FERC last week shut down the possibility of Entergy and other smaller MISO South capacity providers bypassing a provision within MISO’s availability-based capacity accreditation rules.

In a series of orders, FERC turned down Entergy Arkansas and Mississippi, East Texas Electric Co-op and Arkansas Electric Cooperative Corp. and municipal utilities Conway Corp. of Arkansas, Jonesboro’s City Water and Light, and West Memphis Utilities’ requests for exemptions of MISO’s rule to consider thermal resources that take longer than 24 hours to start up as unavailable, assigning them a zero capacity credit (ER23-1140; ER23-1199; ER23-1154; ER23-1186).

In each case, FERC said the parties “failed to demonstrate that the waiver would not result in undesirable consequences, including harm to third parties.”

The commission said that while granting the exemptions would raise the resources’ accreditation values, it would also reduce MISO’s systemwide unforced capacity to seasonal accredited capacity ratio. A reduction in the ratio would decrease the final accreditation values of MISO’s other capacity resources, it said. MISO uses the ratio to determine supply ahead of its capacity auction. The RTO calculated it incorrectly last year, holding up its first-ever seasonal capacity auction.

This year, FERC similarly denied the Southern Minnesota Municipal Power Agency’s and Cleco’s requests for waivers of the 24-hour lead time threshold under the new accreditation. (See FERC Denies Exemption Requests from MISO Accreditation Rule.)

Entergy requested exemptions for its gas-fired Gerald Andrus Power Plant in Mississippi, its partial ownership interests in Units 1 and 2 of the coal-fired Independence Steam Electric Station in Arkansas and its majority interest in Units 1 and 2 of the coal-fired White Bluff Steam Electric Generating Station in Arkansas. Before the capacity auction, the utility said without the waivers, it risked a supply shortfall in Mississippi. (See Entergy Seeks Exemptions from MISO Accreditation Rules.)

MISO’s first seasonal capacity auction using the new availability-based accreditation came and went in spring without any capacity shortages. (See 1st MISO Seasonal Auctions Yield Adequate Supply, Low Prices.)