STUDIES OF FERRO-RESONANCE CIRCUITS

Abstract

In case of resonance circuit a, we assume that the In. ductance of the circuit in independent of the urr+ant and is constant. This is actually true if the m%petic field of the indaatw ae flown preponderantly in elr, for exple mound over head linea, underground cables or in the leakage paths of rotating machines or transformers. wewer if the magnetic field flows tirely or to a large part through iron, the circuit has no longer a constant Inductance; rather this will, decrease with larger current a and magnetic field Ara gthe. lice the phenomena in lit erure occuring at a critical value of applied voltage where the non linear inductance varLable with the magnitude of the forcing function reaches a value go as to reaonate with the fixed capacitor is awn as ferroreacnauce. This is probably the reason for using the term fermre* nance to describe the by teresia behavior. The present problem is to study the behavior of ono llatory circuits under the influence of magnetic saturation in the iron core of the transformers connected to the long transmission line to deliver power at the load ventre. Here it is tried to consider the effect of the variation of the distance at which the fault occurs in the transmission line. It Is knoua that for a particular system the line p araaet ere are fixed and they are taken in per unit length. The lose conponolt of capacitance of the line is neglected. Now as the distance of the fault is increased from the sending and, than the mgnitu4e of the inductance resistance and capacitance increases. The aknorme,l voltages which may occur at to instants will be dependent on the magnitude of the capacitance which comes across the 0 t ran ate rifler, The transformer may be ass sd to be a non .linear ' inductor. A graphical mdthod is suggagtad in Chapter U for calculating abnormal voltages and the conclusion is drai1 that the effect of the disc nee of fault is directly related to the a ormal voltage and currents produced. As the distance Is increased the m njtudes of the over voltages also increases. This analysis Is based under the assumption of sinusoidal variation of current and a steady state voltage characteristic is obtained from the circuit equation, though it is tzue that the current in the non linear circuit is not a aims- amide: function l it it is composed of har onics. In Chapter III attest is made to give mathenatical treatment for the non linear circuit ori sing under above motioned circumstances, in the study of these non linear circuits with a.c. applied voltage, ro rous sothenatical treatment has been found practl. caUy ispoesible, but under certain 4lifying assumptions, however, the solution is being given which seise to describe the nature of the phi ,mans, in general