The application of the Equal Area Criterion in ferroresonance

The paper presents a novel technique, a ferroresonance discriminance method of potential transformer, which is adaptive to distinguish whether the system will be excited to be in ferroresonant condition or not, based on time-varying vector analysis method and the Equal Area Criterion. First of all, the time-varying vector mathematical model and IS curve are established according to the zero-mode ferroresonant circuit coming from a typical distribution system. Subsequently, three equilibrium points of the system are all discussed according to the time-varying vector mathematical model and IS curve. Eventually, with the formula definitions of stability margin (S_a) and disturbing quantity (S_dmax) which is according to the IS curve, the ferroresonance discriminance method of potential transformer is established through comparing S_a with S_dmax. Large amounts of ATP simulation tests show that the ferroresonance discriminance method of potential transformer is efficient and accurate.