Electric field measurement in SF6 employing electric field induced second harmonic generation

Abstract Boasting a compact structure and excellent power transmission performance, the engineering deployment of DC gas-insulated switchgear (GIS) and gas-insulated transmission lines (GILs) remains constrained by insulation issues and insufficient understanding of the flashover characteristics of surface electric-fields, motivating the need for high precision, non-intrusive field diagnostics. An electric-field measurement system based on electric-field-induced second-harmonic(E-FISH) is developed to address non-intrusive DC-field sensing in SF6. This study investigates the effects of gas pressure and laser energy on the second-harmonic response and electric-field measurement performance in pressurized SF₆, and analyses the competing effects of molecular-density enhancement and phase mismatch. A focused-beam integral model is employed for quantitative analysis of non-uniform electric fields, providing a basis for further application of E-FISH to DC GIS/GIL diagnostics.