1632 maxTime, TAL, and repetition delay clarification

Created: 27 Jun 2018

Status: Discussion (red)

Part: Part 8-1 (2011; Edition 2)

Links:

Page: 88

Clause: 18.1.1

Paragraph: 9

Category: Issue for edition 2 of this part

Issue

maxTime is specified as: This MMS component shall be as defined in IEC 61850-6 the source supervision time in ms
(supervision heartbeat cycle time).
It is unclear if maxTime is the maximum repetition delay (e.g. the slowest repetition) or the maximum TAL which is carried in the GOOSE message. This needs to be clarified as there is a definite relationship between TAL and repetition rate.

Proposal

Clarify the relationship between maxTime, TAL, and retransmission delay. If maxTime is the maximum TAL, then state that maxTime = maximum TAL and the retransmission delay <= maxTime/2. If maxTime is the supervision heartbeat cycle time (retransmission delay), then state that maxTime <= TAL/2.

Also, align the relationship of maxTime, TAL, and retransmission with the upcoming amendment so that implementations may only need to change once. State that the retransmission interval must be <= TAL/2.

Discussion	Created	Status
The issue is however not relevant for Ed2 testing. Ed2 testing shall verify that a subscriber shall detect a timeout after a TAL related timer expiration. A PIXIT entry documents the behavior. Ed2.1 8-1 FDIS specifies: MinTime This MMS component shall be as configured in SCL by the scl.tGSE.MinTime; it configures the sending delay on a data change between the first immediate sending of the change and the first repetition in ms. The PIXIT shall document the minimum MinTime supported by the implementation. MaxTime This MMS component shall be as configured in SCL by the scl.tGSE.MaxTime attribute; it configures the maximum repetition time in ms used in the published GOOSE messages. The PIXIT shall document the minimum MaxTime supported by the implementation; the maximum MaxTime is per standard defined by the value of sixty (60) seconds. NOTE: Conflicting definition from IEC 61850-6:2009/AMD1:2018 are superceeded with these definitions, and will be removed from IEC 61850-6:2009/AMD1:2018. Each message in the retransmission sequence carries a timeAllowedToLive parameter that guarantees the time before which the publisher publishes the next message. The specific retransmission intervals used by any GOOSE publisher are a local issue within the allowed range specified by MinTime and MaxTime. The keys in Fig 10 have been updated with: 1) GoEna is set to TRUE. 2) Publisher issues GOOSE.request. A retransmission timer is started; the actual timeAllowedtoLive parameter value shall be at least the value of the retranmission time (max retranmission time is determined by the SCL configuration scl.tGSE.MaxTime). SqNum is set to 0. 3) retransmission expiration timer indicates time for retransmission. SqNum is incremented skipping 0 on overflow. 4) Upon retransmission, a GOOSE.request is issued and the next retransmission interval is used to start retransmission timer. 5) A change of value for one of the DataSet members is detected. StNum is incremented. SqNum is set to zero. 6) All GOOSE messages and re-transmissions shall be stopped when the GoEna is set to FALSE. The keys in Fig 11 have been updated with: Key 1) Subscriber receives valid GOOSE.indication. Starts expiration timer with timeAllowedtoLive formula as specified in the GOOSE subscriber PICS. 2) timeAllowedtoLive expiration is detected. 3) Receives a valid GOOSE indication or valid retransmission The GOOSE PICS becomes a new entry: GOOSE Subscriber tolerance as a formula involving last received GooseMessage.TimeAllowedtoLive before declaring the association lost Subscribers: 2*TAL + Offset ms Publishers: - Value/Comment: TAL is taken from the last received GOOSE message.	05 Nov 18	Discussion (red)
I agree that a clarification is needed for the ED2.1. As discussed in WG10 NYC, the 8-1 FDIS draft is under work and will be circulated again in the WG10. The issue is however not relevant for Ed2 testing. Ed2 testing shall verify that a subscriber shall detect a timeout after a TAL related timer expiration. A PIXIT entry documents the behavior.	27 Jun 18	Discussion (red)

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