May 4th had the makings of a typical day. I rode my bike to work in the morning, and got a call from a coworker about 10 minutes before arriving to my building. He wanted to move a piece of equipment in order to test it in another area of the lab. He wanted a hand when I got there. “No problem.” I said.
I arrived, changed out of my riding clothes, and walked to the other end of the lab. Young, my coworker, hadn’t arrived yet, so I went over and started to unplug the equipment. It was only a single connection, albeit a big one: one hundred and fifty amps, 3 phase, 480VAC. The type of plug for this power is necessarily big, about the length of your forearm with a cable about as thick. Because of the weight, the plug has a screw collar to secure it to the receptacle, which is another large device permanently hung on the wall by a licensed electrical contractor when the feed gets installed.
Due to legal liability electrical contractors typically do not complete the work after the receptacle. They will bring power to the building, and distribute it within the building to receptacles, but their work stops there. Apparently with custom made hardware and prototypes like I work with, they perceive too much risk that bad information from engineers or poorly designed equipment can lead to legal responsibility if they were to connect power and have something fail.
So one of the Apple technicians cut the wire, stripped the leads, and made the connections inside before attaching the connector housing and closing it up. Or so it seems… The team responsible for the equipment blames it on the electrical contractor, who they say wired the plug side before they made the final connections to the bus inside the equipment. The electrical contractor of course denies this. Either way, the job was done with negligence, and very poor workmanship.
Back to the unplugging. I walked into the test cell and made sure the equipment was off. I then unscrewed the collar, began to slide out the plug, and BANG! One of the phases dislodged from its precarious connection to the pin inside and shorted to the connector housing. A big arc, shock, flash and bang immediately erupted from the connector and onto my hand which was wrapped around the housing. Upstream, the disconnect tripped* due to the huge overcurrent. This probably a few 10s of miliseconds after the phase first began arcing and shorted to ground. This deenergized the circuit.
I was figuratively blown away and had to take a moment to realize what had happened. I was still standing and my heart and mind were racing. I looked down at my blackened hand and tried to take stock of my overall condition. I then walked out and found some coworkers who had started to make their way over after hearing the bang and correctly assumed arc flash. When what happened began to settle in, I sat down and tried to relax. I called our EHS coordinator to inform him of the incident and describe what happened. I was directed to urgent care and was taken for treatment by one of the coworkers.
My first stop was for an exam and an EKG. I was then sent to the ER for blood tests, more exams, and observation. Apparently if the immediate shock, burn, or heart issues don’t get you, kidney shutdown a few hours afterward can. All of this was very scary. I called Megan while at the urgent care and she came quickly to the ER once it was apparent where I was headed.
Luckily as of today it seems that all is well, and given the potential realm of outcomes I was very lucky. I ended up with a terrible scare but only minor physical impacts**.
Emotionally, on the day of the event, the closeness of it hadn’t hit me. After leaving the ER Megan and I stopped to get falafel for a late lunch, just like we might on a normal weekend. It wasn’t until a few days later, when I had been back to work and seen the damaged equipment that it did. My confidence around this equipment has been shaken and my faith in my coworkers attention to detail has been too. Its going to be difficult to get comfortable being in the lab again. Shortly afterward I decided to be more reserved with my involvement in HV systems and I told my close coworkers that I’m no longer going to be lending a hand in this area. They all had the same reaction, that my decision was totally understandable, but I imagine it will cause some difficultly at times in the future.
It’s still on my mind daily when at work, considering I’m surrounded by high power equipment in the lab, but outside of work things seem back to normal. Megan and I both got a serious reminder about how easily things can change, but luckily this time, they didn’t have to. Though even now, as I’m typing this, my stomach is churning a bit at the thought of how a small change in circumstance could have led to a much worse outcome.
*In the post incident investigation, it was found that the disconnect failed as well. The evidence of the huge current interrupted was displayed by a black coating of carbon inside and out of the enclosure. **My hand was sore for a few days, the burn was first degree, and my second EKG a week later confirmed that nothing of major concern was going on with my cardiac system. — ## Media URLs recovered – https://www.cosgrove.blog/wp-content/uploads/2018/05/IMG_8433-scaled.jpg _(present on live cosgrove.blog)_ – https://www.cosgrove.blog/wp-content/uploads/2018/05/IMG_8435-scaled.jpg _(present on live cosgrove.blog)_ – https://www.cosgrove.blog/wp-content/uploads/2018/05/IMG_8436-scaled.jpg _(present on live cosgrove.blog)_ – https://www.cosgrove.blog/wp-content/uploads/2018/05/IMG_8437-scaled.jpg _(present on live cosgrove.blog)_ ## Recovery notes Full post (~946 words). Live was truncated mid-story after electrical incident intro. Lost to the sands of time…
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