Padmount Project Application Brief
2.8 MVA Step-down
Transformer
We Energies Solves Load
Growth Puzzle With VFI
Padmount Transformer
Profile:
Situation:
Design Considerations:
We Energies is an $8.4 billion investor owned utility serving over 1 million residential,
commercial and industrial customers in Wisconsin and Upper Michigan.
A 14 MVA substation in Hartland, Wisconsin contains two 7-MVA power
transformers, 24.9 kV – 8.32 kV. This scheme offers reliability in case of the
removal from service of one of the two units. Total load increased above
the substation’s allowable loading of 8.5 MVA, threatening reliability. The
nearby Cottonwood Substation (168 MVA) could supply the bulk of one of
the Hartland substation feeders at 24.9 kV, but supplying it directly would
have necessitated replacing all of the existing 15 kV underground cable,
switchgear, and transformers feeding the 1.5 MVA subdivision load.
• A need to re-establish the high reliability designed into the Hartland Substation.
• Considerable cost of purchase and installation of new 24.9 kV conductor,
switchgear, and transformers, and a desire to defer that cost.
• The existing 15 kV underground conductor offered varying amounts of
remaining service life, having been installed over the course of 20 years,
starting in 1971.
• In a residential setting, low-profile aesthetics were important.
Design Solution:
A single, 2.8 MVA padmount transformer with an integral Kyle® Vacuum Fault
Interrupter (VFI) breaker, equipped with single-phase trip capability on the
8.32 kV side. We Energies has switches at locations #1, #2 and #3 (see schematic,
over), enabling the transformer to feed the load in question, or to feed additional
feeder load in the event of a substation feeder cable or transformer outage in
the Hartland Substation.
Cottonwood Substation
138-24.9 kV
#1
Switch
N.C.
2 X 84 MVA, 3PH.
2.8 MVA, 3PH.
24.9-8.32 kV
1.5 MVA
Subdivision
Load
#2
Switch
N.O.
VFI TRANSFORMER
VFI Padmount
Transformer
(See photo)
1 MVA
Feeder
Load
7 MVA
Other
Loads
#3
Switch
N.C.
VFI Padmount Transformer
Hartland Substation
24.9-8.32 kV
Other
Loads
2 X 7 MVA, 3PH.
Design Benefits: Combining the VFI
breaker and transformer in a single,
compact, dead front piece of
equipment:
1) Maintained the high reliability
originally built into the Hartland
substation. In fact, either of its
two 7 MVA Transformers or the
new 2.8 MVA VFI Transformer
could be taken out of service
without disruption to customers.
2) Delayed the expense of
replacing underground cable,
transformers, and switchgear.
When this upgrade does occur,
the VFI Transformer can be
moved to a new location to
perform a similar function.
3) Minimized real estate needs due
to its small size.
4) Allowed an unobtrusive installation
at the edge of a local city park.
Equipment/Product Listing:
Cooper Power Systems 2.8 MVA
Vacuum Fault Interrupter (VFI) Pad
Mounted Transformer, 24.9 kV –
8.32 kV, with single-phase trip on
the secondary side.
The Players: We Energies’ Engineers
and Cooper Power Systems.
For further product or application
information, access reference
documents online, at:
http://epic.cooperpower.com/
A) Bulletin No. 02039
B) Bulletin No. 97055
C) Bulletin No. 01033
World Headquarters
2300 Badger Drive, Waukesha, WI 53188, USA, Telephone (262) 896-2400 • Fax (262) 896-2313
E-mail: cooper@cooperpower.com • Web site: www.cooperpower.com
© 2003 Cooper Power Systems Inc.
Kyle® is a registered trademark of Cooper Industry, Inc.
Bulletin No. 03011 (4/03); New Issue
PRINTED IN USA