DA Proves its Mettle: Automation Averts Extended Outage Following a Transmission Line Incident

Naperville, Illinois, is located 30 miles west of Chicago, and is perennially listed among the US’s most desirable cities. The city runs a progressive municipal electric and water utility with over 90% of electric customers fed from underground facilities. In 2006, Naperville’s population was 142,000, with 56,300 electric meters and a peak demand of 388 MW.

Following a successful Distribution Automation (DA) trial in 1997, Naperville has been systematically automating its transmission and distribution systems to improve service reliability and increase customer satisfaction. To date, over 60% of distribution feeders are automated with S&C’s IntelliTEAM® Automatic Reconfiguration System using a mix of overhead and pad mounted switchgear. In addition, source-transfer schemes have been implemented at the transmission level through substation automation.

Last fall, Naperville’s automation system was put to the test: A vehicle collided with a transmission pole, locking out a vital link in the city’s 138-kV transmission grid. The accident resulted in a total outage at one major substation, and three adjacent substations experienced partial losses. Almost immediately, 13,626 customers – almost 25% of Naperville’s customer base – lost power.

Within seconds, the multi-layered automation systems went into action. In less than two minutes, 9,103 customers (67%) had their electrical service restored automatically. IntelliTEAM reconfigured the system to restore power to 5,848 (64%) of these customers, while the remaining 3,255 (36%) were re-energized by automatic transfer algorithms implemented at the substation level.

During the next 14 minutes another 4380 customers (32%) were manually restored by control room dispatchers using SCADA to operate substation bus ties and distribution assets. At this point, only 143 customers (1%) were still out of service, since they could not be restored automatically or re-energized remotely. Repair crews restored the last customers manually 81 minutes after the accident. DA minimized even this outage by allowing repair crews to be immediately dispatched to where they would be most effective. DA averted the need for crews to first patrol the lines before executing manual switching operations to re-route de-energized feeders to alternate sources of supply.

Naperville’s investments in automation essentially averted a major catastrophe, with only 1% of potentially affected customers experiencing an outage longer than one hour. How can automation improve reliability on your electric system?

Learn more by contacting your local S&C sales office. Additional information on S&C’s automation products and services is also available on S&C’s website.