Cut the Copper
Joe Guentert is owner and sole proprietor of Power Distribution Systems, located in Charlotte, NC. He is a 1969 graduate of the University of Notre Dame (dual majors of Electrical Engineering and Business Management). He had an 18-year career with General Electric Company, with various assignments around the U.S., and worked five years as a vice president of IEM, Inc, Fremont, CA.
Let’s discuss the copper
June 20, 2012
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.
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.
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.
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.
Helping Joe on these blogs posts is Brian Steinbrecher, an electrical engineer focused on medium-voltage power distribution systems. His 30 year career includes work with an end-user (IOU), a manufacturer of power systems equipment, and as a system designer/consultant. Brian has a wide breadth of experience within the utility segment from systems design to equipment specifications and from system studies to construction and start-up. He has written many technical documents, papers, and reports and holds over a dozen active patents.
A good portion of Brian’s career was with Cooper Power Systems where he performed engineering and marketing work in behalf of their major product groups. Prior to moving into his current role, Brian was the Director of Engineering for a product group at Cooper. Brian is currently the Owner and Principal Engineer at Galt Engineering Solutions located in Brookfield, Wis.
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Thursday, 28-06-12 09:04
Very informative. Thanks for sharing. This is a great idea for making a structural design of cable trays. Love to hear more from you!