Howard HI-104 Single-Phase Pad Transformer - Manual (Page 18)

Document 2.4.96, Revision 0
March, 2013
18
Single-Phase Pad-Mounted Compartmental-Type Distribution Transformers
On double-door style transformers the fuse can be
inspected and replaced through the cover-mounted
handhole using the following procedure.
1. Make sure that the transformer is completely de-
energized and that the tank and all primary and
secondary terminals are securely and effectively
grounded.
2. Vent the tank by operating the pressure relief
valve, being careful to avoid any hot fluid that
might be expelled from the PRV.
3. Remove the tank hand-hole cover.
4. Identify the fuse block assembly.
5. Remove leads attached to each end of the car-
tridge fuse, being careful not to drop any nuts or
washers into the tank.
6. Unbolt the fuse and replace it with a new fuse of
the appropriate rating. Tighten the fuse mounting
fasteners according to the recommended torque
values in Table 4.
7. Re-install the tank hand-hole cover. Refer to
“Opening the Transformer Tank” for instructions.
Bay-O-Net Fuse
The optional Bay-O-Net is a fluid-immersed, draw-
out, dead-front fused disconnect device that is rated
for load-break operation. It is designed to be oper-
ated with a live-line tool (hot stick or shotgun stick)
and should not be operated by hand. The Bay-O-Net
device is located in the terminal compartment near
the high-voltage bushings. The Bay-O-Net is avail-
able as an expulsion fuse device or as a full-range
current-limiting fuse device. Personnel should read
and follow the instructions provided by the Bay-O-Net
device manufacturer for proper operating procedures
and safety information.
The Bay-O-Net is designed to provide protection for
the transformer and the distribution system and
is not intended as a disconnect device for routine
transformer operation. The Bay-O-Net does not
provide a visible disconnect and should not be relied
on as the sole indication that the transformer is de-
energized.
When the Bay-O-Net is provided as an expulsion fuse
device, it is equipped with a series-connected fluid-
immersed isolation link, or if specified by the custom-
er, a series-connected partial-range current-limiting
fuse. Isolation links and partial-range current-lim-
iting fuses are designed to blow in the event of an
internal transformer fault. A transformer with a blown
isolation link or partial-range current-limiting fuse
cannot be re-energized and must be removed from
service.
▲
! WARNING
FAILURE TO FOLLOW THE INSTRUCTIONS
BELOW COULD RESULT IN DEATH OR SERIOUS
PERSONAL INJURY, AND COULD ALSO RESULT
IN DAMAGE TO THE EQUIPMENT.
• Bay-O-Net fuse devices are not recommend-
ed for fault closing. The Bay-O-Net device
should not be used to re-energize a trans-
former that is suspected to be faulted.
• Operate the pressure relief valve to vent pres-
sure in the transformer tank before unlatch-
ing a Bay-O-Net device to prevent hot oil from
being expelled during fuse removal. Be care-
ful to avoid hot fluid that might be expelled
from the PRV.
• Operate the Bay-O-Net device with a live-line
tool (hot stick or shotgun stick). Never oper-
ate the Bay-O-Net device by hand.
• After replacing a blown fuse, the transformer
should be re-energized from a remote loca-
tion.
• Never rely of Bay-O-Net removal as the sole
indication that the transformer is de-ener-
gized.
The following procedures are intended as a general
guide for operation of the Bay-O-Net device. Person-
nel should also read and follow the instructions
provided by the Bay-O-Net device manufacturer for
proper operating procedures and safety information.
On single-door style transformers open the flip-top
hood and secure it in the open position. On double-
door style transformers open both compartment
doors and engage the prop rods on each door to
latch them in the open position.
Remove Fuse Holder—The following procedure
should be used to withdraw the fuse holder from the
Bay-O-Net housing.