Even though it was sunny that day, Highland Light and Power director Dan Cook likes to refer to last August’s power outage as being caused by “the perfect storm.”
On Aug. 23, 2014, a “mechanical failure” in the main 138-kilovolt (kV) transmission line that feeds the city fell to the ground just east of St. Jacob, leaving the entire city without power for about nine hours.
In case of such a failure, the city has a backup plan. Coupling electricity produced from its own diesel generators with power available from as Ameren Illinois through a smaller transmission line, the city should have been able to keep the lights on.
The power plant in Highland houses nine diesel-powered generators, which the city owns. They can generate 18 and 20 megawatts of electricity, depending on the weather conditions. In periods of extreme temperatures, the engines are less efficient, but that is still enough to power the entire city on a balmy day.
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That is not the case, however on days when everyone is running their air conditioners. Such was the case during last year’s blackout, when the temperature recorded by News Leader weather statistician Jeff Menz was 92 degrees.
That’s where the backup from Ameren is supposed to come in. The power from Ameren comes from an agreement between the company and the Illinois Municipal Electric Agency (IMEA), a cooperative of municipality-owned power companies around the state, including Highland, that pool resources to buy electricity.
Ameren Illinois provides the city with backup through a 34.5 kV line that comes into the city from the east. But this is an “as-available” source.
“This means that, depending on the time of year and the energy needs of our own customers, we can provide electric service to the city if their electrical assets are not functioning,” Illinois Ameren spokesperson Brian Bretsch said. “The available capacity of this source is significantly less than Highland’s peak load.
“(But) during the outage in Highland last year, switching to use this backup source was delayed while we fed power to Alton to restore an outage that affected the Alton hospital,” Bretsch said.
“So, it was a combination of everything to make a perfect storm,” Cook said.
Bretsch said “as a courtesy” an Ameren supervisor, whose residence was impacted by the outage, also reached out to the city’s Light and Power Department to offer his support for Highland’s restoration efforts after the outage.
“When (Highland) determined it would need assistance to repair its equipment, our supervisor reached out to one of Ameren Illinois’ alliance contractors to help.
“Our electric supervisor should be commended for his efforts, particularly when you consider that he was recovering from knee surgery at the time of the outage,” he said.
Some positive things have come about as a result of the outage, according to Bretsch.
“The incident did enable us to exchange names and numbers of current electric-related contacts with the city,” he said.
When asked what does Ameren see as a long-term solution to the issue, Bretsch said it will be up to Highland officials to decide.
“We will support them as we can,” he said. “We did follow-up with IMEA, who followed up with Highland, to let them know about our support of their restoration efforts.”
Following the outage, the IMEA has worked closely with the city and Ameren, to look for short- and long-term solutions, said IMEA spokesperson Rodd Whelpley.
“Most of the short-term solutions have involved city-owned facilities,” Whelpley said.
Cook said the city will be making improvements shortly to its diesel generator plant controls.
“That should facilitate quicker response in the event of a future need for generator plant operation during a total power outage,” he said.
Cook believes the new controls, which are expected to cost around $335,000, will also help prevent future “black starts” at the Highland Power Plant.
A black start is the process of restoring an electric power station or a part of an electric grid to operation without relying on the external transmission network. Normally, the electric power used within the plant is provided from the station’s own generators.
“The new controls will improve reliability and in order to fire things up if the city loses power transport into Highland,” Cook said. “Right now, we have to wait for a sync signal from Ameren.”
The city has also extensively reviewed and strengthened its outage response capabilities with its utility personnel in the past year, according to Whelpley.
IMEA has also been working with Ameren’s planning engineers to monitor available backup capacity on the Ameren transmission system and look at possible system improvements or switching reconfigurations that could benefit Highland.
“These efforts should reduce the chance of future outages and limit any outage duration, although no procedures will totally eliminate the possibility of a future outage,” Whelpley said.
He said as to the longer-term solution, a second transmission interconnection with Ameren that can carry Highland’s full load is the most likely.
“This may be accomplished with construction of a second 138 kV line or by reinforcing Ameren’s existing lower voltage sub transmission system that currently is capable of providing some backup for Highland during periods of peak usage,” Whelpley said.
IMEA and the city have met with Ameren many times in the past year on these issues, Whelpley said.
IMEA is also working with Ameren on a project to exchange more real-time operating data collected by IMEA’s remote metering systems.
“This will further enhance the ability of our operating personnel to provide a more timely assessment of outage conditions and initiation of restoration activities,” Whelpley said.