POWER DEVICE TERMINAL BACKUP SWITCH UNIT OF AN UPS

When a power outage occurs, an uninterruptable power supplies may lose all grid connections including a neutral connection which may be connected to ground. To avoid the loss of a ground connection to the power circuits of the UPS, a switch unit may be used to selectively connect a neutral conductor of the circuit to a ground terminal. The switch unit may comprise a power relay, a fast switch device (FSD), and a controller. The power relay and FSD may be connected in series between the neutral conductor of the circuit and a ground terminal. The controller may be configured to: close the FSD when the voltage between ground and neutral (Vng) goes above a first threshold, open the FSD when the voltage between any grid connection and neutral (Vg) goes above a second threshold, and close the FSD when Vg is below the second threshold.