Tuesday, September 25, 2018

NYISO Stakeholders OK Change on Reliability Margins

NYISO’s Management Committee agreed Wednesday to relax its minimum 20-MW constraint reliability margin value in its initiative to price transmission constraints on 115-kV facilities.

The ISO’s Tariff currently requires at least 20 MW be set for any non-zero constraint reliability margin value used in the day-ahead and real-time markets

David Edelson, NYISO manager of operations performance and analysis, noted as an example that a 20-MW CRM equals 13% of the rating for 115-kV lines with post-contingency limits of 150 MW, limiting them to 130 MW in dispatch.

nyiso constraint reliability margin

115-kV transmission line | Exponential Engineering

By contrast, for a 345-kV circuit with a 1,550-MW post-contingency rating, a 20-MW CRM represents only about 1% of the line rating.

Edelson said the ISO wants to limit CRMs to no more than 10% of a facility’s rating to allow for the continued pricing of transmission constraints on lower-voltage lines.

NYISO wants to change the Tariff to permit CRMs of less than 20 MW until it can implement enhancements under its constraint-specific transmission shortage pricing project. The ISO said the timing of that project is subject to stakeholders’ prioritization and scheduling.

The ISO would publish on its website a list of transmission facilities and interfaces assigned a CRM other than 20 MW.

The rule change will be presented to the Board of Directors for approval in September. The committee approved the proposal unanimously by a show of hands.

— Rich Heidorn Jr.

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