33
Instrument Transformers
Control Power Transformer
Control power transformers, up to 15kVA single phase, with
the associated primary fuses, may be mounted on a rollout
tray in positions D and F. CPT’s larger than 15kVA single
phase, and all three phase CPT’s, are stationary mounted,
either in the rear of the switchgear section, or in the lower
front cell, or remote. If the CPT is located in the rear of the
section, the primary fuses are mounted on a rollout fuse tray
which is located in position F in the lower front cell. If the CPT is
located in the lower front cell, the primary fuses are mounted
on a rollout fuse tray which is located in the upper cell in posi-
tion D, and position C must be empty.
The secondary molded case circuit breaker is normally mounted
on the front of the CPT rollout tray, interlocked with the tray so
that the circuit breaker must be open before the tray can be
withdrawn or inserted. For large units, the secondary molded
case circuit breaker may be mounted separately, and key inter-
locked with the rollout fuse tray so that the secondary circuit
breaker must be locked open before the rollout fuse tray can
be withdrawn.
Operating Sequence
•
To Disconnect VT Rollout
(Refer to
Figure 30
) For dis-
connecting voltage transformers from the primary circuit,
grasp the handle/interlock bar on each side of the rollout
tray, and rotate the handle upward while pulling the handle
horizontally towards the center of the unit. The handle will
lodge in a “notched” area in the mounting bracket, and
the interlock portion of the handle will be withdrawn from
the guide rails on the side of the cell. When both handles
are operated to the raised position, the rollout tray will be
free to move. Withdraw the extension rails on each side of
the cell to their fully extended position. Then, using the
handles on the rollout tray, pull the tray in a smooth
motion from the fully inserted (connected) position to the
fully withdrawn (disconnected) position.
•
To Connect VT Rollout
Connecting (inserting) the voltage
transformer rollout tray is the reverse of the disconnecting
operation. The handle/interlock bars must be in their fully
raised position, with the interlock bar withdrawn on each
side of the rollout. Push the rollout tray in firmly to the fully
connected position. Then, push the extension rails in to
their fully inserted position. When this is done, holes in the
extension rails should align with holes in the cell structure,
which will allow the handle/interlock bar to be released,
locking the rollout tray into the connected position in the unit.
•
To Disconnect CPT Rollout or CPT Fuses
(Refer to
Figure 31
) Withdrawal of a CPT rollout or a CPT fuse roll-
out is similar to withdrawal of a VT rollout, except that the
secondary circuit breaker must be opened before the roll-
out tray can be withdrawn. If the secondary molded case
circuit breaker is mounted directly on the rollout tray, the
circuit breaker will be mechanically interlocked with one of
the handle/interlock bars. If the circuit breaker is separately
mounted, the circuit breaker will be key interlocked with
the handle/interlock bar. Opening of the circuit breaker will
allow operation of the key interlock, which will make the key
available. This key should then be inserted in the key inter-
lock on the rollout tray, to allow the tray to be withdrawn.
•
To Connect CPT Rollout or CPT Fuses
Connecting
(inserting) the control power transformer rollout tray or
CPT fuse tray is the reverse of the disconnecting operation.
The secondary molded case circuit breaker must be in the
open position, and if a key interlock is involved, the key
must be inserted in the interlock cylinder on the rollout
tray. The handle/interlock bars must be in their fully raised
position, with the interlock bar withdrawn on each side of
the rollout. Push the rollout tray in firmly to the fully con-
nected position. Then, push the extension rails in to their
fully inserted position. When this is done, holes in the
extension rails should align with holes in the cell structure,
which will allow the handle/interlock bar to be released,
locking the rollout tray into the connected position in the
unit. Once the rollout tray is fully inserted and the
handle/interlock bars fully extended, molded case circuit
breaker may be closed, either directly if mounted on the
rollout tray, or indirectly if a key interlock is involved.
Hazardous voltages.
Can cause death, severe personal injury or
property damage.
Do not place hands or objects into rollout trays
until fully withdrawn from cell.
When inserting or withdrawing a rollout tray,
always complete the action in one continuous
motion.
WARNING
