Influence of particles on AC and DC electrical performance of gas insulated systems at extra-high-voltage

Abstract

Abstruct-High-voltage breakdown measurements were made in two similar particle contaminated coaxial test systems, one with AC and the other with DC voltages. Information is presented on the effects of particle size, shape, and material for both SF6 and N2 gases at pressures up to 15 atm in a plain coaxial gap and a coaxial gap including a posttype support spacer. Particle motion and location were found to strong ly influence insulation performance. Measured values of electric fields which lifted and drove the particles, so that they bounced vertically and laterally, compare favorably with calculated levels. Movement into the the higher stress region at the center conductor was correlated with the initiation of sparkover. These breakdowns could be at levels more than a factor of five lower than those obtained when contamination was not introduced. Large variations in breakdown voltage of as much as 3 to 1 encountered under DC correspond to conditions where particle motion could be restricted, presumably by corona discharge, to motion near the outer electrode. AC sparkover levels were typically at the lower limits of the DC range. Both free and attached particles on the dielectric spacer surface would trigger flashover at the same low levels as were measured in the gas gap.

Review of high-voltage gas breakdown and insulators in compressed gas

“…Particles can be moved onto the insulators by the electric field and can, subsequently, initiate breakdown [1,17,51,52,60,[64][65][66]. The insulator flashover characteristics with particles are very similar to the particle-initiated gas breakdown characteristics.…”

Understanding the partial discharge activity of conducting particles in GIS under DC voltages using the UHF technique

“…Considerable research work was carried out to understand the particle movement/partial discharge activity in SF 6 filled GIS under AC voltages [6][7][8]. Similar work under the DC voltages is at infancy stage [7][8][9].…”

“…Considerable research work was carried out to understand the particle movement/partial discharge activity in SF 6 filled GIS under AC voltages [6][7][8]. Similar work under the DC voltages is at infancy stage [7][8][9]. The partial discharge (PD) pulses that occur in the insulation structure are of short duration, which involves rise and fall times of a nanosecond or less, signals in the ultra high frequency (UHF) range (300-3000 MHz) are excited [10,11].…”

Partial Discharges Characteristics of Harmful Conducting Particles Around Spacer Under AC Voltage in Atmospheric Air

“…However, after a long time operation, failures in GIS are also hard to avoid. Meanwhile, it is reported that the presence of contaminating particles has long been recognized as a major factor on insulation failure in GIS [1]. Currently, from the viewpoint of maintenance of electric equipment, many attempts have been made to analyze the cause and mechanism of failures by analyzing partial discharges (PD) signals generated by the particles [2,3].…”