Let’s discuss the copper

Data center owners are opting for even larger servers, adding even more copper.


Last week, we discussed the differences in construction costs and copper requirements between the competing approaches of locating medium-voltage transformations outdoors, and connecting the secondary loads via large underground duct banks, versus moving the transformations indoors, in close proximity to the loads.


Image of multiple duct banks with 12 4'' conduits. Courtesy: Joe Guentert 


The differences between the two approaches are becoming more pronounced recently, as more and more data center owners are opting for 230 V servers, and are distributing large critical power at 415 Y/240 V. That necessitates a full-size (and sometimes, an OVERSIZED) neutral, which adds at least another third to the tonnage and the cost of the copper in secondary feeders. I have seen some very large data center designs on the boards recently that will have more than 4 million lbs of copper in underground duct banks or cable tray, just to get 600, 480, or 415 V utility power and generator power into the low-voltage main distribution switchgear lineups, before the power is even distributed to any loads.


Some large data center owners who are moving to modular containers in their centers also have moved to switchgear containers and skid-mounted unit substations outdoors, close-coupling the transformations to the secondary switchgear. That removes all the copper between the transformer and the switchgear, but then adds back even MORE copper on the distribution feeders from the switchgear into the loads.


I’ve seen “modular” projects recently where the secondary switchgear was located outdoors, close-coupled to substation transformers, eliminating the need for a 4000 A or so secondary duct banks into the building. But those 4000 A trunk feeders were then replaced by branch distribution feeders in duct banks or cable tray having a total aggregate ampacity of 10,000 A or more, to distribute to the loads.


Image of multiple duct banks with 16 4'' conduits. Courtesy: Joe Guentert


I think that this pronounced trend of load growth cries out more loudly than ever before in history for a real and true “loadcenter” approach, with the transformations located right down in the center of the loads, where little 4000 A braided flex links like these, connecting a transformer to its secondary switchgear, can replace all those duct banks and hundred of tons of copper.


Image of 4000 A braided flex links, connecting a transformer to its secondary switchgear. Courtesy: Joe Guentert


If you can accept that this makes sense, what are the options? Until fairly recently, almost all of the loadcenter substation transformers that went inside data centers since 1995 were either VPI dry-type or epoxy cast coil construction.

No comments
Consulting-Specifying Engineer's Product of the Year (POY) contest is the premier award for new products in the HVAC, fire, electrical, and...
Consulting-Specifying Engineer magazine is dedicated to encouraging and recognizing the most talented young individuals...
The MEP Giants program lists the top mechanical, electrical, plumbing, and fire protection engineering firms in the United States.
Salary survey: How much are you worth?; Dedicated outdoor air systems; Energy models and lighting
Fire, life safety in schools; Fire protection codes; Detection, suppression, and notification; 2015 Commissioning Giants; Emergency and standby power in hospitals
HVAC and building envelope: Efficient, effective systems; Designing fire sprinkler systems; Wireless controls in buildings; 2015 Product of the Year winners
Designing positive-energy buildings; Ensuring power quality; Complying with NFPA 110; Minimizing arc flash hazards
Implementing microgrids: Controlling campus power generation; Understanding cogeneration systems; Evaluating UPS system efficiency; Driving data center PUE, efficiency
Optimizing genset sizing; How the Internet of Things affects the data center; Increasing transformer efficiency; Standby vs. emergency power in mission critical facilities
As brand protection manager for Eaton’s Electrical Sector, Tom Grace oversees counterfeit awareness...
Amara Rozgus is chief editor and content manager of Consulting-Specifier Engineer magazine.
IEEE power industry experts bring their combined experience in the electrical power industry...
Michael Heinsdorf, P.E., LEED AP, CDT is an Engineering Specification Writer at ARCOM MasterSpec.