Utility grounding systems (e.g., transmission line footings, substation ground grids, distribution pole grounds) must be offset from buried pipelines to avoid damage due to arcing. A lightning strike to the tower can form both an ionized path to the pipe and a flash over a phase insulator. Fault current to the pipe can then cause wall failure. This Phase 1 study proposes parameters for the testing of soil breakdown for impulse, power frequency, and power arc sustainment initiated by lightning. An arc model based on electrical input power and thermal dissipation provides physical insight into the breakdown process, helps optimize test parameters and procedures, and allows interpolation among a limited number of tests.
KEYWORDS: Lightning, Shared right of way, Pipeline to grounding offset, Soil ionization, Soil breakdown, Soil arcing, Pipeline damage