Caleb Tennis Data Center Lightning Protection

August 3, 2010 by · Leave a Comment 

One of the projects we focused on this summer was analysis and fortifying Data Cave’s lightning protection system.  I wanted to share a little bit about what we’ve learned.

First, some background: our building is well protected from lightning strikes by what’s known as transient voltage surge suppression (TVSS).  This is similar to the surge protection strips most of us have at home that we plug our valuable electronics into.  However, we have three fold protection within Data Cave:

  1. Incoming protection at the electrical mains.  Our switchgear has built in TVSS on the incoming power lines, rated for 250kA.  This technology basically clamps the line voltage in case of a spike, due to lightning or some other disturbance, and keeps it from entering further into the building.
  2. Electrical power that is being sent to the critical IT equipment goes through our flywheel UPS units.  In these units we convert the AC power to DC power, then back to AC, as part of the rectification process.  Any surges or sags get filtered out by these units.
  3. Our data suite Power Distribution Units also have TVSS units on them, which is what connects directly to the IT loads, in case any surges were somehow able to make it to this point.

One of the TVSS Modules protecting Data Cave's incoming power

So overall, we have great surge suppression.  So imagine our surprise earlier this summer when a large thunderstorm came through, and a nearby lightning strike caused some damage to the hardware that controls the automated gates to the facility.  In addition, we had some power over ethernet switches inside of our building also go “flaky”, for lack of a better term. This prompted us to investigate what was really going on, and what we could do to better protect ourselves (and our customers).

Our Findings

The fence and gates that surrounding our data center were in the process of being installed, but not finished, when the internals to the data center itself were commissioned.  Something that was overlooked in this process was the protective grounding of these items from lightning strikes, which is a different beast than just grounding them from an electrical safety issue.

The fence posts themselves stick into the ground, and in general that means the fence is grounded.  But in our condition, it’s not “well grounded”.  The soil in this area is a bit sandy to a bit clay like, and thus to achieve a good earth ground we prefer to go 20 feet deep.  The fence posts are only about 3 feet deep, which means they aren’t achieving as good of ground as they could be.  To fortify this, we drove 20 foot copper ground rods in periodically along the perimeter of the fence, and bonded the post to the rod, to give better overall grounding.

Copper grounding of fence post

In addition, we looked at the gates themselves.  Our fence gates were custom made, and attach on custom build pylons and hinges.  They are controlled by a motorized arm that opens and shuts them, but otherwise sit as is.  And they are not well grounded at all, because they are suspended in the air.  Again, from a lightning perspective this was something that could be fixed by the simple addition of a grounding cable to the fence hinge.

Grounding of the gate

Other outdoor circuits

In examining the fence and gate, another vulnerable spot we found was in the underground conduit that goes from inside of our data center to the gates.  Because the gates are electrically controlled, they need electrical power – which is provided from inside of our building via an underground conduit.  In addition, our gates are key carded to allow customers and staff in upon a swipe, so data cabling was also necessary.

However, these two electrical lines now represent two new pathways for lightning to enter our building.  While our incoming electrical lines to the facility are protected, if lighting was to strike the gate, it could go “backwards” through the wiring and back into our building in the opposite direction!

Circumventing this is easy.  First, we installed transient voltage surge suppression devices directly at the electrical service at the gate, so in case of a lightning strike it would suppress any large voltages that may generate.  Then we protected the data cabling by the use of inline ethernet surge suppression devices.  These devices cause any voltage spikes that may be generated to be suppressed on the data lines as well, limiting any kind of backfeed into the building.

L-com Connectivity Products - HGLN-CAT5-2 - Surge Protector,  Bulkhead,  10/100 Base-T Shielded Cat5,  Power-Over-Ethernet Comp

Ethernet surge suppression device

Conclusion

With the addition of better lightning protection of things outside of the building, we feel better equipped at mitigating future lightning strikes in the area.

In a future post we plan to highlight some of the existing lightning protection features of Data Cave and how they work to keep lightning away in the first place.

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