A New Look at Reliability of Asphalt-Mica Insulation in Large Conventionally Cooled Turbine Generators

Kuzawinski, Joseph G.; Wolff, George M.

doi:10.1109/tpas.1970.292689

Cited by 3 publications

(1 citation statement)

References 2 publications

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“…Even if thermal cycles with a maximum conductor temperature of 1228C are combined to elevated electrical stresses [18], 1500 load cycles applied on mica-epoxy insulations have been shown to be insufficient to result in electrical breakdown. However, asphalt-mica insulations are known to be prone to delaminations due to thermal cycles [2,19,20]. The observation, that the choice of the insulation system has an influence on the formation of delaminations due to thermal cycles [19,21,22], has been confirmed in laboratory experiments [8,23,24].…”

Section: Introductionmentioning

confidence: 94%

Retardation of electrical tree propagation by resin degradation

Weiers¹,

Keller²,

Hutter

et al. 2006

Int Trans Elec Energy Syst

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SUMMARYIn order to improve insight into the effect of delaminations between the conductor and the groundwall insulation on the ageing of high voltage rotating machinery insulation, the influence of the polymer degradation on tree growth has been studied. Simultaneous partial discharge measurements and photograhic observations have been conducted in order to investigate the effect of the degradation of the resin on electrical tree propagation. The photographic observation indicates that the degradation of the resin retards the tree propagation after the tree having failed to penetrate a mica barrier. As the resin is degraded and in part rendered conducting, the partial discharges change both in magnitude and in terms of phase resolved partial discharge patterns. These partial discharge measurements are promising to improve insight into the processes involved in winding insulation ageing, when photographic observations are unattainable. Moreover the differences found between various resins offer an explanation why various types of winding insulation have been found to differ in their capability to withstand thermal cyclic ageing.

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Section: Introductionmentioning

confidence: 94%

Retardation of electrical tree propagation by resin degradation

Weiers¹,

Keller²,

Hutter

et al. 2006

Int Trans Elec Energy Syst

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Estimating the remaining service life of asphalt-mica stator insulation

Timperley

Michalec

1994

IEEE Trans. On energy Conversion

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Synchronous generators were manufactured with asphalt bonded, mica flake insulation from 1917 to the 1950's.There is a large fleet, perhaps two thousand, of these machines still in service today. This paper presents the results of a well documented series of field tests, many to failure, on 20 asphalt-mica insulated fossil and hydro synchronous generators on the American Electric Power system and laboratory tests on over 30 spare asphalt-mica stator bars and coils at AEP's Dolan Laboratory.The paper clearly shows that a straightforward ac overpotential test and a simple graphical evaluation and analysis can be used to confidently determine the remaining service life of asphalt bonded, mica flake insulated synchronous generators that have been well maintained and operated within design limits.

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Significance of Defects Inside In-Service Aged Winding Insulations

Sumereder

Weiers

2008

IEEE Trans. Energy Convers.

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A New Look at Reliability of Asphalt-Mica Insulation in Large Conventionally Cooled Turbine Generators

Cited by 3 publications

References 2 publications

Retardation of electrical tree propagation by resin degradation

Retardation of electrical tree propagation by resin degradation

Estimating the remaining service life of asphalt-mica stator insulation

Significance of Defects Inside In-Service Aged Winding Insulations

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