Sensitivity analysis of a parallel-plate method for measuring the dielectric permittivity of high-voltage insulating materials

Ascertaining the dielectric character of polymeric insulation materials is of particular interest for comparative studies that use accelerated ageing and samples from decommissioned installations. In the case of polymeric samples, the possibility of physical deformation within the sample holder adds additional variability to comparative measurements. Using readily obtainable instrumentation, this study undertakes a systematic sensitivity analysis of a parallel-plate capacitance measurement approach for polymeric materials that only has one capacitance plate in contact with the sample, avoiding issues of sample deformation. The analysis demonstrates that the biggest contributor of uncertainty in the measurement of the relative permittivity and loss tangent is the precision with which the plate-plate and plate-sample separation is determined. The measurements show that the determination of loss tangent can be susceptible to uncertainties arising from electrical noise, but that these can be controlled further by utilising more refined instrumentation.