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#134644 - 11/24/02 12:25 AM Main Switches  
Trumpy  Offline

Joined: Jul 2002
Posts: 8,223
SI,New Zealand
We recently had a Shut-down in a local factory, to upgrade the 11kV/400V tranny,
after the work was done and the transformer was re-energised, I had the task of throwing the Main Isolator,(a heap of remedial work, had been done in the factory),and as I went to throw the switch,
(a 1000A ACB), it got stuck half-way,resulting in a flash and a bang!.
How do you guys feel about throwing High current Isolators?, personally they give me the Willies.
Your thoughts please?.

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#134645 - 11/24/02 08:57 AM Re: Main Switches  
sparky  Offline
Joined: Oct 2000
Posts: 5,311
oh, you mean that first spark up...

.... depending on the x-former proximity, and impedance, the AIC could exceed your 'main isolator' [Linked Image]....not good.

personally, i position myself at arms length, look only as i position my left
(because i'm a righty), then look away and throw the switch/dico/main,etc..

even if the entire install has been gone over in detail, there could be a bad component (as was your Main Isolator?)

having been flashed hard sticks in your mind does'nt it?? [Linked Image]

#134646 - 11/30/02 01:51 AM Re: Main Switches  
Trumpy  Offline

Joined: Jul 2002
Posts: 8,223
SI,New Zealand
After I had replaced(Hooked Up), the DDO fuses, with all of the Isolators OFF, there was still a spark at the top terminal of the DDO's,(Xformer load), but we had a lot of new 400V gear, installed during the Shut-Down period, by other firms as well, I had to make sure that the people where ready for the power, to be connected, as it was not Locked Out, at their Isolator, as is required
by law.
But Sparky, I feel more comfortable, replacing a DDO fuse, than throwing a 1000A
Main Switch, at least you've got a certain amount of Manual control over a DDO fuse, if
it blows.

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