How many instances of each LN?

Owned by Rodney Hughes
Last updated: 19 Oct 2014
5 min read
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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:

  • If there are several stages to one function (i.e. for multi-zone relay), each stage shall be a separate instance of the LN. Examples are PDIS (n zones) or PTOV (2 stages).
  • Multiple instances shall be used if LNs of the same LN class are operating with different settings in parallel.

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)

  • Z1P-PDIS1.PhStr = something
  • Z1P-PDIS1.GndStr = n/a
  • Z1G-PDIS2.PhStr = n/a
  • Z1G-PDIS2.GndStr = something

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:

  • Z1-PDIS1.PhStr
  • Z1-PDIS1.Gnd.Str

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)

  • OCStage1-PTOC1.StrVal with corresponding
    • OCStage1-PTOC1.Str.phsA
    • OCStage1-PTOC1.Str.phsB
    • OCStage1-PTOC1.Str.phsC
    • OCStage1-PTOC1.Str.neut
    • OCStage1-PTOC1.Str.general
    • OCStage1-PTOC1.Op.phsA
    • OCStage1-PTOC1.Op.phsB
    • OCStage1-PTOC1.Op.phsC
    • OCStage1-PTOC1.Op.neut
    • OCStage1-PTOC1.Op.general
  • OCStage2-PTOC2.StrVal with corresponding
    • OCStage2-PTOC2.Str.phsA
    • OCStage2-PTOC2.Str.phsB
    • OCStage2-PTOC2.Str.phsC
    • OCStage2-PTOC2.Str.neut
    • OCStage2-PTOC2.Str.general
    • OCStage2-PTOC2.Op.phsA
    • OCStage2-PTOC2.Op.phsB
    • OCStage2-PTOC2.Op.phsC
    • OCStage2-PTOC2.Op.neut
    • OCStage2-PTOC2.Op.general
  • OCStage3-PTOC3.StrVal with corresponding
    • OCStage3-PTOC3.Str.phsA
    • OCStage3-PTOC3.Str.phsB
    • OCStage3-PTOC3.Str.phsC
    • OCStage3-PTOC3.Str.neut
    • OCStage3-PTOC3.Str.general
    • OCStage3-PTOC3.Op.phsA
    • OCStage3-PTOC3.Op.phsB
    • OCStage3-PTOC3.Op.phsC
    • OCStage3-PTOC3.Op.neut
    • OCStage3-PTOC3.Op.general
  • OCStage4-PTOC4.StrVal with corresponding
    • OCStage4-PTOC4.Str.phsA
    • OCStage4-PTOC4.Str.phsB
    • OCStage4-PTOC4.Str.phsC
    • OCStage4-PTOC4.Str.neut
    • OCStage4-PTOC4.Str.general
    • OCStage4-PTOC4.Op.phsA
    • OCStage4-PTOC4.Op.phsB
    • OCStage4-PTOC4.Op.phsC
    • OCStage4-PTOC4.Op.neut
    • OCStage4-PTOC4.Op.general
  • EFStage1-PTOC5.StrVal with corresponding
    • EFStage1-PTOC5.Str.phsA
    • EFStage1-PTOC5.Str.phsB
    • EFStage1-PTOC5.Str.phsC
    • EFStage1-PTOC5.Str.neut
    • EFStage1-PTOC5.Str.general
    • EFStage1-PTOC5.Op.phsA
    • EFStage1-PTOC5.Op.phsB
    • EFStage1-PTOC5.Op.phsC
    • EFStage1-PTOC5.Op.neut
    • EFStage1-PTOC5.Op.general
  • EFStage2-PTOC6.StrVal with corresponding
    • EFStage2-PTOC6.Str.phsA
    • EFStage2-PTOC6.Str.phsB
    • EFStage2-PTOC6.Str.phsC
    • EFStage2-PTOC6.Str.neut
    • EFStage2-PTOC6.Str.general
    • EFStage2-PTOC6.Op.phsA
    • EFStage2-PTOC6.Op.phsB
    • EFStage2-PTOC6.Op.phsC
    • EFStage2-PTOC6.Op.neut
    • EFStage2-PTOC6.Op.general
  • EFStage3-PTOC7.StrVal with corresponding
    • EFStage3-PTOC7.Str.phsA
    • EFStage3-PTOC7.Str.phsB
    • EFStage3-PTOC7.Str.phsC
    • EFStage3-PTOC7.Str.neut
    • EFStage3-PTOC7.Str.general
    • EFStage3-PTOC7.Op.phsA
    • EFStage3-PTOC7.Op.phsB
    • EFStage3-PTOC7.Op.phsC
    • EFStage3-PTOC7.Op.neut
    • EFStage3-PTOC7.Op.general

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

  • MainProt_PTRC1.Str.phsA
  • MainProt_PTRC1.Str.phsB
  • MainProt_PTRC1.Str.phsC
  • MainProt_PTRC1.Str.neut
  • MainProt_PTRC1.Str.general
  • MainProt_PTRC1.Op.phsA
  • MainProt_PTRC1.Op.phsB
  • MainProt_PTRC1.Op.phsC
  • MainProt_PTRC1.Op.neut
  • MainProt_PTRC1.Op.general
  • MainProt_PTRC1.Tr.phsA
  • MainProt_PTRC1.Tr.phsB
  • MainProt_PTRC1.Tr.phsC
  • MainProt_PTRC1.Tr.neut
  • MainProt_PTRC1.Tr.general

 




 

 
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As per 7-4 Ed2 cl 5.11.1

·        If there are several stages to one function (i.e. for multi-zone relay), each stage shall be a separate instance of the LN. Examples are PDIS (n zones) or PTOV (2 stages).

·        Multiple instances shall be used if LNs of the same LN class are operating with different settings in parallel.

So you definitely need 3 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)

Z1P-PDIS.PhStr = something

Z1P-PDIS.GndStr = n/a

Z1G-PDIS.PhStr = n/a

Z1G-PDIS.GndStr = something

With corresponding

Z1P-PDIS.Op and Z1G-PDIS.Op

– this would imply 6 PDIS for a 3 zone relay (Z1P-, Z1G-, Z2P-, Z2G-, Z3P-, Z3G-)

 

But equally crystal clear is just

Z1-PDIS.PhStr

Z1-PDIS.Gnd.Str

Similarly Z1-PDIS.Op.phsA vs  Z1-PDIS.Op.neut is also crystal clear

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

 

Same goes for PTOC for a 3 stage OC and 3 stage EF relay

 

I talk about this in my Modelling slides as per attached (let me know if you want to register for the next course …. J )

 

As you can see if I use individual instances Z1P-PDIS and Z1G-PDIS, then Aph-G Z1 fault 

Z1P-PDIS.Op.phsA = 1

Z1P-PDIS.Op.phsB = 0

Z1P-PDIS.Op.phsC = 0

Z1P-PDIS.Op.neut = n/a

Z1P-PDIS.Op.general = 1

 

Z1G-PDIS.Op.phsA = n/a

Z1G-PDIS.Op.phsB = n/a

Z1G-PDIS.Op.phsC = n/a

Z1G-PDIS.Op.neut = 1

Z1G-PDIS.Op.general = 1

A-B Z1 fault

Z1P-PDIS.Op.phsA = 1

Z1P-PDIS.Op.phsB = 1

Z1P-PDIS.Op.phsC = 0

Z1P-PDIS.Op.neut = n/a

Z1P-PDIS.Op.general = 1

 

Z1G-PDIS.Op.phsA = n/a

Z1G-PDIS.Op.phsB =n/a

Z1G-PDIS.Op.phsC = n/a

Z1G-PDIS.Op.neut = 0

Z1G-PDIS.Op.general = 0

So there are 6 values – although note Z1G-PDIS.Op.general is the same meaning as Z1G-PDIS.Op.neut

 

 

 

But if I use the intended semantic Z1-PDIS.Op.phsA and Z1-PDIS.Op.neut, then Z1-PDIS.Op.general makes sense as

APh-G Z1 fault

Z1-PDIS.Op.phsA = 1

Z1-PDIS.Op.phsC = 0

Z1-PDIS.Op.phsB = 0

Z1-PDIS.Op.neut = 1

Z1-PDIS.op.general = 1

A-Bph Z1 fault

Z1-PDIS.Op.phsA = 1

Z1-PDIS.Op.phsB = 1

Z1-PDIS.Op.phsC = 0

Z1-PDIS.Op.neut = 0

Z1-PDIS.Op.general = 1

So I only need to publish 4 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 require 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

 

Same for PTOC 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.

So again not really operating in parallel with the same speed performance

Hence the second approach is more accurate

1                OCStage1-PTOC1.StrVal with corresponding

1.1            OCStage1-PTOC1.Str.phsA

1.2            OCStage1-PTOC1.Str.phsB

1.3            OCStage1-PTOC1.Str.phsC

1.4            OCStage1-PTOC1.Str.neut

1.5            OCStage1-PTOC1.Str.general

1.6            OCStage1-PTOC1.Op.phsA

1.7            OCStage1-PTOC1.Op.phsB

1.8            OCStage1-PTOC1.Op.phsC

1.9            OCStage1-PTOC1.Op.neut

1.10         OCStage1-PTOC1.Op.general

2                OCStage2-PTOC2.StrVal with corresponding

2.1            OCStage2-PTOC2.Str.phsA

2.2            OCStage2-PTOC2.Str.phsB

2.3            OCStage2-PTOC2.Str.phsC

2.4            OCStage2-PTOC2.Str.neut

2.5            OCStage2-PTOC2.Str.general

2.6            OCStage2-PTOC2.Op.phsA

2.7            OCStage2-PTOC2.Op.phsB

2.8            OCStage2-PTOC2.Op.phsC

2.9            OCStage2-PTOC2.Op.neut

2.10         OCStage2-PTOC2.Op.general

3                OCStage3-PTOC3.StrVal with corresponding

3.1            OCStage3-PTOC3.Str.phsA

3.2            OCStage3-PTOC3.Str.phsB

3.3            OCStage3-PTOC3.Str.phsC

3.4            OCStage3-PTOC3.Str.neut

3.5            OCStage3-PTOC3.Str.general

3.6            OCStage3-PTOC3.Op.phsA

3.7            OCStage3-PTOC3.Op.phsB

3.8            OCStage3-PTOC3.Op.phsC

3.9            OCStage3-PTOC3.Op.neut

3.10         OCStage3-PTOC3.Op.general

4                OCStage4-PTOC4.StrVal with corresponding

4.1            OCStage4-PTOC4.Str.phsA

4.2            OCStage4-PTOC4.Str.phsB

4.3            OCStage4-PTOC4.Str.phsC

4.4            OCStage4-PTOC4.Str.neut

4.5            OCStage4-PTOC4.Str.general

4.6            OCStage4-PTOC4.Op.phsA

4.7            OCStage4-PTOC4.Op.phsB

4.8            OCStage4-PTOC4.Op.phsC

4.9            OCStage4-PTOC4.Op.neut

4.10         OCStage4-PTOC4.Op.general

5                EFStage1-PTOC5.StrVal with corresponding

5.1            EFStage1-PTOC5.Str.phsA

5.2            EFStage1-PTOC5.Str.phsB

5.3            EFStage1-PTOC5.Str.phsC

5.4            EFStage1-PTOC5.Str.neut

5.5            EFStage1-PTOC5.Str.general

5.6            EFStage1-PTOC5.Op.phsA

5.7            EFStage1-PTOC5.Op.phsB

5.8            EFStage1-PTOC5.Op.phsC

5.9            EFStage1-PTOC5.Op.neut

5.10         EFStage1-PTOC5.Op.general

6                EFStage2-PTOC6.StrVal with corresponding

6.1            EFStage2-PTOC6.Str.phsA

6.2            EFStage2-PTOC6.Str.phsB

6.3            EFStage2-PTOC6.Str.phsC

6.4            EFStage2-PTOC6.Str.neut

6.5            EFStage2-PTOC6.Str.general

6.6            EFStage2-PTOC6.Op.phsA

6.7            EFStage2-PTOC6.Op.phsB

6.8            EFStage2-PTOC6.Op.phsC

6.9            EFStage2-PTOC6.Op.neut

6.10         EFStage2-PTOC6.Op.general

7                EFStage3-PTOC7.StrVal with corresponding

7.1            EFStage3-PTOC7.Str.phsA

7.2            EFStage3-PTOC7.Str.phsB

7.3            EFStage3-PTOC7.Str.phsC

7.4            EFStage3-PTOC7.Str.neut

7.5            EFStage3-PTOC7.Str.general

7.6            EFStage3-PTOC7.Op.phsA

7.7            EFStage3-PTOC7.Op.phsB

7.8            EFStage3-PTOC7.Op.phsC

7.9            EFStage3-PTOC7.Op.neut

7.10         EFStage3-PTOC7.Op.general