A new dielectric response model for water tree degraded XLPE insulation - part a: model development with small sample verification

Water tree degradation in underground XLPE insulated cables is a growing, worldwide problem. This form of degradation is ultimately fatal for affected cables, and therefore the detection of damaging trees in power cable insulation is vital for distribution companies to avoid catastrophic failure. Dielectric response measurements, in both the time and frequency domains, can generate valuable information about the condition of the cable. However, the interpretation of how these dielectric response measurements relate to water tree density and length is a difficult task. This paper will present a new dielectric response model for water tree degraded XLPE insulation. The model is based on finite element analysis to determine the electrical behaviour of water tree degraded insulation. Preliminary simulations will verify the model development by comparing the results to small sample pulsed electro-acoustic (PEA) measurements performed by other researchers. The importance of a strong non-linearity mechanism for accurate modelling will also be elucidated.

[1]  J. Kawai,et al.  Dynamic behavior of interconnected channels in water-treed polyethylene subjected to high voltage , 2002 .

[2]  J. J. O'Dwyer,et al.  The theory of electrical conduction and breakdown in solid dielectrics , 1973 .

[3]  Ying Li,et al.  Pulsed electroacoustic method for measurement of charge accumulation in solid dielectrics , 1994 .

[4]  J. Smit,et al.  Composition and growth of water trees in XLPE , 1992 .

[5]  Y. Ohki,et al.  Time-resolved space charge observation in water-treed XLPE , 1998, 1998 Annual Report Conference on Electrical Insulation and Dielectric Phenomena (Cat. No.98CH36257).

[6]  D. Tu,et al.  Mathematical analysis and interpretation of pulsed electro-acoustic system , 2000, Proceedings of the 6th International Conference on Properties and Applications of Dielectric Materials (Cat. No.00CH36347).

[7]  E. Moreau,et al.  The structural characteristics of water trees in power cables and laboratory specimens , 1993 .

[8]  Ying Li,et al.  Experimental investigation on the cause of harmfulness of the blue water tree to XLPE cable insulation , 1999 .

[9]  T. Takada,et al.  Space charge distribution measurement in lossy dielectric materials by pulsed electroacoustic method , 1994, Proceedings of 1994 4th International Conference on Properties and Applications of Dielectric Materials (ICPADM).

[10]  I. Radu,et al.  Electric field calculations in polymers in the presence of water trees , 1995, Proceedings of 1995 IEEE 5th International Conference on Conduction and Breakdown in Solid Dielectrics.

[11]  Erling Ildstad,et al.  Correlation between AC breakdown strength and low frequency dielectric loss of water tree aged XLPE cables , 1998 .

[12]  Victor N. Kaliakin,et al.  Introduction to Approximate Solution Techniques, Numerical Modeling, and Finite Element Methods , 2001 .

[13]  T. Saha,et al.  A new dielectric response model for water tree degraded XLPE insulation - part b: dielectric response interpretation , 2008, IEEE Transactions on Dielectrics and Electrical Insulation.

[14]  Robert J. Ross,et al.  Inception and propagation mechanisms of water treeing , 1998 .

[15]  T. Toyoda,et al.  Conductivity and permittivity of water tree in polyethylene , 1999, 1999 Annual Report Conference on Electrical Insulation and Dielectric Phenomena (Cat. No.99CH36319).

[16]  Steven A. Boggs,et al.  Effect of semicon-dielectric interface on conductivity and electric field distribution , 2002 .

[17]  H. Faremo,et al.  Understanding water treeing mechanisms in the development of diagnostic test methods , 1998 .

[18]  H. Janah,et al.  Influence of diffusion on some electrical properties of synthetic cables , 1992, [Proceedings] 1992 Annual Report: Conference on Electrical Insulation and Dielectric Phenomena.

[19]  R. Eriksson,et al.  Dielectric spectroscopy for diagnosis of water tree deterioration in XLPE cables , 2001 .

[20]  L. Dissado,et al.  A Study of the Factors Influencing Water Tree Growth , 1983, IEEE Transactions on Electrical Insulation.

[21]  I. Radu,et al.  The effect of water treeing on the electric field distribution of XLPE. Consequences for the dielectric strength , 2000 .

[22]  Tatsuo Takada,et al.  Comparison between the PEA method and the PWP method for space charge measurement in solid dielectrics , 1998 .

[23]  Robert J. Ross,et al.  Dielectric properties of water trees , 2000, Proceedings of the 6th International Conference on Properties and Applications of Dielectric Materials (Cat. No.00CH36347).

[24]  Y. Ohki,et al.  Space charge formation in water-treed insulation , 1998 .

[25]  Y. Ohki,et al.  Space charge behavior under ac voltage in water-treed PE observed by the PEA method , 1997 .

[26]  Nathan Ida,et al.  Introduction to the Finite Element Method , 1997 .