by David Brender, PE
As the world moves away from paper material, data centers are essential in storing credit card information, various confidential government materials, and other sensitive information that could potentially put an individual or country at risk. Without proper protection systems in place, these critical facilities expose themselves to Mother Nature’s disastrous effects, which could result in expensive downtime and even data loss. Such crises are never expected, but by installing code-exceeding lightning protection and grounding systems, their occurrence can be greatly mitigated and, in some cases, even prevented.
Since severe weather systems cannot be prodded or manipulated, all facilities run the risk of potentially experiencing a direct lightning hit to their primary power line, building, or other electrical equipment. Fortunately, simple and inexpensive techniques—such as proper electrical and grounding systems—can help prevent or reduce problems.
Center design and lightning protection
A direct lightning hit to a data center’s primary power line can potentially cause data loss, downtime, and expensive repairs. However, if the center has a proper grounding system in place, it will continue functioning without interruption, much like Suncoast Schools Federal Credit Union’s data center located near Tampa, Florida.
The bank’s data center is situated in one of the most lightning-prone cities in the United States. To minimize the risk of downtime or data loss, the bank installed a low-resistance, heavy-gage copper grounding system (under 5 ohms), along with a multilayer surge protection. The investment in a proper protection system paid off on the day lightning struck the center.
The bolt hit the center’s 480-V service entrance cable and destroyed the electric meter and socket, but did no other damage. The grounding system, coupled with the cascading transient voltage surge suppressors (TVSS), directed the lightning surge to the earth before it could do any damage downstream. No one in the center even knew the facility had been hit.
The added protection prevented the bank’s expensive data-processing equipment and important financial data from being damaged or destroyed. No equipment damage, no downtime. With proper grounding and lightning protection systems in place, facility managers can ensure uninterrupted uptime for their tenants.
The purpose of a lightning protection system is to provide a low-impedance, easy path through which the lightning energy can flow. These systems neither attract lightning to structures, nor do they repel it. Rather, they intercept the lightning and channel the energy onto a low-resistance path. Lightning systems and surge-protection devices must be connected to a low-impedance ground electrode system to operate. The grounding resistance should be checked upon installation and annually or semiannually thereafter, depending on experience encountered. Five ohms to earth or less is recommended. Since the use of the building framing steel as a down conductor introduces the lightning energy directly to the interior of the building—where it can damage the data or equipment or couple to the electrical wiring—separate copper conductors insulated from the structural steel are recommended as down conductors.
To work effectively, the entire grounding system needs to be properly designed using listed connectors and corrosion-resistant materials. Copper and its alloys are the most-common materials used for reducing power quality problems. Unlike other materials, copper avoids oxidation complications, allows for superior reliability, and provides corrosion resistance at connections. (Other material options include galvanized steel and, for certain soil chemistries, stainless steel. However, the latter is expensive for this application and not particularly common.)