CTA to begin construction on new Red Line substation near Morse

CTA will begin construction this weekend of a new electrical substation just south of the Morse Red Line station. A brick structure as tall as a three-story building will rise on the narrow sliver of embankment on the east side of the tracks, abutting Glenwood Avenue at Farwell.

The first stage of construction is the driving of sheet piling alongside the northbound express track, so that the sloping embankment can be removed. That work will continue around the clock from early Friday to early Monday, according to a notice from Ald. Joe Moore (49th). Farwell will be closed from Wayne to Glenwood, and there may be temporary electrical outages as well.

The electrical substation will convert 12,600-volt alternating current from ComEd to the 600-volt direct current that flows to trains via the third rail. It will provide the power needed to keep trains running at peak hours under full-load conditions, such as when air conditioners are running.

Tall and narrow building

At 34 feet in height, the building will be a bit shorter than the Rogers Park three-flats across Glenwood. To accommodate the narrow site, it will be just 19 feet deep and 181 feet long, according to CTA spokesperson Catherine Hosinski. Download the architectural drawings.

The east elevation, facing Glenwood, will feature four tall arches and two shorter ones on the south section of the building, which will be only 19 feet tall. At track level, CTA riders will see six brick arches immediately east of the northbound express track. A large equipment entrance will be on the south face, where a new retaining wall will create a wider stretch of Glenwood.

Electrical details

The CTA would not disclose details of the electrical system “due to safety and security reasons.” But the drawings provided to Ald. Moore, combined with the basic information provided by the CTA, give an idea of the substation’s function and design.

A typical substation, the CTA said, includes two conversion systems to provide redundancy. In each case, the incoming power is routed through protective switchgear, a transformer that reduces the voltage, and then a rectifier that changes the alternating current to the direct current used by the CTA. (While most of the CTA fleet still runs on direct current, the new 5000 Series cars use alternating current. Those trains convert third-rail power from DC back to AC.)

Adjacent CTA substations, at Chicago Avenue in Evanston and Montrose in Uptown, are wider and shorter than this one will be. The tall, narrow configuration suggests that the electrical equipment will be arranged vertically on two floors, though the CTA would not confirm this.

The CTA said that the optimal distance between substations is approximately two miles, dependent on loads. The new substation will ensure that there is sufficient power available for the system in the future.

This story originally published at CTA Station Watch.


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  • I'm sure these will be thyristor conversion units & not the old motor generator sets that were originally used & may still be in use on some parts of the system.

  • And Patrick gets credit for noting that the cars convert DC back to AC. Most can't figure that out, and think, for instance, that somehow AC is conveyed on the third rail.

  • In reply to jack:

    I count myself among the people who were confused in thinking that once all of the cars had AC propulsion that the third rail would be converted to AC to save having to convert in the cars themselves. I was set straight a while back and upon further research found that there seem to be no AC third rail systems anywhere in the world. There are plenty of AC overhead systems, though.

  • In reply to eBob:

    So when they convert to all AC propulsion eventually, they'll still have to convert it twice? That seems like a waste, but not sure if there is another way if there are no AC third rail systems in existence.

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