Created: 17 Dec 2020
Part: Part 7-4 (2020; Edition 2.1)
Links: #1756 Event driven schedules – Extend description , #1755 Event driven schedules – Add DO to stop schedule by event
In behalf of the German VDE/FNN project group (PG Steuerbox):
Applying the standard’s schedule definitions to practical use cases caused some discussion on how to interpret part 7-4.
IEC 61850-7-4 annex K.2.4 states: “In case, for whatever reason, the schedule cannot start at the time given by the occurrence of a start time setting, but afterwards, then the schedule will run sharply as if it has started at the time given by the start time setting. Said in other words, the schedule won’t shift the scheduled values based on the real-time start.”
German VDE FNN Project Group Steuerbox concluded that an enabled periodic schedule would run as if enabled with its most recent (periodic) start time, if it were still running from this start. Because it affects interoperability of the specified devices, we decided to discuss the issue with the community.
The attachment shows the issue with examples.
Chapter K.2.4 of part 7-4 (2020) shall be amended:
A schedule assumes status 'running' from 'not ready', if the following conditions are true:
1) the schedule is well-formed (has starting times, output values etc.)
2) if a UTC Start time (setTm) is present, it lies in the past
3) if the schedule is cyclic, there exists a cyclic start time (last cyclic start Time from setCal, lcst), for which is
lcst <= now <= lcst + (SchdIntv * NumEntr).
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