SPP DISIS cycle assigns network upgrade responsibility

Southwest Power Pool studies interconnection requests through a consolidated Definitive Interconnection System Impact Study cycle. Requests are examined together and assigned responsibility for the network upgrades their combined injection requires.

Wind-heavy footprints produce a characteristic pattern: constraints appear on long radial paths and on interfaces to neighbouring regions rather than at the point of interconnection. Upgrade sets are therefore large, shared, and sensitive to the composition of the study group.

The financial structure this creates is asymmetric. A project's own contribution to a constraint may be modest while its allocated share of the upgrade is not, because allocation follows study methodology rather than intuition about causation.

For a developer, the operative question before entering a cycle concerns the composition of the study group, because withdrawals inside a group trigger restudy under the tariff. For a lawyer, the operative documents are the study report and the interconnection agreement's provisions on restudy and cost reallocation.

What to watch: withdrawal timing within the cycle, which determines whether surviving projects face a restudy before or after their own investment decisions.