See Also
During any constrained minimization there is a cost associated with enforcing the equality constraints and the binding inequality constraints. These costs are known as the marginal costs.
In Simulator OPF marginal costs are calculated for the following record types:
Bus MW Equality Constraints
The Bus MW marginal costs tell the incremental cost to supply one additional MW of load at the specified bus. These values can be viewed on the OPF Bus Records display; they can also be contoured or viewed on the one-lines using bus fields.
In the absence of any binding inequality constraints (such was Line MVA constraints) all of the bus marginal costs in an area should be identical. Bus marginal costs can only be determined for buses that are in areas or super areas on OPF control.
Bus Angle Constraints
The Angle Marginal Cost is the incremental cost to keep the angle at a bus within the specified enforcement tolerance. These values can be viewed on the OPF Bus Records display.
Area MW Equality Constraints
The Area MW marginal costs tell the incremental cost for the specified area to import one additional MW of load from the system slack bus. These values can be viewed on the OPF Area Records display; they can also be contoured or viewed on the one-lines using area fields. In the absence of any binding inequality constraints the area MW marginal cost is identical to the bus MW marginal costs for all the buses in the area. When there are binding inequality constraints this is no longer the case.
Super Area MW Equality Constraints
The Super Area MW marginal costs are identical to the area marginal costs except they apply to super areas rather than areas.
Interface MW Constraints
The Interface MW marginal costs tell the incremental cost of enforcing the interface MW constraints. These values are only nonzero if the interface constraint is actually active (binding); they can be viewed using the OPF Interface Records display.
Line/Transformer MVA Constraints
The Line/Transformer marginal costs tell the incremental cost of enforcing the line or transformer MVA constraint. These values are only nonzero if the line or transformer constraint is actually active; they can be viewed using the OPF Line/Transformer Records display.