Jean Rivenc

An overview of electrical properties for stress grading optimization

The scope of the following paper is to present, both from a theoretical and a practical point of view, some aspects involved in stress grading in the general configuration where insulated HV conductors pass through a grounded screen. The difference between capacitive and resistive materials is discussed; particular attention is devoted to the rules governing the potential and the field distribution in both cases. The case of a capacitive varnish with nonlinear permittivity is discussed and a comparison with materials of constant permittivity is made. The experimental behavior of nonlinear semiconducting materials used in practice are examined and a discussion is given on the possible use of resistive materials of constant conductivity. Finally, practical considerations are listed as basic rules for optimizing the grading effect.

A physical model to explain electrostatic charging in an automotive environment; correlation with experiments

Electrostatic shock is a very common feature in an automotive environment. Such a phenomenon may be detrimental for the embarked electronic devices and/or the passengers. The work presented in the following deals with this latter aspect and consists of the research of physical solutions able to avoid the human body voltage rise up and its associated discharge. This paper is focused on the determination of the cause of its appearance and on the development of an appropriate model able to predict the charging values versus the different characteristics of the materials used inside the car. The paper presents a model of the occupant charging during the exit from a car and its correlation with the measured values, in a real situation. Getting a better understanding of the individuals static build up could allow us to find a reliable solution to avoid both static charge accumulation (and electrostatic voltage increase) on the human body and shock risk.

Quantification of Flow Electrification in the Context of a Tank being Filled with a Dielectric Liquid

Contact of the walls of a tank with the liquid it is being filled with creates an electrical double layer of charge at the interface between the two materials, independently of their respective nature. On the liquid side, movement of this layer of electrical charge by the filling or draining of the tank induces a streaming current, which provides useful information concerning the intrinsic flow electrification phenomenon occurring near the tank walls. Indeed, the flow of the liquid modifies the electroneutrality of the solid/liquid interface, which is reestablished with the generation of a new electrical charge in the electrical double layer via complex physicochemical reactions in the form of a wall current. Moreover, this process of charge generation is modified if the liquid entering the tank already contains a certain amount of charge and may even invert the sign of the charge generated. This paper provides a detailed description of an experimental setup that allows measuring, the amount of charge entering with the liquid in a tank being filled and the intrinsic amount of charge generated at the wall of the tank independently of the charge coming with the liquid. These methods were validated by analytical models with an acceptable precision level for an industrial approach. Techniques for analyzing the impact of the charge entering the tank on the one generated intrinsically at the walls are also explored, but their validation is still under study.