Commercially available programs can run thousands of buses and allow easy switching between modes. Input all data from the single-line diagrams and the data collection effort into a short circuit program. Step 3: Determine The Bolted Fault Currents Unit substation with one or two primary feeders.MCC with one or two feeders, one or both energized.Unit substation with two transformers with secondary tie opened or closed.t is important to determine the available short-circuit current for modes of operation that provide both the maximum and the minimum available short-circuit currents. Generators running in parallel with the utility supply or in standby.Utility interface substation secondary bus tie breaker open or closed. One or more utility feeders in service.In a site with a simple radial distribution system there is only one mode of operation-normal-but a more complex system can have many modes. Step 2: Determine The System Modes Of Operation Arc flash boundary plus#While the data required for this study is similar to data collected for typical short-circuit and protective- device coordination studies, it goes further in that all low-voltage distribution and control equipment plus its feeders and large branch circuits must be included. Regular site employees who are familiar with the site and its safety practices may be able to do this part of the job best. Even for a plant with nominally up-to-date single-line diagrams, time-current curves, and short-circuit study on a computer, the field part of the study will take about half of the effort. The largest effort in an arc-flash hazard study is collecting the field data. Step 1: Collect The System And Installation Data
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