Recording and analyzing the July 2 cascading outage [Western USA power system]

On July 2, 1996, a short circuit on a 345-kV line in Wyoming, USA, started a chain of events leading to a breakup of the Western North American power system. Five islands formed with controlled and uncontrolled load shedding, uncontrolled generation tripping, and with a blackout in Southern Idaho. The Western power system is operated by power companies belonging to the Western Systems Coordinating Council, which had a peak 1996 summer load of around 118,000 MW. July 2 was the third and, until the August 10 large-scale power failure, the most disruptive of a series of Western system breakups. The first was caused by the January 17, 1994, Northridge California earthquake. The second breakup occurred in the early morning hours of December 14, 1994, and, like July 2, originated in Southern Idaho and Wyoming. Modern computer and communication technologies greatly facilitated dissemination of information, analysis, report writing and event simulation for the July 2 cascading outage. This article analyzes the breakup, relying heavily on recordings from portable power system monitors which are installed at key locations and serve as primary components of a wide-area measurement system project.