Up Close & Personal With Arc-Flash

400A FuseCan an arc-flash occur at 240V? The answer is yes, it can!

More than two (2) decades ago, I was an Electrical Maintenance Supervisor then in a ceramic manufacturing company. Electric kilns were used to fire ceramic tiles. The electric kilns are rated 1,200kW at 240V, 3 phase. The kilns got their own dedicated substations. The heaters for the kilns were divided into separate circuits each of which were protected by 400A fuses.

Due to the critically of the product, shutdown of the kiln to replace a busted fuse or heating element is not practical. This process need to be done live.

Electricians are trained to this. They are competent to do the job and have been doing it for years. This however, made them over confident taking some short-cuts sometimes. More so, they always say, it is just 240V, it will not electrocute us. This was during the time that arc-flash issues were still taken for granted unlike electrocution.

In one of the graveyard shift, I was awaken by a knock on the door that one of the electricians got a burnt on the face due when replacing a 400A fuse.

The electrician’s face seems like burnt by pouring a hot oil. His eye brows and lashes were all gone, it was fortunate that his eyes were not damaged. He was able to report back to work in just 4 weeks.

Investigation have indicated that he was replacing a 400A fuse without using the proper tool. He just used his electrician plier and when he tried to pushed through the fused holder, his plier slipped to the adjacent phase which created a short-circuit and then an arc-flash. The fuse holders involved in the accident were totally welded.

Up close and personal experience with arc-flash. It happened on a 240V system. So for all those just say, it’s just 240V , it will not kill me. Be careful with arc-flash, it may be too late before you realize you are a victim.