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Electrical Engineering

, Volume 101, Issue 4, pp 1189–1197 | Cite as

Effect of oil impregnated paper thickness and impulse waveshapes on voltage–number characteristics

  • Zeenath Ameena MubarakEmail author
  • Usa Savadamuthu
Original Paper
  • 69 Downloads

Abstract

Inter-turn insulation plays a major role in the dielectric integrity of any transformer. Though the inter-turn insulation thickness is designed based on standard lightning impulse (LI) voltage distribution, the insulation fails due to various types of overvoltages from switching impulse (SI) to very fast transient overvoltages (VFTO). Moreover, the insulation gets degraded due to many factors such as service ageing, exposure to repeated applications of overvoltages due to various reasons, etc. The effect of the repeated impulses is characterized using the voltage–number (VN) characteristics recommended by CIGRE Working group C4.302. Based on the design and rating of the transformer, the thickness of the inter-turn insulation is normally changed. To quantify and compare the impulse breakdown strength and degradation due to repeated impulses under SI, LI and VFTO, different thicknesses of oil impregnated paper, ranging from 0.25 to 0.75 mm are considered. Experiments are carried out to obtain the VN characteristics for all the cases. VN characteristics are mathematically modeled by enhancing the existing exponential model to incorporate the thickness of insulation and are then validated experimentally. Based on the model parameters, the effect of the various waveshapes and the degradation due to repeated impulses are quantified and compared with the standard LI.

Keywords

Inter-turn insulation thickness SI LI VFTO Repeated impulses VN characteristics 

Notes

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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Division of High Voltage Engineering, College of Engineering, GuindyAnna UniversityChennaiIndia

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