UFC 3-560-01
6 December 2006
Including change 1, 7 December 2006
9-2.1.3 Interrupter Switches. Interrupter switches are designed to be opened under
load. Metal-enclosed interrupter switches have sometimes been used in place of circuit
breakers as a more economical switching method.
9-2.1.4 Inching. The method of opening manually operated non-load break-type
disconnects in a gradual manner is called inching, when the operator believes there is
no load current. If a small arc occurs from the charging current, it has been assumed
that a cautious opening would allow the arc to be broken; however, inching is
dangerous and is prohibited.
9-2.2
Oil Switches. The consequences of operating a faulty oil switch, or closing
into a faulted circuit with an oil switch are likely to be catastrophic and, often fatal.
Switching procedures will be used to make sure that no energized oil switch is operated
while workers are in the vicinity. Unless the switch has been equipped for remote
operation (at least 20 ft (6 m)) away, the switch must be completely deenergized by an
upstream device before switching. The switch must be locked out and tagged out
before allowing maintenance. In addition, no energized high-voltage oil switch must be
operated unless routine maintenance has been performed within the past year. The
switch must be deenergized at the nearest upstream device following the lockout/tagout
procedures of Chapter 6. Once maintenance has been performed on the switch, the
switch shall be considered operational following the guidelines of this paragraph. Oil
switches must incorporate a mechanical stop to prevent inadvertent operation to
ground. Any abnormalities or defects discovered in any oil switch must be reported to
an authorized individual.
9-2.3
SF6 Switches. Follow all precautions specified by the manufacturer. Inspect
the switch before operating it for any signs of degradation, such as low SF6 pressure or
signs of SF6 leakage (accumulation of powder around seals). Verify that the SF6
pressure gauge is in the green zone before operating the switch; operating a switch with
low SF6 pressure can result in internal flashovers that will damage the equipment and
cause personal injury. Before energizing the switchgear for first use, verify that the
shipping caps on all bushings and bushing wells have been replaced with elbows or
insulated protective covers or plugs. The switchgear must be deenergized and
grounded prior to conducting any maintenance, SF6 sampling, or SF6 filling procedures.
9-2.4
Oil-Filled Vacuum Switches. Follow all precautions specified by the
manufacturer. Inspect the switch before operating it for any signs of degradation, such
as oil leakage; operating a switch without oil can result in internal flashovers that will
damage the equipment and cause personal injury. Before energizing the switchgear for
first use, verify that the shipping caps on all bushings and bushing wells have been
replaced with elbows or insulated protective covers or plugs. The switchgear must be
deenergized and grounded prior to conducting any maintenance, oil sampling, or oil
filling procedures.
9-4
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