A Broadband Model of a Potential Transformer

ABSTRACT

In this paper, a broadband circuit model of a potential transformer (PT) based on fractional calculus and circuit augmentation method was proposed to improve the high frequency characteristic while providing physical significance of the existing traditional equivalent circuit model with simple structure. In order to comprehensively reflect on the characteristics of hysteresis of the iron core , a fractional model of the magnetic hysteresis loop in iron core measured by a no-load experiment was set up instead of the single-value magnetization curve of previous model. Besides, the original equivalent circuit model was calculated at low frequencies, and the circuit augmentation method (CAM) was employed to extend the compatibility of the original equivalent circuit model in the wide range of frequency. The element values were calculated by the Brune method of synthesis. For validity, comparisons between the simulation and experiment of a 10 kV single-phase oil-immersed PT with lightning overvoltage and switching overvoltage were conducted, respectively. The results showed that the broadband model presented in the paper had good accuracy while reserving the physical significance of original equivalent circuit model.

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