Calculation of the Electrical Field Constraint and the Potential Breakdown Risk in Partially Humid High Voltage Generator Stator Bar Insulation

During recent years, one of the main causes of large generators failure reported worldwide is related to the stator insulation defaults. For the majority of studied cases, the insulation weakness is the result of cooling system problems, generally water micro-leakage located between the water joint box and the end of the stator bars. Experimentations have been conducted over more than one year on several stator bars to determine the water propagation law in the main insulation. The goal of this article is to estimate the potential breakdown risk of high voltage generator stator bars presenting different levels of humidity content. The risk estimation is based on electrical field constraint calculation using a finite element model.

[1]  T. P. Hong,et al.  Effect of humidity on the high voltage characteristics of epoxy/glass insulation , 2004, Proceedings of the 2004 IEEE International Conference on Solid Dielectrics, 2004. ICSD 2004..

[2]  J. Verdu,et al.  Structure-properties relationships for densely cross-linked epoxide-amine systems based on epoxide or amine mixtures , 1989 .

[3]  D. Vizireanu,et al.  Experimentation on humidity propagation in high voltage alternator stator bar insulation , 2007, 2007 Electrical Insulation Conference and Electrical Manufacturing Expo.

[4]  T. P. Hong,et al.  Effects of hydrothermal aging on the dielectric properties of epoxy composites , 2003, Proceedings of the 7th International Conference on Properties and Applications of Dielectric Materials (Cat. No.03CH37417).

[5]  T. P. Hong,et al.  Anisotropy of the dielectric properties of laminated epoxy insulation subjected to water absorption [power generator insulation] , 2004, The 17th Annual Meeting of the IEEE Lasers and Electro-Optics Society, 2004. LEOS 2004..

[6]  W. M. Banks,et al.  Non-destructive examination of composite joint structures: a correlation of water absorption and high-frequency dielectric propagation , 1996 .

[7]  F. Thominette,et al.  Factors governing water absorption by composite matrices , 2002 .

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