Research on Ferroresonance of Electromagnetic Voltage Transformer in 550kV HGIS

For a 550kV HGIS electromagnetic voltage transformer(PT), ferromagnetic resonance occured after the disconnector was opened. In this paper, firstly, considering the ferromagnetic resonance condition, the fault disintegration, fault recording, and operating overvoltage datas were analyzed to analyze the causes of ferromagnetic resonance.Then a HGIS simulation model was built by EMTP-ATP to calculate very fast transient voltage which was caused by opening operation of disconnector. According to the results, the VFTO amplitude at the PT is not large, but the wave front steepness reaches 2837kV/ μs, which is harmful to the inter-turn insulation of the PT primary winding. It may cause partial inter-turn short circuit and then induce core saturation. Finally, the preventive measures of ferromagnetic resonance are proposed.