WECC-0124 BAL-004-WECC-3 Technical Support 5
BAL-004-WECC-3
Automatic Time Error Correction
Technical Justification
To
Modify Requirement R1
WECC-0124 Drafting Team
October 3, 3016
155 North 400 West, Suite 200
Salt Lake City, Utah 84103-1114
Western Electricity Coordinating Council
WECC-0124 BAL-004-WECC-3 Technical Support 5
Executive Summary
UPDATE AS A SUMMARY AFTER THE PAPER IS WRITTEN.
Table of Contents
Introduction 2
Section Title 2
Subsection Title 2
Supporting Topic 2
Western Electricity Coordinating Council
WECC-0124 BAL-004-WECC-3 Technical Support 5
Introduction
The WECC-0124 BAL-004-WECC-3 project was initiated by WECC stakeholders in response to large accumulations of inadvertent energy.
This white paper serves as the technical justification for modification to BAL-004-WECC-2, Automatic Time Error Correction (ATEC), Requirement R1. If the proposed changes are accepted the document version will change to BAL-004-WECC-3.
Changes to Requirement R1 will result in more stringent Balancing Authority operations. The outcome of tighter controls will be reduced inadvertent interchange.
These tighter controls will encourage BAs to operate their systems in a more coordinated and responsible manner, by discouraging out-of-balance operations for extended periods of time or by relying on external resources to meet their obligations and thereby affecting other entities within an Interconnection. This is particularly true when another entity is reacting to a grid event while unaware that the first entity has not restored its Area Control Error (ACE).
Background
Month end issue – changing the basis on which we measure R1. Threshold was purposely large because as stated thresholds were met very quickly.
R1 is going to require BAs to reference the WIT tool calculation – singular tool.
The 3-hour payback? Keep or toss?
According to the Automatic Time Error Correction (I IATEC) definition of Hour (H) as the number of hours to payback Primary Inadvertent Interchange (PII) energy, ATEC was originally implemented with the goal intent of reducing large accumulations of inadvertence by implementing mechanisms for prompt balancing. that Balancing Authorities (BA) would payback PII energy balances over the subsequent three hours (H=3). Without tightened accumulated PII (PII accum)[1] thresholds, ATEC cannot: 1) effectively manage PII accumulations in a timely manner, 2) discourage persistent BA-induced system frequency deviations, or 3) automatically manage Time Error Corrections.
FERC acknowledged that “[l]arge accumulations of primary inadvertent [energy] point to an invalid implementation of ATEC, loose control, metering or accounting errors.”[2] Further, FERC noted that a “BA that is operating out-of-balance for an extended period of time is ‘leaning on the system’ by relying on external resources to meet its obligations and could affect other entities within an Interconnection, particularly if another entity is reacting to a grid event while unaware that the first entity has not restored its ACE.”[3] Unchecked, this operational practice produces large accumulations of Primary II energy forcing correspondingly sustained Secondary II energy accumulations in other BAs.
Current Requirement R1
Requirement R1 in the currently approved BAL-004-WECC-2 states:
R1. Following the conclusion of each month each Balancing Authority shall verify that the absolute value of its Accumulated Primary Inadvertent Interchange (PII accum) for both the monthly On-Peak period and the monthly Off-Peak period are each individually less than or equal to:
1.1. For load-serving Balancing Authorities, 150% of the previous calendar year’s integrated hourly Peak Demand,
1.2. For generation-only Balancing Authorities, 150% of the previous calendar year’s integrated hourly peak generation.
The current Requirement R1 creates a number of concerns.
Source Data is Missing
Requirement R1 has no defined source data for BA peak demand/generation on which to base the 150% threshold.[4] In the absence of hard data on which to base the 150% threshold, the 150% limit was anecdotally set to accommodate reportedly large month-end corrections (e.g. 5,000 MWh) incurred by large BAs. Further, in the current Requirement R1, the PII accum limit is expressed in terms of the previous year’s peak load or generation. This lack of support is particularly troublesome for new BAs joining the interconnection that do not have an historical reference on which to establish a PII accum limit.
Current PII accum can be Reduced
The 150% peak demand/generation threshold can be further refined to enhance reliability. This in particularly true as most BA’s PII accum does not exceed 15% of peak demand/generation on average. Outside of former-CPS2 boundaries for Area Control Error (ACE), Automatic Time Error Correction (ATEC) cannot effectively manage the after effects of BAL-001-2 Real-Power Balancing Control Performance frequency-based controls that allow BAs to more aggressively extract and push energy onto neighboring BAs. With such large PII accum thresholds, BAs extract and push energy onto other BAs adversely affecting system frequency and thereby forcing all other BAs to adjust their controls in support of system frequency (via Frequency Bias components of BA ACEs). Additionally, Requirement R1 creates an environment in which BAs can lean on the system indefinitely. For BAs that make month-end meter reading adjustments (per Requirement R7), these corresponding adjustments to PII accum can easily push them over the PII accum limit currently defined by Requirement R1.
Proposed Requirement R1
The proposed Requirement R1 for BAL-004-WECC-3 would state:
R1. Each Balancing Authority shall operate its system such that the month-end absolute value of its On-Peak and Off-Peak, Accumulated Primary Inadvertent Interchange (PII accum), occurring after hour ending 23 (HE23) and prior to any month-end corrections, as calculated by the Reliability Coordinator’s Interchange software, meets the following criteria: [Violation Risk Factor Medium:] [Time Horizon: Operations Assessment]
· Is less than or equal to the greater of either 500 MWh or 60 * L10, expressed in MWh, for the Balancing Authority Area.[5]
The proposed Requirement R1 adjusts the PII accum limit down from 150% peak load/generation to a 60 * L10 (expressed in MWh) BAs and thereby encourages BAS to operate in a more reliable manner.
The proposed requirement recognizes that when the current Requirement R1 was implemented, PII accumulations decreased. On average, BAs implementing the current R1 are operating their systems to within 15% of peak load or generation. Lauding that performance, the proposed R1 builds on that success by encouraging BAs to operate their systems in such a manner that reliance on the resources of another BA is diminished. This becomes increasingly important when the sink BA taps resources of a source BA that have otherwise been committed to meet responsibilities of the source BA. In essence, this approach helps diminish double reliance on resources.
Unlike its predecessor, the proposed R1 more closely tailors the operational thresholds to the specific size of the BA. It achieves this goal by setting PII accumulation thresholds that take into account the L10 of each BA. It also sets a minimum 500 MWh threshold which will serve to provide smaller BAs, particularly gen-only BAs, with sufficient room to operate as they integrate more intermittent renewable resources. This approach would not require BAs to revise any PII accumulation calculations that it may be performing on its own; rather, it looks only to the RC-approved PII accumulation calculations currently being calculated by the Western Interchange Tool (WIT).
It is hoped that further restrictions to the amount of PII that BAs can carry should serve to reduce the need for Manual Time Error Corrections and thereby constrain Time Error to within existing PEAK RC clock Time Error capabilities of +/- 99.999 seconds.[6]
Finally, as to implementation of the proposed R1, no new systems would be required. Because the tools are already in place BAs should incur no additional costs to implement the requirement. That said, some BAs may incur varying energy costs due to direct purchase of resources as opposed to more indirect reliance on other systems. Although this impact the marketplace it is not expected that the magnitude of the impact would sufficient enough to significantly alter existing pricing.
Conclusion
TO BE WRITTEN AFTER THE FACTS ARE IN.
Western Electricity Coordinating Council
[1] “Balancing Authorities in the Western Interconnection developed a process for controlling frequency that includes payback of PII. When a Balancing Authority includes the ATEC term in its ACE equation, it provides for automatic payback of its PII. The automatic payback of PII affects automatic payback of the corresponding Secondary Inadvertent Interchange of other Balancing Authorities through the frequency component of their ACE.” WECC-0068 BAL-004-WECC-1, Automatic Time Error Correction (WECC), NERC Filing, Consolidation of NERC and Control ACEs – Using the Same ACE for Control and NERC Reporting, April 18, 2012, Attachment I, P.2.
[2] FERC Order No.723, Western Electricity Coordinating Council Regional Reliability Standard Regarding Automatic Time Error Correction, 18 CFR Part 40, Docket No. RM08-12-000, Issued May 21, 2009, P. 27
[3] Disturbance Control Standard—Contingency Reserve for Recovery from a Balancing Contingency Event Reliability Standard, 18 CFR Part 40, Docket No. RM16-7-000, Issued May 19, 2016, P. 22. “The ATEC component causes an otherwise balanced Balancing Authority to push or pull energy from the grid, which may cause frequency to shift away from 60 Hz. Through the frequency bias term of their ACE equation, every other Balancing Authority reacts to this frequency shift in the oppositedirection, movingto keep frequency at or near 60 Hz. This exchange has an effect similar to the first Balancing Authority exchanging multiple Interchange Transactions with all other Balancing Authorities.” WECC-0068 BAL-004-WECC-1, Automatic Time Error Correction (WECC), NERC Filing, Consolidation of NERC and Control ACEs – Using the Same ACE for Control and NERC Reporting, April 18, 2012, Attachment I, P.4.
[4] The 150% threshold was adopted by the WECC-0068 BAL-004-WECC-1 Automatic Time Error Correction Drafting Team (DT) in Posting 1 of that project. The DT adopted the threshold in response to a comment provided by the Bonneville Power Administration (BPA) stating: “Each BA should be allow [sic] to take any action they feel necessary (with in compliance) at any time to keep within a specific amount. BPA would like to recommend that each BA have a maximum of 150% to 200% of peak load from the previous year as the maximum amount of inadvertent that a BA can have. Eliminate R1 and keep R2.” The DT adopted a reasonable threshold based on consensus as opposed to empirical data. No all WECC-0068 respondents agreed that the 150% level should be adopted; some suggested a tighter operational limit based on L10. See WECC-0068, Posting 2, Q2, Comment by Avista. Others suggested that setting the limits might be more accurate if based on inadvertent flow. See WECC-0068, Posting 2, Q4, Powerex. The industry did not further raise the issue after Posting 2. See also WECC-0068 BAL-004-WECC-1, Automatic Time Error Correction (WECC), NERC Filing, Consolidation of NERC and Control ACEs – Using the Same ACE for Control and NERC Reporting, April 18, 2012, Attachment I, P.4-5.
[5] The associated Measure will be added when the Requirement is finalized. Forms of acceptable evidence of compliance with proposed Requirement R1 could include but would not be limited to: 1) data, screen shots from the WECC Interchange Tool (WIT), 2) archived data as captured from the RC-approved WIT, or 3) production of data from any other databases, spreadsheets, displays.
[6] WECC-0068 BAL-004-WECC-1, Automatic Time Error Correction (WECC), NERC Filing, Consolidation of NERC and Control ACEs – Using the Same ACE for Control and NERC Reporting, April 18, 2012, Attachment I, P.6-7.