HOW TO FAIL THE MEASURE OF DC CONDUCTIVITY OR RESISTIVITY OF POLYMERIC MATERIALS
Résumé
The advent of HVDC and MVDC applications arrived with a challenge for the dielectric's community: the determination of the conductivity of insulating materials under DC stresses, particular challenging for non-linear materials. Usually obtained from current-voltage (I-V) tests, this work shares a series of faults (and learnings) resulted from the struggle to tailor a reproducible and repeatable protocol for electrical current measurements of polymeric insulating samples. I-V measures have been conducted for epoxy and silicone samples under various electric fields, temperatures and water contents. Results shows that, if the objective is to fail in I-V measurement, it is enough to: Underestimate the structure/microstructure relationship of departure; underestimate key physical parameters during the test; and underestimate the structure/microstructure changes during the test. For each case, illustrations and quantification have being given. Because the electrical current seems to be highly biased by the system characteristics, and since the conductivity calculated from the Ohm's law has no physical meaning in non-Ohmic regions, the intrinsic conductivity of polymeric insulating is hardly attainable.
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