This question comes up from time to time. When conducting an arc flash hazard calculation study, sometimes, owners do not want to have a short circuit and coordination study performed as part of the overall project. They may offer up past studies etc. Here we go!



When performing an arc flash study, do you include a NEW short circuit and coordination study?

• Yes, We conduct a NEW short circuit and coordination study
• No - we use an existing study or other data
• Something else
• We don't perform studies

Typically a combination of the two new and existing.

[SIZE=4]Once the project scope has been clearly defined and the process of information gathering begins, if there is existing information available that is relevant to the scope of work it will be reviewed and checked in the field for certification that the data is still accurate [brkr., settings, fuse data, etc.] also a review of the data along with any existing plans will help determine the accuracy of the existing information provided. Once this task is complete the information will be used in the creation of a new system model based on a combination of existing and new information / data. When using a model provided by someone else it gets tricky in the liability arena so you have to be sure of the source and comfortable with the work and input data performed by someone else. In some cases the contract will define what information is provided by the owner/others and is assumed to be accurate as a starting point, however the information is still reviewed for accuracy prior to incorporating into a new or using a third party provided model.[/size]

A couple of times we had to "educate" the owner about the validity of their previous study. I am surprised at how many owners believe a study is a one shot deal and once they check it off their list, it never needs reviewed and is valid forever. One time the owner was insistent they would not pay for a revised short circuit and coordination study and we had to use their old one. We said the only way we would do that is if they accept ALL liability for the previous study and put it in writing. They quickly understood the problem at that point.