Abstract
It is commonly recognized that correct transformer model (particularly topological one) is a key element for any ferroresonance simulations. This paper represents a line of reasoning by which a reliable model of a voltage transformer (VT) can be constructed given substantial uncertainties in its parameters and characteristics. Starting with catalog data for electric steels and typical leakage inductances of 6-kV VTs, a model of an isolated neutral network with three inductive VTs is initially fitted to reproduce in detail its ferroresonant behavior for a chosen network capacitance. Then, validity of the network model is verified by accurate predictions of ferroresonance processes for all other capacitance values available and thus different ferroresonance modes recorded during full-scale factory tests. Possibilities to simplify the VT model by neglecting dynamic, and then entire core losses and hysteresis are also shown.
Highlights
The list of network configurations and excitation scenarios fraught with ferroresonance phenomena seems almost endless [1]
The voltage transformer is always considered to be an element, whose model is crucial for studying network resonance behavior
In spite of trustworthy analytical tools developed to date, impacts of several transformer characteristics are studied numerically in different combinations in the growing ferroresonance literature
Summary
The list of network configurations and excitation scenarios fraught with ferroresonance phenomena seems almost endless [1]. The experimental test bench was equipped with a three-phase bank of singlephase three-winding VTs. The fact that the ferroresonance can occur at different capacitance values of the same network points out that its reason lies in the magnetic nonlinearities of the transformer core. Often mentioned in studying resonance phe nomena, is the involvement of hysteresis [16,17,18,19,20] and the influence of nonlinear core loss dependencies on voltage and frequency [21,22] It should be noted, that the role of these factors is mainly dis cussed when simulating series ferroresonant circuits [1,23], in which the transformer is fed through a series capacitor [21].
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