IESO Board Market Rule Amendment Determinations
June 11, 2026
The IESO’s Board of Directors has approved the following market rule amendments:
- Updates to Contingency Event Definitions (MR-00491-R00): This amendment aligns the defined terms for most severe single contingency and second most severe single contingency, with the defined terms used by the Northeast Power Coordinating Council (NPCC) and the North American Electric Reliability Corporation (NERC). The effective date of this amendment is September 9.
- Updates to IESO Monitoring Requirements: Synchrophasor Data (MR-00487-R00): This amendment extends the existing synchrophasor requirements for transmitters and generators to storage participants and makes other changes to these existing requirements. The effective date of this amendment is December 2.
The amendment proposals and the Board’s reasons for adopting the amendments, are available on the Proposed Market Rule Amendments web page.