Investigation of Partial Discharge Phenomena in Artificial Cavity in Epoxy Cast Resin Insulation System

Abstract

It is crucial for proper insulation design of cast resin transformer to consider voids and delamination which might exist in cast molding because of several surface boundaries between resin and conductor. Such defects in the insulator lead to reduction of the life of the apparatus. In this report, we investigate the relation between the void size and apparent charge of partial discharge (PD) occurring in a model simulating the insulation system of cast resin transformer. It is also important to determine necessary PD detection sensitivity of PD test in a factory as well as in a field. In this paper, we also discuss the detection sensitivity by considering the relation between charge and void radius using formula derived by L. Niemyer, M. Pedersen and their colleagues in the late 1980's to apply to the case of the cast resin transformer. Experiments were also performed to obtain PD inception voltage (PDIV) of epoxy resin slab including an artificial void with a given size. Investigation was also made on the effect of X-ray irradiation to the epoxy resin on PDIV characteristics.

Effect of lightning impulse prestress on AC partial discharge characteristics in cast resin transformer

“…In order to examine the effect of X‐ray irradiation, PD characteristics were measured under X‐rays with a set power of 10 W using the same X‐ray module as in a previous report . In addition, we applied a standard lightning impulse voltage for prestressing, and measured PDIV and PDEV as explained above.…”

“…We previously conducted basic studies on insulation diagnosis of cast resin transformers and insulation properties of microvoids in resin as well as on effectivity of X‐ray irradiation for microvoid detection, thus aiming at improvement of defect diagnosis inside cast resin transformers. On the other hand, one must understand how lightning impulse withstand voltage tests, conducted as part of preshipment inspection of cast resin transformers, affect subsequent partial discharge (PD) tests.…”

Investigation of partial discharge characteristics induced by X‐ray irradiation in artificial cavity in epoxy resin

“…As a part of this research, we investigated the fundamental mechanisms of PD behavior in epoxy resin voids [1][2][3][4][5].…”

“…We have conducted studies aiming at radical improvement of partial discharge (PD) control and detection in broad terms of diagnosis, design, and testing of the insulation systems of cast devices. As a part of this research, we investigated the fundamental mechanisms of PD behavior in epoxy resin voids [1][2][3][4][5].…”