today`s trend is toward distributed generation, but aggregating at the substation runs counter to that.”

Looking ahead to this summer, ComEd plans to double the temporary installations to a total capacity of 213 MW at seven Chicago area sites (about 30 MW installed per site). Caterpillar units will be installed at 5 north side locations, and Aggreko units will be operating at the Calumet (south side) and Crawford (west side) generating stations. Extent of their use will again be dictated by “marginal costs with decisions based on the price of power,” said Svachula. n

Caterpillar Aggreko

Click here to enlarge image

Temporary power systems, such as this Caterpillar power module installation, provide generating capacity for ComEd customers` summer cooling demands.

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The Clarion Energy Content Team is made up of editors from various publications, including POWERGRID International, Power Engineering, Renewable Energy World, Hydro Review, Smart Energy International, and Power Engineering International. Contact the content lead for this publication at

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