One of the most well-known ferroresonance circuits includes an inductive voltage transformer (VT) which is energized through the grading capacitance of a high voltage circuit breaker, Figure 8. To equally divide the switching transient voltage between the interrupters of a high voltage circuit breaker, multi-interrupter circuit breakers are usually equipped with the grading capacitances in parallel with the interrupting chambers. When the circuit breaker is open, the disconnected bus is still partially energized through the grading capacitors. If a VT is connected to the bus, the magnetizing inductance of the VT core can resonate with the grading capacitors and be driven into saturation and constitutes a ferroresonance condition. The magnetizing inductance of a high voltage VT is large and in the order of kH. Therefore, it can be easily excited by the small stray capacitance of the busbars, or the small capacitance of the circuit
breakers which is in the order of a few hundred pF up to around 1nF. As discussed before, this type of ferroresonance can be damped out by a loading burden at the VT secondary.