Abstract
Creeping discharges over insulator surfaces have been related to the presence of triple junctions in compressed gas insulated systems. The performance of dielectric materials frequently utilised in gaseous insulating high voltage applications, stressed under triple junction conditions, has been an interesting topic approached through many different physical perspectives. Presented research outcomes have contributed to the understanding of the mechanisms behind the related phenomena, macroscopically and microscopically. This paper deals with the electrical detection of creeping discharges over disc-shaped insulator samples of different dielectric materials (polytetrafluoroethylene (PTFE), epoxy resin and silicone rubber) using atmospheric gases (dry air, N2 and CO2) as insulation medium in a point-plane electrode arrangement and under AC voltage application. The entire approach implementation is described in detail, from the initial numerical field simulations of the electrode configuration to the sensing and recording devices specifications and applications. The obtained results demonstrate the dependence of the generated discharge activity on the geometrical and material properties of the dielectric and the solid/atmospheric gas interface. The current work will be further extended as part of a future extensive research programme.
Highlights
Triple junctions are defined as points where the gaseous medium, dielectric material and electrode meet leading to local electric field enhancements
This paper examines the development of creeping discharge over disc-shaped insulator samples of different dielectric materials, namely polytetrafluoroethylene (PTFE), epoxy resin and silicone rubber, which are frequently utilised in high voltage technology applications
Flashover tests results showed that, for the examined electric field distribution and for all the examined insulating gaseous media, lower flashover voltages were measured for electrode configurations with insulating materials having higher relative permittivity
Summary
Triple junctions are defined as points where the gaseous medium, dielectric material and electrode meet leading to local electric field enhancements. When a certain electric field level is reached, the initiation of discharge activity is possible. In the case of their appearance, such phenomena become present at voltages below the optimised rated operating and withstand levels of the affected apparatus, introducing additional concerns in the overall effort of designing effective and reliable insulating systems. The most common discharge phenomenon linked with enhanced electric fields in the vicinity of solid dielectric-gas interface is the streamer creeping discharge. Characteristics of single streamer events in homogenous electric field arrangements have been reported [1,2] where the Energies 2019, 12, 2970; doi:10.3390/en12152970 www.mdpi.com/journal/energies
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