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2021-05 Modifications to PRC-023 | Standard Authorization Request

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Start Date: 06/29/2021
End Date: 07/28/2021

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Hot Answers

MISO offers the following perspective for consideration by the Standard Drafting Team (SDT) as the issue under consideration appears to be one of Dependability (tripping when needed) and Security (preventing overtripping when not needed) and determining what requirements are needed to provide the most reliable result.

As stated in the “Background” section on the Project 2021-05 page, the requirement to allow tripping in a Standard whose intent is to block tripping, has led to some entities disabling their OOSB relays. If that is the case, it appears the answer should be to clarify the requirement as opposed to retiring it, to retain the Dependability aspect of the requirement. Alternatively, there may be a justification to retire the requirement; however, it is not clearly stated in the SAR. If the latter is the case, the SDT should clarify that in the SAR.

Recommendation: Modify “Industry Need” section as indicated below or revise the statement to justify why retiring the Dependability requirement will not result in less reliable operation:

“Requirement R2 should be clarified or removed  because it has been interpreted to restrict the setting of OOSB elements making compliance with PRC-026 more difficult.

MISO suggests there may be a way for Dependability and Security objectives to be achieved at the same time (below).  

Dependability: The provisions in PRC-023 that require tripping for three-phase faults during stable power swings should remain.  To the extent a short-circuit fault occurs on a transmission line at the time of a stable power swing, protection systems must be capable of detecting the fault, distinguishing it from the stable power swing and tripping the line accordingly.

For lines identified as meeting one or more of the four criteria outlined in PRC-026-1 R1, ensuring fault protection during stable power swings could be accomplished by installing either two redundant line differential schemes (where line differential schemes respond to all short-circuit faults but not to high loading or power swings) or a primary line differential scheme and a backup phase distance relay scheme (such as a DCB scheme). 

Security: At the same time, the protection system should also be designed to avoid tripping on stable power swings in accordance with NERC PRC 026-1.

Out-of-step blocking could be employed to block tripping of the backup phase distance relay scheme for a stable power swing, but the line differential scheme would not be subject to supervision by the out-of-step blocking scheme as line differential relays do not respond to loading or power swings, and thus the line differential relay could ensure tripping for three-phase faults even when a stable power swing exists just prior to the fault.

Given the relatively few number of lines where stable power swings are typically an issue (i.e., meet one or more of the four criteria in PRC-026-1 Requirement 1), the above approach would provide superior protection to a scheme that disables fault protection during a stable power swing, thus exposing a power system to a potential catastrophic event.  Given the possibility of multiple faults occurring close in time due to a common root cause (e.g., area weather patterns that tend to cause multiple transmission short-circuit faults such as lightning or wind), it is important to maintain short-circuit fault protection at all times, and this can be done in a manner that also avoids false tripping due to stable power swings.

For this reason, we do not see the need to modify PRC-023-1 to remove the requirement that fault protection is in place during stable power swings.

Bobbi Welch, On Behalf of: Midcontinent ISO, Inc., , Segments 2

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Exelon supports the proposed SAR.  

Daniel Gacek, On Behalf of: Exelon, , Segments 1, 3, 5, 6

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Other Answers

David Jendras, On Behalf of: Ameren - Ameren Services, , Segments 1, 3, 6

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Dennis Chastain, On Behalf of: Tennessee Valley Authority - SERC - Segments 1, 3, 5, 6

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Duke Energy, Segment(s) 1, 5, 6, 4/11/2019

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LaTroy Brumfield, On Behalf of: American Transmission Company, LLC, , Segments 1

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N/A.

Leonard Kula, On Behalf of: Independent Electricity System Operator, , Segments 2

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Not applicable for HQP

Carl Pineault, On Behalf of: Hydro-Qu?bec Production, , Segments 1, 5

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Thomas Foltz, On Behalf of: AEP, , Segments 3, 5, 6

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The requirement R2 and the attachment A 2.3 cause interpretation confusion and the proposal to remove both from the requirements would allow the normal functioning of the OOSB relays during power swing conditions.

Dwanique Spiller, On Behalf of: Berkshire Hathaway - NV Energy - WECC - Segments 5

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While not related to the SAR’s concerns, the standard should define the period a TO, GO, or DP has to bring a circuit in compliance with R1 following notification by the PC of the circuit’s inclusion on a list of circuits per application of Attachment B within standard itself. This period was previously defined in the Implementation Plan PRC-023-3, and was carried forward to PRC-023-4 by a FERC order (in Docket RD18-6-000) approving a second-filed errata to the RAS Implementation Plan. It seems inappropriate for a time period requiring ongoing use to be included in an Implementation Plan rather than the body of the standard. Any SDT assigned to revise PRC-023-4 should also address this issue, but if not, the SDT needs to define the period in the new Implementation Plan.

Anthony Jablonski, On Behalf of: ReliabilityFirst , , Segments 10

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While we do not necessarily agree completely with the arguments and justifications put forth in the SAR, :

  • If industry confusion due to R2 and exclusion A2.3 has indeed led to utilities disabling the OOSB elements(for which no substantiating data have been provided in the SAR) without first making sure that disabling OOSB cannot lead to system instability that could cause cascading phenomena and eventual system collapse,     then,      
  • we do agree with the objective of the SAR that removal of such confusion is a good thing and would recommend that the decision to enable or disable OOSB should occur on a case-by-case basis after the required studies are performed.

Jeremy Lorigan, On Behalf of: Seminole Electric Cooperative, Inc., , Segments 1, 3, 4, 5, 6

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Daniela Atanasovski, On Behalf of: APS - Arizona Public Service Co., , Segments 1, 3, 5, 6

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Scott Langston, On Behalf of: Tallahassee Electric (City of Tallahassee, FL), , Segments 1, 3, 5

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R2 was included in PRC-023-4 for the express reason that, should a FAULT on the protected element occur during heavy load flows anticipated by the standard, OOSB elements will not detect the transition from a load condition to a FAULT as a swing and block tripping for that condition. Absent this requirement, there is a definite possibility that OOSB elements would restrain tripping for these FAULT conditions, and thereby result in a un-cleared fault. Similarly, Attachment A, 2.3 endeavors to assure that FAULTS during stable power swings will be detected and cleared.

Jeanne Kurzynowski, On Behalf of: CMS Energy - Consumers Energy Company - RF - Segments 3, 4, 5

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Jamie Monette, On Behalf of: Allete - Minnesota Power, Inc., , Segments 1

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Southern Company, Segment(s) 1, 3, 6, 5, 1/14/2021

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Texas RE agrees Requirement R2 should be evaluated for the reasons given in the SAR.  Texas RE recommends the drafting team consider an exception process to allow for out-of-step relays to trip for unstable power swings that may fall within the criteria in Requirement R1.

Rachel Coyne, On Behalf of: Texas Reliability Entity, Inc., , Segments 10

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Andrea Jessup, On Behalf of: Bonneville Power Administration, WECC, Segments 1, 3, 5, 6

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Lindsay Wickizer, On Behalf of: Berkshire Hathaway - PacifiCorp, , Segments 6

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FE Voter, Segment(s) 1, 3, 5, 6, 4, 2/23/2021

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None

Alan Kloster, On Behalf of: Great Plains Energy - Kansas City Power and Light Co. - MRO - Segments 1, 3, 5, 6

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Donna Wood, On Behalf of: Tri-State G and T Association, Inc., , Segments 1, 3, 5

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MEC supports MRO NSRF comments.  MEC notes there are two opposing concerns, a potential conflict between PRC-026 and PRC-023 versus possible tripping.  MEC believes the SAR should move forward even if there is a scope question and would like the SDT to investigate NERC standard conflict concerns between PRC-026 and PRC-023.  It’s MEC’s understanding that if a transmission line is identified for PRC-026, a way to comply with PRC-026 is to enable Out-Of-Step blocking, but PRC-023 R2 interferes with that solution by too restrictively burdening the settings for the outer blinder technology to be dependable, therefore causing more compliance issues for the Transmission Owner to solve, hence why entities are removing the schemes.

Terry Harbour, On Behalf of: Berkshire Hathaway Energy - MidAmerican Energy Co., , Segments 1, 3

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The NSRF offers the following perspective for consideration by the Standard Drafting Team (SDT) as the issue under consideration appears to be one of Dependability (tripping when needed) and Security (preventing overtripping when not needed) and determining what requirements are needed to provide the most reliable result.

As stated in the “Background” section on the Project 2021-05 page, the requirement to allow tripping in a Standard whose intent is to block tripping, has led to some entities disabling their OOSB relays. If that is the case, is the answer to eliminate the dependability requirement in favor of security or is there a way to clarify the standard to balance and achieve both objectives at the same time?  If not, the SAR should be updated for clarity.

Dependability: The provisions in PRC-023 that require tripping for three-phase faults during stable power swings should remain.  To the extent a short-circuit fault occurs on a transmission line at the time of a stable power swing, protection systems must be capable of detecting the fault, distinguishing it from the stable power swing and tripping the line accordingly. 

For lines identified as meeting one or more of the four criteria outlined in PRC-026-1 R1, ensuring fault protection during stable power swings could be accomplished by installing either two redundant line differential schemes (where line differential schemes respond to all short-circuit faults but not to high loading or power swings) or a primary line differential scheme and a backup phase distance relay scheme (such as a DCB scheme). 

Security: At the same time, the protection system should also be designed to avoid tripping on stable power swings in accordance with NERC PRC 026-1. 

Out-of-step blocking could be employed to block tripping of the backup phase distance relay scheme for a stable power swing, but the line differential scheme would not be subject to supervision by the out-of-step blocking scheme as line differential relays do not respond to loading or power swings, and thus the line differential relay could ensure tripping for three-phase faults even when a stable power swing exists just prior to the fault.

Given the relatively few number of lines where stable power swings are typically an issue (i.e., meet one or more of the four criteria in PRC-026-1 Requirement 1), the above approach would provide superior protection to a scheme that disables fault protection during a stable power swing, thus exposing a power system to a potential catastrophic event.  Given the possibility of multiple faults occurring close in time due to a common root cause (e.g., area weather patterns that tend to cause multiple transmission short-circuit faults such as lightning or wind), it is important to maintain short-circuit fault protection at all times, and this can be done in a manner that also avoids false tripping due to stable power swings.

For this reason, we do not see the need to modify PRC-023-1 to remove the requirement that fault protection is in place during stable power swings.

MRO NSRF, Segment(s) 2, 4, 1, 6, 3, 5, 7/1/2021

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EEI supports the proposed SAR.    

Mark Gray, On Behalf of: Edison Electric Institute, NA - Not Applicable, Segments NA - Not Applicable

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OKGE, Segment(s) 6, 1, 3, 5, 3/22/2021

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MPC supports MRO NERC Standards Review Forum (NSRF) comments.

Andy Fuhrman, On Behalf of: Minnkota Power Cooperative Inc. - MRO - Segments 1, 5

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The NPCC RSC agrees with the proposed scope as described in the SAR.

NPCC Regional Standards Committee no NGrid, Segment(s) 10, 2, 4, 7, 3, 1, 5, 6, 7/19/2021

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No additional comments.

ACES Standard Collaborations, Segment(s) 1, 5, 3, 4, 7/28/2021

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Maryanne Darling-Reich, On Behalf of: Black Hills Corporation, MRO, WECC, Segments 1, 3, 5, 6

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-        ITC agrees with the proposed scope of removing R2 but for a different reason than the SAR’s rationale.  Modern relays which ITC is familiar with incorporate standard logic in OOSB functions to ensure tripping for 3ph faults during a power swing or loading inside the first blinder.  Furthermore, it is a matter of good engineering practice to ensure tripping during conditions such as a swing or heavy line loading.  This requirement is therefore simply an administrative burden without improving reliability. PRC-026 already ensures that if OOSB is needed that reliable fault detection is maintained.

-        ITC disagrees with the proposed scope removal of Att A 2.3. With the removal of R2, the confusion with Att A 2.3 is addressed and we should not anticipate what OOST for stable power swings may exist in the future that need to be covered by this exclusion.

Gail Elliott, On Behalf of: International Transmission Company Holdings Corporation - MRO, RF - Segments NA - Not Applicable

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Hot Answers

Expand the scope of the SAR to align “trip” and “operate” terminology in PRC-023 with PRC-026.

If modifications to PRC-023 move forward, the SDT should consider addressing another problematic aspect of the standard; i.e. the use of the term “operate” in lieu of “trip” in the various criteria associated with Requirement 1.  Aligning the wording in PRC-023 with PRC-026 would help to ensure clarity and consistency of application.

The term “operate” typically applies to the operation of a single relay element whereas the term “trip” typically applies to the tripping of one or more circuit breakers, and thus the isolation of a protective zone.  Having said this, an entire transmission relay scheme is often comprised of multiple relay elements, and thus more than one element must “operate” to initiate a “trip”.  Therefore, if the goal is to avoid a false trip, all that is necessary is to ensure at least one of the relay elements will not operate.  It is not necessary to ensure all relay elements associated with the protective relay scheme will not operate.

For example, in a direction comparison blocking scheme, the Zone 3 mho distance element (21) is often supervised by a non-directional overcurrent unit (50), and both elements must operate to initiate a trip.  The non-directional overcurrent relay element must reach for faults on the opposite end of the line and possibly beyond to facilitate remote backup protection, and this requirement often means the overcurrent relay element must be set such that it could operate under high levels of loading (particularly for longer lines), but this will not result in a line trip since the Zone 3 mho distance element will not operate, thus the scheme should be compliant with the spirit of PRC-023, which is to avoid false tripping under high loading conditions.  However, one could interpret the term “operate” as applied to individual relay elements in Requirement 1 based on the way the standard is drafted, and this interpretation would require that none of the relay elements are allowed to operate under load, which is an unnecessary requirement that makes compliance much more challenging. 

While to date the interpretation of the standard is to avoid tripping and this should be the intent of the standard, the actual application is not well aligned with that interpretation.

Expand the make-up of the SDT to include a representative from an end-user perspective

MISO agrees with the SAR that the core of the SDT should consist of individuals from the TO, GO and DP functions. That said, we also recommend the SDT consider including an individual(s) from an end-use perspective; i.e. one TOP and/or one TP on the SDT.

Bobbi Welch, On Behalf of: Midcontinent ISO, Inc., , Segments 2

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Daniel Gacek, On Behalf of: Exelon, , Segments 1, 3, 5, 6

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Other Answers

David Jendras, On Behalf of: Ameren - Ameren Services, , Segments 1, 3, 6

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N/A

Dennis Chastain, On Behalf of: Tennessee Valley Authority - SERC - Segments 1, 3, 5, 6

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No additional comments at this time.

Duke Energy, Segment(s) 1, 5, 6, 4/11/2019

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LaTroy Brumfield, On Behalf of: American Transmission Company, LLC, , Segments 1

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N/A.

Leonard Kula, On Behalf of: Independent Electricity System Operator, , Segments 2

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No comments

Carl Pineault, On Behalf of: Hydro-Qu?bec Production, , Segments 1, 5

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Thomas Foltz, On Behalf of: AEP, , Segments 3, 5, 6

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Following additional points should be considered.

  • R1 criteria 6 should be removed as it is not used. This has just been used as a place holder after subsequent revisions in PRC-023-3 and PRC-023-4'
  • Attachment A 2.4 should be removed as it is not used. This has just been used as a place holder after subsequent revisions in PRC-023-3 and PRC-023-4.

Dwanique Spiller, On Behalf of: Berkshire Hathaway - NV Energy - WECC - Segments 5

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Anthony Jablonski, On Behalf of: ReliabilityFirst , , Segments 10

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Jeremy Lorigan, On Behalf of: Seminole Electric Cooperative, Inc., , Segments 1, 3, 4, 5, 6

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None

Daniela Atanasovski, On Behalf of: APS - Arizona Public Service Co., , Segments 1, 3, 5, 6

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Scott Langston, On Behalf of: Tallahassee Electric (City of Tallahassee, FL), , Segments 1, 3, 5

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Jeanne Kurzynowski, On Behalf of: CMS Energy - Consumers Energy Company - RF - Segments 3, 4, 5

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Jamie Monette, On Behalf of: Allete - Minnesota Power, Inc., , Segments 1

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Southern Company, Segment(s) 1, 3, 6, 5, 1/14/2021

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Rachel Coyne, On Behalf of: Texas Reliability Entity, Inc., , Segments 10

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BPA is presently facing a situation where we need to add an OOSB function to two transmission lines, but PRC-023 R2 prevents us from doing so with the existing relays.  We can see the need to take a closer look at PRC-023 R2 to possibly eliminate the issues that this requirement creates.

Andrea Jessup, On Behalf of: Bonneville Power Administration, WECC, Segments 1, 3, 5, 6

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Lindsay Wickizer, On Behalf of: Berkshire Hathaway - PacifiCorp, , Segments 6

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N/A

FE Voter, Segment(s) 1, 3, 5, 6, 4, 2/23/2021

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None

Alan Kloster, On Behalf of: Great Plains Energy - Kansas City Power and Light Co. - MRO - Segments 1, 3, 5, 6

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Donna Wood, On Behalf of: Tri-State G and T Association, Inc., , Segments 1, 3, 5

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MEC supports MRO NSRF comments.

Terry Harbour, On Behalf of: Berkshire Hathaway Energy - MidAmerican Energy Co., , Segments 1, 3

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  • Expand the scope of the SAR to align “trip” and “operate” terminology in PRC-023 with PRC-026.

If modifications to PRC-023 move forward, the SDT should consider addressing another problematic aspect of the standard; i.e. the use of the term “operate” in lieu of “trip” in the various criteria associated with Requirement 1.  Aligning the wording in PRC-023 with PRC-026 would help to ensure clarity and consistency of application.

The term “operate” typically applies to the operation of a single relay element whereas the term “trip” typically applies to the tripping of one or more circuit breakers, and thus the isolation of a protective zone.  Having said this, an entire transmission relay scheme is often comprised of multiple relay elements, and thus more than one element must “operate” to initiate a “trip”.  Therefore, if the goal is to avoid a false trip, all that is necessary is to ensure at least one of the relay elements will not operate.  It is not necessary to ensure all relay elements associated with the protective relay scheme will not operate. 

For example, in a direction comparison blocking scheme, the Zone 3 mho distance element (21) is often supervised by a non-directional overcurrent unit (50), and both elements must operate to initiate a trip.  The non-directional overcurrent relay element must reach for faults on the opposite end of the line and possibly beyond to facilitate remote backup protection, and this requirement often means the overcurrent relay element must be set such that it could operate under high levels of loading (particularly for longer lines), but this will not result in a line trip since the Zone 3 mho distance element will not operate, thus the scheme should be compliant with the spirit of PRC-023, which is to avoid false tripping under high loading conditions.  However, one could interpret the term “operate” as applied to individual relay elements in Requirement 1 based on the way the standard is drafted, and this interpretation would require that none of the relay elements are allowed to operate under load, which is an unnecessary requirement that makes compliance much more challenging. 

While to date the interpretation of the standard is to avoid tripping and this should be the intent of the standard, the actual application is not well aligned with that interpretation.

  • Expand the make-up of the SDT to include a representative from an end-user perspective

The NSRF agrees with the SAR that the core of the SDT should consist of individuals from the TO, GO and DP functions. That said, we also recommend the SDT consider including an individual(s) from an end-use perspective; i.e. one TOP and/or one TP on the SDT.

 

MRO NSRF, Segment(s) 2, 4, 1, 6, 3, 5, 7/1/2021

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Mark Gray, On Behalf of: Edison Electric Institute, NA - Not Applicable, Segments NA - Not Applicable

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OKGE, Segment(s) 6, 1, 3, 5, 3/22/2021

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MPC supports MRO NERC Standards Review Forum (NSRF) comments.

Andy Fuhrman, On Behalf of: Minnkota Power Cooperative Inc. - MRO - Segments 1, 5

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NPCC Regional Standards Committee no NGrid, Segment(s) 10, 2, 4, 7, 3, 1, 5, 6, 7/19/2021

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Thank you for the opportunity to comment.  ACES appreciates the efforts of drafting team members and NERC staff in continuing to enhance the standards for the benefit of reliability of the BES.

ACES Standard Collaborations, Segment(s) 1, 5, 3, 4, 7/28/2021

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Maryanne Darling-Reich, On Behalf of: Black Hills Corporation, MRO, WECC, Segments 1, 3, 5, 6

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-        PRC-026 already ensures that if OOSB is needed that reliable fault detection is maintained.

Gail Elliott, On Behalf of: International Transmission Company Holdings Corporation - MRO, RF - Segments NA - Not Applicable

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