Howard Network Transformers - Manual (Page 5)

Catalog Section 94-10
Network Transformers
Issued: April 9, 2010
Howard Industries, Inc.
Laurel, MS 39440
www.howardtransformers.com
Copyright © 2010 Howard Industries, Inc.
5
Network Transformer
94-10
Howard network transformers are available with a wide
range of features and accessories in order to satisfy the
requirements of even the most demanding applications.
Contact the factory or your area sales representative for
the availability of other design options not listed.
Standard Features and Accessories
Howard network transformers are supplied with the follow-
ing standard features and accessories:
• Self-cooled power ratings (ONAN)—300 kVA through
2,500 kVA, three-phase
• High-voltage rating—from 2.4 kV through 34.5 kV
• High-voltage taps—Per ANSI C57.12.40.
• Low-voltage ratings—through 600 Volts
• BIL levels—Per ANSI C57.12.40
• Excitation limit—Per ANSI C57.12.00
• Average temperature rise—55ºC/65ºC
• Frequency—60 Hertz
• Impedance and impedance tolerance—Per ANSI
C57.12.40
• Audible sound levels—Per ANSI C57.12.40
• Service location—vault-type network transformers are
suitable for installation in above-ground dry vaults
where occasional submersion is possible. Subway-
type network transformers are suitable for installation
in subsurface vaults where frequent or continuous
submersion is likely. Subway type designs are suit-
able for subway or vault applications.
• Cooling/insulating fluid—Type II mineral oil with oxida-
tion inhibitor
• Fluid preservation system—sealed tank
• Main tank—copper-bearing steel construction, with
sub-base, main cover, and the following standard ac-
cessories:
− Dial-type magnetic liquid-level indicator (without
alarm contacts) welded to tank
− Dial-type thermometer (without alarm contacts)
− Combination drain and bottom filter valve
− Filling plug and upper filter press connection
− Top liquid sampling plug
− Air test provision
− Grounding pad welded to tank
− Lifting provisions for complete unit
− Lifting provisions for main tank cover
− Cover-mounted, pad-lockable tap changer switch
under protective pipe cap for de-energized opera-
tion (on units supplied with high-voltage taps)
− Bolted hand hole cover
− Corrosion-resistant steel fastening hardware
− Secondary throat suitable for mounting network
protector, with mounting holes, guide pins, gas-
ket, and steel plate shipping guard
− Subway-type radiator panels (when required by
design)
− Pressure-relief valve (subway type)
• Primary terminal chamber—sealed enclosure welded
to main tank above the primary switch chamber, with
the following standard accessories:
− Bolted cover with, gasket, guide pins, and lifting
provisions
− Drain plug
− Liquid filling plug
− Liquid level and vent plug
− Three replaceable primary bushings between
terminal chamber and switch chamber, with ter-
minals
− Primary entrance consisting of one of the follow-
ing two methods: 1) wiping sleeves or 2) dead-
front bushing bushings
• Primary switch chamber—sealed enclosure welded to
main tank beneath the primary switch chamber, with
the following accessories:
− Bolted cover with, gasket, guide pins, and lifting
provisions
− Three-pole, three-position, 200 Ampere, non-
interrupting high-voltage switch and external
operating handle with latch
− Electrical interlock on switch
− Dial-type magnetic liquid level indicator welded to
chamber (without alarm contacts)
− Liquid filling plug
− Air test provision
− Drain valve
− Mineral oil insulating fluid
• Low-voltage termination consisting of the following:
− Three externally replaceable bushings bolted to
the tank within the secondary throat
− Three flexible connectors for electrical connection
to a network protector
− Low-voltage neutral connection welded to the
tank
• Paint finish—catalyzed epoxy primer plus catalyzed
urethane enamel topcoat; 3.0 mils nominal dry thick-
ness
• Nameplate—non-corrosive diagrammatic nameplate,
permanently attached with non-corrosive hardware
Features and Accessories