1822   Functional constraint object non-volatility ambiguous

Created: 04 Apr 2022

Status: Discussion (red)

Part: Part 7-2 (2020; Edition 2.1)


Page: 29

Clause: 5.7

Paragraph: Table 4


Definition of SP and CF and DC and SG each have same words "Initial value shall be as configured; value shall be non-volatile".
Upon restart, this could be interpreted as:
1. Values from SCL are used
2. Values from local non-volatile memory are used

Which is correct (or is this a "local issue")?
Is there some expectation that a device "know" that it is under initial configuration and to discard non-volatile values?


Remove all Table 4 references to "non-volatile".
The expectation is that any changes to objects of these types cause an IID file to be generated with updated values. Somehow indicate that these updated IID files are expected to be incorporated into the SCD file.

Discussion Created Status
seems we need more discussion.

As mentioned, it has relation to 80-7; but as well what was proposed in the second Amendment to 7-3.

So new proposal to keep explanation as is for the moment but make it a future issue.
22 Nov 22 Discussion (red)
21-Nov Proposal is ambiguous. How does a device "know" whether to use the value from the SCD file or the value last changed (online or device front panel)? 61850-8-1:2004 (informative) Annex D.2 described a method (activate) to determine whether a SCL file was used to reconfigure the device (i.e. all of the values from SCL file were applied) but this was deleted in Ed2. If the 21-Nov proposal is adopted then the [Val] elements present in the SCD file cannot be used for any purpose because the device can choose to use different values. This means that many of the use cases for SCL will not be possible (simulation, etc.) 22 Nov 22 Approval (Editoral)
Proposed clarification editorial change:
behind "Initial value shall be as configured; value shall be non-volatile"
", which means, that if the value has been changed online, upon restart that changed value shall be applied instead of the configured initial value"

Note that from a system management perspective, an ICT could any time retrieve the current active values from the device (using MMS or Proprietary Communication means) and would be able to export the updated IID file. It would be nevertheless a user choice to keep these updated online values within the SCL representation of the device or not.
21 Nov 22 Approval (Editoral)
On restart with same SCL, the device maintains the non-volatile changes.

If the device consumes updated SCL, the non-volatile values should be overridden. Before downloading new SCL to device any existing online changes should be considered and reflected in the SCD if necessary.

It is an implementation issue if the online changes are being conserved for future system engineering.

This should be clarified in -80-7

From a 7-2 perspective non-volatile means that upon restart, the online changed values are conserved.
20 Jun 22 Approval (N/A)
Non-volatile means that upon restart, the online changed values are conserved.
It is a local issue, if the online changed values are considered in the ICT during the next IID export.
If deviation between the SCL values and the online model are likely to cause a system engineering issue, then the user shall consider to not modify the online values.
10 May 22 Triage


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