A study of ferroresonance in underground distribution network for 15MVA, 33/11 kV injection substation

Abstract

This provides an overview of ferroresonance phenomena, modeling aspects and practical experience in recognizing and mitigating the effect of  ferroresonance in the power network. In particular, we will present symptoms of ferroresonance. In this study, ferroresonance phenomenon are investigated under the modelling of the underground cable of 15 MVA, 33/11/0.415 kV with four feeders supply over 31 distribution transformers of  Garki 1 service unit, Abuja, conducted using MATLAB/SIMSCAPE software package. The network is subjected to switching resulting in the formation of a series LC combination prone to ferroresonance. The waveforms and total harmonic distortion charts obtained are observed, analyzed and then  used to design Harmonic filters which have been implemented to mitigate ferroresonance in the network. The simulated ferroresonance  phenomenon was suppressed using Shunt Active Harmonic Filter connected in parallel to the network. A reduced harmonic content and dampened event when compared to a non-filtered event was observed. Application of Shunt Active Harmonic filter reduces ferroresonance effect by 67.743%. Keywords: Ferroresonance, Transformer, MATLAB/Simscape, Harmonic Distortion, Power system Modelling, Saturable inductor, Capacitance