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Please provide your organization’s comments on the 2026 ISO Planning Standards Update - Draft final proposal and September 17 meeting.
Pacific Gas and Electric Company (PG&E) appreciates the opportunity to comment on the California Independent System Operator Corporation’s (CAISO) Draft Final Proposal for the 2026 ISO Planning Standards Update. PG&E generally supports CAISO’s proposed updates and offers the following recommendations and requests for clarification.
Voltage Standards
In reviewing the most recent updates to the ISO Planning Standards, PG&E noted the inclusion of the Los Esteros 230 kV bus as a facility-specific exception to the voltage limits applicable to PG&E’s system.
PG&E understands that the proposed 245 kV high-voltage limit for the Los Esteros 230 kV bus is driven by the underlying cable rating, however the intended operating target for the bus remains 242 kV. Accordingly, PG&E recommends that CAISO retain Los Esteros within the “All other buses” category for purposes of the voltage limits applied in planning studies. This approach would maintain consistency between the planning study voltage limit and the intended operating target.
CAISO Cascading Study Analysis
PG&E supports CAISO’s proposed criteria for identifying potential separation cascading and uncontrolled system separation, as well as the subsequent cascading analysis methodology presented during the September 17, 2026 stakeholder meeting.
PG&E recommends, however, that CAISO provide additional clarification regarding how different categories of load loss will be treated when applying the 1,000 MW cascading threshold. The following table summarizes PG&E’s understanding of how the different load loss categories should be treated. PG&E requests that CAISO confirm whether this understanding is consistent with CAISO’s proposed application of the cascading criteria.
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Load-loss Category
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Count Toward the 1,000 MW Cascading Threshold?
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Load lost directly because of the initiating contingency / fault isolation (NERC Consequential Load Loss)
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No
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Load intentionally shed by an intended remedial action scheme (RAS) or special protection system (SPS) action
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No. (already included in the standard)
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Incremental load loss because a subsequent overloaded facility trips during the cascade
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Yes
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Load lost through an island created by subsequent cascading outages
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Yes
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Load lost because a RAS action causes further overloads or subsequent uncontrolled trips
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Yes
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Supplemental Criteria Related to Requirement R6 of NERC Reliability Standard FAC-014-3
While PG&E supports CAISO’s proposal to incorporate supplemental facility rating criteria related to Requirement R6 of NERC Reliability Standard FAC-014-3, PG&E recommends a minor revision to the proposed language in Section 9.1 to clarify that the facility ratings provided to RC West are submitted by the participating transmission owner (PTO) through the CAISO Transmission Registry.[1 The Draft Final Proposal currently states that facility ratings provided to RC West by the PTO shall be used in CAISO’s planning assessments.
PG&E proposes the following revision in underline:
Section 9.1, Facility Rating Criteria
Facility ratings provided to RC West by the PTO, via the CAISO Transmission Registry, shall be utilized, unless an approved project exists that increases the facility ratings or a documented technical rationale supports the use of the less limiting ratings.
PG&E appreciates CAISO’s consideration of these comments and looks forward to continued participation in the 2026 ISO Planning Standards Update stakeholder process.
[1] See CAISO’s Presentation, page 13, from September 17, 2026 stakeholder meeting.
