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Instrument Transformers
Control Power and Voltage Transformers-
General Information
When required, voltage transformers (VTs), or a control power
transformer (CPT), or fuses for a CPT can be mounted on a
withdrawable rollout fuse tray. Each auxiliary cell (A = upper,
or B = lower) can contain up to two rollout trays. See Table 5
for various rollout tray positions. Rollout trays are designed
with metal extensions on each end of the primary fuses.
These extensions wipe across a flexible copper strap mounted
on the cubicle as the rollout tray is withdrawn. This action will
ground each side of the primary fuses to remove any residual
charge from the fuses or transformers, and grounds the primary
fuses when the tray is fully withdrawn.
As the rollout tray is withdrawn, insulating shutters move to
cover the cubicle primary disconnect stabs. Note: The insulating
shutter is only a part of the primary insulation system, and the
outer surface of the insulating shutter will not be at ground
potential. It should not be assumed, therefore, that personnel
can contact the insulating shutter with complete safety.
Voltage Transformers
One, two, or three voltage transformers with primary fuses
may be mounted on the rollout tray located in positions C, D,
E, and/or F. See the "Operating Sequence" section for discon-
necting, connecting or withdrawal instructions.
Typical rollout tray and transformer locations are shown in the
side views in Figure 29.
Table 5. Rollout Tray and Transformer Positions
Cell
Position
Rollout Tray May Be Used for:
A (Upper)
C
Voltage Transformer (VT)
D
Voltage Transformer (VT) or Control Power
Transformer (CPT) (up to 15kVA single phase)
(Fuses for CPT may be installed in position D if
position C is empty and the CPT is located in
positions E & F)
B (Lower)
E
Voltage Transformer (VT)
F
Voltage Transformer (VT) or Control Power
Transformer (CPT) (up to 15kVA single phase)
or Fuses for Control Power Transformer (CPT)
with CPT installed in rear of section or remote
(over 15kVA single phase, or any three phase)
32
Courtesy of NationalSwitchgear.com
GMI
BREAKER
E
VT
F
CPT
FUSE
MCB
FEEDER CIRCUIT BREAKER/AUXILIARY
C
VT
D
CPT
FUSE
MCB
E
VT
F
FUSE
AUXILIARY/AUXILIARY
Figure 29. Typical VT, CPT, and CPT Fuse Rollout Locations
H1
H2
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