ComEd Works to Improve T&D System Reliability

By Steven M. Brown, Associate Editor

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Commonwealth Edison is making positive strides with its reliability improvement initiative, but there is still work to be done.

Given their druthers, Commonwealth Edison officials probably would have preferred that the summer of 1999 had never happened. Temperatures in Chicago were high that summer, and so were tempers as a number of power failures plagued ComEd’s distribution system leaving some customers without electricity for days.

One of the more serious outages-and consequently, one of the more well-documented in the press-occurred Aug. 12, 1999. A combination of two failing 69-kV cables, a transformer out for maintenance and failures on two other transformers prompted blackouts lasting up to 11 hours in Chicago’s downtown area. The outage affected about 2,300 customers and brought trading to a halt at the Chicago Board of Trade. At the time, the monetary loss to local businesses as a result of the outage was reported to be in the neighborhood of $100 million. Two weeks prior to that costly outage, another outage left some 60,000 customers without power for up to two days.

Customers were angry. City Council members were angry, and vocal about it. Mayor Richard Daley, a frequent critic of ComEd over the years, was downright livid-and even more vocal than the City Council. After the Aug. 12 power failure, Daley directed remarks toward the utility that likely reflected what many in the city were thinking: “We are sick and tired of them, and they had better change.”

ComEd’s response: It would change, and it would change for the better.

Evidence of that change came with the Sept. 15, 1999, launch of a two-year $1.5 billion reliability improvement plan. The plan identified five specific areas for improvement:

  • Maintenance;
  • Equipment protection/monitoring;
  • Load and capacity;
  • System optimization;
  • And organization and management.

Now past the halfway point of its two-year reliability plan, ComEd has announced that outages per customer in summer 2000 were down 19 percent from the same period in 1999. Additionally, the average duration of outages per customer in summer 2000 declined by 25 percent when compared with 1999 numbers. While ComEd chairman and chief executive officer John W. Rowe pointed out that cooler summer 2000 temperatures likely contributed to the decline in outage numbers and durations, he also said that the utility’s performance during severe storms showed that ComEd was on the right track.

“We have made substantial progress in every area this year,” Rowe said. “However, we still have a long way to go to improve reliability and regain the confidence of our customers. We are only at the halfway mark of our improvement plan, and we will continue to work at a fast pace.”

ComEd’s accomplishments during the first year of the two-year improvement plan include:

  • Completed 27,000 maintenance projects on overhead distribution lines.
  • Inspected more than 5,000 circuit miles of overhead transmission lines.
  • Installed new switches on overhead distribution lines to allow ComEd to route power around problem areas and reduce the number of customers affected by outages.
  • Completed work on substations that were loaded at more than 110 percent of capacity on the hottest summer days.
  • Replaced 45 members of ComEd management.
  • Stayed on schedule to complete upgrades at six Chicago substations identified as critical to system reliability.
  • Continued installation of an upgraded supervisory control and data acquisition (SCADA) system.

SCADA Improvements

Specific improvements under way include continued work on improving the SCADA system in ComEd substations. While ComEd has had some form of SCADA in place since the late 1970s and early 1980s, Bob Holmgren, ComEd’s system protection and control director, said that since about 1998, his department was given direction to put SCADA in basically every ComEd substation with a breaker. Holmgren said that project should be completed by the end of 2002.

Holmgren also said immediate SCADA improvements are being made at two of ComEd’s major substations as a response to last summer’s reliability problems. The improvements at those substations should be complete by summer 2001, Holmgren said.

Two fairly recent enhancements to ComEd’s SCADA system are starting to show real benefits, according to Holmgren and Ed Kram, ComEd’s reliability analysis and planning manager. A PI Historian and Maintenance Management Workstation (MMW) complement the functionality of the existing SCADA system to help ComEd analyze SCADA data and focus in on the most important pieces of that data. The historian serves to archive data pulled in by the SCADA system. The MMW works in conjunction with the historian and acts as a kind of intelligent data mining tool with the ability to accept user-definable algorithms.

“MMW allows us to turn raw data into usable information,” Kram said. “It gives us a way to focus on important data instead of looking through thousands of feeder and transformer points to try to find a needle in the haystack.”

Using the PI Historian in conjunction with the MMW, ComEd has started a system load management program, referred to internally as the “Hot List” program. The program involves using the MMW to mine data stored in the historian to build a day-ahead forecast tool that looks at every SCADA-enabled feeder and transformer. Based on the current day’s peak load, ComEd can forecast for the next day which parts of the system may exceed allowable and near-emergency ratings.

“Basically, it (the Hot List program) gives the operations and maintenance people time to address potential problems before it’s too late,” Kram said. “It works as a predictive tool. We can apply a forecast down to each feeder and each transformer, which gives us the ability to deal with things that were abnormally switched or load growth that was faster than our planners had anticipated. It gives us the ability to correct a lot of situations early, before we have an all-out firefight on our hands.”

Kram said that ComEd utilized this “Hot List” program throughout summer 2000 and had a great deal of success with it. Holmgren agreed that the added functionality has made SCADA a much more useful tool for ComEd in its battle against system overloads.

“We’re really just starting to find out what we can do with the historical data because it’s never really been available to us before,” Holmgren said. “In the past, if you wanted to look at SCADA data you had to play back a one- or two-day tape of everything. This is really a step forward.”

Automated Switching

Another area of recent focus for ComEd has been in the application of automated intelligent switching to its sub-transmission and distribution lines. In 1997, ComEd began installing automatic line reconfiguration switches (ALRS) on some of its 34-kV lines, Kram said. Since 1998, the utility has been engaged in a three- to four-year program to automate all of its 34-Kv sub-transmission lines by installing ALRS. The complete installation will consist of roughly 600 switches installed on about 260 34-kV lines. By the end of this year, Kram expects about 60 percent of the 34-kV lines to be automated. ComEd is also engaged in a pilot program to try similar automation schemes on its 12- and 4-kV distribution lines.

“We don’t have plans to automate everything, but we are trying different schemes to see what works best for us,” Kram said.

The automated switches utilize peer-to-peer communications and fault directionality sensing to reroute power around faults on line sections. When the switches work as they are intended to, the number of customers affected by sustained power interruptions should be reduced.

While the switches are capable of intelligently rerouting power without operator intervention, they also tie back into the SCADA system via spread-spectrum radio. “Operators can look on our intranet to see the status of all the switches,” Kram said. “They can operate the switches remotely, or if it’s in automatic mode, the switch will just do its thing upon loss of voltage. It will react accordingly and reconfigure lines to the appropriate configuration.”

Kram pointed out that while no scoring system has been developed to quantify the results of the 34-kV lines already automated via ALRS, he has seen improvement in how the system operates.

Still Work to be Done

Holmgren and Kram both expressed satisfaction with the work that has been done to date to improve the reliability of ComEd’s T&D system. Both seem to believe that the events of summer 1999 will serve ultimately to strengthen operations at ComEd. Holmgren remarked that not only have capital programs-such as adding capacity and the installation of improved SCADA-been given a higher priority than they received in the past, but the corporate mindset at ComEd has undergone a change for the better as well.

“I think we’re a better operating company now, and we’ll be better in the future because of what happened in summer 1999,” he said. “We were already working on a lot of these reliability projects, but those events served to move us ahead a little more quickly.”

Kram said that being able to leverage SCADA information through the PI Historian and MMW should help ComEd avoid major events like those of summer 1999. With the ability to look more closely at relay operations and to look deeper into the substation, ComEd should be able to achieve a greater level of event avoidance, he said. Having the ability to gather and more intelligently analyze data will be the key to bolstering reliability.

“The real promise lies in getting that data and putting smarts behind it to make it serve your management and your people,” Kram said. “You don’t necessarily have to automate everything on the system, but you have to at least acquire data from the system and get it out where your people can use it.

“We’re doing that, and we saw positive results from it this summer.”

But while ComEd made it through summer 2000 relatively unscathed and reached an encouraging halfway point of its reliability improvement program, the utility’s T&D system strength was again called into question in early October. On Oct. 8, a circuit breaker explosion at ComEd’s Jefferson substation left parts of downtown Chicago without power for about six hours. The outage affected approximately 12,000 ComEd customers.

ComEd spokespeople said that the Oct. 8 outage was “totally unrelated” to the outages of 1999, and the utility has vowed to re-examine 30 circuit breakers similar to the one that failed. While the Oct. 8 circuit breaker explosion and resultant power outage may well have been a freak occurrence, this latest outage points to the fact that an often-neglected, overworked T&D infrastructure cannot be completely cured in haste. ComEd’s improvement plan provides much-needed medicine, but there is still work to be done before the utility’s infrastructure regains long-term reliability and customer confidence is restored.


  • 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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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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