This standard pertains to the requirements for direct acting current and voltage protective functions of: a) direct-acting overcurrent electromechanical trip devices b) direct-acting overcurrent electronic trip systems c) reverse-current trip systems for dc circuit breakers d) undervoltage trip devices that are integral with low-voltage ac and dc power circuit breakers covered by IEEE Std C37.13?@ IEEE Std C37.14?@ and IEEE Std C37.16?.1 Additional information@ communication and/or additional internal or external protective functions or devices are not covered by this standard. This standard should not be interpreted to restrict the inclusion of such functionality in the device. Purpose The purpose of this standard is to provide the requirements for direct-acting overcurrent and/or undervoltage protective systems associated with low-voltage power circuit breakers. It is aligned with the requirements of related assemblies@ including low-voltage power circuit breaker (IEEE Std C37.13@ IEEE Std C37.14@ IEEE Std C37.16@ and ANSI C37.50) and metal-enclosed low-voltage power circuit breaker switchgear (IEEE Std C37.20.1? and ANSI C37.51). This standard includes minimum requirements for available settings and time delay characteristics as well as operational and calibration requirements. The functional requirements for the overall circuit breaker@ including test requirements (whether design@ production@ or conformance) are specified in the latest versions of IEEE Std C37.13@ IEEE Std C37.14@ IEEE Std C37.16@ and ANSI C37.50.