Howard HI-104 Single-Phase Pad Transformer - Manual (Page 26)

Document 2.4.96, Revision 0
March, 2013
26
Single-Phase Pad-Mounted Compartmental-Type Distribution Transformers
front construction are usually provided with exter-
nally-clamped porcelain high-voltage bushings for
connection to the high-voltage source. Bushings are
usually provided with tin-plated eye-bolt terminals
that are suitable for connection to either aluminum
or copper conductors.
▲
! WARNING
FAILURE TO FOLLOW THE INSTRUCTIONS
BELOW COULD RESULT IN DEATH OR SERIOUS
PERSONAL INJURY, AND COULD ALSO RESULT
IN DAMAGE TO THE EQUIPMENT.
Do not place excessive cantilever load on a low-
voltage or high-voltage bushing.
Low-Voltage Bushings
Single-phase pad-mounted transformers are usu-
ally provided with externally-clamped molded low-
voltage bushings, with or without spade terminals.
When threaded terminals are installed, a backup nut
should be installed and tightened against the termi-
nal to ensure an adequate connection that will not
loosen or overheat. Secondary line leads should be
securely attached to the terminal to ensure a low-
resistance connection and prevent overheating.
Space-Saver™ transformers may be provided with
block-mounted wire-lead low-voltage leads. These
should be crimped to the secondary line leads using
the appropriate crimp connectors and crimping tool.
Follow instructions provided by the crimping tool
manufacturer.
Current Transformers
Optional current transformers (CT’s) are designed to
be mounted around each low-voltage line terminal
for metering applications. Transformers are shipped
from the factory with CT leads shorted together and
grounded. If the CT’s are not connected to a meter-
ing load, they must remain shorted and grounded to
avoid hazardous voltage at the CT secondary termi-
nations.
▲
! WARNING
FAILURE TO FOLLOW THE INSTRUCTIONS
BELOW COULD RESULT IN DEATH OR SERIOUS
PERSONAL INJURY, AND COULD ALSO RESULT
IN DAMAGE TO THE EQUIPMENT.
CT leads must be connected to a metering load
or short-circuited and grounded before the trans-
former is energized to avoid hazardous voltage
at the CT terminals.
Accessory Brackets
An accessory bracket (parking stand) is provided on
dead-front construction, located inside the terminal
compartment near the high-voltage bushings. This
bracket is used as a mounting location for portable
feed-through bushings, insulated standoff bushings
and other similar accessory devices. Follow acces-
sory manufacturer’s instructions for mounting and
using any accessory devices.
Terminal Compartment
Single-phase pad-mounted compartmental-type
transformers are designed and constructed to be
tamper resistant according to the requirements of
IEEE Standards C57.12.28 or C57.12.29, as appli-
cable, and as such are provided with an enclosed
terminal compartment, a penta-head security bolt
and provision for a padlock. Standard penta-head
sockets can be obtained from Snap-On Company
(P/N B2191) or from other tool distributors.
Single-Door Terminal Compartment
The single-door style pad-mounted transformer is
designed with a terminal compartment consisting of
hinged flip-top hood and base sill. The hood can be
opened after removing the padlock and disengaging
the penta-head security bolt. The hood can be com-
pletely removed when in the fully-open position.
Before leaving the installation site, make sure the
terminal compartment is closed and secure, using
the following procedure.
− Close the flip-top hood.
− Fully engage the penta-head security bolt.
− Install a suitable heavy-duty padlock.
− Carefully check the transformer to make