IEEE C37.238-2017 IEEE Standard Profle for Use of IEEE 1588™ Precision Time Protocol in Power System Applications.
3. Defnitions, special terms, and word usage For the purposes of this document, the following terms and defnitions apply. The IEEE Standards Dictionary Online should be referenced for terms not defned in this clause. 5 3.1 Defnitions absolute time: Time maintained by the international standards laboratories that form the basis for the International Atomic Time and Coordinated Universal Time timescales. boundary clock (BC): A clock that has multiple Precision Time Protocol ports in a domain and maintains the timescale used in the domain. It may serve as the source of time, i.e., be a master clock, and may synchronize to another clock, i.e., be a slave clock. (IEEE Std 1588-2008) clock: A device participating in the Precision Time Protocol (PTP) that is capable of providing a measurement of the passage of time since a defned epoch. (adapted from IEEE Std 1588-2008) NOTE—In the case of PTP ordinary and boundary clocks that are properly synchronized, the epoch is the epoch of the timescale in use. In the case of PTP transparent clocks, the epoch is locally defned and not necessarily aligned with the timescale. 6 default: When applied to attribute values and options means the confguration of a Precision Time Protocol device as it is delivered from the manufacturer. (IEEE Std 1588-2008) device time inaccuracy: Time inaccuracy evaluated or measured between the time signal at the input of a device and the time signal that this device generates. (IEC/IEEE 61850-9-3:2016) NOTE 1—Device time inaccuracy includes the uncertainties in the computation of the path delay assuming an ideal Pdelay_Resp from an upstream neighbor, and the uncertainty introduced in responding to an ideal Pdelay_Req from a downstream neighbor. NOTE 2—This defnition applies to transparent clocks, boundary clocks, and media converters. distribution time inaccuracy: Time inaccuracy evaluated or measured between the time signal at the output of a grandmaster and the time signal at the input of a slave clock. IEEE C37.238 pdf download.