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INSTRUMENT
TRANSFORMER INSTALLATIONS
When instrument
transformers are required,
they shall normally be
mounted in an instrument
transformer cabinet or in
a metal-clad switchgear
compartment. The Energy
Technology Services
Department will help
choose a location if space
limitations do not provide
for a conventional
installation.
Current and voltage
transformers will be
furnished and delivered to
the job location by
Company Representatives.
The Customer shall mount
the metering transformers,
then furnish and install
1 1/2 inch rigid or
intermediate galvanized
metallic conduit from the
instrument transformer
cabinet or compartment to
the meter location
designated by the Energy
Technology Services
Department. Thin wall,
flexible. PVC or non
ferrous conduit is not
acceptable for metering.
Long runs may require use
of 2 inch conduit, pull
boxes, and a pull line.
Instrument
Transformer Cabinets
Instrument transformer
cabinets shall not be used
as junction boxes.
Connections to other
meters or current
transformers shall not be
made in the instrument
transformer cabinet.
However, for more than one
conductor per line
installations, it is
permissible for individual
conductors to feed
different circuits on the
load side of the current
transformers.
Instrument transformer
cabinets shall be of
sufficient size to contain
all the instrument
transformers and
conductors, giving
consideration to possible
future removal and
replacement of the
transformers. The factors
which determine the
cabinet size are the size
and number of conductors,
the point of entrance and
exit of conductors, and
the size, type, and number
of instrument
transformers. Recommended
minimum sizes for
instrument transformer
cabinets are shown in Table III.
For all installations
higher than 480 volts,
and for any questions
about a specific
installation regarding the
minimum allowable size of
the instrument transformer
cabinet consult the Energy
Technology Services
Department. See
Figure 15.
Instrument transformer
cabinets shall have hinged
double doors. Cabinets
that are 10 by 24 by 32
inches or smaller may have
a hinged single door. All
instrument transformer
cabinet doors shall be
sealable with pad lock
type meter-sealing
devices. Adequate
clearance shall be
provided and maintained in
front of the cabinet to
allow the cabinet doors to
be fully opened, and to
allow the removal and
installation of the
instrument transformers.
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