Arc Flash at CO Hydroelectric Station Sends 5 to Hospital

Georgetown, CO – Five employees were taken to the hospital following an arc flash at Xcel Energy’s Cabin Creek Hydroelectric generating station last month. Their injuries were not life threatening, and all were treated and released the same day. Xcel Energy self-reported that about eight employees and a few contractors were on-site at the time, and all were evacuated. The incident was initially reported as a fire, but upon further investigation turned out to be an arc flash.

The arc flash at Xcel Energy’s Cabin Creek Hydroelectric generating station occurred within Unit B, inside a self-contained concrete block. Because that particular station provides power only during periods of high demand, there were power outages or interruption of service to customers. The Cabin Creek hydroelectric plant was the site of an infamously fatal flash hydroelectric arc flashfire in 2007 which resulted in the death of 5 contract workers within a permit required confined space. Read more from original source.

When an arc flash happens, it does so without warning and is lightning quick. The result of this violent event is usually destruction of the equipment involved, fire, and severe injury or death to any nearby people. An Arc Flash is an electrical explosion due to a fault condition or short circuit when either a phase to ground or phase to phase conductor is connected and current flows through the air. Arc flashes cause electrical equipment to explode, resulting in injury or death to workers and destruction of electrical equipment. In an Arc Flash, temperatures may exceed 35,000°F (for perspective, the surface of the sun is estimated to be near 9000°F). These extreme temperatures cause rapid heating of surrounding air and extreme pressures, resulting in an arc blast. The arc flash/blast often vaporizes all solid copper conductors in a piece of equipment as the copper expands up to 67,000 times its original volume. The arc flash/blast produces fire, intense light, pressure waves and produces flying shrapnel. There are a variety of reasons why an Arc Flash can occur, but  most are preventable and ultimately attributable to human error. Many arc flashes occur when maintenance workers are manipulating live equipment for testing or repair and accidentally cause a fault or short circuit. Improper tools, improper electrical equipment, corrosion of equipment, improper work techniques and lack of electrical safety training are just some of the events that can lead to a devastating arc flash or arc blast.

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Electrical Arc Shuts Down Washington DC Transit Network

WASHINGTON (AP) — The transit network in the nation’s capital remained hobbled Tuesday morning following an electrical malfunction that filled a busy subway station with smoke, killing one woman and sending dozens of people to hospitals.

The accident occurred around 3:30 p.m. Monday on aelectrical arc Virginia-bound yellow line train that had just left the L’Enfant Plaza station in downtown Washington, one of the system’s busiest stations.

The National Transportation Safety Board was investigating the accident, which happened at the beginning of the Monday afternoon rush hour and led to the first fatality on Washington’s Metro system since a 2009 crash that killed eight passengers and a train operator.

NTSB investigator Michael Flanigon told reporters late Monday night that an electrical “arcing” involving the high-voltage third rail led a train to stop in a tunnel and quickly filled the tunnel with smoke. An arcing occurs when electricity from the third rail comes into contact with another substance that conducts electricity, such as water.

“The third rail is high-voltage direct current, and if that current starts arcing to another conductor that it is not designed to connect with, you get a flash,” Flanigon said. “In certain cases, that arc can start sort of feeding on itself, and it actually generates gases that are more conductive.”

The yellow line remained shut down Tuesday morning, and the system’s orange, blue and silver lines were on a reduced schedule. Service on the green and red lines was normal.

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