2040   SimSt definition needs to be clarified

Created: 10 Jun 2026

Status: Discussion (red)

Part: Part 7-4 (2020; Edition 2.1)

Links:

Page: 81

Clause: 6.2.3.2

Paragraph: Table 17

Issue

The definition of SimSt as written in IEC 61850-7-4 is misleading and could be misconstrued and interpreted that once you stop receiving and accepting simulated messages, you should revert to SimSt=False.

However, SimSt reflects that we have received a simulated message and changed to simulation state. This bit should remain asserted even when we stop receiving simulated messages. It should only be reset when LPHD.Sim is reset to False.

See also https://iec61850.tissue-db.com/tissues/2039 for clarifying the subscription supervision state machine in 61850-7-1.

Proposal

Suggest revising the definition of SimSt to "Status indicating that the subscription has switched to processing simulated messages"

This also needs to be fixed in Table 7.1 Semantics that explains SimSt.

Discussion Created Status
The state machine Figure in IEC 61850-7-1 - is representing the transition - [TAL Expired ]
from the state "subscription simulated GOOSE" {subscription active, subscription of simulated GOOSE }
to the state "wait for Simulated GOOSE" {subscription not active, subscription of simulated GOOSE}


7-4 defines St as "If true, the subscription is active"

In the 7-1 state machine:
subscription not active stands therefore for St = FALSE
subscription active stands therefore for St = TRUE


7-4 defines SimSt as "If true, the subscription is receiving simulated message"
In the 7-1 state machine:
subscription of simulated GOOSE stands for SimSt = TRUE

SimSt is therefore true in both states:
"subscription simulated GOOSE"
"wait for Simulated GOOSE"

This is also aligned with IEC 61850-90-28 DPAS.






29 Jun 26 Discussion (red)
open for discussion 10 Jun 26 Discussion (red)
change state to accepted 10 Jun 26 Accepted

 

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