Abstract:

In the nongrounded neutral system,the ground capacity and the excitation inductance of primary windings of a Y0 type electromagnetic voltage transformer compose a loop to the ground.Due to over-voltage and over-current operation in the system,the ferromagnetic element of the voltage transformer is saturated,which causes the resonance and easily leads to the damage of the transformer.A practical case analysis and simulation calculation are involved to certify the conditions of ferrosonance caused by the saturation of the core of the electromagnetic voltage transforme and the harmonic elimination measure.Thereafter,the improvement suggestions is proposed for the existing test standards of excitation characteristics of the electromagnetic voltage transformer,which provide a basis for the equipment selection and fault analysis.

Key words: nongrounded neutral system, electromagnetic voltage transformer, ferroresonance, excitation characteristics