High voltage phase to ground arc calculation example

Consider 242kV rated overhead line and 5 kA phase to ground fault cleared within 1 second by upstream expulsion fuse. Incident Energy, Hazard Risk Category, Assumed Working distance and Typical Personal Protective Equipment (PPE) will be determined based on NFPA 70E procedure for estimating incident energy exposure for live line work on overhead open air systems.

We start with entering system line voltage and clicking on [Calculate Gap and Distance] button to determine assumed arc gap and assumed working distances based on the NFPA 70E procedure. In our example, they would be equal to 14 and 35 inches respectively.

Figure 1 - Phase to Ground Arcs in Air Front Screen

System Summary and Calculation Results including Incident Energy, Hazard Risk Category, Assumed Working distance and Typical Personal Protective Equipment (PPE) will be displayed by hitting [Next] button.

Figure 2 - Phase to Ground Arc Results

By pressing [Save Results] button, the results will be saved to a text file for future reference or printing. You can save results for different jobs under different names. By choosing Open from File menu (see Figure 1 above) you can open an existing results file, inspect its current content, do simple editing operations including Cut, Copy and Paste to and from the clipboard, Save and Print. If you need more complex editing, import the file into your favorite text manipulation processor (MS Word as an example) and do what you need to do.