Reinforcement Guidelines Study update

In the 2013 Assessment, the objective of this study was to ensure that the impacts of the proposed Reinforcement Guidelines were identified across the ATC transmission system. To identify potential reliability and cost impacts, ATC screened the transmission system per the following guidelines:

Based on NERC reliability standards, ATC’s Planning Criteria and past practices, ATC will generally reinforce for the following limiting BES and non-BES scenarios:

  • TPL-001-0.1: NERC Category A (System Intact): Instability, cascading, or voltage and flows outside appropriate limits. Planning to shed load is not an acceptable mitigation procedure.
  • TPL-002: NERC Category B (Single Contingencies): Instability, cascading, or voltage and flows outside appropriate limits. Planning to shed load is not an acceptable mitigation procedure.
  • TPL-003: NERC Category C (Select Multiple Contingencies): Voltage collapse, cascading, or unplanned/uncontrolled load loss.  Voltage and flows outside appropriate limits need to be mitigated. Pre-contingency economic generation redispatch may be appropriate mitigation.  Planning to shed load can be an acceptable mitigation procedure.
  • Prior Maintenance plus Category B: At appropriate maintenance period load levels, instability, cascading, or voltage and flows outside appropriate limits – planning to shed load is not an acceptable mitigation procedure.

Generally, there are circumstances under which the risk of a multiple contingency event to ATC and its customers may be sufficiently severe and may warrant reinforcement or other mitigation consideration:

  • Generator instability for Category C, D2, and D3,
  • Loss of load exceeds 300 MW,
  • Loss of load between 100 and 300 MW, examine specific situations,
  • Loss of load is less than 100 MW, examine specific situations, if controlled load shed is feasible reinforcement may not be justified, and
  • Prior maintenance + Category C when planned or controlled loss of load exceeds 300 MW.

As part of the screening process, several scenarios were analyzed in order to identify potential impacts:

  • NERC Category C3 (NERC Category B + System Adjustments + NERC Category B),
  • NERC Category C1, C2, and C5, and
  • NERC Category B.

The powerflow cases used for this screening were from the 2012 10-Year Assessment and included the 2022 Summer Peak and 2022 70% Load West-to-East Flow bias (off-peak), adjusted for the maintenance load level. In the off-peak model, prior maintenance outages were studied as well.

This screening was completed as part of the 2013 10-Year Assessment based on the Summer Emergency Rating (Rate B). The amount of load at risk was determined and separated into three categories: less than 100 MW load at risk, 100-300 MW load at risk, and greater than 300 MW load at risk. The results are summarized in Table 1 and Table 2 for the Summer Peak and Off-Peak cases, respectively.

Attention: The internal data of table “82” is corrupted!
Attention: The internal data of table “83” is corrupted!

After discussion with ATC stakeholders and management, it was determined that preliminary solutions would be developed for outages where studies indicated that more than 300 MW of load was at risk. Associated cost impacts to address these needs were also developed. Examples of projects that could address the identified outages are summarized in Table 3.

Table 3

Potential ProjectOutage TypeCost Estimate (M)
Rebuild Y-54 Paddock-Shaw 69 kV linePrior + C1$10
Rebuild Y-153 Colley Road-Shaw 69 kV linePrior + C1$10
Uprate Maple-Saukville 138 kV linePrior + C5$5
New Hilltop-Pine 115 kV lineC3$40
Examples of Potential Projects to Address >300 MW Load Lost

These results are for information only.  At this time, ATC is proposing no projects to address the identified issues.

Going forward, ATC is continuing to consider the guidelines described above to promote consistent solution development across its planning groups. Any projects that are identified will continue to be reviewed and discussed through internal and stakeholder processes to confirm whether development is warranted.