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The motivation for this book was the increase in the appearance of ferroresonance oscillation in substations. The price pressure on the operating authorities and as well on component manufacturers i.e. for instrument transformer, power transformer and grading capacitors for high-performance circuit breakers has led to gradually increasing demands on power system and components.
In the IEC Dictionary the following definition can be found for ferroresonance: "a resonance of the capacitance of an apparatus with the inductance of saturable magnetic circuit of an adjacent apparatus".
Ferroresonance refers to non-linear oscillations that can occur in power systems where inductive components with a ferromagnetic core, together with capacitances and an AC voltage source comprise a system capable of oscillation.
In contrast to a linear resonant circuit, a circuit with non-linear inductance exhibits no well-defined resonance frequency. A sinusoidal source voltage of a fixed frequency can excite different frequencies (harmonic and subharmonic frequencies). In addition, the amplitude of the excited oscillations is not limited only by the power loss in the resonant circuit. For each oscillation mode, a resultant oscillation amplitude can be found.
This book provides an overview of the undesired phenomenon of ferroresonance oscillations in high and medium voltage networks in connection with the inductive voltage transformers (VT). Ferroresonance oscillations can cause considerable damage to the VT and neighboured equipment. Because of the various forms of manifestation, cases of ferroresonance are not always recognized as such.
The book is addressed to designers and operators of high voltage power installations and manufacturers of inductive voltage transformers.

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Minkner, R.
Ruthard Minkner has industrial experience in high voltage systems and stability problems of non-linear systems. He taught the subjects "High voltage engineering" and "servomechanism" at the University of Applied Science in Burgdorf CH, and was guest professor at the State University of Washington (USA). He was Convenor of several IEC working groups. Joachim Schmid is R&D manager for instrument transformers, chairman of the Swiss national commission CES TK 38 and convenor of several IEC working groups. Holger Däumling is manager for customer problems in substations, expert for three phase ferroresonance oscillations in medium and high voltage networks. Udo Prucker is R&D manager of the leading company for SF6 insulated high voltage instrument transformers for GIS and AIS applications. Besides the field of gaseous insulation his special interest is in simulation of ferroresonance phenomena. Reinhold Bräunlich is CEO of the association: FKH, Fachkommission für Hochspannungsfragen (High Voltage Testing and Engineering Commission), responsible for high voltage tests and other measurement in high voltage substations. Martin Hofstetter is manager in a Swiss utility, and is responsible for design of the high and medium voltage grid of his company. Long-time practice provided the authors with consolidated knowledge and experience in the field of ferroresonance. They are renowned experts in responsible positions.

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