A surge protective device includes a first electrical terminal, a second electrical terminal, and an overvoltage protection circuit connected between the first electrical terminal and the second electrical terminal. The overvoltage protection circuit includes a spark gap assembly between the first electrical terminal and the second electrical terminal. The spark gap assembly includes a first spark gap (SG) electrode and a second SG electrode defining a spark gap therebetween, and a trigger circuit operative to ignite a main electric arc between the first and second SG electrodes across the spark gap. The trigger circuit includes a groove defined in the second SG electrode, and a trigger member disposed in the groove. The trigger member is operative to assist formation of a trigger arc.