## Summary

This chapter presents designs of electric automobiles with either battery or fuel cells as energy sources, cogeneration plants including the analysis of gas turbines, pumped-storage hydro plants, supercapacitor power plants, compressed-air storage facilities, magnetic storage plants, and flywheel storage power plants. The transient frequency control of an isolated power plant (islanding operation), the frequency variation […]

## Application Example 12.41: Ferroresonance in Three-Phase, Three-Limb Transformer

The ferroresonance study for this application example is performed for an unloaded Y-Y three-phase, three-limb transformer supplied by a three-phase source (Fig. 12.95). The transformer primary and secondary windings are rated at 440 V and 55 V (1 kVA), respectively, and operate at a nominal frequency of 50 Hz. 440 V three-phase feeder system three-phase […]

## Utilization of cables with low capacitance

Application Example 12.39: Susceptibility of Transformers to Ferroresonance Consider a power transformer with l = 0.63 Wb-turns at 0.5 A (assume linear l-i characteristics). The equivalent system capacitance is C = 100 m F and the fre­quency is 60 Hz. Is this transformer susceptible to Ferroresonance conditions? Therefore, XC/XT = 0.055 < 40 that is, […]

## Ways to Avoid Ferroresonance

There are a few techniques to limit the probability of ferroresonance: • The grounded-Y/grounded-Y transformer – when the neutral of the transformer is grounded, the capacitance to ground of the line (cable) is essentially bypassed, thus eliminating the series LC circuit which can initiate ferroresonance. Another approach is to use banks made up of three […]

## Power System Conditions Contributive to Ferroresonance

The important question is what conditions in an actual power system are contribu – tive (conducive) to ferroresonance? Some conditions may not by themselves initiate the problem, but they are necessary so that when other conditions are present in a power system, ferroresonance can occur. There are four prerequisites for ferror – esonance [11] • […]

## Understanding Ferroresonance

Ferroresonance is known to be caused by the interaction of power system capaci­tances with nonlinear inductances associated with wound magnetic cores in power transformers and instrument voltage transformers. Many stable and unstable operating points (ferroresonance modes) are possible due to the constantly chang­ing transformer inductances during its magnetizing and demagnetizing cycles. Sources of capacitances can […]

## The Nonlinear Electric and Magnetic Circuits of Power Transformer

An accurate and relatively simple nonlinear three-phase transformer model for (a) symmetrical, (un)balanced and (non)sinusoidal operation including harmonic dis­tortions, DC biasing, sag/swell and ferroresonance is proposed and implemented in references [44–48]. It is based on the simultaneous solution of electric and magnetic equivalent circuits of three-phase, three-limb transformers. The model has also been tested for […]

## Ferroresonance in Power Transformers

Ferroresonance is one of the longest recognized power quality disturbances in the history of AC power systems, spanning nearly a century of accumulated research [11, 36]. The symptoms of ferroresonance are regarded as most serious and Fig. 12.91 Simulation results over the 24 h period for medium charge rate (4 h @ Pcharger= 3.6kW) with […]