This report documents an experimental programme designed to investigate the High Energy Arcing Fault (HEAF) phenomena. The most recent international nuclear power plant (NPP) operating experience with HEAF events is documented in the Organisation for Economic Co-operation and Development (OECD) Nuclear Energy Agency (NEA) report titled “OECD Fire Project – Topical Report No. 1: Analysis of High Energy Arcing Fault (HEAF) Fire Events”, NEA/CSNI/R(2013)6. The Topical Report No. 1 details the causes and damaging effects of forty-eight HEAF events with fires, and recommends that an international experimental study be conducted to provide data for the development of more realistic HEAF consequence predictive models and provide data to better characterise HEAF events in probabilistic risk assessments (PRA). The NEA project detailed in this report included full-scale laboratory experiments where HEAFs were induced in actual NPP three phase electrical enclosures. Electrical, thermal, and pressure data were recorded to better understand the HEAF phenomena. The report documents twenty-six full scale experiments conducted over a three-year period.