Case Studies - Electrical

A load circuit interrupter (LCI) like this one was installed in an industrial facility, powering a transformer at 4160 volts. The transformer failed and needed to be replaced. The electrician turned off power to the transformer by opening the LCI and locking the handle into the open position. Unfortunately, due to a design defect, part of the switch contacts remained engaged, so that one of the leads remained energized at over 2000 volts. While replacing the transformer, the electrician contacted the energized lead and was electrocuted.

Aluminum wiring has been known since the 70s to lead to connectivity problems, overheating, and even fires. This photo illustrates the phenomenon, where the aluminum wire was screwed to an electrical outlet, but over time, the wire became loose. The loose connection resulted in extreme heating at the receptacle. Fortunately for the homeowner, the outlet just stopped working before a fire could happen. Other aluminum wiring failures have had much more catastrophic results.

An unfortunately curious squirrel was exploring the energized conductors in this substation that served a small town in the northern midwestern US. When his body spanned an electrical insulator, it initiated an electrical arc. If the substation protection had been working properly, a circuit breaker would have been opened and the only damage sustained would have been to the squirrel. Maintenance personnel, however, had disabled the automatic protection while doing maintenance, and forgot to re-enable it. The error resulted in hundreds of thousands of dollars in damage, and left a town without power for hours.

An electrician was drilling a hole in a deenergized vertical bus bar that was part of this commercial switchboard. Unfortunately, he did not realize that the work he was doing posed a hazard but when a metal shaving from the drill fell onto the energized bus bars below, an arc flash occurred that melted a considerable amount of copper and destroyed the switchboard.

The crack in this electrical bushing, which was part of the 13.8 kV power distribution system for a large resort hotel, was not observed by those assembling the system, and remained undetected until a major rain storm filled the manhole with water and bridged the path to ground with water, allowing a system fault that spread to damage other equipment in the same manhole. The improper procedures of the maintenance personnel caused additional damage, and the hotel was out of service for 3 days while repairs were made. Unfortunately, the hotel was at maximum occupancy, so the business interruption loss cost the hotel millions.

When an electrical lineman was working on these 13.8 kV connections in a substation, he thought the cubicle was deenergized, like the others were in the row of cubicles. However, a less common configuration was present, and no signage was present to warn him of the irregularity (as required by code). Consequently, an arc flash occurred which ultimately killed the lineman.

This bundle of wires forms an electrical connection for a large number of lights in the top half of a tanning bed. Maintenance personnel did not fully insert the connector when they completed their work on the bed, and the connection severely overheated and generated a very large quantity of smoke. While the failure did not result in a full-fledged fire, the smoke damage was extensive throughout the facility and led to considerable business interruption while cleanup and repairs were being made.

This indoor substation was in poor repair and severely outdated when maintenance personnel entered it to cleanup debris from the room. They believed the entire substation to be deenergized, and no warnings or signage were present to advise them that the leads into the facility and the blades on the disconnect associated with the incoming power were still energized. Consequently, one of the maintenance workers accidently initiated an arc flash and was killed.