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Purpose of Disconnect Switches In HV Substation
electrical-engineering-portal
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In general, they consist of a conducting blade, hinged at one end, and a stationary contact on the other, both
terminals mounted on suitable insulators that conform to the common insulator requirements of BIL coordination
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These
simple switches, called disconnects, or disconnecting switches, are usually installed on both sides of the
equipment or line upon which work is to be done
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As a further precaution, they may be opened by means of an insulated stick that helps the operator
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keep a distance from the switch
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Although not designed to be closed to energize the line or equipment with which they are associated, in certain
circumstances they may be closed, using special care to close them firmly and rapidly
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Air break switches have characteristics similar to disconnects, but have the stationary contacts equipped with arc
suppressing devices that enable them to be opened while energized, but recognizing a limitation as to the current
that may be safely interrupted
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Another type has a flexible
“whip” attached to the stationary
contact that continues the
contact with the moving blade
until a point is reached at which
the whip snaps open very
rapidly extinguishing any arc
that may form
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Both types function similarly as larger units do in circuit breakers
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They have higher current breaking capacity than air break switches and are particularly suited
for underground systems or where moisture or pollution make air switches impractical
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138 kV Disconnects Switches (VIDEO)
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Words from Robbie Oleksyn (author):
These 138kv disconnects switches have Joslyn current interrupters on them you can see them the grey tubes on the
contact point, they didn’t work properly that was the issue
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Cant see this video? Click here to watch it on Youtube
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Resource: Power & Transmission Distribution – A
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Pansini (get this book at Amazon)

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