CITEL MS200-120Y AC Power Din Rail Surge Protector for 120/240VAC Datasheet Contact Us AC Network: 3PH, 4W+G, 120/208Vac, Wye Application: Control Panel, Pump Panel, Power Cabinet In order to limit the effects of lightning or switching transients to acceptable levels for critical equipment and installations, the most effective solution is to install a protection device against these events. We call this an "SPD" (Surge Protective Device), they are deployed into the wireless network at the input to a distribution bus or directly at a sensitive load. The purpose is to harmlessly divert damaging surges away from your sensitive equipment before any disruption occurs.