UFC 3-560-01
6 December 2006
Including change 1, 7 December 2006
9-2.1
Air Switches. Many air switches cannot be opened if there is a load on the
line, a large magnetizing current from a transformer, or a heavy charging current from
an unloaded transmission line. Be sure to know the interrupting capabilities of each
switch being operated.
9-2.1.1 Disconnect Switches. Disconnect switches of the non-load break-type must
not be used to interrupt loads and magnetizing currents, unless an engineering review
has determined the disconnect switch can safely interrupt the actual current. Switch
sticks will be used when necessary to provide the minimum working and clear hot stick
distances. Assume disconnect switches are of the non-load break-type unless you
have positive proof otherwise. Operate non-load break-type switches on the following
basis:
9-2.1.1.1 Disconnect switches can be used to open a live line when not under load.
9-2.1.1.2 Disconnect switches can be used to open sections of deenergized lines
where these lines parallel other high-voltage lines. Use caution because induced
voltages can build up in the deenergized line and create dangerous switching
conditions.
9-2.1.1.3 Evaluate the hazard before using disconnect switches to open a tie line or to
break two parallel high-voltage lines.
9-2.1.2 Airbreak Switches. Gang-operated airbreak switches equipped with arcing
horns may be rated for load-break operation, or they may only be rated for interrupting
the magnetizing current of transformers or the charging current of lines, or to make and
break line parallels. Provide ground mats for the operator to stand on for all substation
airbreak switches when operating. Either fixed or portable small iron-mesh mats must
be used. The mats must be electrically connected to the operating rod and the
substation ground grid to equalize the ground gradient and prevent any potential
differences in case of insulation failure or flashover. Appropriate arc flash rated
personal protective equipment, rubber gloves, and hotsticks must be used when
operating airbreak switches.
9-2.1.2.1 The hinges of airbreak switches must be sufficiently stiff (and kept in this
condition) so that after the blades have been turned into the open position they will not
accidentally fall back on their line-side energized clips.
9-2.1.2.2 The switch must be inspected after it has been opened to see that all blades
have opened the proper distance. Single-throw airbreak switches must be opened to
the maximum amount. Double-throw airbreak switches must be opened so that the
blades clear both sides of the switch by the same amount.
9-2.1.2.3 Install locks on all airbreak switch-operating mechanisms. Airbreak switches
will be kept locked except when opening or shutting the switch.
9-3
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