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Modeling the Hysteresis Characteristic of Power Transformer Core for the Assessment of Inrush Current and Providing a Method to Reduce this Current

Hassani Kaboutarkhani, Reza | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42959 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Vakilian, Mehdi
  7. Abstract:
  8. Inrush current as an inherent phenomena in transformer energizing cause to dramatic increase in current which flow through windings of transformer in first periods of energizing. first peak of inrush current can exceed even to several orders of nominal current but it decrease with time and at last after damping process it reaches to nominal currents. In large transformer this time can exceed to several minutes and cause damage to winding insulation, mechanical defects, wrong response of protection system and interrupting loads. Magnitude of this current has a close relation with residual flux. In this thesis a method for calculation of inrush current in single phase and three phase transformers with hysteresis characteristic and residual flux consideration will represented. In this survey we model hysteresis loop by Jiles-Atherton method. In first step, hysteresis characteristic and inrush current measured in a single phase 220V/380V 5kVA transformer and Jiles-Atherton method parameters obtained in order to simulate hysteresis loop and compare it with measured one. Then for evaluation of our method for obtaining inrush current a comparison between our measurements and our simulation will be done. This measurements repeats for 3times with different residual flux and different angle of
    energizing in each phase. In next step hysteresis characteristic of a three phase 0.4/20kV 500kVA distribution transformer measured and hysteresis parameters will obtained then base on our method we calculate inrush current in this transformer. Our method has ability
    to calculate states which phases energized in different times. In the last step base on method of calculating inrush current in three phase transformer, we represent a method to reduce inrush current base on optimum energizing time in different phases
  9. Keywords:
  10. Power Transformer ; Hysteresis Ring ; Inrush Current ; Jiles-Atherton Model ; Residual Flux

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