Load Break Air Switch

[Redskinsdb21]

What do these terms mean in this type of switch?

Load Break? Does that simply mean it can be operated under load?

Air Switch? Does that mean that it doesnt have any special insulation such as SF6 etc.? Just operates in atmosphere?

 

[jghrist]

Correct on both counts.

 

[SilverfoxUK]

As jghrist says you are correct.

Many of the switchfuse isolators had ratings of maybe 32A or 63A. This was the current they could pass but not safely break. Take the load off the circuit and then open the isolator. Look to a domestic distribution board. Always switch the MCBs off before operating the main isolator.

SF6 will be well indicated and you need to look for a pressure gauge that should be in the green. If it isn't get away from it and isolate it up stream. another type is the vcb where the contacts are in a bottle under vacuum.

 

[crshears]

Another type, not sure who makes it, is of the centre-rotating double-break configuration, where the closed switch contacts sit inside a surrounding pocket of nylon or a nylon-like analogue, such that the arc generated during the initial parting of the contacts during opening generates an arc-extinguishing gas by dissociation of the nylon; once the arc successfully breaks on all three phases, the insulation of the visibly open isolation point is provided by air only.

Numerous load break switches use an interrupter head of some type in series with an air switch, such that when opening the sequence is: interrupter opens, air switch opens, interrupter closes. When closing, air contacts alone go from open to close.

There are horn gap equipped load break air switches out there, meaning they have no other arc interrupting medium, but there are less and less of them all the time as they are gradually being replaced with newer switches that have better breaking capabilities and are thus less operationally restrictive, requiring less adjustments by the control room operator prior to opening . . . not that that's necessarily a good thing; as a matter of course my usual process when performing LT switching was always, to the maximum extent practicable, to zero the reactive current flow through the switch to be opened, regardless of type, so as to minimize voltages disturbances to the customers on the feeders being switched. The next generation of operators often couldn't be bothered, and would routinely make then break, relying on switch telemetry merely to confirm opening or closing of all three switch phases without making prior adjustments to preclude large step changes when opening.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[che12345]

"...#1. What do these terms mean in this type of switch? Load Break? Does that simply mean it can be operated under load? #2. Air Switch? Does that mean that it doesnt have any special insulation such as SF6 etc.? Just operates in atmosphere?"
You had received leaned advice from various experts, all of which are correct and valid.
I would like to add some clarity on "switches" used in LV per IEC, which differs from NEC; for your consideration.
1. Per IEC 60947-3 differentiates between " Disconnector", "Load-break switch", "Switch-disconnector" ...
1.1 A "Load-break switch" can, under normal conditions in the circuit, if applicable with specified overload conditions, make, conduct and break current and, under specified abnormal conditions such as a short-circuit, conduct these short-circuit currents for a specified period. Ref ABB Switchgear Manual.
Che Kuan Yau (Singapore)