This recommended practice is intended to define the application and performance requirements for a low-voltage uninterruptible power supply (UPS) system used for service in power generating stations. This recommended practice addresses only requirements for semiconductor ac to ac converter systems (static) with dc electric energy storage capability. This recommended practice is not intended to address other types of UPS systems. This recommended practice is intended to cover application requirements, such as load information and service conditions, performance requirements and design, routine testing requirements for inverters with or without rectifier/chargers, and transfer switches only. The application requirements for batteries and battery chargers are excluded from this recommended practice. They can be found in other documents. This recommended practice is not intended to address equipment or component design requirements, safety-related design criteria, or requirements for equipment qualification and preoperational/surveillance testing.