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<p>Power transformers operating at elevated temperatures are exposed to oxidative environments that initiate irreversible chemical degradation within their insulation systems. Considerable reduction in partial discharge inception voltage is observed with the thermally aged synthetic ester fluid, irrespective of the type of voltage applied—AC or harmonic AC or DC or lightning impulse. Under harmonic AC voltage, intensive discharges were observed with the thermally aged specimens; however, both the intensity and pulse width of the UHF and fluorescent fiber signal decreased with increasing THD content. The chromophore moieties give rise to larger carbonaceous particle, due to continued degradation results in increased probability of such discharges at lower voltages. The PD inception voltage measured using both the UHF and fluorescent fiber techniques exhibits negligible variation under AC and DC voltages, provided the area under the UV–Vis absorption curve remains minimal for the insulating fluid used during measurement. Fluorescent fiber sensing under lightning impulse voltage shows strong potential for PD-based condition monitoring. Singular discharge events are predominantly observed immediately following the peak of the applied voltage waveform during PD inception. The absorbance characteristics of the thermally aged synthetic ester fluid, through UV–Vis spectroscopy, reveal the shifts and increased intensity in the absorbance curve as the aging progresses. The observed Stokes shift with the thermally aged insulating fluid clearly indicates characteristic changes in its excitation–emission matrix (EEM) spectra. The shift in excitation–emission maxima in 3D EEM spectra with thermally aged fluids strongly supports the argument that fluorescent fiber losses sensitivity toward partial discharge detection, irrespective of voltage profiles. Rheological studies clearly indicate that an elevation in temperature of the fluid leads to a reduction in the storage modulus, consequently diminishing the elastic characteristics across the entire range of angular frequency. Additionally, the changes in loss factor characteristics of thermally aged SE fluid suggest that a late-phase transition affects its flow behavior.</p>

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Understanding the thermal aging impact of synthetic ester fluid adopting fluorescent fiber sensing technique by rheological study

  • 期刊论文

  • 发表日期：

    2025年7月23日

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  • Mridula,
  • Ramanujam Sarathi,
  • Ramesh Laxminarayan Gardas,
  • Michael G. Danikas

摘要

Power transformers operating at elevated temperatures are exposed to oxidative environments that initiate irreversible chemical degradation within their insulation systems. Considerable reduction in partial discharge inception voltage is observed with the thermally aged synthetic ester fluid, irrespective of the type of voltage applied—AC or harmonic AC or DC or lightning impulse. Under harmonic AC voltage, intensive discharges were observed with the thermally aged specimens; however, both the intensity and pulse width of the UHF and fluorescent fiber signal decreased with increasing THD content. The chromophore moieties give rise to larger carbonaceous particle, due to continued degradation results in increased probability of such discharges at lower voltages. The PD inception voltage measured using both the UHF and fluorescent fiber techniques exhibits negligible variation under AC and DC voltages, provided the area under the UV–Vis absorption curve remains minimal for the insulating fluid used during measurement. Fluorescent fiber sensing under lightning impulse voltage shows strong potential for PD-based condition monitoring. Singular discharge events are predominantly observed immediately following the peak of the applied voltage waveform during PD inception. The absorbance characteristics of the thermally aged synthetic ester fluid, through UV–Vis spectroscopy, reveal the shifts and increased intensity in the absorbance curve as the aging progresses. The observed Stokes shift with the thermally aged insulating fluid clearly indicates characteristic changes in its excitation–emission matrix (EEM) spectra. The shift in excitation–emission maxima in 3D EEM spectra with thermally aged fluids strongly supports the argument that fluorescent fiber losses sensitivity toward partial discharge detection, irrespective of voltage profiles. Rheological studies clearly indicate that an elevation in temperature of the fluid leads to a reduction in the storage modulus, consequently diminishing the elastic characteristics across the entire range of angular frequency. Additionally, the changes in loss factor characteristics of thermally aged SE fluid suggest that a late-phase transition affects its flow behavior.