Lightning – The Most Unpredictable Failure Mode

We were called to a customer’s site very early on a Saturday, around 5am. The previous night a group of thunderstorms had rolled through the area knocking out power. The customer was reporting that after the storm, several machines in the plant were not coming back on after the loss of power and they wanted us to diagnose which devices needed service to get them back up and running. These types of failures are common after a large storm, a lot of the time effecting units first in line to the mains power, such as supplies and switchgear. When we arrived at the plant, the first thing we noticed was that all of the lights were off. We found that strange considering the customer had told us just a little while before that power had been restored. We walked into the plant and – under the light of a couple of flash lights- we spoke to the maintenance manager we were there to meet and inquired as to the lack of power. He told us that just before we arrived they found a plumbing issue near their power room and had to shut off everything until it was resolved. He said there was about half an inch of standing water in that area. Curious we asked what kind of plumbing issue had caused this. He replied “why don’t I show you” and guided us to the source of the problem. It was a water fountain near the break room that had apparently made a small pond across the floor. By the time we got there they had turned off the water supply line and several workers were busy with squeegee mops trying to clean up the mess as fast as possible. We asked what had happened to cause this. He said “once the power came back on and everyone was getting the machines back up, someone came over here and noticed water dumping out of the bottom of the fountain. We don’t know yet what caused the leak. We are waiting on the plumber. Could have been the refrigerant coils froze over and caused a pipe to bust.”

Knowing that we would not be able to work until the power came back on, we patiently waited until the plumber arrived. The first thing he did was open up the housing to the fountain and we were shocked by what we saw. This was not a simple leaking pipe. The copper coil inside had completely exploded and the pipe going to the supply line was melted. After examining the unit it became clear what had happened. Current from a lightning strike had traveled along the copper plumbing in the building and went to ground inside the fountain. We immediately wanted to visit the power room and check out things there.  As we entered the power room, we noticed that almost every single breaker had definite signs of arcing, mostly localized around the throw switch itself. But the most amazing thing we found was in the TVS – or transient voltage surge suppression system. This unit is designed to keep unwanted spikes in voltage, such as what you would get from a lightning storm, from effecting other equipment in the building. The power room was equipped with exactly seven TVS systems and six were completely blown. The maintenance manager turned to us and said “I don’t know if I find that comforting or just creepy.” We didn’t either.

So there you have it. Nearly everyone that has worked with electronics for any length of time has a strange lightning story. If you do, please post a comment below! We would love to read them!

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