EXPERIMENTAL INVESTIGATION OF FERRORESONANCE AND MITIGATION MEASURES IN 35 KV ISOLATED NETWORKS

Abstract

Ferroresonance is a nonlinear dynamic phenomenon that appears in the electric power system between a non-linear inductances and system capacities excited by a sinusoidal voltage source. The most common non-linear elements of the electric power system are the iron core inductances of power and measuring transformers, reactors, etc. in which saturation of non-linear elements can occur. As a consequence of ferroresonance there may be a significant increase in the voltage value and under the certain conditions an excessive increase of the current value across the transformer terminals. This phenomenon can lead to damage of the measuring transformers and other equipment used in the network. Ferroresonance is one of the most common low-frequency electromagnetic transient phenomena that appear in the isolated power networks. Therefore, special attention must be on analyzing the probability of ferroresonance occurrence in electric power systems. In this paper, ferroresonance measurement results will be given. The waveform of the phase to ground voltage and wave form of the open delta voltage is obtained. Also, the Fourier transformation is performed on these signals. Proposed measurements are conducted in the real 35 kV distribution network with isolated neutral point. Also, efficiency of some experimentally tested mitigation measure will be presented within this paper.