The culprit for a dark campus last Tuesday afternoon was a rotted tree north of the Applied Sciences Complex -- and unfortunately along a major electrical line owned by the city of Ames. The tree's topple shortly before 3 p.m. shut down electrical power on two transmission lines to Ames, impacting not only the city and the Iowa State campus, but their power plants as well.
"It all happened in seconds, so there was no way to prepare for it," said ISU utilities director Jeff Witt. "The [power plant] equipment shuts down automatically when systems fail to prevent damage or injury.
"The longer we're down, the harder it is to come back," he added.
With the regional transmission system destabilized by the shutdown, about 30 minutes passed before Iowa State received the electrical power needed to restart its power plant. The first task was to make and pump clean water back into the boilers, and at 8:30 p.m., the first generator was turned on. By 9:30 p.m., it was generating power, and by 10:30 p.m., all campus buildings had electricity.
"[Restarting the plant] is a very methodical process," Witt explained. "Our staff knows what they have to do, but we have to be safe about it and we have to be careful not to damage the equipment."
Generating, purchasing electricity
However, Witt said that immediately following the outage, Iowa State also was communicating with city and MidAmerican officials to try to purchase available electricity. The university received approval from MidAmerican a few minutes after 5 p.m. to use more power than what was needed to restart the power plant. It was enough to restore power to about eight buildings on campus.
Iowa State typically purchases part of its electrical needs every day, so this was not unusual, Witt said. In fact, at the time of the outage, the university was buying about 40 percent of what it was using.
Prioritizing buildings for restored service considers a building's activities, especially research activities, and equipment, especially items such as freezers, Witt said.
"We make the best choices we can based on our knowledge of the buildings and the amount of power available," he said. "It's not a perfect process and most people understand that."
With the power plant's cogeneration capabilities, it was producing steam (for hot water and other building needs) by 10 p.m. Plant operators restarted the chilled water system (for air conditioning) around midnight, and by 4:30 a.m. Wednesday, Witt said, that system had returned to normal levels.
Elsewhere in Ames
The city owns two gas turbines for emergency situations and they were used to help make up the difference for city customers. Power was restored to most of Ames in less than an hour. At the time of the outage, the city was buying about 50 percent of its electrical power. Witt said the city's primary generator came back online at midnight.
University and city staff still are reconstructing what happened last week, with an eye on prevention in the future.
"This could happen again, so we want to be as prepared as we can be," Witt said. Shorter outages typically have shorter recovery periods, he noted.
The last time campus was without power for this long was in the 1970s, when a fire at the power plant shut down the plant and the campus grid.