全城停电

Ames的人越来越多，公寓楼和豪斯也越盖越远，可发电厂的容量一直没变，夏天家家都用空调时就会出问题，负载太大了。去年七月份最热最闷的时候是家家都装primer timer(避免每家都同时运行空凋)，外加把学校的几个电老虎（cluster computer等设备）关闭掉。

今年还没进入七月份呢，问题就出来了。昨天下午正在办公室用电脑，刷的一下电脑黑屏了，日光灯也灭了，出去看走廊上应急灯倒是开了。还有人被关在了电梯里，大家花了老大劲才把那人给弄出来。路上交通灯也没有，不过大家倒是很有次序的按stop sign开车。警察也很快出来指挥交通了。大概过了一个多钟头，大部分地方就又来电了。

Posted on city of Ames website http://www.cityofames.org/:

Tree Limb Causes Citywide Electric Outage

Posted Date: 6/19/2012 3:30 PM

AMES, Iowa – An electric outage reported just before 3 p.m. today affected the entire city for approximately 10 minutes before power was restored to parts of the city. The cause of the outage was large tree limb that touched two phases of the 161 kV transmission line between the Stange Road substation and the Boone Junction substation (near Boone, Iowa).

The majority of city was restored by 4 p.m. By 4:15 p.m., the outage was isolated to two feeder lines from the Dayton Avenue substation. The outage originally included the Ames Power Plant and the Iowa State University Power Plant.

Assistant Electric Director Brian Trower said the tree limb tripped the transmission line so no power was flowing. “When that tripped, our local generation at the Ames Power Plant did not match the load we were trying to serve, which creates a situation called under frequency,” Trower said. Because there was more demand for electricity than the Ames Power Plant could produce, “the entire city tripped.”

Once the tree limb was cleared from the transmission line, the line was re-energized and electricity was restored throughout the city. “Basically, we started over to re-establish the system,” Trower said.

An outage of this size is unusual, but the situation reinforces the importance of Ames Electric Services’ pursuit of another electric tie-in to the south, Trower said. “This is a compelling example of why additional transmission is needed.”