Chicago, IL – An electrical arc flash blew the panel off a transformer in downtown Chicago last week, injuring three Chicago Transit Authority maintenance workers and leaving hundreds in the area without power.
The arc flash relayed to a transformer, sparking a flash fire at an electrical substation near the intersection of North State and East Lake streets. Three workers were injured. Two were in critical condition with serious burns, and a third worker was also taken to the hospital but in good condition.
Chicago Fire Department spokesperson Larry Langford said the fire took place at a Chicago Transit Authority substation powered by ComEd. ComEd reported that the accident caused an issue with a circuit breaker, which left approximately 500 customers in the area without power.
An Arc Flash is an electrical explosion caused by 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, which often result in injury to workers and destruction of electrical equipment.
In an arc flash, temperatures may exceed 35,000° F (for reference, the surface of the sun is estimated to be 9000° F). This discharge of extremely high temperature causes rapid heating of surrounding air and extreme pressures, creating an arc blast. The arc flash and blast usually vaporize all solid copper conductors which expand up to 67,000 times their original volume when vaporized. The arc flash and blast produce fire, intense light, pressure waves and flying shrapnel.
A variety of things can trigger an Arc Flash, but most are preventable and can be traced back 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/or a lack of electrical safety training are some of the failures that can lead to a devastating arc flash or arc blast.
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. Proper safety and protection measures must be taken to limit the damage from an arc flash which include conducting an arc flash study, short circuit study, and NFPA 70E electrical safety training.
Contact a member of the Martin Technical Electrical Safety & Training staff today to learn how to protect your workers and your business from the risks of Arc Flash.
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