1782   Clarification of when to ignore the check bits

Created: 22 Jul 2021

Status: Discussion (red)

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

Links:

Page: 165 of INF

Clause: 20.5.2

Paragraph: Table 110

Issue

In accordance with Ed.2.0 Tissue #1377, Ed.2.1 states on 'Check':

In case that the addressed function respective data object does not support these checks, the appropriate check bits shall be ignored and the command be handled.

The statement "does not support these checks" requires refinement.

The statement rules how to behave in the case of a non-alignment between a control command asking for checking and a device not supporting the check. The defined behaviour is very valid in the case of not matching configuration or misssing device capability. A control command would never be executed.

This Tissue is to ask for a confirmation that the statement is to be understood as mentioned, and not:

If a function is configured in an IED, matching with the check bit configuration in the client, but for a root cause out of the process the function does not support the check (example: VT fuse blown - no synchrocheck possible).
In such cases a control command should be rejected.

Proposal

Propose to change the statement "does not support these checks" to

"does not support these checks due to missing device capability or configuration"

Discussion Created Status
Originally, the "non check" was being the exception in the operation: "do not check interlocking or do not check synchrocheck".
In case the configuration (or implementation) imposes that synchrocheck resp. interlocking cannot be ignored or cannot be bypassed, then a negative response indicates that the "bypass request" fails.
The 7-2 definition currently uses that exception model "does not support these check": ignore the check bits, if the checks are irrelvant for the application: Operate(LEDRs, check=with synchrocheck) -> leads to ignore the check="with synchrocheck" condition.

propose to add in the table:
"In case the addressed function respective data object DOES support the bypass BUT not allowed to perform the bypass operation per configuration (do not ignore safety check), then a negative response shall be returned to the client that the bypass request fails (Inconsistent-parameters).
14 Sep 21 Discussion (red)

 

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