1311   How is range supposed to work if instMag is not present in the CDC

Created: 17 Sep 2014

Status: Not Applicable

Part: Part 7-3 (2010; Edition 2)

Links:

Page: 71

Clause: 8

Paragraph: Table 64

Category: Issue for edition 2 of this part

Issue

The definition of "range" is the following (from the table): "Range in which the current value of instMag or instCVal.mag is. It may be used to issue an event if the current value changes and transitions to another range. Range shall be used in the context with configuration attributes like hhLim, hLim, lLim, llLim, min and max as shown
below."

However, what happens if instMag is not in the CDC (e.g. in MV it is optional). Is range still allowed to be present in the CDC, if so what is it applied against?

Proposal

There are 3 possibilities:

1). Make the presences of "range" conditional on instMag being present, instead of optional.

2). Change the definition of "range" in the table that specifies an order of evaluation (e.g. first instMag, second mag if instMag is not present).

3). Clarify that even though instMag is not externally exposed, it is the "local" value.

Note, there are more instances of where this confusion could occur besides just MV.

Discussion Created Status
It is already stated in NOTE 3 in chapter 6 / page 67 of Edition 2 that the optional presence of instMag only affects the visibility:

NOTE 3 The presence of the attribute instMag is optional, that only affects the visibility of that value to the communication. The instantaneous value may be required for the internal behaviour of the function, e.g. to perform the deadband calculation as explained with the attribute mag. 		24 Apr 15 Not Applicable
Proposal:
add in MV.range
instMag can be a local value, i.e. does not need to be visible over the communication for implementing the range attribute.
add in CMV.range
instCVal.mag can be a local value, i.e. does not need to be visible over the communication for implementing the range attribute.
add in CMV.rangeAng
instCVal.ang can be a local value, i.e. does not need to be visible over the communication for implementing the rangeAng attribute. 		05 Mar 15 Discussion (red)
The solution is clearly point 3.instMag can be an 'invisible' local value, or identical to mag. Observe that if a client bases its process picture on reporting, it might get range events without appropriate mag event, even if instMag is visible / readable - as it does not generate events. 17 Sep 14 Discussion (red)

 

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