A system and method for detecting and isolating an electromagnetic pulse (“EMP”) along first phase, second phase, and third phase electrical lines electrically connected to a monitored infrastructure so as to protect the monitored infrastructure, the method for detecting and isolating includes a phase unit receiving electric signal data from a sensor electrically connected individually to each of the first phase, second phase, and third phase electrical lines, respectively, upstream of and associated with the monitored infrastructure. The method includes determining if the received electric signal data associated with the respective electrical line is indicative of an E1 component of an EMP and, if so, actuating an isolation subsystem in less than 300 nanoseconds to electrically isolate the respective electrical line against electrical communication with the monitored infrastructure.