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Proposed Revision Request Detail Help
PRR Life Cycle*****Stakeholder Meeting on Recommendation****
PRR Details
PRR #
1699
Title Clarifications on how intertie transmission corridor and intertie scheduling limits constraints are used for imbalance reserves
Date Submitted 8/14/2026 9:13 AM
PRR Category A
Priority Normal
Owner Martin, Michael (CAISO)
Status Stakeholder Meeting on Recommendation
Status End Date 10/13/2026 11:59 PM
Related BPM Market Operations
BPM Section 6.6.8 Imbalance Reserve Product
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Existing Language

​See Attached

Proposed Language

​See Attached​

Reason For Revision

Imbalance Reserve awards from intertie resources are subject to applicable Intertie Transmission Corridor (ITC) and Intertie Scheduling Limit (ISL) constraints. These constraints ensure that sufficient intertie scheduling capability is available for Energy schedules, Ancillary Service awards, and Imbalance Reserve awards cleared in the IFM.  This PRR details the design and includes formula-level detail​

Click here to view the Recommendation Details for this PRR
BPM PRR Submitter

Martin, Michael (CAISO)
Modified BPM language proposed by the PBM Chnage Management Coordinator

​Approve BPM as Submitted

Identification of the authorship of comments

Action

Approve the BPM PRR as submitted

Intertie scheduling limits constrain only import/export and transfer schedules at the associated interties. Energy schedules and capacity awards for supply and demand resources inside a BAA are not constrained by intertie scheduling limits. The intertie/transfer capacity is reserved in the base scenario for all energy schedules and capacity awards for the relevant intertie resources (transmission profile), hence these constraints need not be enforced in the IRU/IRD deployment scenarios.
Statement of apparent requirements of the BPM PRR

Priority and rank for any BPM PRR requiring a CAISO system change

Proposed effective date(s) of the BPM PRR

Other recommended actions

Announcements
1. An intertie resource receiving IR must hold transmission covering its day-ahead energy schedule plus its full IR award.  That requirement reflects that delivery to the CAISO boundary relies on transmission outside CAISO's control, which CAISO cannot redispatch, so transmission capability for the full award is the assurance that the award can be delivered.  By applying the full IR award to the corresponding ITC/ISL constraint, the market gives matching treatment on the CAISO side of the boundary, so the award is deliverable on both sides of the interface. 
2. The deployment factor involves a policy choice about how much tail deliverability risk to accept.  At an intertie, this risk has more severe consequences than for internal constraints.  The market can relieve internal transmission congestion by re-dispatching units but a binding intertie limit is different because once the intertie is full, re-dispatching units cannot create more import capability.  The market can reduce another import schedule or add an export schedule as counterflow, but neither would bring additional energy into the BAA.  Once an intertie reaches its limit, every new MW you add forces an existing MW out, so the net change is zero.  So if an intertie IR award must deliver energy when needed, the market must reserve 100% of the required transmission capability in advance. 
3. CAISO has long reserved full intertie scheduling capability for AS imports, so this applies a similar precedent.


Posted On - 10/1/2026 8:14 AM
Intertie scheduling limits constrain only import/export and transfer schedules at the associated interties. Energy schedules and capacity awards for supply and demand resources inside a BAA are not constrained by intertie scheduling limits. The intertie/transfer capacity is reserved in the base scenario for all energy schedules and capacity awards for the relevant intertie resources (transmission profile), hence these constraints need not be enforced in the IRU/IRD deployment scenarios.
Posted On - 9/28/2026 8:17 AM
See additional comment on reasoning for design.
Posted On - 9/28/2026 8:14 AM
Impact Analysis
PRR 1699 - Impact Analysis Form.doc    
Notes:
Initial Comments
Can CAISO provide more explanation as to why it is proposing to treat transmission reservations for Imbalance Reserve awards across the interties differently than other Imbalance Reserve awards?
9/16/2026 9:06 AM
Logged By - alan.meck@pge.com (CAISO)
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ISO response provided by Michael Martin:
Here is the technical reason of why we fashioned intertie constraints in such a way:

For interties, the full IRU and IRD capacity is reserved to be able to deploy if uncertainty is materialized.

For the import limit:
For energy, capacity is reserved for import and export system resources (allowing cancelation). For import system resources, capacity is reserved for AS in the upward direction, and imbalance reserve up. For export system resources, capacity is reserved for imbalance reserve down. Exporting IRD implies that the exporting EDAM BAA would need to receive an import of energy of the same amount of the IRD.

For the export limit:
For energy, capacity is reserved for import and export system resources (allowing cancelation). For import system resources, capacity is reserved for AS in the downward direction, and imbalance reserve down. For export system resources, capacity is reserved for imbalance reserve up. Exporting IRU implies that the exporting EDAM BAA would need to increase an energy export of the same amount of the IRU.
9/21/2026 8:34 AM
Responded By - Madrigal, Radha (CAISO)
Recommendation Comments
No Recommendation Comments available for this PRR.
Attachments