They will need to tell you where. I would think in a perfect world they would provide it at the service point but you never know what they're going to give you so you should clarify.
Well, it SHOULD BE, but utilities play by their own rules. Hence, it’s best to actually ask for the details. Hopefully they will be cooperative and clarify it for you...
One time I got a value of 105k from the POCO, at the xformer secondary, which was IIRC about 85k at the service equipment. I wanted it to be under 65 so I pumped out the UG vault and got the info off the transformers. Turned out to be about 55k at the service equipment (assuming infinite primary). I have often gotten twice the value from POCO as using actual transformer data and infinite primary. Obviously having some extra margin for transformer upgrades and replacements is prudent, it depends on the situation.
Interesting. I've realized here in NYC they'll typically give you 109,500 amps.... I've received this same number for large multi-family residential buildings and for a much smaller building. It didn't make sense to me that the number was the same.
And this seems to possibly answer why I keep getting 109,500 amps... maybe they take the number from a chart.
One of my 'finer' moments... I didn't know what IIRC was, and thought it was a technical term that I missed somewhere. I can always count on Google to laugh at me with its response: If I Recall Correctly
. My 2nd fact learned today.
I learned what a Sun dog was yesterday. Never heard of it before. Apparently there are moondogs too.One of my 'finer' moments... I didn't know what IIRC was, and thought it was a technical term that I missed somewhere. I can always count on Google to laugh at me with its response: If I Recall Correctly
It works for assuring that equipment might have enough withstand rating, but when it comes to arc flash incident energy calculations, you can be well off if you don't know the actual available fault current.
That I would presume is for what they might expect for typical impedance for that size of transformer. Actual one used could be slightly different. It may or may not include any consideration of supply side impedance or some sort of value based on a few details and assumptions as well.
I think the impedance they gave me was the total thevenin equivalent of the utility which includes the transformer impendence. The thevenin equivalent encompasses all the impedances in the distribution system
Is this information helpful without them providing you the Xfmr X/R ?
Yes, this information is very helpful even without the transformer X/R.
Doesn't every transformer get shipped with an X/R on its build tag.
