IEEE C37.238a-2023

This amendment adds another TLV to the Announce messages, containing details of the latest Leap-second event specified by the International Earth Rotation and Reference Systems Service (IERS). The fields comprise the date of the latest event, plus the total accumulated seconds offset after the event. The TLV will also indicate for how long the latest event information may be considered valid (so clocks in holdover may continue to provide UTC time for more than 12 hours after loss of a time source).

The purpose of this standard is to facilitate adoption of IEEE Std 1588-2008 for power system applications requiring high-precision time synchronization. IEC/IEEE 61850-9-3:2016 and this standard specify a common subset of PTP parameters and options to provide global time availability, device interoperability, and failure management. This set of PTP parameters and options allows IEEE 1588-based time synchronization to be used in mission critical power system protection, control, automation, and data communication applications.

Amendment Standard - Active. This amendment to IEEE Std. C37.238™-2017 specifies a LEAP_SECOND_EVENT TLV to enable grandmaster-capable clocks to distribute leap second event and validity information in advance.