Simulation studies in ferroresonant phenomena on distribution transformers

Abstract

Ferroresonance phenomena often appear in any typical distribution systems consisting of drop-out fuse cutouts, overhead lines or power cables and a distribution transformer. Single-pole energization and fuse operation may lead to ferroresonance overvoltages, resulting in electrical equipment damage. The occurrence of ferroresonance depends on several factors including size and length of line, power rating and type of distribution transformer. This thesis presents two case studies involving ferroresonance phenomena.

The first case studies the lengths of overhead lines and underground cables which create enough capacitive reactance for ferroresonance. The critical lengths are estimated by hand calculation and computer simulation. The obtained results show that the system with underground cables has much lower critical length in comparison with that of overhead lines. The critical length decreases with increasing conductor size and decreasing power rating of transformer.

The second case studies the effect of low-loss transformer in comparison with the conventional one. It is found that using the low-loss transformer has more chance to face ferroresonane phenomena.