Analysis of Fire Accident Mechanisms and Protection Improvements in Outdoor Grid-Connected PV PCS

The increasing deployment of photovoltaic (PV) generation has raised concerns regarding the fire safety of outdoor power conversion systems (PCS). This study investigates a fire accident involving a 250kW grid-connected PV PCS through field inspection, event analysis, damaged components, and 3D X-ray CT analysis. Fire damage was concentrated around the DC-link capacitor bank, plate busbars, insulation layer, and IGBT stack. The observed localized melting, perforation, and insulation damage indicate that insulation degradation and surface discharge between the plate busbars may have contributed to the accident progression, although the initial ignition source could not be conclusively identified. The creepage distance of the insulation structure was additionally evaluated with reference to IEC 60664-1 considering pollution degree and material group. Based on the accident analysis, improvements including strengthened busbar insulation design and inspection, PV-side rapid shutdown, and coordinated DC/AC isolation are proposed. The results will provide a basis for improving PCS fire prevention, inspection, and protection designs.