Recently, there are increasing interest in studying the ferroresonance phenomenon, due to the various problems it causes to power quality and the destruction of network parts, insulators and consumer devices. As the ferroresonance leads to a significant increase in voltage or/and current with harmonic presence, both of which represent a threat to the stability of the electrical network and its parts. The influence of ferroresonance on the distribution system is crucial because the distribution system is the network's closest part to the consumer, and any effect it has will have an impact on the customer. This paper presents a state of the art of ferroresonance problem. The most visible signals for ferroresonance and analytical methods used to indicate its occurrence are presented. The investigation of ferroresonance in the radial distribution system and the effect of integrating Distributed Generation (DG) into the distribution zone on this phenomenon are presented. The latest methods used to mitigate and prevent ferroresonance are discussed. Furthermore a technique for suppressing ferroresonance is implemented. The ferroresonance in power transformer and the effect of load variation on it will be presented. PSCAD/EMTDC software is used to simulate the study.