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This paper reports on experimental investigations dealing with the impact of dissolved and disperse water on the breakdown strength of open oil gaps and the flashover behavior of solid/liquid interfaces in a uniform electrical AC field using clean as well as carbonized transformer oils. The measurements reveal that in technically clean oil with disperse water at small gap distances the breakdown strength can for subsequent voltage stresses be significantly higher after the first initiation of a breakdown than during the fmt readings while for larger gap spacings this effect cannot be noticed. Moreover, it is shown in this contribution that especially for practically relevant long gap distances carbonized oils can exhibit a better electrical strength in the presence of high absolute water contents than clean oil. This finding applies to the breakdown voltage of open oil gaps as well as to the flashover behavior of soliaquid interfaces.

One major task in developing electric cars is to control electromagnetic interferences (EMI)

-Changing the drive train of combustion engine cars from mechanical power transmission to an electric traction network for electric driven vehicles (EV) is a challenge for the EMC performance of the entire system. To reduce electromagnetic interferences, the electric high voltage (HV) traction system consists of entirely shielded housings and cables. In lack of alternatives recent component level EMC measurement methodologies for low voltage (LV) systems are also used for novel HV components. These methods have been developed for automotive LV harnesses, which consist of multiple bundled unshielded single wires. In contrast HV networks are manufactured of coaxially shielded cables and this change in network topology is not considered in EMC testing yet.This contribution investigates the effect of changed network topologies within HV systems on component level EMC tests. Therefore the recent state of art in component level testing is presented and the differences of LV and HV network topologies are discussed. An adaption of the component level test setup for HV components is introduced and a minimized HV system investigated. Results of a case study on an inverter for a hybrid car are presented and the impact of the measurements in the design of HV systems will be discussed.