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The1996 Western North America blackouts were two widespreadpower outages that occurred acrossWestern Canada, theWestern United States, andNorthwest Mexico on July 2 and August 10, 1996. They were separated by six weeks and were believed to have been similarly caused by excessive demand during a hot summer.
Though they affected millions, the blackouts were largely an inconvenience rather than emergencies. On both occasions, airport operations continued, and power was restored within minutes or hours.
The blackouts raised concerns about the then-recent debates regarding deregulating electricity utilities.[1][2]: 50
On July 2, 1996,California and thecoastal Pacific Northwest imported extensivehydropower from theinland Pacific Northwest andCanada and thermal power from the easternRockies. North American grid managers regularlysimulate possible grid conditions toplan for contingencies, but had not investigated these particular long-range power flows.[2]: 31–32 Although managers did not realize it, the system operated close to adynamical singularity, and grid response to a smallreactive power deficiency in the Idaho area would involve very large and very rapid voltage changes all across the system.[3] A briefgrounding and misconfigured relay then effected the deficiency, andprotective devices separated large segments of the grid faster than operators could react.[2][3] The power failure affected parts ofAlberta andBritish Columbia in Canada, western Mexico, as well as Idaho, Montana, Utah, New Mexico, California, and Arizona, affecting more than two million people.[4]Most power was restored in an hour or two.
The following day, transmission lines disconnected in a similar manner, but precautionary limits imposed on the transmission system following the July 2 blackout prevented cascading failure.[2]: 31 [5]
PresidentBill Clinton directed theUnited States Department of Energy to investigate the reasons for the widespread power outage and whether it could have been prevented.[citation needed]
On August 10, 1996, the western electric grid experienced another massive blackout.[6]Bonneville Power Administration had failed toadequately clear their right-of-way, and multiple linesarced to nearbyvegetation.[2]: 47 At 2:06 p.m., the Big Eddy-Ostrander line flashed and grounded to a tree. At 2:52 p.m., the John Day–Marion line (also owned by BPA) flashed to a tree. Due to a circuit breaker being out of service, this also took the Marion–Lane line out of operation. At 3:42 p.m., the Keeler–Allston line arced and grounded to a tree nearHillsboro, Oregon, west ofPortland. It was the fourth power line in Oregon to fail in less than two hours. Five minutes later, at 3:47 p.m., the 230 kV Ross–Lexington line (also owned by Bonneville Power Administration) flashed and grounded to a tree nearVancouver, Washington, across theColumbia River from the Portland/Hillsboro area. This started a small fire. One minute later, at 3:48 p.m., the 13 turbines atMcNary Dam, on the Columbia about 190 miles upstream from Portland, tripped off line.[7]
Without thereactive power supplied by the McNary dam, the grid was susceptible to a large voltage-frequency oscillation.[3] To the control circuits on thePacific Intertie, thetroughs of thisstanding wave appeared as though the Pacific Northwest had inadequate power generation, and the Intertie shut down, separating customers in thePacific Southwest from power supplies to the north.[2][5]
This power outage affected customers in seven western US states, two Canadian provinces, andBaja California, Mexico. Approximately 7.5 million customers lost power for periods ranging from several minutes to six hours. The outage stretched from Canada to New Mexico and knocked out power to 4 million customers amid a triple-digit heat wave.[citation needed]