Systems and methods for protecting an electrical component in an alternating current system that includes a transformer are disclosed. In one aspect, a circuit includes a switch assembly connected between a transformer neutral of a transformer and a ground and having an open position and a closed position. In normal operation, the switch remains in a closed position. The circuit further includes a DC blocking component positioned in parallel with the switch assembly and connected between the transformer neutral and the ground, a voltage probe connected between the transformer neutral and ground and configured to monitor an instantaneous voltage level at the transformer neutral, and a control circuit configured to control the switch assembly, the control circuit including a sensor configured to actuate the switch assembly to an open position at least upon detection of a harmonic signal in at least one phase of the transformer or a predetermined threshold of DC or quasi DC current between the transformer neutral and the ground.