Comments on Technical white paper and April 13, 2023 data submission working group discussion

FERC Order No. 881 - managing transmission line ratings

Comment period
Apr 13, 02:00 pm - Apr 27, 05:00 pm
Submitting organizations
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Salt River Project
Submitted 04/27/2023, 02:08 pm

Submitted on behalf of
Salt River Project


Amber Clinkscales (

1. Please provide your organization's comments on the technical white paper and April 13, 2023 data submission working group discussion:

Salt River Project Agricultural Improvement and Power District (SRP) appreciates the opportunity to comment on the technical white paper and working group discussion for the FERC Order No. 881 -Managing Transmission Line Ratings Initiative. The CAISO technical white paper reiterates information provided in the monthly webinars but additional details regarding hierarchy checks has not yet been provided. Accordingly, SRP has the following requests:


  1. Please clarify what information CAISO will require transmission providers to provide, specifically in the hierarchy and reasonability checks, so that transmission providers can align internal accounting efforts with the CAISOs requirements.
  2. Please clarify the expectation for flagging changes or exceptions to ratings that are exempt from AARs.

Submitted 04/27/2023, 04:59 pm


Richard Buckingham (

1. Please provide your organization's comments on the technical white paper and April 13, 2023 data submission working group discussion:

SMUD Comments on:

FERC Order No. 881 – Managing Transmission Line Ratings

Phase 2

Technical White Paper

April 6, 2023

Submitted by Richard Buckingham 4/27/2023


  1. SMUD acknowledges the need for PTO and TOP entities to coordinate their AAR methodology and implementation and supports the CAISO’s efforts to facilitate such coordination.  The steps outlined in the Whitepaper need to proceed in a timely manner with sufficient time for testing on a small scale (i.e. sooner is better) before ramping up to a larger scale.
  2. As a thematic comment, SMUD notes that the expectation of the FERC in adopting Order 881 was that it would be minimally burdensome to obtain significant benefit, citing from Commissioner Danly’s concurrence with the order at paragraph 3, “In addition, AAR is a just and reasonable replacement rate because the record evidence shows the additional costs are incremental and will provide significant benefits.”
    1. Based on the above, SMUD suggests that the use of AAR and seasonal ratings for 10-day out ATC and curtailment decision (including DA, HA congestion) focus on paths and facilities with recent DA, HA and RT congestion.
    2. In addition – PTO’s and TOPs should prioritize assessing which facilities will be limited by ratings not affected by ambient conditions.  For example, the Transmission Agency of Northern California has advised the Western Area Power Administration (the TOP for the California-Oregon Transmission Project or “COTP”) that it thinks the COTP will be limited by the series capacitor ratings for normal and emergency conditions and not affected by ambient conditions.  So, unless such facilities are removed from service (not often), they will be the limiting elements.  Also, recently the CAISO notified stakeholders that several PG&E 500-kV facilities have limiting substation elements.  If these elements are not affected by ambient conditions, then most of the Northern California 500-kV system is not so affected.  But we know that the output of Northern CA hydro has a significant impact and already mitigate and plan accordingly.
    3. At SMUD, for example, our total system import and export TTCs are determined by a nomogram for reliability as described in our ATCID – and not affected by ambient conditions.  The import TTC at the combination of tie-points as determined by the combined total usage from the CAISO/PG&E and WAPA transmission systems.  Therefore, SMUD’s CAISO tie-points are not impacted by ambient conditions.  SMUD’s ATC amount will be the limiting factor at SMUD’s CAISO and WAPA tie-points.
    4. Focusing 881 compliance efforts on which facilities will not be affected by ambient conditions and developing robust AARs for the facilities with congestion incidence should be considered in this process in order to minimize implementation costs and obtain significant benefits.
  3. The communication of AAR and related data should use systems with known compatibility with the existing tools that support ATC and EMS calculations.  Creation of thousands of new ICCP points could be problematic.  Support for feeding the current rating values from the TR process to EMSs via ICCP should be tested early on and limited to the most significant data points.
  4. As has been discussed, at tie-points in particular, PTOs and TOPs need to establish some input data coordination and validation and account for variations of reported temperatures– especially for tie-points where a limitation on conductor temperatures (if it is the applicable element) may have a different temperature along the length of the lines –(e.g. for lines that extend from different elevations and climate conditions).
  5. As a non-jurisdictional entity, SMUD will make reasonable efforts to develop AARs for its relevant system elements in accordance with the RC West data directives where materially useful and where the costs of doing so are reasonable, consistent with the and FERC’s expectations described above.  Where ambient conditions do not impact the ratings, SMUD will provide the applicable facility ratings or applicable TTC amount in the required format.
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