2021-02 Modifications to VAR-002 | Standard Authorization Request

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Start Date: 04/14/2021
End Date: 05/13/2021

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As suggested in the background section of Project 2021-02 Modifications to VAR-002, similar considerations that were used to justify the R4 exception for individual units of dispersed power producing resources also reasonably apply to R3. A “single voltage control point” for the entire facility of the dispersed power resource can help to facilitate a more valuable voltage control profile for the TOP giving a more concise and useful picture of the facility voltage capability/overview.

Additionally, modifications to the applicability for R3 should be evaluated for relevance to R1 and R2. If clarifications are needed to address whether the R3 requirement is applicable at the individual dispersed power resource covered in BES definition inclusion I4 or only in aggregate at the facility level, then those clarifications should be made in such a way that R1 and R2 are addressed as well. For a given facility, this determination most reasonably depends on whether voltage control occurs at the individual inverter or at the facility level.

Lastly, there may be some ambiguity as to what constitutes the R1 and R2 “generator” for dispersed power producing resources. Does each individual dispersed power producing resource constitute a “generator”? Alternately, is a greater than 75 MVA collection of aggregated dispersed power producing resources a “generator”?  It may be reasonable to assign to each GOP of a facility containing I4 dispersed power-producing resources to coordinate with the TOP to define what level of aggregation constitutes a “generator” at each facility for the purposes of compliance with VAR-002.

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

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AEP agrees with the scope of the proposed SAR. However, from a transmission reliability point of view and in regard to dispersed generating resources, it should be preferable to write R3 in terms of overall voltage control status of the wind, solar, or other dispersed generation facility rather than merely exclude individual wind machines or solar inverters from being reported on. In this regard, an R3 status change would most likely be the PPC (Power Plant Controller) status for reporting to the TOP. AEP also suggests expanding the scope to include R4 for a similar reason. From a transmission reliability point of view, it should be preferable to write R4 in terms of overall reactive capability of the wind, solar, or other dispersed generation facility rather than merely exclude individual wind machines or solar inverters from having to be reported on. In this regard, an R4 change in reactive capability report could specify a minimum threshold of percent reactive capability reduction for reporting to the TOP. This approach would remove a possible loop-hole that would not require reporting even if several individual wind machines or solar inverters may be out of service and substantially reduce overall facility reactive capability. In addition, R4 would benefit from additional clarity by making it clear that if the change in capacity of a generator doesn’t reduce the reactive capability by a significant and specified amount, that this change in capacity would not have to be reported.

While not the intended purpose of the proposed SAR, we believe additional clarity is needed within VAR-002 to clearly indicate that this standard obligates the GO and GOP *only*. VAR-002’s obligations include numerous references to the Transmission Operator, however the TOP’s obligations are already clearly defined in VAR-001. We believe these references to the Transmission Operator should be removed entirely from VAR-002’s obligations. If such references are still believed to be necessary, consideration might perhaps be given to provide direct linkage to VAR-001’s obligations, for example as a footnote or similar within VAR-002.

VAR-002 R4 requires that “Each Generator Operator shall notify its associated Transmission Operator within 30 minutes of becoming aware of a change in reactive capability”, however there is no obligation within VAR-001 which clearly obligates the Transmission Operator to provide notification requirements for a change in reactive capability. AEP recommends that consideration be given to expand the scope of the Project 2021-02 SAR to provide these clarifications within VAR-001.

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

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Other Answers

While I agree that clarity may be needed due to the manner in which VAR-002 is currently written, I believe a more effective and efficient method to get this information is via the data specifications in accordance with TOP-003. This allows each TOP to specify exactly what it needs for RTM and RTA purposes. If clarity is needed in TOP-003, then this should be addressed by the Operational Data Exchange Simplification SAR from the SER Phase 2 team that is currently on the list of upcoming projects and which includes evaluation of the VAR-002 requirements.

John Allen, On Behalf of: City Utilities of Springfield, Missouri, , Segments 1, 3, 4

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

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

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Hot Answers

As the technology continues to develop in regards to dispersed power resources and inverter-based resources, the ability of TOPs to have operational awareness of their voltage control profile will continue to be a concern. The use of a large number of resources within a single facility can pose quite a challenge in the area of compliance, compliance documentation, and operational supervision.  A “streamlined” approach to ensure TOPs maintain visibility of the voltage control could be provided by treating dispersed power resources in aggregate rather than requiring reporting for individual disbursed power producing resources in dispersed power producing resource facilities.

As illustrative examples, a fairly typical size of new wind turbines installed in the US is 2-3 MW, so a wind farm reaching the 75MW threshold for inclusion I4 would likely consist of at least 25 individual turbines. Solar farms utilizing central inverters might have similar sizes for individual inverters, but a farm using string inverters would likely have at least 2-4x as many smaller individual inverters.

As background, note that the Project 2014-01 standards drafting team (SDT) explicitly declined to modify R3. On pages 3 and 4 of the Project 2014-01 consideration of comments posted October 28, 2014 for recommended applicability changes to VAR-002-4, the SDT stated:

At least one commenter questions whether the exception that is being proposed for Requirement R4 also should be applied to Requirement R3, reasoning that otherwise, the Generator Operator will be required to report status changes for AVRs or other voltage controlling devices for each individual generating unit of a DGR.

The DGR SDT understands that the generation facilities subject to Inclusion I4 of the BES definition can be comprised of individual generating units that are typically controlled by centralized voltage/reactive controllers that can be considered alternative voltage control devices as listed in Requirement R4. Additionally, there are generation facilities that perform this voltage/reactive control at the individual power producing resource. The DGR SDT has determined that a status change of these controllers should be reported regardless of which voltage/reactive control design is used at a facility, which explains why the exclusion was not extended to Requirement R3. The exclusion in Requirement R4 was intended to exclude reporting of an individual generator at a dispersed generating facility coming offline as a change in reactive capability. For these reasons the DGR SDT respectfully declines to adopt the commenter’s recommendation.

            Further, on page 2 of the Project 2014-01 consideration of comments posted June 12, 2014 for the DGR Draft White Paper, the SDT had previously stated:

The SDT understands that a GOP’s voltage controlling equipment and Elements differ based on the type of generation facility, and that indeed system configurations vary. However, a “one size fits all” approach would not be appropriate due to the unique characteristics of dispersed generation. Each generation facility may have a different methodology to ensure the facility has an automatic and dynamic response to changes in voltage to ensure the voltage schedule is maintained. It is implied, for example, in NERC VAR-001-3 that each GOP and TOP should understand capabilities of the generation facility and the requirements of the transmission system to ensure a mutually agreeable solution and schedule is used.

This review team considers philosophy outlined by the previous SDT in June 12, 2014 to be adequate, namely that the GOP/TOP should coordinate to understand the capabilities of the facility and the requirements of the transmission system. To the extent that the language of R3 is deemed inadequate to address dispersed power producing resources covered by BES definition inclusion I4, the applicability of R1-R3 should be clarified to address the various possibilities for voltage control methodology of such resources. Simply copying the R4 applicability statement to R3 may be inappropriate since some facilities may rely solely on voltage control at individual power producing resources.  An alternative could be for GOPs of facilities containing I4 dispersed power-producing resources to be required to coordinate with the TOP to document what level of aggregation is selected for each facility’s VAR-002 compliance. 

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

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It should be noted that determining the true reactive capability limits of a generating resource is technically challenging. While the calculations to determine incremental reactive capabilities may be beneficial in some regard, such information does not have a direct impact to the reliability of the BES, at least from a reactive resource perspective. Demonstration of these limits may be difficult due to system conditions, and are very dependent on system conditions at the time of the demonstration. While not necessarily germane to the core intent of this draft SAR, we believe the topic warrants a separate discussion in its own right.It should be noted that determining the true reactive capability limits of a generating resource is technically challenging. While the calculations to determine incremental reactive capabilities may be beneficial in some regard, such information does not have a direct impact to the reliability of the BES, at least from a reactive resource perspective. Demonstration of these limits may be difficult due to system conditions, and are very dependent on system conditions at the time of the demonstration. While not necessarily germane to the core intent of this draft SAR, we believe the topic warrants a separate discussion in its own right.

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

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Other Answers

NERC staff and/or Standards Committee members should consider if this project is needed or if it can be consolidated with the Operational Data Exchange Simplification project. 

John Allen, On Behalf of: City Utilities of Springfield, Missouri, , Segments 1, 3, 4

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

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None.

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

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