Study on micro bridge impurities in oil-paper insulation at DC voltage: their generation, growth and interaction with partial discharge

To investigate the characteristics of micro bridges and their interactions with partial discharge (PD) in oil-paper insulation under DC voltage, an experimental platform with two-copper-electrode models is established. Generation and growth of micro bridge impurities are observed. PDs in experimental process are detected and analyzed. The result shows that the generation and growth of micro bridges have three stages based on their quantity and shape. At first stage PD accelerates the generation of micro bridges. At second stage the grown bridges trigger stronger discharges. At the last stage a so-called "hazardous bridge" that triggers highly intensive PDs emerges, through which breakdown happens. Therefore, bridges and PDs promote each other to cause insulation failure. In addition, impurities at the second stage are observed to transform into pile-like, bridge-like or particle-like shapes. The transformation process is considered to relate with the change of composition force on fiber bundles. Besides, a "cluster discharging" phenomenon is observed at the second stage, which is associated with the generation and disappearance of micro bridge impurities.

[1]  Renate Bever,et al.  Partial Discharge Testing under Direct Voltage Conditions , 1982, IEEE Transactions on Aerospace and Electronic Systems.

[2]  G. Chen,et al.  Pre-breakdown characteristics of contaminated power transformer oil , 2007, 2007 Annual Report - Conference on Electrical Insulation and Dielectric Phenomena.

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

[4]  Ramanujam Sarathi,et al.  Investigation of partial discharge activity of single conducting particle in transformer oil under DC voltages using UHF technique , 2009 .

[5]  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..

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

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

[8]  E. Gulski,et al.  Sensitivity check for UHF PD detection on power transformers , 2004, Conference Record of the 2004 IEEE International Symposium on Electrical Insulation.

[9]  R. Tobazeon,et al.  Behaviour of free conducting particles and their role on breakdown in oils under AC and DC voltages , 1992 .

[10]  H. Okubo,et al.  PD and BD Probability Distribution and Equi-Probabilistic V-t Characteristics of Oil-Filled Transformer Insulation , 1982, IEEE Power Engineering Review.

[11]  J. A. Kok,et al.  Electrical Breakdown of Insulating Liquids , 1964 .

[12]  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.

[13]  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.

[14]  Udo Fromm,et al.  Partial Discharges in Gaseous Voids for DC Voltage , 1994 .

[15]  Deepa K Tiku,et al.  dc Power Transmission: Mercury-Arc to Thyristor HVdc Valves [History] , 2014, IEEE Power and Energy Magazine.

[16]  Li Yanming,et al.  Digital detection, grouping and classification of partial discharge signals at DC voltage , 2008, IEEE Transactions on Dielectrics and Electrical Insulation.

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

[18]  G. Bhuvaneswari,et al.  Analysis of Converter Transformer Failure in HVDC Systems and Possible Solutions , 2009, IEEE Transactions on Power Delivery.

[19]  G. Wilson,et al.  Experimental studies of influence of DC and AC electric fields on bridging in contaminated transformer oil , 2015, IEEE Transactions on Dielectrics and Electrical Insulation.

[20]  Shigemitsu Okabe,et al.  Insulation characteristics of oil-immersed power transformer under lightning impulse and AC superimposed voltage , 2014, IEEE Transactions on Dielectrics and Electrical Insulation.

[21]  Hongyan Nie,et al.  Breakdown characteristics of converter transformer insulation under composite AC and DC voltage , 2009, 2009 IEEE 9th International Conference on the Properties and Applications of Dielectric Materials.

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

[23]  M.D. Judd,et al.  Partial discharge monitoring for power transformer using UHF sensors. Part 2: field experience , 2005, IEEE Electrical Insulation Magazine.

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

[25]  J. Ozawa,et al.  DC Flashover Voltage Characteristics and Their Calculation Method for Oil-Immersed Insulation Systems in HVDC Transformers , 1986, IEEE Power Engineering Review.

[26]  Wang Zhan-jie,et al.  Simulation of AC and DC Electric Field for 800 kV Grade High Voltage Disconnector , 2011 .

[27]  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).

[28]  R. Sarathi,et al.  UHF technique for identification of partial discharge in a composite insulation under AC and DC voltages , 2008, IEEE Transactions on Dielectrics and Electrical Insulation.

[29]  J. Fabian,et al.  Partial discharge behavior of mineral oil and oil-board insulation systems at HVDC , 2012, 2012 IEEE International Conference on Condition Monitoring and Diagnosis.

[30]  G. Hoogenraad,et al.  Digital HVDC partial discharge testing , 2000, Conference Record of the 2000 IEEE International Symposium on Electrical Insulation (Cat. No.00CH37075).

[31]  P.H.F. Morshuis,et al.  Partial discharge classification at DC voltage , 1995, Proceedings of 1995 IEEE 5th International Conference on Conduction and Breakdown in Solid Dielectrics.