The SDSA2040D 3-phase Surge Suppressor is designed to be connected to an open grounded configured 240V Delta electrical system. There is no ground reference for that 240V ungrounded type service, so no ground wire is part of that SDSA2040D SPD. The excess voltage that is coupled on any phase of that 3 phase Delta configured service is equally distributed to all 3 phases so the connected equipment receives an equal voltage level rise and decay. Therefore it is held, absorbed and dissipated within the device.
