With a recent factory upgrade, I had the
un-enviable task of throwing the Main Isolator, back into service, and got the handle stuck half way, I heard and saw welding of the contacts inside the Isolator
(1000A@400V).
How would you go about opening or closing a
High current Isolator, have I got it all wrong?.

[This message has been edited by Trumpy (edited 11-26-2002).]

What I have allways done is;

Remove as much load as possible.

When you go to throw the switch, commit to the action and close it fast and hard.

If you have a chance to examine the switch de-energised always take the opportunity to do it. Often these switches haven't been moved in years and then we expect them to operate like new. A little lubrication helps a bunch.

GJ

GJ

An "ACB" is mentioned, and on the North-American continent, there are 3 types of breaker construction in that range—air-{frame}, insulated-case and molded-case. In my experience, air-frame breakers are generally "rackable," meaning they can be mechanically exercised/checked to operate in a test position—unenergized.

After the fact, I would want to determine if the fault duty was too high, and if the breaker manufacturer provided any maintenance instructions. Sounds like you were able to sidestep a potentially serious accident. Because of the breaker misoperation, it integral ground-fault protection may have been useless.

In the US, NFPA 70E {Electrical Safety Requirements for Employee Workplaces} calls for evaluation of arc-blast hazards, and appropriate personal protective equipment.

Sorry, the part that said ACB, should have read Isolator, this is now amended.
Have since locked off the supply and cleaned the contacts and lubed the operating mechanism, works like a charm, now.
But this was an old metal-clad unit(the norm
in Industrial installations, over here).

In the US, NEMA {nema.org} has somewhat applicable standards that are on line—ICS2.3-1995 Annex A ‘Maintenance of Motor Controllers After a Fault Condition.’

These are basically common sense, but seem worth reviewing. Handy for establishing that endless “paper trail.”