Thermal Cyclic Degradation of Coil Insulation for Rotating Machines

Mitsui, H.; Yoshida, Katsuhiko; Inoue, Y.; Kenjo, S.

doi:10.1109/tpas.1983.317999

Cited by 16 publications

(9 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Loss factor and partial discharge measurements during thermal cycling tests [8,14,16,17] on high voltage winding insulations confirm the formation of delaminations between the strand and the groundwall insulation ( Figure 1) which is also observed in rotating machinery [1,7]. However, there are insulation systems for which both breakdown voltages and voltage endurance are not reduced even after several hundred temperature cycles.…”

Section: Introductionmentioning

confidence: 52%

“…Considerable efforts have been undertaken in order to understand how each of these stresses and their superposition contribute to the mechanisms of the ageing of winding insulations. Investigations on electrical ageing at constantly elevated temperatures show that insulation life decreases rapidly as the temperature of the insulation is increased above the glass transition temperature T g of the thermosetting binder resin [8][9][10][11]. Depending on the porosity of the mica and the type of impregnant [12,13], an optimum temperature near 908C can be determined [14].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Retardation of electrical tree propagation by resin degradation

Weiers¹,

Keller²,

Hutter

et al. 2006

Int Trans Elec Energy Syst

View full text Add to dashboard Cite

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.

show abstract

Section: Introductionmentioning

confidence: 52%

Section: Introductionmentioning

confidence: 99%

Retardation of electrical tree propagation by resin degradation

Weiers¹,

Keller²,

Hutter

et al. 2006

Int Trans Elec Energy Syst

View full text Add to dashboard Cite

show abstract

“…The effect of thermal stress on the insulation degradation has been evaluated, and Fig. 12 presents one example of the characteristics of loss tangent (tan δ) [3]. After the thermal cycle test, we fixed the electrodes on the bar surface divided by some interval in the longitudinal direction to make clear the relationship between the location of the bar and its insulation degradation.…”

Section: Degradation Factors Affecting the Winding During Operationmentioning

confidence: 99%

“…With regard to the evaluation methods related to these deterioration factors, there have been no papers published that include quantified data about the residual breakdown voltage related to the residual insulation life, although there have been papers [3,4] that summarized the general experimental data.…”

Section: Introductionmentioning

confidence: 99%

Study on vibration caused by electromagnetic force in the end portion of large‐capacity cylindrical synchronous machines: Improvement of electromagnetic force estimation and verification of degradation on winding insulation

Nagano

Tokumasu

Fujita

et al. 2008

Electrical Engineering Japan

View full text Add to dashboard Cite

SUMMARYA new method for analyzing electromagnetic force in the end-winding portion of large-capacity synchronous generators is provided and evaluated in comparison with 3D FEM electromagnetic analysis. In addition, a method for estimating end-winding vibration during on-load operation is suggested by measured data at factory testing. Moreover, an evaluation method for insulation degradation after operation is proposed for large-capacity cylindrical synchronous machines, where the end-winding portion is the longest and electromagnetic forces on it are the greatest of all rotating machinery.

show abstract

“…The cyclic shear stresses weaken the bond between the conductor strands and the groundwall insulation and can eventually result in delaminations at the conductor insulation interface and between the laminated mica tape layers in the groundwall [3,4]. Once the voids caused by delaminations and fatigue cracks have grown large enough, partial discharge (PD) sets in and erodes the epoxy resin through oxidation of the polymer chains.…”

Section: Introductionmentioning

confidence: 99%

A new test method for assessing the impact of thermal cycling on hydrogenerator stator insulation

Brugger

2010

2010 Annual Report Conference on Electrical Insulation and Dielectic Phenomena

View full text Add to dashboard Cite

A fast growing amount of renewable energy from wind or solar plants with their inherent production fluctuations requires conventional backup and storage capacity in order to keep grids stable. Hence, hydropower plants in Switzerland are increasingly selling peak energy in a liberalized European electricity market. This development leads to higher start/stop-cycle frequencies of their hydrogenerators and some older machines are also subjected to more starts per year than they were originally designed for. In consequence the high voltage insulation system in the stator conductor bars is stressed by a higher number of thermal cycles which might shorten machine lifetimes significantly. In this paper a new test for assessing the impact of thermal cycling in modern mica/epoxy insulation systems is pre- sented. The new method isolates insulation aging exclusively caused by thermal cycling by the use of cycles with short heating intervals and a maximum temperature close to the glass transition point of the insulation system's binder (epoxy) resin. The insulation aging condition is monitored withnon-destructive measurements of the Dissipation Factor and Partial Discharges during, and a destructive voltage endurance test after completion of the thermal cycling. A first implementation of the new test method with 1.500 cycles resulted in no severely greater deterioration of the cycled group compared to an uncycled group but shows the necessity of further investigation.

show abstract

Thermal Cyclic Degradation of Coil Insulation for Rotating Machines

Cited by 16 publications

References 6 publications

Retardation of electrical tree propagation by resin degradation

Retardation of electrical tree propagation by resin degradation

Study on vibration caused by electromagnetic force in the end portion of large‐capacity cylindrical synchronous machines: Improvement of electromagnetic force estimation and verification of degradation on winding insulation

A new test method for assessing the impact of thermal cycling on hydrogenerator stator insulation

Contact Info

Product

Resources

About