Units and stations
The dispatchable unit registry, with the constraint equations that carry each unit on their left-hand side and how many of those actually bound in the observation window. A unit's exposure is a join, not a lookup: DUID to connection point to constraint id.
Reading this page
The registry comes from DUDETAILSUMMARY for identity and region, DUDETAIL for capacity, and STATION and PARTICIPANT for names. The constraint list is the walk from the unit's CONNECTIONPOINTID through SPDCONNECTIONPOINTCONSTRAINT, and the bind counts come from DISPATCHCONSTRAINT.
A unit with no constraints is not a unit with no constraint risk. Plant outages act through flows and requirements, not through equations named after the plant: a week with three large units offline can produce no constraint carrying any of their names, while the corridors that carry the replacement flows bind harder.
And an equation names a condition, not a wire. When a line goes out, the system-normal id goes quiet and an outage-conditional twin takes over the same corridor, so a per-id history silently fragments across the handover.
Both patterns are field notes from the week of 2026-07-18 to 2026-07-25, verified minute-level against DISPATCHCONSTRAINT and the network outage book. Chapter 7 works through them.