Main tie main switchboard and arc flash label

[anbm]

Switchboard with main-tie-main configuration and be fed from (2) dedicated utility transformers (each transformer feeds one end of switchboard). The switchboard carries "DANGER" arc flash label (No safe PPE exists, Energy work prohibited).

Since the switchboard has above label, I am wondering if one utility transformer fails, will the trained maintenance person or electrician risk his life to approach the switchboard and activate the key switch so the entire switchboard can be fed from one transformer (assuming one transformer is still able to serve all load). Is this something that the code and real situation conflict?

 

[GoldDigger]

Yes! But the solution is to change the situation rather than the Code to make it safe.

The official solution is to fit each of the breakers with remote actuators so that the electrician can stand around the corner in his bathing suit if he wants to while operating the main and tie handles.

Tapatalk!

 

[jim dungar]

Since the switchboard has above label, I am wondering if one utility transformer fails, ...

If one source fails, you no longer know how much Incident Energy exists. There maybe PPE for this 1 source system.

But as GoldDigger suggested, engineer the problem away by adding remote operation.

 

[Tony S]

I?ve done it a couple of times.

We had two intake subs each fed by 2 x 20MVA 33/11KV utility transformers. On both occasions one of the pair failed on Buchholz.

Each time I isolated and locked the failed 11KV incoming OCB while the utility isolated the 33KV. Then it was close the bus-section. OK some loading on the plants had to be reduced to let one transformer take the load.

But as GoldDigger said, although it was possible to close the bus-section at the OCB I used the remote station. If it goes bang, I don?t want to be stood near it.

I?ve had an 11KV OCB fail in a remote substation. My assistant was chiselling bits out of the brickwork afterwards. No amount of PPE is going to stop the shrapnel.

There was always an argument as to whether the out going feeders from the failed section should be opened before closing the bus-section.

More fun is if you needed to close the bus-section with both sides live. That?s a long story, one that I?ll not go in to now.