Arc Fault Blasts

[industrialelectrician]

We have a 12.5kv transformer from the utlity company that we are knocking down to 480v and feeding an MCC. I was told today by an electrical engineer that the arc blast would be much higher on the 480v side than on the 12.5kv side even if both sides theoretically had 200 amps each. Can anyone explain why that would be in laymans terms because when he was explaining it to me he really confused me? Sorry if this is a dumb question, I haven't got alot of experience on the industrial side.

 

[charlie tuna]

Re: Arc Fault Blasts

remember arc fault is a function of both voltage and current. it probibly has something to do with overcurrent protective fusing and how fast they operate. buseman has a video concerning this, and is very interesting --- many industrial accidents could be reduced by proper fusing.....

 

[charlie]

Re: Arc Fault Blasts

It is just like welding. You transform the voltage down so you can get more amperage to weld with and you will have more amperage available at 480 volts than you will at 12,470 volts.

 

[ron]

Re: Arc Fault Blasts

One of the biggest reasons that the incident energy (arc fault) is higher on the secondary of a step down transformer (medium voltage to low voltage), is that the gap between phases are smaller on the low voltage side. Making it easier for those electrons to jump ship through the air from one phase to the other, or phase to ground.

 

[jim dungar]

Re: Arc Fault Blasts

Arc fault blasts are a function of current and time (incident energy). Medium voltage systems typically have less fault current available and the resulting blast is usually (but definitely not always) sufficient enough that the arc is extinguished faster than at 480V.