Ferroresonance and Preisach theory

Ferroresonance is a condition where energy is transferred between the inductance of the ferromagnetic device and the system capacitance. Where the source of energy is sufficient to overcome the damping in the system, the ferroresonant state can be sustained until intervention is made to clear the condition. Many cases of ferroresonance have occurred in electrical power systems over the years. Consequently, more interest in ferroresonance has been shown by engineers, as they come across ferroresonance conditions themselves. Articles and papers have been written on many aspects of ferroresonance from simply recording actual cases of ferroresonance or giving a qualitative analysis of suspected ferroresonance cases to computer aided modelling. Most solutions use a simple mathematical expression to represent the nonlinear B/H characteristic of the transformer core. and most ignore the effects of hysteresis. Hysteresis is normally ignored, because of its mathematical complexity. The theory proposed by F. Preisach (see Zeitschrift Fur Physick, 94, p.277, 1935) provided a basis by which the whole of the magnetic characteristic could be accurately predicted. This theory is discussed