February 20, 2013

What Wouldn’t You Touch With A 10 Foot Pole? 13,200 Volt Switch Gear Scheduled Maintenance

Last Saturday, we performed routine scheduled maintenance on our primary electrical gear within our Baltimore facility. Since I know many of you are very technically minded, I thought it may be fun to share some details.

Edge has a primary feeder into the Baltimore datacenter from the local utility (Constellation Energy). The feeder is attached directly to the city’s electrical grid and fed from 4 separate outside substations. While the typical connection in your home or office runs at 208 volts, our electrical connections operate at 13,200 volts. All of these high capacity electrical systems generate a considerable amount of vibration which causes connections to loosen over time. If you’ve ever walked by one of those large green electrical transformers outside and heard the hum, that is the vibration caused by transforming electricity from one voltage to another.

If you really want to geek out, the American Physics Institute explains “When current reverses 60 times a second the iron core of the transformer undergoes magnetetostriction twice during each cycle. In other words, 120 times per second induced fields cause the core to stretch slightly; a meter-sized transformer might stretch or shrink by only a micron but this would be enough to set up an audible 120-Hz hum.”

So back to non-geek speak. So how do you find a loose connection without turning anything off? First thing we do is a Thermal Scan of every electrical connection and component in a datacenter. Chances are, if it’s showing orange or red (temperature) its loose. The pictures we see look like this:

We determine the connections to service and then bring in the guys with the “10 foot pole”. Because we use 2N electrical distribution systems in every datacenter to ensure redundancy, it’s easy to flip between electrical systems and tighten any connections as needed.



The real fun starts when you start working on high voltage gear. Our maintenance crew has to take many safety precautions to ensure life safety including dressing up in special suits, funny hats, and literally using a 10 foot pole to de-energize the system.

Edge GeneratorsFirst we cut the entire datacenter over to generator power. Here is what an Automatic Transfer Switch looks like running on generator power. This device cuts power between the utility power and generator power for the entire data center when we need it, or should there ever be a power failure.


Then, the guy with the funny hat comes in to disconnect utility power:

Then, they take the entire system apart for cleaning and to tighten all the connections.

After the team was done, cleaning, tightening and lubricating, there were only two things left to do. Put everything back together again.

And lastly pat each other on the back for a job well done with no interruption of service completed on schedule and without incidents. Nice and boring, just the way we like it.

Kudos to the infrastructure team for great planning and execution.

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