Resistive Ferroresonance Limiter for Potential Transformers

The ferroresonance or nonlinear resonance is a complex phenomenon, which may cause overvoltage in the electrical power system and endangers the system reliability and operation. The ability to predict the ferroresonance in the transformer depends on the accuracy of the transformer model used. In this paper, the effect of the new suggested ferroresonance limiter on the control of the chaotic ferroresonance and duration of chaotic transients in a potential transformer including nonlinear core losses is studied. To study the proposed ferroresonance limiter, a single phase 100？VA, 275？kV potential transformer is simulated. The magnetization characteristic of the potential transformer is modeled by a single-value two-term polynomial. The core losses are modeled by third order power series in terms of voltage and include core nonlinearities. The simulation results show that the ferroresonance limiter has a considerable effect on the ferroresonance overvoltage. 1. Introduction The ferroresonance is typically initiated by saturable magnetizing inductance of a transformer and a capacitive distribution cable or transmission line connected to the transformer. In most practical situations, ferroresonance results in dominated currents, but in some operating “mode”, may cause significant high value distorted winding voltage waveform, which is typically referred to as ferroresonance [1]. Although occurrences of the “resonance” involves a capacitance and an inductance, there is no definite resonant frequency. In this phenomenon, more than one response is possible for the same set of parameters, and drifts or transients may cause the response to jump from one steady-state response to another one. Its occurrence is more likely to happen in the absence of adequate damping [1]. Researches on ferroresonance in transformers have been conducted for more than 80 years. The word ferroresonance first appeared in the literature in 1920. Nonlinear dynamical tools for studying ferroresonance have been used in [2]. Practical interests have shown that the use of series capacitors for voltage regulation could cause ferroresonance in distribution systems [3]. Ferroresonant behavior of a 275？kV potential transformer, fed from a sinusoidal supply via circuit breaker grading capacitance, has been studied in [4, 5]. The potential transformer ferroresonance from an energy transfer point of view has been presented in [6]. A systematical method for suppressing ferroresonance at neutral-grounded substations has been studied in [7]. A sensitivity analysis on power transformer ferroresonance of