AFR 1 smart load is an instrument designed to monitor and protect measuring voltage transformers (PT) against the potentially harmful effects of ferroresonance in a high voltage distribution network. Ferroresonance occurs between the inductance of the transformer and the capacitance of the MV lines or switching equipments. Ferroresonance can be initialized by switching, disconnection, ground connection or by other transient event. During the ferroresonance a significance overvoltage and concurrent current peaks can occur due to the saturation of the magnetic circuit of the VT. This often leads to a falat destruction of the VT.