Howard HI-104 Single-Phase Pad Transformer - Manual (Page 22)

Document 2.4.96, Revision 0
March, 2013
22
Single-Phase Pad-Mounted Compartmental-Type Distribution Transformers
Low-Voltage Circuit Breaker
The optional low-voltage circuit breaker is mounted
inside the tank and is fluid immersed. The breaker
uses an automatic trip system to help protect the
transformer from damage caused by overloads and
short circuits. The presence of a low-voltage circuit
breaker will be indicated on the transformer name-
plate.
▲
! 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 rely solely on the circuit breaker to
de-energize the transformer secondary. Al-
ways ground the secondary terminals before
performing work.
• Even with the circuit breaker in the OPEN
position, there may be sufficient capacitive
coupling to cause a shock hazard at the sec-
ondary terminals.
• Operate the low-voltage circuit breaker with
a live-line tool (hot stick or shotgun stick).
Never operate by hand.
The circuit breaker is a thermal trip device provided
for transformer protection. It is not intended as a
disconnect device for routine transformer operation.
The circuit breaker does not provide a visible discon-
nect and should not be relied on as the sole indica-
tion that the secondary is de-energized. The circuit
breaker operating handle is located in the terminal
compartment near the low-voltage bushings and
is designed to be operated with a live-line tool (hot
stick), as follows.
— To open the circuit breaker, rotate the
handle so that the pointer is at the OPEN
(“O”) position.
— To close the circuit breaker, rotate the
handle, so that the pointer is at the
CLOSED (“C”) position.
— To reset the circuit breaker after it has
tripped, rotate the handle, so that the
pointer is at the RESET (“R”) position.
Then rotate the handle, so that the
pointer is at the CLOSED (“C”) position.
The circuit breaker may be provided with an optional
emergency overload capability. The emergency
overload lever is located adjacent to the main operat-
ing handle. To provide continued service during an
overload situation, rotate the emergency overload
lever to temporarily raise the breaker trip setting.
Rotation of the lever is variable, so that more or less
overload capability can be selected. Overload opera-
tion should be minimized to prevent excessive loss of
transformer life. When shipped from the factory, the
emergency overload lever is secured with a meter
seal to prevent accidental operation.
Magnex Interrupter
The optional Magnex Interrupter is an over-current
protective device and load-break switch, which is
internally mounted under oil and connected into the
high-voltage circuit of the transformer. The inter-
rupter coordinates with an internal protective link or
internal current-limiting fuse, so that the interrupter
operates first for overloads or faults on the load side
of the transformer. The presence of a Magnex Inter-
rupter will be indicated on the transformer name-
plate. The following procedures are intended as a
general guide for operation of the Magnex Interrupt-
er. Personnel should read and follow Cooper Power
Systems Magnex Interrupter Installation Instructions
S340-34-1.
The operating handle is located in the terminal
compartment and is designed to be operated with a
live-line tool (hot stick), as follows.
− To open the interrupter, rotate the handle
upward in a counterclockwise direction,
until the spring-loaded contacts open and
the handle is in the OPEN position.
− To close the interrupter, rotate the handle
downward in a clockwise direction, until
the handle is against the physical stop
in the CLOSED position. When in the
CLOSED position, the interrupter will oper-
ate automatically due to an over-current
condition or rise in oil temperature.
− To reset the interrupter after it has
tripped, rotate the handle upward in a
counterclockwise direction to the OPEN
position, and then downward in a clock-
wise direction, until the handle is against
the physical stop in the CLOSED position.