By Amanda Durish Cook

FERC on Wednesday granted MISO a six-month reprieve from a Tariff provision requiring it to include minimum zonal reserve requirements in its modeling of broader system reserve requirements.

The RTO currently calculates minimum reserve requirements using offline studies conducted three days in advance of a day-ahead market run, but it has said that study results aren’t always accurate because actual operating conditions, including transmission constraints, can deviate from original study assumptions.

A case in point: In early April, scarcity pricing was triggered in MISO because an offline study predicted an 84-MW minimum contingency reserve for Zone 6 covering Indiana and a slice of Kentucky, but it failed to account for actual transmission and generation outages modeled in the day-ahead process. Generation and transmission outages in MISO caused an outflow of energy from Zone 6, creating scarcity conditions for reserves and sending prices as high as $1,100/MWh.

In mid-July, MISO said it was evaluating changing the algorithm behind its minimum reserve requirement to reflect energy flow constraints. (See MISO Ponders Reserve Scheduling Fix.)

In its filing, the RTO told FERC it needed a waiver of “inflexible” offline studies while it holds stakeholder meetings exploring an additional modeling step to account for constraints and prepares a Tariff filing. It also noted that it could decide to permanently remove offline studies from the process.

MISO filed for the waiver last month, and the commission acted quickly given that the RTO has entered its shoulder season typified by planned outages (ER17-2466).

“MISO requests expeditious action on this waiver request because the conditions that could potentially lead offline studies to set minimum reserve requirements have previously occurred in the months of October and November,” FERC said.

The waiver remains in effect until April 12, 2018.

FERC allowed the waiver on the grounds that it will remedy current reserve price distortions through “ineffective constraint relief when minimum reserve requirements do not properly reflect real-time non-deliverability of reserves” and “protect the markets from price signals that do not properly reflect or resolve real-time reserve deliverability issues.”