Obtaining the available fault current from the electric utility can go well or can be quite frustrating. Regardless of whether you use this important information for a short circuit study, arc flash study or one of the many other studies, what is your experience?

Stories are welcome and a few have discussed their experiences on the forum in the past.

Here is the question:

How easy or difficult is it to obtain fault current data from the utility?
Easy
Some follow up required
Really difficult
Depends on the utility
Not applicable to me

Some are easy to work with and glad to help.
Some act like they don't know what you're talking about.
Some will get the info with some prodding.
Some make the process very difficult and charge you for it.
Some just refuse to provide the data.

We do a lot of work with small municipalities that run their own electrical system. Quite often they don't have an engineering staff or capability to run SC calc's down to a specific transformer. When I run across this situation, I request the nameplate information for their substation transformer. They're happy to provide that information. This usually will get you to within 1 kA available fault on the secondary of your service transformer. What I've found is the available fault doesn't drop off tremendously with overhead distribution unless they've got a section with really small ampacity conductors. If we're way at the end of a distribution circuit and a good portion is underground, I'll ask for feeder sizes and approximate lengths from the substation and run the available SC calculations myself.

Most of the larger utilities in my region oblige with the available SC readily once you tell them it's for arc flash.

Very interesting conversation. I've had to pay $400/service in California for utility information. That's the only place it's cost anything. My worst-case scenario is a utility in Florida that I actually spoke to, and then called and emailed (cc'ing the client) at least 25 times and finally gave up. The problem there is the utility's transformer is actually in a Connex box in the parking lot. I can't even see it so we have absolutely nothing to work with.

I have a lot of work with a local utility that will only give real utility information for primary metered services and a basic infinite bus table for secondary metering.

I recently got utility information for a service where they wouldn't confirm the transformer size, and stated the following for the "2000 Amp service":
Minimum Installed 3-phase Available Short Circuit Current: Symmetrical: 3-phase = 12,800Amps RMS; X/R = 5.7
Guaranteed 3-phase Available Short Circuit Current: Symmetrical: = 43,200 Amps RMS; X/R = 6.1

That's quite a range, and used terminology I've never seen before. Wouldn't the "Guaranteed" fault current supersede the "Minimum Installed" value?

I've always been curious why "we" have let utilities get away with only providing infinite bus calculations. It's silliness in my estimation.

I get it that they might change the transformer. I get it that they might change the way a building is fed, maybe from a different substation. I get it that they might change the pole-top fuses. I understand these things. However, if we could have an honest conversation about the inadequacies of using infinite bus with them I'd think they'd come up with a different strategy. Why is it allowed for them to change a transformer, change fuses, etc. without even notifying their client that they did? How is that OK?

How can we start a groundswell of pressure on utilities to have this information more readily available? Maybe it's time to become a lobbyist

A few years back, I had an issue getting the needed data from a utility. They originally claimed it was Proprietary Information, I challenged that and then they claimed it was information not readily available, challenged that and got a lot of stonewalling. I took the issue to the state PUC where I had to educate the PUC person who then discussed it with the PUC engineering. I had to educate the PUC engineering on available fault current and how it makes a big difference with incident energy values.

The PUC had a sitdown with the utility and the utility then provided the information and was directed to come up with a policy on providing this information.

I recall you and I talking about that Barry. Good to hear you FINALLY got some traction.

Mike

When working with clients, I'll start by asking them to contact the utility first and I'll engage if they come up empty. In some cases, I find absolutely no help on transformer nameplate data, it the nameplate can even be located. When lacking this very basic information, at times I even had to make a wild guess as the the kVA rating of the transformer, just to get started. Thankfully, most times, I work downstream of the utility transformer on the LV side, behind the meter of the facility. Sometimes I can find the needed information there.

It's not very fun, that's for sure

~Doug

After that many levels of red tape, what was your confidence in the results they gave you?

~Doug