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A custom-made modular high-precision dielectric spectrometer for quantifying aging-induced molecular changes in (sub-)picofarad polymeric samples is presented. Validation and characterization of the setup's performance is obtained by quantifying the change in the dielectric response of an epoxy polymer following the exposure to thermal, hygrothermal and ultraviolet radiation stress. It is shown that the observed changes in the dielectric spectra can be resolved with a relative precision better than 5·10−5 and are in line with previous studies employing commercial instruments on samples of higher capacitance. This setup is intended to serve as a blueprint for a sensitive and extensible (because modular) measurement tool for studying the pre-breakdown dynamics in low-capacitance recessed or disc-shaped specimens as used, e.g., in high-voltage insulation testing. [ABSTRACT FROM AUTHOR]

Recently it was shown that it is possible to predict the breakdown voltages of arbitrary electrode configurations under standard voltage applications for electron attaching gases with a stepped leader model originally proposed for SF6. In this contribution this model was applied to the hydrofluoroolefin HFO1234ze. The parameters, which are necessary for the modeling, are derived from measurement of statistical and formative time lags in an electrode configuration with a homogeneous background field with a small protrusion. The parameters are used to predict the breakdown voltage for technical relevant geometries and standard voltage wave shapes. To verify these predictions, breakdown experiments in nearly homogeneous and strongly inhomogeneous field configurations with AC and lightning impulse voltage application of both polarities were performed. The hydrofluoroolefin exhibits insulation properties which are quite similar to those of SF6. Therefore it could be considered as admixture for high voltage gaseous insulations or as replacement in medium voltage equipment. For applications using the pure gas the temperature and pressure range has to be limited to prevent liquefaction. The good match between the simulations and the experiments gives evidence that the model can be applied to a broad range of other novel electron attaching gases as well. [ABSTRACT FROM AUTHOR]