Streamer Propagation and Breakdown in a Very Small Point-Insulating Plate Gap in Mineral Oil and Ester Liquids at Positive Lightning Impulse Voltage

Abstract

This article presents the results of comparative studies on streamer propagation and breakdown in a point-insulating plate electrode system in mineral oil and two ester liquids. The studies were performed for a 10-mm gap and a positive standard lightning impulse. The work was focused on the comparison of light waveforms registered using the photomultiplier technique. The results indicated that both esters demonstrate a lower resistance against the appearance of fast energetic streamers than mineral oil. The reason for such a conclusion is that the number of lightning impulses supplied to the electrode system for which the above-mentioned fast streamers appeared at a given voltage level was always higher in the case of ester liquids than mineral oil. In terms of breakdown, the esters tested were assessed as more susceptible to the appearance of breakdown in the investigated electrode system. The number of breakdowns recorded in the case of esters was always greater than the corresponding number of breakdowns in mineral oil. This may be supposed on the basis of the obtained results that imply that, in both synthetic and natural ester, the formed breakdown channel, which bridged the gap through the surface of pressboard plate, is characterized by higher energy than in the case of mineral oil.

Characteristics of Negative Streamer Development in Ester Liquids and Mineral Oil in a Point-To-Sphere Electrode System with a Pressboard Barrier

“…The next measurement procedure was carried out after a 20 min break wherein during this time the liquid sample was stirred. Based on our own experience [15,16,19], as well as recommendations of the standards [11,12], it was decided that the liquid samples would not be changed to a new one after a given measurement procedure. This was because breakdown was not reached during the tests.…”

“…Since the evaluated negative lightning impulse breakdown voltage oscillated around 125 kV with ca. 5-7 kV of standard deviation, it was assumed that a value of 100 kV would be the right starting value at which streamers will develop as a basic, slow mode [18][19][20][21]. Then the subsequent lightning impulses were supplied to the electrode system with the assumed voltage step (∆U) equal to 5 kV.…”

“…The higher frequency of light pulses registered the more frequent step lengthening of the occurring discharge channels. The higher peak values of the light pulses reflect the higher energy of the discharge itself [15][16][17][18][19][20][21].…”

Power Transformer Diagnostics, Monitoring and Design Features

“…However, as the chemical compositions of these fluids are very different than those for mineral oils, new specification standards for non-mineral oils have been produced. In this Issue a comparison study of streamer propagation and breakdown between Ester liquids and mineral oil was conducted by Rozga [3].…”

A New Switching Impulse Generator Based on Transformer Boosting and Insulated Gate Bipolar Transistor Trigger Control

“…On account of the frequent failures of high voltage power equipment [1][2][3], more attention has been increasingly focused on the impulse withstand voltage test in the field [4], which has become a more stringent and effective method of evaluating the insulation status of power equipment [5][6][7][8]. The traditional impulse generator is built on a Marx circuit, which has been widely applied in high voltage testing and insulation assess for many years.…”