Uninterruptible power supply provide backup power, protecting equipment from damage in the event of grid power failure. An uninterruptible power supply (UPS) is a type of device that powers equipment, nearly instantaneously, in the event of grid power failure, protecting the equipment from damage. The three major types of UPS system configurations are online double conversion, line-interactive and offline (also called standby and battery backup). These UPS systems are defined by how power moves through the unit.