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Several degradation mechanisms may affect polymeric insulation system reliability. Some authors postulate that, even in a perfect dielectric, nanoscale cavities can enlarge due to various mechanisms (from mechanical fatigue to lowering of the degradation reaction energy barrier) up to a point where highly energetic phenomena, which bring about breakdown, can be incepted. Other authors are more focused...
Partial discharge (PD) in a void reflects degradation of insulating material and, therefore, is utilized for insulation diagnosis. Although it is well known that PD pattern changes with voltage application, it is not clear how the pattern change is related to material degradation or how it is related to final breakdown. We simultaneously observed PD characteristics and light emission from partial...
Partial discharge (PD) pattern recognition and interpretation is still often the key to assess the presence and the nature of defects inside electrical insulation. In the case of external PD source, as when surface partial discharges are concerned, the PD pattern can be strongly influenced by the environmental conditions. This work presents the experimental outcome of a PD measurement campaign performed...
To develop a high temperature superconducting (HTS) transformer, the insulating materials used should be characterized at cryogenic environment. An attempt has been made to measure the AC, standard impulse and bi-directional oscillatory non-standard impulse breakdown strength and the corresponding partial discharge. Kraft paper and press paper used in transformer insulation were used for characterizing...
Polymeric nanocomposite materials have shown a big potential for an impact in wire wound rotating machine stator insulation. Small wire wound machines, in fact, have a mainly organic stator winding insulation which is easily degraded by partial discharge (PD) activity. In this kind of equipment, then, the presence of PD activity leads to failure in a very short time. Nanofilled polymeric materials,...
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