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14A-11
SEPTEMBER 2007HUBBELL / CHANCE COMPANY – CENTRALIA, MISSOURI
®
®
POWER SYSTEMS, INC.
DesignFeatures
The jaw socket and hinge terminal castings of the D7 are bronze with
tin-plated NEMA terminal pads. The blade is a round tubular copper
with attened ends to allow for a silver/copper contact. A four-point silver
plated contact is supplied on the jaw end to make the switch easier to
open and close. An all-copper current path is provided.
Interrupters
Chance Duogap
®
expulsion interrupter converts any D7 to a loadbreak
switch. Built-in sockets on each switch accept the interrupter. The
Duogap may be ordered with the switch or may be hotstick-installed
for load management conversion. For more on the Duogap, see Bulletin
No. 14-9405.
Terminal Pads, Arcing Horns
Two-hole NEMA terminal pads are standard. The D7 terminal pads
are bronze with tin-plating to provide low-resistance efcient current
transfer.
A stainless steel arcing horn is provided to pick up load current, thus
preventing burning or arc pitting on the main contacts.
Insulators
The Vee conguration of the insulators simulates a low prole with less
bulk and a pleasing visual appearance. The gray-tone insulator for the
unitized D7 switch is NEMA 3-inch BC.
15 thru 34.5 kV Switch Base and Bearings
The base castings consist of high strength, high corrosion resistant
aluminum alloy. This lightweight aluminum is comparable to bronze in
almost all metal technical categories, such as: ultimate tensile, tensile
yield, elongation, hardness, modulus of elasticity, thermal conductivity,
and electrical conductivity. Bearings are high-strength, high-density
Delrin, for smooth pivotal action.
Conductors are dead-ended to each individual switch base. Pull-off holes
are designed for a 6,000-lb. working load rating. The switch frame is
limited to an unequal loading of 700 lb.
Common Support
The 4 x 4-inch common support member is furnished in either galva-
nized-steel or berglass tubing. The “interphase” shaft which connects
the three rotating insulators is constructed of the same material as
the crossarm.
Controls
Controls are either all metal or metal with a vertical berglass section.
Three options combine the metal or insulated interphase shaft with the
metal or berglass common support.
Chance 15.5, 27 and 38 kV Duogap expulsion
interrupters .
The arcing horn will pick up load current upon
closing to prevent burning or arc pitting on the
main contact surfaces.
Unitized and Pre-Assembled
Type D7 Switches — Unitized
15 to 38 kV 600 Amperes