Mechanism analysis of ferromagnetic resonance of electromagnetic voltage transformer in neutral ungrounded system

In the neutral point ungrounded power distribution system, due to the nonlinear characteristics of the electromagnetic voltage transformer (PT) excitation inductance, ferromagnetic resonance overvoltage is easily generated under certain conditions, which seriously affects the safe operation of the system. This paper takes the Yecheng substation 6 kV distribution network as the model, and uses ATP-EMPT electromagnetic transient calculation software to theoretically analyze the characteristics and mechanism of ferromagnetic resonance caused by electromagnetic voltage transformer, and points out the main problems of ferromagnetic resonance in PT operation. This article discussed the existing harmonic elimination measures, proposed some effective suppression schemes and demonstrated the effectiveness of some mainstream harmonic elimination methods. The author's work can provide a good reference for the prevention and control of ferromagnetic resonance overvoltage, and it also has high practical value for improving the power supply safety and reliability of the distribution network. (paper)