Howard HI-102 Overhead Transformer - Manual (Page 17)

Document 2.4.95, Revision 0
May, 2013
17
Fluid-Filled Overhead Distribution Transformers
surge arrester is designed to be fluid immersed and
mounted inside the transformer tank. It is recom-
mended that the fluid-immersed MOV arrester not
be exposed to an average fluid temperature exceed-
ing 90°C (194°F) or a maximum fluid temperature
exceeding 125°C (257°F).
Disconnect the fluid-immersed MOV surge arrester
before performing impulse, induced-potential or
applied-potential tests; otherwise, the arrester may
be damaged. Reconnect the surge arrester after
testing and before placing the transformer back into
service. Refer to “Opening the Transformer Tank” for
instructions.
Low-Voltage Circuit Breaker
The optional fluid-immersed, low-voltage circuit
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 nameplate. The circuit breaker
coordinates with an internal protective link or
internal current-limiting fuse, so that the breaker
operates first for overloads and faults on the load
side of the transformer.
▲
! 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. Always
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
ungrounded secondary terminals.
• Use a live-line tool (hot stick or shotgun stick)
to operate the low-voltage circuit breaker.
Never operate the breaker by hand.
The circuit breaker operating handle is located on
the side of the transformer tank and is designed to
be operated with a live-line tool (hot stick), as fol-
lows.
− 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 optional
emergency overload capability. The emergency
overload lever is located adjacent to the 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.
When specified, the circuit breaker can be provided
with an overload signal light. Illumination of the
signal light indicates that the transformer has been
heavily overloaded. The signal light remains illu-
minated until the breaker handle is rotated to the
RESET (“R”) position.
The circuit breaker is not intended as a disconnect
device for routine transformer operation. The circuit
breaker does not provide a visible disconnect and
should not be relied on as the sole indication that
the transformer secondary terminals are de-ener-
gized.
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 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