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Document name / System Performance
Document Categorization White Paper
Category / ( ) Regional Reliability Standard
( ) Regional Criteria
( ) Policy
( ) Guideline
(X) Report or other
( ) Charter
Document date / April 29, 2014
Adopted/approved by
Date adopted/approved
Custodian (entity responsible for maintenance and upkeep)
Stored/filed / Physical location:
Web URL:
Previous name/number / (if any)
Status / ( ) in effect
( ) usable, minor formatting/editing required
( ) modification needed
( ) superseded by ______
( ) other ______
( ) obsolete/archived

System Performance

Document Categorization White Paper

April 29, 2014

Background

WECC’s TPL-001-WECC-RBP-2.1, System Performance Regional Business Practice (RBP) containssystem performance requirementsfor the demonstration ofacceptable voltage performance on other systems for system steady state, post-Contingency, transient and post transient conditions. With the approval of NERC Reliability Standard TPL-001-4, in requirements R5 and R6, Planning Coordinators (PC) and Transmission Planners (TP) are required to have criteria or methodologies containing similar voltage performance requirements as TPL-001-WECC-RBP-2.1 against which entities must demonstrate adherence when conducting operating and planning assessments. This presents the following issues for entities conducting assessments in the Western Interconnection.

  1. The NERC requirements do not contain the specificity contained in the corresponding WECC requirements presenting the question of how to resolve the differences between the two sets of assessment methodologies.
  2. The NERC requirements shift the responsibility for the voltage performance criteria or methodologies from the region to PCs and TPs, which allows for each individual PC or TP to adopt more and less stringent voltage performance criteria and methodologiesthan contained in TPL-001-WECC-RBP-2.1affecting existing and future transmission system ratings.
  3. Concern that PCs and TPs will not adopt uniform voltage performance criteria and methodologies throughout the Western Interconnection.

The Reliability Subcommittee identified the following approaches to address the issues above.

  1. Develop a WECC Guideline to replace TPL-001-WECC-RBP-2.1 that PCs and TPs would adopt as their voltage performance criteria or methodologies,
  2. Develop Regional Criteria[1] to replace TPL-001-WECC-RBP-2.1 as permitted by the NERC Rules of Procedure 313,
  3. Develop a regional variance to NERC TPL-001-4 requirements R5 and R6 to incorporate the more restrictive provisions contained in TPL-001-WECC-RBP-2.1.

Develop Guideline

The Reliability Subcommittee would develop a voltage performance guideline that would be adopted all or in part by PCs and TPs.

Pros

  1. The development of a WECC Guideline encourages PCs and TPs to adopt consistent voltage criteria and methodologies in the Western Interconnection.
  2. A guideline allows PCs and TPs the same specificity and flexibility as the current business practices, whichpermits the adoptionof less stringent voltage performance at specific busesrather than a one size fits all approach. Just as in the TPL business practice other PCs and TPs are allowed to use the less stringent performanceat the buses where the less stringent performance is permitted, which maintainspart of the provisions of requirement WR2.
  3. A guideline may be modified more quickly than Regional Criteria or a Regional Reliability Standard (RRS) when issues arise within the guideline because adoption only requires a subcommittee and standing committee approval.
  4. The adoption of a guideline allows flexibility when developing refinements to requirements such as those presented with the adoption of the composite load model.
  5. Allows flexibility in developing refinements to existing WECC requirements necessitated by NRC voltage requirements and Fault-Induced Delayed Voltage Recovery (FIDVR) refinements.

Cons

  1. WECC Guidelines by their nature are recommendations that may be modified by PCs and TPs. As such PCs and TPs do not have to receive industry concurrence when adoptingprovisions different than those in the guideline when they develop their voltage criteria and methodologies as required by TPL-001-4. To make a guideline more effective in the Western Interconnection PCs and TPs would have to agree to adopt the basic concepts developed by a WECC forum.
  2. Development of a guideline may permit PCs and TPs to develop more stringent performance requirements such as required by NRC; however, such flexibility might adversely impact existing ratings, SOLs, and IROLs.
  3. PCs and TPLs may disagree with where other PCs and TPs have set their voltage criteria, which may increase the debate when conducting rating studies.

Develop Regional Criteria under NERC Rules of Procedure, Rule 313

WECC standards drafting team would develop voltage performance criteria that would be adopted by PCs and TPs with very few refinements.

Pros

  1. The development of WECC voltage criteria is permissible when criteria are necessary to implement, to augment, or to comply with Reliability Standards. The adoption of WECC wide voltage criteria ensures consistency between the voltage criteria adopted by each PCs and TPs.
  2. Criteria have a higher degree of accountability than WECC Guidelines. As in the past when WECC adopted criteria, all PCs and TPs in WECC would be expected to adopt WECC’s voltage criteria without modification. This process allows industry vetting when developing the voltage criteria.
  3. Regional Criteria do not require NERC and FERC approval permitting refinements to be made more quickly.
  4. The adoption of consistent WECC voltage criteria would reduce the fear that PCs and TPswould adopt more stringent voltage criteria that may reduce transfer capabilities, SOLs, and IROLs.

Cons

  1. Regional Criteria developed under Rule 313are not NERC Reliability Standards within WECC and therefore are not enforceable under authority delegated by NERC pursuant to the Delegation Agreement between WECC and NERC.[2]
  2. Adoption of the current business practice as criteria requires the adoption of a method that does not address the FIDVR phenomenon. Although a number of proposals have been made to address the phenomenon, these proposals have not been vetted or tested.
  3. Adoption of an exception process, as permitted with the current business practice, negates the importance of voltage criteria consistency between PCs and TPs.
  4. Requires changes to WECC Board policy.

Develop WECC Regional Variance to TPL-001-4 Requirements R5 and R6

A WECC regional standards drafting team would develop voltage performance varianceto TPL-001-4 requirements R5 and R6 that is mandatory and enforceableto PCs and TPs.

Pros

  1. The WECC Document Categorization Policy recommends that documents that have potential to adversely impact reliability be made mandatory and enforceable.
  2. The development of WECC Regional Variance will ensure that PCs and TPs adopt uniform voltage performance criteria and methodologies throughout the Western Interconnection.
  3. Requires the development of clear voltage requirements that are performance based and enforceable through sanctions.
  4. Requires all PCs and TPs methodologies and criteria contain the same specificity in voltage performance.

Cons

  1. The voltage performance requirements in the Disturbance-Performance Table (Table W-1) contain requirements that cannot be achieved at load buses when FIDVR phenomenon due to stalling of single-phase compressor motors (such as in residential air-conditioners and refrigeration) are observed. Because the FIDVIR phenomenon can occur during a normally cleared fault and cannot be prevented the current requirements in TPL-001-WECC-RBP-2.1 cannot be adopted without modification and field testing. A performance requirement that properly addresses FIDVIR needs to be developed before submitting a WECC variance because mandatory enforced reliability standards are difficult to modify without technical justification.
  2. The current requirements in TPL-001-WECC-RBP-2.1allow for individual systems or groups of systems to apply less stringent requirements when other systems are permitted to have the same impact on that part of the system for the same category of disturbance. A requirement permitting such adjustments may be perceived by NERC and FERC as reducing reliability in the Western Interconnection and would not be permitted in a regional variance to a NERC requirement.A WECC variance to a NERC Reliability Standard may require a one size fits all approach.
  3. In FERC Order N0. 796 regarding generator verification reliability standards the Commission stated that NERC should use the Nuclear Regulatory Commission’s (NRC) requirements when implementing Reliability Standards to assure that there is consistency between the Reliability Standards and the NRC requirements. The NRC has more stringent voltage performance requirements at nuclear facilities than currently contained inTPL-001-WECC-RBP-2.1. As a result, the current performance requirements will need to be adjusted to ensure consistency with NRC requirements. This may not be acceptable to entities whose ratings, SOLs, and IROLs are adversely impacted by implementing more stringent performance requirements.
  4. Several current WECC TPL-001-WECC-RBP-2.1 requirements result in the mixing of methodology, performance, modeling, and results together into one requirement. In a WECC variance requirements would need to remove methodology and modeling (how) from existing requirements.

Attachment A

Background References

TPL-001-WECC-RBP-2.1

WR2.Individual systemsor a groupofsystemsmayapplyrequirements that differ fromspecificrequirementsinTableW-1for internal impacts.Iftheindividual requirementsarelessstringent,other systemsare permittedtohavethe sameimpactonthat partoftheindividual system forthesamecategoryof disturbance.Iftheserequirementsaremorestringent,theserequirements may not beimposed on other systems.Thisdoes notrelievethesystemor groupofsystemsfromWECC requirementsfor impactsonother systems.[3]

TPL-001-4

R5.Each Transmission Planner and Planning Coordinator shall have criteria for acceptable System steady state voltage limits, post-Contingency voltage deviations, and the transient voltage response for its System. For transient voltage response, the criteria shall at a minimum, specify a low voltage level and a maximum length of time that transient voltages may remain below that level. [Violation Risk Factor: Medium] [Time Horizon: Long-term Planning]

R6.Each Transmission Planner and Planning Coordinator shall define and document, within their Planning Assessment, the criteria or methodology used in the analysis to identify System instability for conditions such as Cascading, voltage instability, or uncontrolled islanding. [Violation Risk Factor: Medium] [Time Horizon: Long-term Planning]

R8.Each Planning Coordinator and Transmission Planner shall distribute its Planning Assessmentresults to adjacent Planning Coordinators and adjacent Transmission Planners within 90 calendar days of completing its Planning Assessment, and to any functional entity that has a reliability related need and submits a written request for the information within 30 days of such a request. [Violation Risk Factor: Medium] [Time Horizon: Long-term Planning]

8.1. If a recipient of the Planning Assessment results provides documented comments on the results, the respective Planning Coordinator or Transmission Planner shall provide a documented response to that recipient within 90 calendar days of receipt of thosecomments.

313. Other Regional Criteria, Guides, Procedures, Agreements, Etc.

1.Regional Criteria — Regional Entities may develop Regional Criteria that arenecessary to implement, to augment, or to comply with Reliability Standards, butwhich are not Reliability Standards. Regional Criteria may also address issues notwithin the scope of Reliability Standards, such as resource adequacy. Regional Criteria may include specific acceptable operating or planning parameters, guides, agreements, protocols or other documents used to enhance the reliability of the Bulk Power System in the Region. These documents typically provide benefits bypromoting more consistent implementation of the NERC Reliability Standardswithin the Region. These documents are not NERC Reliability Standards,Regional Reliability Standards, or regional Variances, and therefore are notenforceable under authority delegated by NERC pursuant to delegationagreements and do not require NERC approval.[4]

Attachment B

Comparison of WECC Criteria and NERC Regional Criteria

Because the categorization and use of the term “WECC Criteria” is currently under review within WECC, it is recommended that pursuing either a WECC Criteria as defined in the WECC Document Categorization Policy (Policy) or a NERC Regional Criteria as defined in the NERC Rules of Procedures, Rule 313 should not be pursued until the policy decisions regarding that categorization have been resolved.

The confusion to be resolved prior to using this categorization lies in the use of the terms: 1) WECC Criteria in the Policy, 2) Regional Criteria in the Bylaws, and 3) Regional Criteria in the NERC Rules of Procedure, Rule 313.

Within the WECC Document Categorization Policy, a “WECC Criteria” is defined as:

Definition: A WECC Regional Criterion is a WECC Board-approved document, applicable only in the Western Interconnection, created to establish requirements to address NERC “Fill-In-The-Blank” reliability standards or necessary to implement, to augment, or to comply with NERC or Regional reliability standards or requirements under programs established by the Applicable Governmental Authority in Canada and Mexico, as applicable.

The current interpretation of the definition is that it only applies to documents created in response to a NERC mandatecreated in a NERC “Fill-in-the-blank” (FITB) Standard. FITB Standards are directed solely at regional entities such as WECC and not to any other applicable entity such as a PC or a TP. Under this interpretation the substance of the proposed TOP could not be developed as WECC Criteria.

The defined term “Regional Criteria” as used in the Bylaws reflects the same definition as that of a WECC Criteria (specifically applying to FITB Standards); however, it uses the same term as that used in the NERC Rules of Procedure – the latter having a different definition.

A Regional Criteria as defined by NERC is as follows:

313. Other Regional Criteria, Guides, Procedures, Agreements, Etc.

1. Regional Criteria — Regional Entities may develop Regional Criteria that are necessary to implement, to augment, or to comply with NERC Reliability Standards, but which are not Reliability Standards. Regional Criteria may also address issues not within the scope of Reliability Standards, such as resource adequacy. Regional Criteria may include specific acceptable operating or planning parameters, guides, agreements, protocols or other documents used toenhance the reliability of the Bulk Power System in the Region. These documents typically provide benefits by promoting more consistent implementation of the NERC Reliability Standards within the Region. These documents are not NERC Reliability Standards, Regional Reliability Standards, or regional Variances, and therefore are not enforceable under authority delegated by NERC pursuant to delegation agreements and do not require NERC approval.

As shown, the use of the terms is inter-related but the precise application of the categorization is not settled. Thus, it is suggested that use of the categorization would not be appropriate until the policy determine is made.

Attachment C

Example

Example of the Planning Coordinator responsibility Issue being addressed:

Planning Coordinator ‘A’ is proposing a new 500 kV line project called Project X. In PC ‘A’ Voltage Criteria required in TPL-001-4 requirements R5 and R6, the first swing minimum voltage limit is 75% of nominal.Planning Coordinator ‘B’ responsible for the PC area ‘B’ has a Voltage Criteria established in compliance with TPL-001-4 requirements R5 and R6 that contains a first swing minimum voltage limit of 85% of nominal.In the rating studies for Project X a single contingency outage of the 500 kV line results in voltage performance throughout the Interconnection above the 75% first swing voltage limit complying with PC ‘A’s Voltage Criteria. However in PC ‘B’s area, one of the bus voltages is 80% resulting in a violation of PC ‘B’s Voltage Criteria.

There are two possible options for identifying responsibility to address the low voltage. They are:

  • PC ‘B’ is responsible for addressing the low voltage in Area B because PC ‘B’ is responsible for voltages in its area. (TPL-001-4)
  • PC ‘A’ lowers transfers or institutes other mitigation measures on Project X until the voltage criteria (85% voltage) in PC ‘B’s area is achieved. (current practice)

Some believe that NERC TPL-001-4 Requirements R5 and R6 make it the responsibility of PC ‘B’ to resolve the low voltage issue in area ‘B’. After all, the low voltage is in its area, and it is the responsibility of PC ‘B’ to resolve voltage issues in its area.TPL-001-4 requirement 8.1 only requires that PC or TP respond to the comments on the results of a Planning Assessment. Historically in WECC with the rating process, it has been the responsibility of PC ‘A’ to respect or mitigate the low voltage in area ‘B’. This is a major change to the practices in WECC.Regardless of which interpretation the industry prefers, the entities in the Western Interconnection have identified a need to clarify which is the preferred categorization approach for Project WECC-0100.

WESTERN ELECTRICITY COORDINATING COUNCIL •

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[1]See Attachment A for the difference between a Regional Criteria as approved under NERC Rules of Procedure, Rule 313,and WECC’s Regional Criteria as approved in the WECC Document Categorization Policy and as included in the WECC Bylaws.

[2]NERC Rules of Procedure, Rule 313, Other Regional Criteria, Guides, Procedures, Agreements, ETC.,1. Regional Criteria.

[3] WECC TPL-001-WECC-RBP-2.1, requirement WR2.

[4] NERC Rules of Procedure