ferroresonance

Ferroresonance is a complex nonlinear phenomenon that can occur in electrical power systems containing a series combination of a voltage source, a nonlinear inductor, and a capacitor. The nonlinearity of the inductor, typically due to magnetic saturation of the core, is crucial for ferroresonance to occur. When the system's excitation frequency is close to its natural resonant frequency, and the inductor's characteristic is nonlinear, the system can exhibit large, often undesirable, voltage and current oscillations. These oscillations can be subharmonic, chaotic, or even chaotic with a periodic component.

The threshold for ferroresonance depends on the Q factor of the circuit and the degree of nonlinearity. In practical power systems, ferroresonance can be triggered by switching operations, lightning surges, or faults. The consequences of ferroresonance can be severe, including overvoltages that can damage equipment like transformers, arresters, and bushings, as well as overcurrents that can lead to protective device tripping and system instability. It is particularly prevalent in medium-voltage systems with grounded iron-core reactors or capacitors.

Mitigation strategies for ferroresonance include limiting the inductance or capacitance in the circuit, using damping resistors, employing linear inductors, or designing systems to avoid operating conditions that favor ferroresonance. Understanding the conditions under which ferroresonance can occur is essential for the safe and reliable operation of electrical power networks.