PG&E Information on POI Availability for Cluster 16

The California ISO is providing the following information on the availability of Points of Interconnection (POI) on the PG&E system with known issues for the ISO Resource Interconnection Cluster 16. This information should be of interest to customers seeking to interconnect resource projects to the ISO controlled grid by participating in the Cluster 16 interconnection request window that opens Oct. 1, 2026. 

1. What are the actual implications of the restricted POI list in the PG&E handbook? 

1. Short Circuit Duty (SCD) Limitations G2

PG&E is looking to revise this table to act as a warning that connection to these POIs will likely trigger large-scale short circuit duty mitigations as a result of exceeding the PG&E maximum equipment rating of 63 kA. The large-scale mitigation may not be fully defined during a Cluster Study; in which case placeholder costs will be used (e.g. in C15 the placeholder values were $180M). New POIs will no longer be restricted due to their presence on Table G2.

Additionally, refer to response on question #2.  

 b. Space-Limitations G2-A

Station either has no physical space to expand for new elements, or the station has reached the maximum number of terminals allowed by PG&E standards. New terminals cannot be added at these stations for new projects. Expansions to existing generators already connected or planned at the POI, or new switching stations near the POI will be considered by PG&E.

2. Why can short circuit constraints not be addressed? 

When large stations exceed the maximum equipment rating for short circuit duty, 63 kA, potential solutions such as bus reconfigurations and reactor additions will have power flow implications. Therefore, solutions are not easily derived. The majority of the stations on the short circuit duty restriction list have already been through at least one cycle of this complex mitigation. There will be a point in time when these mechanical equipment limitations will become insurmountable at a given facility, and the intention was to delay this as much as possible by restricting direct connections to certain POIs. Despite these restrictions, fault duty continues to increase at constrained stations from new generation in the vicinity of those stations as well as from TPP capacity projects. In 2025, PG&E began looking at conceptual changes to station configurations in hopes of developing a long-term strategy at key locations. As site-specific concepts become vetted, stations will be removed from the restricted list; however, the upgrades are likely to be very costly.

3. Discuss the decision making around the projects moved to POIs on the restricted POI list (Gates, Tesla).  

In the 2024 reassessment, PG&E developed a conceptual layout modification to Tesla as part of a long-term strategy for fault duty mitigation. This plan enabled the ability to add 230 kV terminals to a new 230 kV bus section. When presented with over a dozen 500 kV POI requests requiring several new 500 kV Switching Stations in the vicinity of Gates Substation in Cluster 15, PG&E proposed a plan to remove existing PG&E assets at Gates Substation in order to enable 500 kV expansion. With this plan now available, PG&E will remove Gates 500 kV from Table G2-A.

4. Confirm if interconnection to following POIs will be allowed for Cluster 16 applications: 

Metcalf – Manning 500kV line  

This line does not have a project sponsor currently and will not be available as a POI until a sponsor is selected. 

New Switchyards required for C15 projects connecting to existing lines. 

All new switching stations are designed for some future expansion capability.  After detailed design starts, this expansion capability may become locked down by land constraints. Prior-cluster new switching stations have been utilized across Clusters several times in the past. The New Dry Lake 500 kV switching station referenced is a viable POI option for C16.

5. Please provide the locations for the new switching stations Dry Lake, Bitterwater, and Harlan. 

Bitterwater Sw Sta 230 kV Latitude: 35°7'28.90"N Longitude 119°17'54.29"W

Harlan Sw Sta 500 kV Latitude: 36°25'24.51"N Longitude 120°24'26.36"W

Proposed Dry Lake 500 kV Sw Sta Latitude: 35°45'14.14"N Longitude 119°44'40.67"W

Please note that certain details regarding SCD limitations and space limitations outlined above will not appear in the Transmission Interconnection Handbook (TIH) until the handbook is updated. There is no ETA for the updated handbook.