1.
Please provide your organization’s comments on the 2026 ISO Planning Standards Update - Issue Paper and July 27 meeting.
Pacific Gas and Electric Company (PG&E) appreciates the opportunity to provide comments on the California Independent System Operator's (CAISO) 2026 ISO Planning Standards Update Issue Paper. PG&E supports the CAISO's efforts to periodically review and update its Planning Standards to ensure they remain clear, technically sound, and responsive to evolving system needs. The comments below identify areas where PG&E requests additional clarification, technical justification, or modifications to the proposed revisions to promote consistent application of the standards and support reliable and efficient transmission planning outcomes.
Voltage Standard
PG&E requests additional explanation regarding the CAISO's proposal to align the voltage limits in its Planning Standards with those contained in Operating Procedure 3100B. PG&E believes that planning standards and operating procedures serve distinct reliability functions and should not be conflated. Planning standards establish the long-term design and reliability criteria used to identify transmission infrastructure needs, while operating procedures provide operational tools and limits for managing real-time system conditions and abnormal system states.
The voltage limits contained in Operating Procedure 3100B are intended to represent reliability thresholds that trigger Reliability Coordinator awareness and operator actions as system conditions approach abnormal operating states. In contrast, transmission planning criteria should reflect the voltage performance required to ensure the system can reliably serve load over the planning horizon without undue reliance on corrective operating actions. As a result, PG&E is concerned that adopting 3100B limits as planning criteria could reduce the identification of needed transmission reinforcements and shift greater reliance onto operational measures such as redispatch, switching actions, voltage control actions, operating nomograms, or other operator interventions.
PG&E is particularly concerned that the proposed changes for the 115 kV and 70 kV systems would permit planning studies to assume operation at voltage levels that exceed PG&E's normal operating targets. This creates a potential disconnect between planning assumptions and actual operating practices and may mask underlying system needs that would otherwise be identified under more stringent planning criteria to support greater voltage control. While operation at these voltage levels may be acceptable under certain system conditions, the fact that an operating limit exists does not necessarily mean it is appropriate as the basis for long-term transmission planning.
PG&E also notes that previous discussions with CAISO recognized an important distinction between planning criteria and temporary operating limits. Specifically, the increase of the 115 kV operational upper voltage limit was understood to be a temporary operational accommodation, not a corresponding change to planning criteria. At the time, maintaining a more stringent planning limit was intended to support the identification of voltage control solutions and ultimately enable improved voltage performance across the 115 kV system. PG&E is therefore concerned that the proposed planning standard revisions may undermine progress made toward long-term voltage control objectives by reducing the likelihood that voltage-related mitigation projects are identified through the planning process.
Absent sufficient technical justification, PG&E recommends that the ISO Planning Standards continue to be based on planning criteria that reflect the voltage performance needed for long-term system reliability rather than on operational thresholds established for real-time system management. Doing so will help ensure that transmission planning continues to identify cost-effective infrastructure solutions needed to reliably serve future load and maintain adequate voltage performance over the planning horizon.
Planning for New Transmission versus Involuntary Load Interruption Standard
PG&E supports the CAISO’s clarification that these planning standards are intended to apply to distribution loads and substations serving distribution load. However, PG&E requests additional clarification regarding how the standards would be applied in scenarios that may not fit neatly within a traditional distribution-only load-serving configuration. In particular, PG&E requests that the CAISO provide further discussion and, where appropriate, illustrative examples describing how these planning standards would be applied in cases involving:
- Substations serving a combination of distribution load and large load customers;
- Multiple large load customers interconnected within the same local area or electrical configuration;
- Clusters of large loads whose aggregate demand may be material, even if no individual customer independently meets the applicable planning threshold.
Additional guidance on how the CAISO intends to evaluate these scenarios would promote consistent application of the standards and improve stakeholder understanding of the underlying planning assumptions and study methodologies.
Supplemental Criteria Related to Requirement R6 of the NERC FAC-014-3 Standard
PG&E requests clarification regarding the intended interpretation of the CAISO 2026-27 Transmission Planning Process Study Plan language related to CAISO’s implementation of NERC FAC-014-3 Requirement R6. Specifically, FAC-014-3 Requirement R6 states:
"Each Planning Coordinator and each Transmission Planner shall implement a documented process to use Facility Ratings, System steady-state voltage limits and stability criteria in its Planning Assessment of Near-Term Transmission Planning Horizon that are equally limiting or more limiting than the criteria for Facility Ratings, System Voltage Limits and stability described in its respective Reliability Coordinator’s SOL methodology."
During a recent WECC audit, the language above from Requirement R6 was interpreted to mean that a PTO must compare its ratings with those used by RC West when RC West sends data to the PTO – i.e., flow is RC West to PTO. However, the 2026-27 Transmission Planning Process Study Plan states:
"Facility ratings provided to RC West by the PTO 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 rating."
PG&E is seeking clarification on whether this study plan language is intended to convey the same compliance objective as Requirement R6. As written, the language could be interpreted to focus on facility ratings provided by the PTO to RC West, which may create uncertainty regarding how CAISO is applying the Requirement R6 comparison between planning assessment criteria and the criteria contained in RC West's SOL methodology. Clarifying this distinction would help ensure a common understanding of the requirement and its implementation in future study plans and planning standards.
CAISO Cascading Study Analysis
PG&E requests additional clarification regarding the proposed cascading study screening criterion that states:
"A facility should be flagged for further evaluation of cascading and uncontrolled system separation if its loading exceeds the lesser of the thresholds defined below: (1) the facility's protection relay trip setting, and (2) 125 percent of the facility's highest rating defined for a duration of 30 minutes or more."
Specifically, PG&E requests clarification regarding the intended application of the term "protection relay trip setting." As written, the criterion appears unclear, and similar to FAC-008, does not address relay elements that are not simply phase overcurrent based (e.g. distance/impedance elements).
PG&E requests that the CAISO provide additional guidance regarding how transmission owners and study entities should interpret and apply this criterion. Additional clarification would promote consistent implementation of the standard and help ensure stakeholders have a common understanding of the screening criteria used to identify facilities requiring further cascading analysis.
