Howard HI-104 Single-Phase Pad Transformer - Manual (Page 20)

Document 2.4.96, Revision 0
March, 2013
20
Single-Phase Pad-Mounted Compartmental-Type Distribution Transformers
Internal Partial-Range Current-Limiting Fuse
The optional internal partial-range (backup) current-
limiting fuse is connected in series with a low-current
interrupting device, such as a weak-link cartridge
fuse or a Bay-O-Net expulsion fuse. The partial-range
current-limiting fuse is designed to clear low imped-
ance (high current) faults, while expulsion fuses are
designed to clear a high impedance fault or overload.
When properly applied, the partial-range current-
limiting fuse will operate only for internal transformer
faults. When a partial-range current-limiting fuse has
blown, the transformer should be considered faulted
and removed from service.
S&C Arc-Strangler
The optional S&C Arc-Strangler is a 200 Ampere,
air-insulated, load-break device that is designed to
be operated with a live-line tool (hot stick or shotgun
stick) and should never be operated by hand. The
Arc-Strangler device may include a full-range cur-
rent-limiting fuse on the switch blade or a clip-style
current-limiting fuse.
The following procedures are intended as a general
guide for operation of the Arc Strangler device. Per-
sonnel should also read and follow the instructions
provided by S&C for proper operating procedures and
safety information. To operate the switch, insert the
live-line tool in the operating hook and pull forward,
swinging the Arc-Strangler open. To remove the Arc-
Strangler, insert the live-line tool in the hinge open-
ing and lift up.
▲
! WARNING
FAILURE TO FOLLOW THE INSTRUCTIONS
BELOW COULD RESULT IN DEATH OR SERIOUS
PERSONAL INJURY, AND COULD ALSO RESULT
IN DAMAGE TO THE EQUIPMENT.
• Arc-Strangler devices are not recommended
for fault closing. Arc-Strangler devices should
not be used to re-energize a transformer that
is suspected to be faulted.
• Operate Arc-Strangler device with a live-line
tool (hot stick or shotgun stick). Never oper-
ate by hand.
• After replacing a blown fuse, the transformer
should be re-energized from a remote loca-
tion.
S&C Fused Switch
The optional S&C fused switch should be operated
according to instructions provided by S&C. S&C tools
should be used to operate an S&C fused switch.
Surge Arrester
The optional surge arrester is used to protect the
transformer and underground cable from damage
due to voltage surges. A surge arrester should be
installed only on systems where the power frequency
voltage at the arrester does not exceed the arrester’s
published maximum continuous operating voltage
(MCOV) value.
▲
! WARNING
FAILURE TO FOLLOW THE INSTRUCTIONS
BELOW COULD RESULT IN DEATH OR SERIOUS
PERSONAL INJURY, AND COULD ALSO RESULT
IN DAMAGE TO THE EQUIPMENT.
• De-energize the transformer from a remote
location and make sure all transformer termi-
nals and bushings have zero voltage before
connecting or servicing surge arresters.
• Disconnect all surge arresters before per-
forming impulse, induced-potential or ap-
plied-potential tests.
Disconnect the 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.
Internal MOV Surge Arrester
The internal metal-oxide-varister (MOV) surge ar-
rester is designed to be fluid immersed and mounted
inside the transformer tank. It is recommended that
the fluid-immersed MOV arrester not be exposed to
an average oil temperature exceeding 90°C (194°F)
and a maximum oil 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 test-
ing and before placing the transformer into service.