Modeling of Partial Discharges from a Spherical Cavity within a Dielectric Material under Variable Frequency Electric Fields
Partial discharge (PD) is a discharge event that does not bridge the electrodes within an electrical insulation system under high voltage stress. In high voltage components, the measurement of partial discharge is used in the performance assessment of an insulation system. Through modeling the discharge process a better understanding of the phenomena may be attained. Previous studies have considered the modeling of PD activity from a cylindrical cavity. However, this is a limited approach as the most common types of cavities found in the insulation materials are either spherical or ellipsoidal. This paper describes the development of a model for a spherical cavity within a homogeneous dielectric. The model developed has been used to study the influence of the applied frequency on partial discharge activity and obtained results are presented.
Simplified hybrid PD model in voids: Pattern validation
The purpose of the present work is to show the validation of a new model to simulate the physical phenomenon of partial discharge (PD) produced in air voids inside insulating epoxy resin. The model has been developed on the basis of a new approach that combines the known circuit model of three capacitors with a model used to describe the behavior of the ionized channel inside of the inclusion during the discharge phenomenon, short-circuiting the capacity that represents the void. The approach is based on time-variable conductance of the void, subjected to multistress conditions: voltage, temperature and pressure. The new approach has been developed from a time variable conductivity model used for the study of the discharge with dielectric barrier (DBD). The different parameters which influence the discharge phenomenon in the void are taken into account through an approach in which a lumped circuit is used to simulate the effects of global PD asset. The results of the multiple simulations have been compared with experimental and simulated behaviors found in the literature on the subject.
Measuring system for phase-resolved partial discharge detection at low frequencies
This paper addresses the measurement of partial discharges (PD) for a range of low frequencies of applied voltage and explores the frequency dependence of PD patterns for a few objects. The aim is to determine the existence of frequency-dependent trends in PD patterns and how these trends can be expressed through use of statistical parameters calculated from the PD patterns. An experimental setup was developed to measure phase-resolved PD patterns for a range of low frequencies, from 1 mHz to 100 Hz. Tests were performed on a few PD-infested objects, including a corona gap, a needle-film object, and a generator stator bar, to demonstrate the measuring system and analysis methods. Statistical operators were used to quantify the PD patterns, and the resulting parameters were then considered as functions of frequency.