AFR Smart Load to Reduce VT Ferroresonance
AFR 1xx smart load is an instrument designed to monitor and protect measuring voltage transformers (VT) 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 lines or switching equipments. Ferroresonance can be initialized by switching, disconnection, ground connections or by other transient events. During the ferroresonance a significant overvoltage and concurrent current peaks can occur due to the saturation of the magnetic circuit of the VT. This often leads to a fatal destruction of the VT.
AFR 1xx acts as a protection of the VT against the unwanted effects of such events. In comparison with other protection methods AFR 1xx is only selectively activated during the occurrence of ferroresonance and stays inactive during the normal operation.
AFR 11x is intended for alone operated VTs, i. e. for single phase measuring, V connection measuring or for one pole power feeders.
AFR 13x is intended for connection into open delta of auxiliary secondary windings of three VTs.