STUDY ON THE ELECTROMECHANICS OF NON-SPHERICAL PARTICLES UNDER ELECTRIC FIELD IN DIELECTRIC SYSTEMS

Abstract

Gas insulated systems such as gas insulated switchgears (GIS) and gas insulated transmission lines (GITL) are widely used in the electric power systems for increasing operational reliability and safety as well as reducing space. Most of failures in operation of gas insulated systems are caused by contaminating conducting particles. To improve the reliability of the systems, many researchers have investigated the movement behavior of the particles as the foundation for particle deactivation. Although the effect of the corona discharge is found on the particle movement, the effect has not been fully explained yet. The objective of this dissertation is to clarify the electromechanics of conducting and dielectric non-spherical particles lying on an electrode under electric field, and the effects of the particle profile and the corona discharge on the particle movement. This dissertation describes analytical and experimental studies on the electromechanics of non-spherical particles under external electric field. For the analysis, the configuration is a conducting or dielectric prolate spheroid lying on or above a grounded plane under uniform electric field. The analysis determines the relationships between the electrostatic quantities and parameters of the configuration. The electrostatic quantities are electric field, induced charge, force, and torque. The analysis is done for two arrangements in which the major axis of the spheroid (i) is perpendicular to the plane or (ii) makes a tilt angle with the plane. In the analysis, the electric field is calculated by using the method of multipole images and the multipole re-expansion in prolate spheroidal coordinates to realize high accuracy. The force and torque are determined from the stress on the spheroid surface which is a function of the electric field. For the experiment, the measurement of lifting electric field and the observation of the particle movement between two parallel-plate electrodes are carried out. The spheroidal particles and the wire particles are used in the experiment. The force and torque on a wire particle in the movement are estimated by using an approximated model of a prolate spheroid for discussion.