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Modelling of a relay function is no doubt complex from both the functional requirement and the manufacturers features.  As a result we often run into some different interpretations of how the function should be represented according to which optional Data Objects/Attributes are included.

However the number of instances of a LN can also be a bit confusing at first glance. Equally just what is the benefit of the PTRC?

As an example how many PDIS elements are needed to model a three zone distance relay?  Or how many PTOC for 4 stage OC, 3 stage EF?

As per IEC 61850-7-4 Ed2 cl 5.11.1:

So you definitely need at least 3 x PDIS for a 3 zone relay

What is perhaps arguable is whether you would prefer to have the following (noting there is no generic .StrVal for PDIS)

This would imply 6 x PDIS for a 3 zone relay (Z1P-PDIS1, Z1G-PDIS2, Z2P-PDIS3, Z2G-PDIS4, Z3P-PDIS5, Z3G-PDIS6)

As you can see if we use individual instances Z1P-PDIS and Z1G-PDIS, then applying the ACD and ACT Common Data Classes from IEC 61850-7-3 for .Str and .Op Data Objects we get:

Aph-G Z1 fault 

  1. Z1P-PDIS.Str.phsA = 1
  2. Z1P-PDIS.Str.phsB = 0
  3. Z1P-PDIS.Str.phsC = 0
  4. Z1P-PDIS.Str.neut = n/a
  5. Z1P-PDIS.Str.general = 1
  6. Z1G-PDIS.Str.phsA = n/a
  7. Z1G-PDIS.Str.phsB = n/a
  8. Z1G-PDIS.Str.phsC = n/a
  9. Z1G-PDIS.Str.neut = 1
  10. Z1G-PDIS.Str.general = 1
  11. Z1P-PDIS.Op.phsA = 1
  12. Z1P-PDIS.Op.phsB = 0
  13. Z1P-PDIS.Op.phsC = 0
  14. Z1P-PDIS.Op.neut = n/a
  15. Z1P-PDIS.Op.general = 1
  16. Z1G-PDIS.Op.phsA = n/a
  17. Z1G-PDIS.Op.phsB = n/a
  18. Z1G-PDIS.Op.phsC = n/a
  19. Z1G-PDIS.Op.neut = 1
  20. Z1G-PDIS.Op.general = 1

A-B Z1 fault

  1. Z1P-PDIS.Str.phsA = 1
  2. Z1P-PDIS.Str.phsB = 1
  3. Z1P-PDIS.Str.phsC = 0
  4. Z1P-PDIS.Str.neut = n/a
  5. Z1P-PDIS.Str.general = 1
  6. Z1G-PDIS.Str.phsA = n/a
  7. Z1G-PDIS.Str.phsB =n/a
  8. Z1G-PDIS.Str.phsC = n/a
  9. Z1G-PDIS.Str.neut = 0
  10. Z1G-PDIS.Str.general = 0
  11. Z1P-PDIS.Op.phsA = 1
  12. Z1P-PDIS.Op.phsB = 1
  13. Z1P-PDIS.Op.phsC = 0
  14. Z1P-PDIS.Op.neut = n/a
  15. Z1P-PDIS.Op.general = 1
  16. Z1G-PDIS.Op.phsA = n/a
  17. Z1G-PDIS.Op.phsB =n/a
  18. Z1G-PDIS.Op.phsC = n/a
  19. Z1G-PDIS.Op.neut = 0
  20. Z1G-PDIS.Op.general = 0

So there are  potentially 20 values just for Zone 1 – although note Z1G-PDIS.Op.general is the same meaning as Z1G-PDIS.Op.neut so some rationalisation may be done by different implementation taking into account the n/a values resulting in only 10 required.

But equally crystal clear is just one instance per zone:

In which case you use the power of the defined semantic to only need 3 x PDIS for a 3 zone relay (Z1-PDIS1, Z2-PDIS2, Z3-PDIS3)

So if we use the intended semantic Z1-PDIS.Op.phsA and Z1-PDIS.Op.neut, then Z1-PDIS.Op.general makes sense with no n/a items in the data model as

APh-G Z1 fault

  1. Z1-PDIS.Str.phsA = 1
  2. Z1-PDIS.Str.phsC = 0
  3. Z1-PDIS.Str.phsB = 0
  4. Z1-PDIS.Str.neut = 1
  5. Z1-PDIS.Str.general = 1
  6. Z1-PDIS.Op.phsA = 1
  7. Z1-PDIS.Op.phsC = 0
  8. Z1-PDIS.Op.phsB = 0
  9. Z1-PDIS.Op.neut = 1
  10. Z1-PDIS.Op.general = 1

A-Bph Z1 fault

  1. Z1-PDIS.Str.phsA = 1
  2. Z1-PDIS.Str.phsB = 1
  3. Z1-PDIS.Str.phsC = 0
  4. Z1-PDIS.Str.neut = 0
  5. Z1-PDIS.Str.general = 1
  6. Z1-PDIS.Op.phsA = 1
  7. Z1-PDIS.Op.phsB = 1
  8. Z1-PDIS.Op.phsC = 0
  9. Z1-PDIS.Op.neut = 0
  10. Z1-PDIS.Op.general = 1

So we only need to publish 10 values.

The interpretation problem is that the second dot point in 5.11.1 might suggest the first approach should be used since the Z1 ph-G settings are operating “in parallel” to the ph-ph settings.  They are in parallel in the sense that they both individually will result a PTRC.Op to be = 1

But in reality they are not operating in parallel as a ph-G element will not operate for a ph-ph fault, or vice versa.

Hence the second approach is actually more accurate.

 

PTOC is a little bit different for phase faults vs earth faults.

Yes both elements may well be in the process of “operating” for a given current, but the EF element (if IDMT) will be operating at a faster rate than the OC element since the fault is much larger x the EF setting current.  Or the EF may be going to operate and the phase element not, or vice versa.  So again not really operating in parallel with the same speed performance.

However there is only one pick up setting for PTOC as PTOC.StrVal - there is no distinguishing .PhStr vs .GndStr settings

Hence for 4 stage OC and 3 stage EF you need 7 x PTOC (the red elements are arguably not applicable within that stage)

This is an excellent demonstration of why you then need a PTRC LN to represent the 3-level OR function of all of these - perhaps even both the PDIS and PTOC instances from a multifunction relay - to just give a combined set of the following, noting the PTRC has the additional .Tr outputs which provide an extended pulse output in addition to the mirror of the .Op signals

 




 

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