Document 2.4.126, Revision 4
October 2017
24
Three-Phase Padmounted Distribution Transformers
When transformers are supplied with bushing wells
only, inserts must be installed in the field before
cable connections can be made. High-voltage
terminations may be configured for radial (three
terminations) or loop feed (six terminations).
Low-Voltage Bushings
Three-phase padmounted transformers are
normally supplied with externally-clamped molded
low-voltage bushings, with or without spade
terminals.
Current Transformers
Molded current transformers (CTs) 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 CTs are not connected to
a metering load, they must remain shorted and
grounded to avoid hazardous voltage at the CT
secondary terminations.
Accessory Brackets
Accessory brackets (parking stands) are provided
on dead-front transformers and are located inside
the terminal compartment near the high-voltage
bushings. These brackets are used as mounting
locations for portable feed-throughs, insulated
standoff bushings and other similar devices.
Flip-Top Terminal Compartment Cover
The transformer may be equipped with a flip-
top terminal compartment cover, which can be
raised to facilitate operation of Bay-O-Net fuses
and to provide clearance for pulling cables into
the terminal compartment. To open the cover,
disengage the center security bolt and rotate the
cover upward. A latch is provided to secure the
cover in the open position.
Door Handle, Security Bolt and Padlock
Three-phase compartmental padmounted
transformers are designed and constructed to be
tamper resistant according to the requirements
of IEEE Standards C57.12.28 or C57.12.29, as
applicable, and as such are provided with a door
handle with interlocking penta-head security bolt
and padlock provisions. To ensure enclosure
integrity and prevent unauthorized entry, the handle
should be latched, the security bolt should be fully
engaged and a suitable heavy-duty padlock should
be installed.
Lift-Off Door Hinges
Lift-off door hinges are provided, so that the
primary and secondary compartment doors can be
removed. The door design prevents their removal
while in the closed position.
Other Accessory Devices
Transformers may be supplied with accessory
devices not discussed in these instructions. In such
cases, contact the Howard Industries Transformer
Division for information.
WARNING
Do not exceed the cantilever load rating of a
low-voltage or high-voltage bushing. FAILURE
TO FOLLOW THIS INSTRUCTION MAY RESULT
IN DEATH OR SEVERE PERSONAL INJURY,
AND/OR DAMAGE TO THE EQUIPMENT.
WARNING
CT leads must be connected to a load or
short-circuited and grounded before the
transformer is energized to avoid hazardous
voltage at the CT terminals. FAILURE TO
FOLLOW THIS INSTRUCTION MAY RESULT
IN DEATH OR SERIOUS PERSONAL INJURY,
AND/OR DAMAGE TO THE EQUIPMENT.
