The influence of magnitude and rise time of applied voltage and the type of oil on streamer growth in a wet-mate DC connector

For the safe design and operation of wet-mate (WM) DC power connector, a time-dependent full thermo-electrodynamic model comprised of Poisson's equation, three charge continuity equations-one each for the positive and negative ions and one for the electrons-, and a thermal diffusion equation is developed to study the streamer initiation and propagation in the oil portion of a WM DC chamber. The electric field dependent molecular ionization mechanism accounts for the source term for free charge carriers, and positive ion/electron recombination, positive/negative ion recombination and electron attachment represent sink terms in the oil section. The solid portion of the WM DC connector is modeled as a perfect insulator. Considering a needle-sphere electrode geometry with electrodes covered by a dielectric solid and oil enclosed by the dielectric solid, it is approached the complicated solid-liquid insulation system envisaged in a WM DC connector after mating. By using the model, the influence of three parameters including magnitude and rise time of applied voltage as well as the type of oil on streamer initiation and propagation is investigated. It is found that the shorter rise time the more prominent streamer growth in the oil portion. For oil comprising only aromatics, an electric field magnitude larger than about 2×10
⁸
V/m is needed to propagate streamers, while this value for the oil comprising naphthenics/paraffinics will be exceeding 4×10
⁸
V/m.