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A small Data center is being built in a seismically active zone so the building and its outdoor 27KV/480V substation are being built on 60m pilings. 1) Do all of the pilings need to be connected to the ground (so they are at the same potential), or just the perimeter, or just the corners? 2) What would you expect the resistance to be? A ground resistance study hasn’t been done yet and I’m not sure how applicable it would be.

Hi Mark,

Thank you for your question regarding data center and substation grounding, it is our pleasure to help.

Data center grounding can get very complex as there are many requirements for clean grounding.  Please see ANSI/TIA/EIA-J-STD-607-A and Motorola R56 for more information regarding data center grounding. 

First of all, you should definitely bond all metal structures to the grounding grid, especially the foundation and pilings.  Metal components within the concrete foundation that are not bonded can allow magnetic fields to form and hazardous differences in potential that could not only affect the operations for the data center, but could be hazardous to personnel as well.  Here is a link regarding using your pilings as grounding.

http://www.esgroundingsolutions.com/blog/337/is-it-possible-to-provide-electrical-grounding-utilzing-planned-structural-deep-earth-shafts

For a data center, you should not be using building steel as an electrode.  You need to bond all the rebar components together, and you must bond the rebar to the grounding system.  You must also provide a clean 5-ohm or less grounding system that is separate from the building steel.  Building steel is an extremely “noisy” environment electrically speaking.

When you are combining a data center along with a high-voltage substation, you must be concerned with a number of factors.  Electrical noise and human safety being primary.  Bottom line, you will need to have the low-impedance fault current path required by the National Electrical Code (NEC) for the proper operation of Over Current Protection Devices (OCPD) such as breakers and fuses (building steel will be bonded to this), AND you will need to have a separate chassis grounding system as required for your data center (this is where your dedicated 5-ohm grounding system would be tied to), and yet another chassis grounding system for high-voltage substation as required under Federal Law 29 CFR 1910.269.  Add into the mix of this telecommunication grounding, lightning protection system grounding, water pipes, gas lines, etc., and you get a very complicated system.

As far as the ground resistivity study goes, it is the single most important data set in grounding and is required for any form of an engineering analysis.  It is impossible to calculate the resistance-to-ground of the system without the soil resistivity data.

Please feel free to contact us directly at 310-318-7151 and we will be glad to speak with you about your project free of charge.

Best regards,

The Engineering Team at E&S Grounding Solutions

 

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