 that the IEC uses its own published PTP standard (IEC 61588) as the PTP reference rather than IEEE 1588. IEC 61588:2009 (Ed. L3E2E Annex J.3 Precision Time Protocol IEC 62439-3:2016 L2P2P version IEC 61850-9-3:2016 from 1588-2008 PTP over HSR and PRP links L2P2P Annex J.4 PTP over HSR/PRP PTP Industry Profile (PIP) variants: L2P2P and L3E2E PTP Utility Profile (PUP) 1588-2019 Update Extensions IEC 61588:2009 (Ed. 3) Update Precision Time Protocol IEEE C37.238-2017 Reprint of 1588-2019 PTP "Power Profile" Update 1588-2019 PTP Utility Profile (PUP) Update IEC 61850-9-3:20xx (Ed. 2) IEC 62439-3:2021 (Ed. 4) PTP Utility Profile (PUP) HSR and PRP Redundancy PTP Industry Profile (PIP) Figure 7-16 Relationship Between PTP Standards for the Power Industry There have been three "editions" of the IEC 62439-3 standard, in 2010, 2012, and 2016. The 2016 edition is a technical revision that replaces the other editions, and there is expected to be a fourth edition published in 2021 that aligns with edition 2 of the 61850-9-3 profile and addresses changes from the new IEEE 1588-2019 version. These profiles make a lot of use of transparent clocks and have a stricter requirement on their per- formance than that of boundary clocks. This profile defines numerous PTP parameters to be specific values, such as restricting the message interval for Announce, Sync, and Pdelay_Ree to be 1 per second. 7.5.1 IEC 61850-9-3 (2016) Power Utility Automation Profile (PUP) As mentioned in the preceding section on IEC 62439-3, this profile is just a replication of the L2P2P profile from Annex C of that standard, with the optional requirement to support HSR/PRP redundancy outlined in Annex A of 62439-3. The goal of this profile is to achieve network time in- accuracy better than +1 us after crossing approximately 15 TCs or 3 BCs. This PUP profile utilizes layer 2 multicast communication according to IEEE 1588-2008 (Annex F) and uses the P2P delay measurement method derived from the default P2P profile in IEEE 1588- 2008, Annex J.4-although with a 