How are you handling the main service label when the utility only gives you infinite bus and max or no primary fusing information? Do you simply label the main as: "Do not work on this energized"?

I have not run into a utility not giving the information. Are dealing with just the Customer Service Rep or the Engineering Dept? Usually I will get that answer from a Customer Rep and then when I explain to them why I cannot use an infinite bus and need to model their OCPD, then I can usually get to the engineering dept.

I would explain that an infinite bus could lead to workers wearing less than adequate PPE, just like the utility had to analyze the arc flash hazard for their workers using their actual fault current you trying to provide the same reasonable level of protection for your employees.

Of course, you could play hardball and inform them that you are contacting the Public Utilities Commission or whatever the regulatory body is to force them to provide this information.

I had that happen once. I responded with a letter to the utility outlining the seriousness involved and stated that the utility will be liable in the event of a serious injury resulting form information they provided.

They quickly responded with the appropriate information. That happened a number of years ago. Now, most large utilities respond with appropriate information as they understand the seriousness of an arc flash incident. Some small utilities and small coops don't have the capability of providing the needed information. In this case I work with them to get the substation transformer impedance information as well as the overcurrent protection for the distribution line. Then I calculate the needed information myself.

The simple answer is yes. I generally put a note on the one-line and the report indicating why the IE value is what it is.

We've had this happen too. If they can't provide that data, we ask them to have a service man stop and take digital photos of the name plates of the transformers for the facility. If they can't or won't provide data for the primary, we state that the results are based on assumptions. But generally, we find the arc flash hazard for most services very high, many exceed 40 calories.

I've had a utility refuse to give protective device information for an arc hazard study because their legal department would not allow it. They did provide the information when I changed the request and said it was for a protective coordination study.

For such a request, I will give you numbers based on infinite bus and the lowest possible replacement transformer impedance. Not what you want for arc flash.

We have had a problem with some of the smaller co-op utility companies giving us the required data. When you get to the engineering manager they will usually help you if you tell them it is for a coordination study. Most have been very helpful though. With the new requirement in NFPA 70 requiring commercial services to have the available fault current though, it has become very easy to work with the utility companies in getting that information.