Electrical Detection of Creeping Discharges over Insulator Surfaces in Atmospheric Gases under AC Voltage Application

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.

Clarifications on the Behavior of Alternative Gases to SF6 in Divergent Electric Field Distributions under AC Voltage

“…According to the pre-breakdown current measurements (see Figure 8) and the optical observations (see Figures 3 and 8), the negative glow streamer mode was identified as the breakdown mechanism for compressed N2. These findings agree with previous investigations [10][11][12][13][14][15]. Figure 9 summarizes the negative and the positive-inception voltage and AC breakdown measurement for 12.77% O2-87.23% CO2 at various pressures up to 10 bar abs.…”

A Comparison of Partial Discharge Sensors for Natural Gas Insulated High Voltage Equipment

“…This means that there was a considerable safety margin built into this equipment to ensure it does not fail during the operation on the network, as it is known that SF 6 has an insulation strength approximately three times that of normal air (not technical air) [ 8 ]. The insulation strength and therefore the different PD results of each alternative natural gas are due to the individual critical reduced electric field strength of each gas [ 8 ] and the method in which streamers and leader channels form and how ‘brittle’ the gas is to allow streamer development [ 27 ].…”

“…Many similar events were recorded for both carbon dioxide and technical air; however, it was not possible to obtain PD measurements for pure nitrogen due to the proximity of PD inception to the breakdown voltage which occurred across the clean gas gap, making it very difficult to obtain multiple stable PD event measurements. strength of each gas [8] and the method in which streamers and leader channels form and how 'brittle' the gas is to allow streamer development [27]. In Figure 8, measured signals from one single PD event are shown for the GIL demonstrator when it was filled with 3 bar CO2 with contaminated particles.…”

Special Issue “Selected Papers from the 2018 IEEE International Conference on High Voltage Engineering (ICHVE 2018)”

“…In papers [9][10][11], the authors addressed issues regarding solid insulating materials: creeping discharges on insulating surfaces surrounded by gaseous insulation, electrical treeing in cross-linked polyethylene (XLPE) and partial discharge surface degradation on silicon rubber, respectively.…”

“…More specifically, paper [9] dealt 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, N 2 and CO 2 ) as insulation mediums in a point-plane electrode arrangement under AC voltage applications. According to the experimental and numerical results, the discharge activity depended highly on the geometrical and material properties of the dielectric and the solid/atmospheric gas interface.…”