Suppression of ferromagnetic resonance overvoltage in CVT and feature analysis of secondary voltage under different faults

Abstract

Aiming at the problem of overvoltage caused by ferromagnetic resonance fault of 220 kV CVT （capacitive voltage transformer） and the problem of false alarm of 3U0 monitoring device， a simulation model is established based on actual parameters， and the influence of each parameter on overvoltage is analyzed. The optimal parameter configuration is given and the circuit topology is optimized， thus effectively suppressing the ferromagnetic resonance overvoltage. The simulation models are established and the secondary voltage data under various working conditions are compared. The simulation results show that both the secondary side grounding recovery and the primary side closing will cause the ferromagnetic resonance， accompanied by the generation of 1/3 harmonics， but the ferromagnetic resonance caused by the former is more serious. The ferromagnetic resonance is suppressed by the speed saturation damper， and the best suppression effect is obtained when the damping resistance is 5 Ω. The parallel fixed resistances at both ends of the damper can effectively improve the suppression effect， and the effect is the best when the resistance is 5 Ω. 3U0 corresponds to different spectrum characteristics under different working conditions， which can distinguish different faults.

Keywords

• capacitive voltage transformer
• ferromagnetic resonance
• damping resistance
• open delta voltage
• isolation switch closing