can I lock a disconnect switch in the closed position

[stevwri]

I have seen some medium voltage disconnect switches locked in the closed position. It appears this was done to avoid some vandalism as the switchgear is not enclosed in a fence. Is this acceptable?

 

[Jerry123]

I believe that most outdoor loadbreaks are manufactured in such a manner that they can be locked in the closed or open position. Locked in the closed position is done for the reason that it’s accessible to unqualified personal that could cause an outage of power or may injure themselves. You will also see this on pad mount outdoor oil/silicon transformers.

 

[advidana]

some of the codes such as NFPA 70 requires that the switch be locked and tagged when someone is working on the load connected to the switch.

 

[advidana]

correction-some of the codes such as NFPA 70 requires that the switch be locked and tagged in the off position when someone is working on the load connected to the switch.

 

[aali2208]

Hi STEVWRI,

Mostly the medium voltage disconnectors are locked by Blocking magnets, Where as High voltage manual drive Disconnectors are mostly available with Padlocking arrangement on both Extremes (Fully Open & Fully Closed). Can u give yr actual requirement why u need to lock that in ON Position If thats an operational requirment the same can be achived by the blocking magnet technique, which is practicing in most cases.

 

[busbar]

Ill-timed loss of power to certain storm-drain pumps could present significant hazard to life and property, like, for example, in New Orleans.

 

[dpc]

The suitability of locking switches closed depends on the application and circumstances. In general, the NEC does not allow this, but does make exception under certain operational and supervisory conditions. In fact, for fire pumps, it is required that the disconnecting means be lockable in the CLOSED position.

For electric utilities, I think it is very common to lock pole-mounted disconnect switches closed to prevent unauthorized operation.

It just depends on your situation.

 

[sngpl]

Yes, you can, and in fact its advisable, to lock the disconnect in order to safe guard against inadvertent opening of the disconnect when energized. Although there should be interlocking with the breaker as well but this is a secondary precautionary measure.

 

[DanDel]

stevwri, typically, the MV switch feeding a transformer may be locked closed with a keyed interlock(Kirk Lock) which only allows the MV switch to be opened after the LV C/B on the secondary of the transformer is opened. This assures that there is no real load on the primary switch (besides the transformer energization current) to limit arcing when it is opened.

 

[jbartos]

Suggestion: It depends on which premises and associated ownership, and Authority Having Jurisdiction.
Also, NFPA 70-2002 NEC makes distinction between 35000V and under and 35000V above. The 35000V above is covered under Transformer Vaults that have locked doors. If the switch is part of service equipment, it shall be behind locked doors.