This tissue has following status: blue
Created: 20 Feb 2016
Category: Issue for edition 2 of this part
Issue: 2nd line of Clause 6.2.3 (Detail quality) says – “If one of these identifiers is set then validity shall be set to invalid or questionable.” Or in other words, if the Validity = Good, then all the bits in the detailed quality shall be 0.
Which means, if you have frames with detail quality “Out of range = True” but with “Validity=Good’, then the frames are illegal/not legit/undefined by the standard.
Now, the question is : What should be the behavior of the Subscriber in such cases?
Of course, the publisher would be non-conforming to the standard if it publishes those illegal frames; but there are two aspects in this:
1. Testing – The Test kit generating such illegal frames
2. Real Operation – The publisher (e.g. a merging unit) which was conforming before, got damaged and now publishes those illegal frames
For the testing, The behavior of the subscriber might be left to the vendor implementation, which in turn could be as simple as ignoring the detail quality, doing nothing and operating as normal.
But for the real operation, this scenario can’t be ignored. Also, there are certain real-time performance requirements for the IEDs and considering that, it might be difficult to check every bit of the quality for every frame.
In such cases, how would you know that the Publisher merging Unit is not good anymore.
Proposal: Shall this issue be just left to the vendor implementation or shall there be a recommended action defined in the standard/ or in any of the TRs? E.g. the Publisher shall reject those frames and block the operation/ shall log such anomalies and raise an alarm after a certain count, etc.