In article ,
Ignoramus30685 wrote:

As I will sometimes test used 460v equipment, using my 240 - 476v, 45
kVA transformer, I would like to somewhat enhance my safety, in
regards to "arc flash" and other such problems.

What I want to do is this:

1) Wear heavy cotton clothing, like a work jacket
2) Wear a welding helmet
3) Stand on a piece of wood
4) Operate stuff with one hand only
5) As I turn something on, have my employee stand by and hold a handle
of a disconnect leading TO the transformer.
6) If he sees or hears anything untoward, he would be instructed to
immediately turn the disconnect off.

Does this make sense?

Not completely.

The problem with arc flash is not really electrocution, it's the thermal
radiation pulse from the flash cooking all exposed body parts in an
instant. All this happens far too fast for a human to react, so for
instance item 6 above is hopeless. All that employee can do is call
911. Should he still be able.

In round numbers, the fastest a human can react to the arrival of an
expected event is about 50 milliseconds.

Circuit breakers are also too slow, and so don't cut the arc off fast
enough, greatly increasing the integrated thermal load. Use fuses
intended for the purpose.

Provide physical barriers to the flash radiation. Welding equipment can
help a great deal, but industrial-scale arc flash can overwhelm even
that. For one thing, the flash can be too fast for the auto-dark
circuit to react in time. One should be able to "press the button"
without being able to see the button.

And the use of remote actuation, such as a long fiberglass pole or a
cord, or a contactor temporarily replacing the button, is a good idea.

As others have said, a little research is in order.

Joe Gwinn

On Jan 16, 10:03*am, Joseph Gwinn wrote:
In article ,





*Ignoramus30685 wrote:
As I will sometimes test used 460v equipment, using my 240 - 476v, 45
kVA transformer, I would like to somewhat enhance my safety, in
regards to "arc flash" and other such problems.

What I want to do is this:

1) Wear heavy cotton clothing, like a work jacket
2) Wear a welding helmet
3) Stand on a piece of wood
4) Operate stuff with one hand only
5) As I turn something on, have my employee stand by and hold a handle
of a disconnect leading TO the transformer.
6) If he sees or hears anything untoward, he would be instructed to
immediately turn the disconnect off.

Does this make sense?

Not completely.

The problem with arc flash is not really electrocution, it's the thermal
radiation pulse from the flash cooking all exposed body parts in an
instant. *All this happens far too fast for a human to react, so for
instance item 6 above is hopeless. *All that employee can do is call
911. *Should he still be able.

In round numbers, the fastest a human can react to the arrival of an
expected event is about 50 milliseconds.

Circuit breakers are also too slow, and so don't cut the arc off fast
enough, greatly increasing the integrated thermal load. *Use fuses
intended for the purpose.

Provide physical barriers to the flash radiation. *Welding equipment can
help a great deal, but industrial-scale arc flash can overwhelm even
that. *For one thing, the flash can be too fast for the auto-dark
circuit to react in time. *One should be able to "press the button"
without being able to see the button.

And the use of remote actuation, such as a long fiberglass pole or a
cord, or a contactor temporarily replacing the button, is a good idea.

As others have said, a little research is in order.

Joe Gwinn- Hide quoted text -

- Show quoted text -

Thjere are many safety guidelines out there regarding arcflash
protection
Check into the equipment supplied by some of the safety equipment
manufactuers for items you need,