Degradation characteristics of oil-immersed pressboard samples induced by partial discharges under DC voltage

To investigate partial discharge-induced degradation characteristics of oil-immersed pressboard under DC voltage, an experimental platform with needle-plane oil-pressboard insulation model is established. The surface condition and DC breakdown voltage of pressboard samples after PD pretreatment are observed and measured. In addition, a fitting formula to evaluate the degradation extent of pressboard samples is proposed. The results show that under constant PD pretreatments, surface roughness of pressboard samples decreases first and increases afterwards. The changing rate is positively correlated with PD intensity. During PD pretreatment, a “whitish-colored circular region” appears at samples' surface and grows with PD intensity. For PD pretreatments of 500 pC and 1000 pC, DC breakdown voltage of pressboard samples remains unchanged. The breakdown spot has no clear carbonization nor creepage trace. For PD pretreatments of 2000 pC and 3000 pC, DC breakdown voltage decreases. The breakdown spot is obviously carbonized and creepage paths emerge around spots. Further analysis indicates that degradation of oil-immersed pressboard samples due to DC PDs is the result of motion activation process induced by electrical and thermal effects under DC electric field.

[1]  Jinzhong Li,et al.  Partial discharge characteristics in oil-paper insulation under combined AC-DC voltage , 2014, IEEE Transactions on Dielectrics and Electrical Insulation.

[2]  P. Morshuis,et al.  Partial discharges at DC voltage: their mechanism, detection and analysis , 2005, IEEE Transactions on Dielectrics and Electrical Insulation.

[3]  J. Ozawa,et al.  DC Flashover Voltage Characeteristics and Their Calculation Method for Oil-Immersed Insulation Systems in HVDC Transformers , 1986, IEEE Transactions on Power Delivery.

[4]  P.H.F. Morshuis,et al.  Quality assessment of HVDC components by PD analysis , 1997, IEEE 1997 Annual Report Conference on Electrical Insulation and Dielectric Phenomena.

[5]  Shigemitsu Okabe,et al.  Deterioration characteristics due to partial discharges in insulating structure constituting gas-filled power transformers , 2010, IEEE Transactions on Dielectrics and Electrical Insulation.

[6]  U. Fromm,et al.  Interpretation of partial discharges at dc voltages , 1995 .

[7]  Ruijin Liao,et al.  Quantitative analysis of ageing condition of oil-paper insulation by frequency domain spectroscopy , 2012, IEEE Transactions on Dielectrics and Electrical Insulation.

[8]  R. Woschitz,et al.  The temperature dependence of the dielectric strength of transformer oil and pressboard insulation at HVDC polarity reversal stress , 2002, Proceedings of 2002 IEEE 14th International Conference on Dielectric Liquids. ICDL 2002 (Cat. No.02CH37319).

[9]  P.H.F. Morshuis,et al.  Partial discharge. Part XXIV: The analysis of PD in HVDC equipment , 1997 .

[10]  Michel Duval,et al.  A review of faults detectable by gas-in-oil analysis in transformers , 2002 .

[11]  A. Cavallini,et al.  Analysis of partial discharge phenomena in paper-oil insulation systems as a basis for risk assessment evaluation , 2005, IEEE International Conference on Dielectric Liquids, 2005. ICDL 2005..

[12]  Bin Liu,et al.  Study on the relationship between damage of oil‐impregnated insulation paper and evolution of phase‐resolved partial discharge patterns , 2011 .

[13]  H. Ayakawa,et al.  New protection method for HVDC lines including cables , 1995 .

[14]  M. Duval,et al.  Monitor for Hydrogen Dissolved in Transformer Oil , 1977, IEEE Transactions on Electrical Insulation.

[15]  E. Mori,et al.  New Apparatus for Detecting H2, CO, and CH4 Dissolved in Transformer Oil , 1983, IEEE Transactions on Electrical Insulation.

[16]  G. Ueta,et al.  Partial discharge-induced degradation characteristics of insulating structure constituting oil-immersed power transformers , 2010, IEEE Transactions on Dielectrics and Electrical Insulation.

[17]  Sujit Banerjee,et al.  Scanning Electron Microscopy Measurements of the Surface Roughness of Paper , 2009 .

[18]  E. Gockenbach,et al.  Experimental investigations on the behavior of decomposition gases in insulating liquids caused by partial discharge and breakdown , 1996, ICDL'96. 12th International Conference on Conduction and Breakdown in Dielectric Liquids.

[19]  J. Jalbert,et al.  Decomposition of transformer oils: a new approach for the determination of dissolved gases , 1997 .

[20]  Ho-Joon Seo,et al.  Development of Gas Detector for Hydrogen Dissolved in Transformer Oil , 2005, 2005 IEEE Instrumentationand Measurement Technology Conference Proceedings.

[21]  Liu Yi.  Developing Processes of Direct Current Partial Discharge of Defects on Ultra High Voltage Converter Transformer Oil-paper Insulation , 2012 .

[22]  F. Nozari,et al.  Power electronics in electric utilities: HVDC power transmission systems , 1988 .