Comment Report Form for WECC-01001
Posting 1
The WECC-0100 TPL-001-WECC-CRT-3, System Performance Drafting Team (DT) thanks everyone who submitted comments on the proposed documents.
Posting
This document was last posted for a 45-day public comment period from October 15, 2014 through December 1, 2014.
WECC distributed the notice for the posting on October 14, 2014. The DT asked stakeholders to provide feedback on the proposed document through a standardized electronic template. WECC received comments from six companies representing five of the eight Industry Segments, as shown in the table on the following page.
Location of Comments
All comments received on the document can be viewed in their original format on the project page under the “Submit and Review Comments” accordion.
Changes in Response to Comment
After consideration of comments received, the DT made the following changes:
- Added
- Reviewed
- Edited
- Changed
Effective Date
The targeted Effective Date for this document is January 1, 2016.
Action Plan
On January 8, 2015, the WECC Standards Committee (WSC) granted the DT additional time to post its responses. A specific time for posting was not given by the WSC; however, the DT was encouraged to meet the established procedural milestones. Responses were due for posting on January 1, 2015.
Contacts and Appeals
If you feel your comment has been omitted or overlooked, please contact the Manager, WECC Standards Processes, W. Shannon Black, at . In addition, there is a WECC Reliability Standards Appeals Process.
The WECC Standards Voting Sectors are:
1 — Transmission Sector
2 — Generation Sector
3 — Marketers and Brokers Sector
4 — Distribution Sector
5 — System Coordination Sector
6 — End Use Representative Sector
7 — State and Provincial Representatives Sector
8 — Other Non-Registered WECC Members and Participating Stakeholders Sector
Commenter / Organization / WECC Standards Voting Sectors1 / 2 / 3 / 4 / 5 / 6 / 7 / 8
3[1] / Edi Von Engeln / NV Energy / X / X / X / X / X
4 / Cain Braveheart on behalf of Chuck Matthews, Electrical Engineer. / Bonneville Power Administration / X / X / X / X / X
5 / Hari Singh / Xcel Energy – Public Service of Colorado / X / X / X / X
6 / Spencer Tacke, Senior Electrical Engineer / Modesto Irrigation District / X / X / X / X / X
7 / Joshua Andersen / Salt River Project / X / X / x / X / X
8 / Orlando A. Ciniglio / Idaho Power Company / X / X / X
Index to Questions, Comments, and Responses
Question
- The drafting team invites comments on all aspects of the proposed document.
- The drafting team invites comments on all aspects of the proposed ….
Summary Consideration: / See summary in the preamble of this document.
Commenter / Yes / No / Comment
Edi Van Engeln /
- Is your organization actively participating with Modeling Validation Working Group?
- participating on the LMTF
- Have you performed the Path rating studies with the composite load model?
- not really SNTI was our last path rating study and we had not completed our model at that time
- Have you performed the TPL studies with the composite load model?
- yes
- How is the proposed WECC Criterion for TPL gauge with the results found in Path and TPL studies with composite load model? (is the criterion, relaxed, satisfactory or stringent based on your study results)
The drafting team reviewed Mr. Von Engeln’s responses and concluded that he may have responded to the WECC-0100 project in error. WECC staff was not able to reach Mr. Von Engeln for clarification. The drafting team took no further action on the comment.
Bonneville Power Administration / R1.1: Steady State Voltages
- BPA believes the requirement should ensure applicable entities apply their established "internal" criterion rather than develop a one-size-fits-all criterion. Steady-state voltages are system dependent where low voltage is defined by minimum service to a utility's customers, and high voltage limits are driven by equipment issues.
- Regarding the proposed criterion posted, BPA believes the meaning of the term "nominal" should be clarified as individual entities use the term differently (e.g. base voltage in simulations, equipment nominal voltage specification, operating voltage schedule, etc.).
- Regarding the proposed criterion posted, BPA believes there is no technical justification for the high voltage for P0 events to be less than P1-P7 events. High voltage is driven by equipment issues, and voltage up to that specified for contingencies may also be acceptable for all lines in service.
- BPA suggests Requirement R1.2 be clarified that shunt reactive devices (added to support and control voltages) are assumed to be able to be switched to maintain an acceptable post-contingency steady-state voltage deviation.
- P2-P7 events should be clarified so the real power margin 1) applies after load shedding for events where load shedding occurs as a result of the contingency; and 2) does not apply to events where non-consequential load loss is allowed.
- BPA proposes the term "Transient voltage response" is changed to "Transient stability voltage response". "Transient voltage response" can imply a shorter time period that includes switching transients (milliseconds versus cycles).
- For P1 contingencies with 1-phase or no-fault, the primary objective should be continuity of service to loads. For other criterion contingencies, the primary objective should be integrity of the grid including generators low "Voltage ride-through" capabilities.
- BPA believes simulations should be conducted to better refine the voltage recovery parameters in the requirement. Simulations should include several scenarios, stressed conditions, and composite load models to help gauge the minimum level of acceptable system performance.
- First bullet: Reference to NERC PRC-023-2 – BPA recommends this be revised to NERC PRC-023-3 as version 2 was retired October 1, 2014.
- Third bullet: BPA requests clarification of the reference to R1.3.2. The requirement seems to refer to transient stability requirements in R1.4.
- BPA believes references to "TPL" in the document should be "TPL-001-4" or referenced by a footnote as "NERC Standard TPL-001-4".
- BPA suggests referencing Attachment 2 from PRC-024-1 as is not referenced in the document other than "Voltage ride through" criteria as defined. Additionally, in PRC-024-1, there is a list of "Voltage Ride-Through Curve Clarifications" (1-5) that are not included in the document - - should they be?
Requirement WR1.1: Steady State Voltages DONE
BPA suggests that the requirement should ensure applicable entities apply their established "internal" criterion rather than develop a one-size-fits-all criterion. The following Rationale is included in the proposed document.
Requirement WR1 is designed to set the minimum threshold at which the Transmission Planner (TP) and the Planning Coordinator (PC) will examine their own systems. For purposes of examining their own systems, the TP and PC can use a more stringent set of criteria than stated in Requirement WR1; however, they may not impose a more stringent set of criteria on neighboring systems.
To help clarify Requirement WR1, the following Rationale block has been added.
Rationale for Requirement WR1:
“Requirement WR1 recognizes that each system has its own unique characteristics that need to be addressed. Rather than lock each entity to a specific study parameter this Requirement sets a basal study parameter coupled with a unique nominal value, established by the Transmission Planner and the Planning Coordinator, to be used in the absence of either a more stringent or less stringent study parameter.
In the context of this document the word “nominal” carries its common definition and is the base voltage used in the entity’s Planning Assessment model. This voltage will vary from entity to entity.
Requirement WR1 does not preclude an entity from using either a more stringent or less stringent criteria. However, when an entity uses a study criteria other than that required in requirement WR1, it must make available the associated Planning Assessment showing the assumptions used (see later Requirement).”
This concept is further embellished in the Rationale box for Requirement WR1.2.
Use of the term “nominal”DONE
See above.
Technical Justification for High Voltage DONE
BPA suggests there is no technical justification for the high voltage for P0 events to be less than P1-P7 events. The drafting team recognizes that studied steady-state voltages will vary from one system to the next. Requirement WR1, subsets WR1.1.1 and 1.1.2 allow the studying entities to establish a unique nominal value that fits its specific system(s). In the context of Requirement WR1 “nominal” is uniquely determined by the steadying entity. The Applicability section also acknowledges that certain elements may be excluded from the WECC Criterion.
To address the issue, the drafting team has redrafted the Requirement as follows:
WR1. Each Transmission Planner and Planning Coordinator shall use the following basal criteria in its Planning Assessment, unless otherwise specified in accordance with Requirements WR2 and WR3: [Addresses NERC TPL R5 and R6]
1.1.Steady-state voltages at all applicable Bulk-Electric System (BES) buses shall stay within each of the following limits:
1.1.1.95 percent to 110 percent of thenominal customer requirement.
1.1.2.90 percent to 110 percent of the nominal equipment protection level.
The drafting team further acknowledges that an exchange of this information is critical to establishing accurate models. To meet this need the drafting team has added the following Requirement and associated Rationale box.
WR2. Each Transmission Planner and Planning Coordinator that uses more stringent criteria in its Planning Assessment than that stated in Requirement WR1 shall apply that criteria solely to its own system.
Rationale for WR2: The purpose of this Requirement is to clarify that an entity may apply a more stringent criterion to its own system; however, it may not impose that more stringent criterion to any other system.
WR3. Each Transmission Planner and Planning Coordinator that uses study criteria different from the basal criteria in Requirement WR1 shall make its Planning Assessment available upon request.
Requirement WR1.2: Post-contingency Steady-State Voltage DeviationDONE
BPA suggests clarification of Requirement WR1.2 to show that shunt reactive devices are assumed to be able to be switched to maintain an acceptable post-contingency steady-state voltage deviation.
The drafting team does not believe that manual switching should be assumed; rather, the existing practice of automatic switching should be retained. Requirement WR1.2 has been redrafted as follows:
1.2Post-Contingency steady-state low voltage deviation at each applicable BES bus serving load (having no intermediate connection) shall not exceed eight percent for P1 events. [Addressing TPL R5]
The 1.2 Rationale box has been elaborated as follows:
“Rationale for Requirement WR1.2:
Requirement WR1.2 establishes a reasonable target that could be met by each entity without incurring costs that would outweigh the benefits. Many legacy systems were not designed to meet a more stringent threshold. The eight percent target of Requirement WR1.2 is established not by a technical study; rather, it is established based on sound engineering judgment. Further, certain entities are bound by state tariffs that establish the percentage rate specifically at eight percent.
By default, only automatic post-contingency actions including capacity or reactor switching are considered when calculating voltage deviation.
Where the Transmission Planner or the Planning Coordinator apply less stringent criteria when studying their own systems, the less stringent criteria would be permissible so long as other Transmission Planners and Planning Coordinators were also allowed to apply the same less stringent criteria to their own systems. For example, if an entity applied manual capacitor or reactor switching to its own system the same criteria would be allowed for the systems of others. By contrast, where the Transmission Planner or the Planning Coordinator applies more stringent criteria to their own systems, that Transmission Planner or Planning Coordinator would not be allowed to impose the more stringent criteria on any system other than its own.”
Requirement WR1.3: Voltage stability
BPA suggests that P2-P7 events should be clarified so the real power margin: 1) applies after load shedding for events where load shedding occurs as a result of the contingency; and 2) does not apply to events where non-consequential load loss is allowed.PENDING
Requirement WR1.4: Transient Voltage Response
BPA proposed that the term "Transient voltage response" be changed to "Transient stability voltage response" because "Transient voltage response" can imply a shorter time period that includes switching transients (milliseconds versus cycles).PENDING
BPA proposes that for P1 contingencies with 1-phase or no-fault, the primary objective should be continuity of service to loads. For other criterion contingencies, the primary objective should be integrity of the grid including generators low "Voltage ride-through" capabilities. PENDING
BPA suggests that simulations should be conducted to better refine the voltage recovery parameters in the requirement. Simulations should include several scenarios, stressed conditions, and composite load models to help gauge the minimum level of acceptable system performance.PENDING
Requirement R2: Cascading and Uncontrolled Islanding
PRC Reference DONE
BPA suggests that the first bullet reference to NERC PRC-023-2 be changed to NERC PRC-023-3 as version 2 was retired October 1, 2014. This change has been made with the caveat that the drafting team will be making every endeavor to avoid incorporation by reference of any extrinsic documents. References such as the PRC may be drafted out in subsequent versions.
BPA suggests referencing Attachment 2 from PRC-024-1 as it is not referenced in the document other than "Voltage ride through" criteria as defined. Additionally, in PRC-024-1, there is a list of "Voltage Ride-Through Curve Clarifications" (1-5) that are not included in the document. The drafting team has considered BPA’s request and notes that the team will endeavor to delete all “incorporation by reference” in subsequent postings. WECC Criteria are designed to be free-standing documents that are not predicated on status and content of extrinsic documents.
Numbering References DONE
BPA suggests that as to the third bullet, the reference to Requirement WR1.3.2 may be inaccurate and should be changed to R1.4 because the requirement seems to refer to transient stability requirements in R1.4. The drafting team appreciates BPA’s observation. Numbering references will continue to change and be corrected each time changes are made to the document. DONE
TPL References
BPA believes references to "TPL" in the document should be "TPL-001-4" or referenced by a footnote as "NERC Standard TPL-001-4". DONE
The drafting team reviewed the document and concluded that all references are accurate as submitted. No changes were made. Incidentally, references to the “TPL” such as those included in the brackets at the end of Requirement will be removed in the final version. They are currently included only as a reference point.
Hari Singh, Xcel Energy - Public Service of Colorado / Xcel Energy (Public Service of Colorado) provides the following comments for consideration by the WECC-0100 Drafting Team:
Steady-state Voltage Limits(R1.1) – Please clarify that these are the default voltage limits for system normal and post-contingency system conditions, and an individual TP/PC may choose to use more restrictive voltage limits for its footprint. Note that the suggested approach is identical to what has been adopted by the Reliability Coordinator for implementing its SOL Methodology for [the] Operations Horizon, and this approach lends itself well to be used in the Planning Horizon.
Steady-state Post-contingency Voltage Deviation (R1.2) – No technical justification has been provided to support the 8% limit and discontinue usage of the existing Table W-1 Post-Transient Voltage Deviation limits of 5% for single (Cat-B or event P1) contingencies and 10% for multiple (Cat-C or events P2-P7) contingencies. Absent a technical justification for change, the existing Table W-1 Post-Transient Voltage Deviation limits must be retained.
Transient Voltage Response (R1.4) – Again, no technical justification is provided for discontinuing usage of the existing Table W-1 Transient Voltage Dip magnitude-duration limits for the Cat-B (event P1) and the Cat-C (events P2-P7) contingencies. Therefore, it is hard to appreciate why the proposed transient voltage response/recovery magnitude-duration limit uses 80% voltage magnitude consistent with the existing Table W-1 magnitude limit, but allows recovery duration of 10 seconds (i.e. 600 cycles) which is significantly longer (15 times) than the existing 40 cycles duration in Table W-1. Further, without any technical justification, it is unclear why it is acceptable to have a voltage recovery duration at load buses that is 3.33 times longer than the 3 seconds allowed at generator buses per the PRC-024 Attachment 2 Voltage Ride-Through Time Duration Curve?
Voltage Instability (R1.3) – This appears to be essentially the same as the existing WR3, albeit stated somewhat differently. However, the re-stated criteria in items (1) and (2) need a better description. For example, it is unclear what is meant by "solve" in this context – does it pertain to steady-state power flow simulation or dynamic/transient stability time-progression simulation? How does this voltage stability criteria correlate to the existing WECC Voltage Stability Methodology document? Lastly, since voltage instability is listed as one of three instability modes within R6 of NERC TPL-001-4, shouldn't R1.3 be included under R2 which addresses the remaining two instability modes of Cascading and uncontrolled islanding?
Potential for Cascading and uncontrolled islanding (R2) – We agree with the first bullet (thermal overload criterion) and the third bullet (unacceptable transient voltage response) as the potential precursors of uncontrolled system instability but cannot appreciate how the second bullet's criterion of one generator pulling out of synchronism can possibly lead to system-wide instability. Again, technical justifications for each of the three bullets would be very helpful.
WECC-0100 Regional Criterion's Scope – Xcel Energy strongly recommends that the acceptable power oscillations damping criterion required as per 4.1.3 in TPL-001-4 should also be addressed within the scope of this project. In fact, we believe that it is as important, if not more important, to have a common criterion for acceptable power oscillations damping applicable in the WECC region, similar to the system planning performance criteria already included in the project's scope.