Generator Auxiliary Use

Units:	MW
Mode:	Output Only
Multi-band:	False
Default Value:
Validation Rule:
Key Property:	No
Description:	Auxiliary use
Detail:

Generator Auxiliary Use is the total of all station auxiliary loads (in-house use):

Auxiliary Use = Aux Fixed + Aux Base × (Units Generating + Units Pumping) + Aux Incr × Generation + (1 / (1 - Aux Incr) - 1) × Pump Load Sent Out Generation = Generation - Auxiliary Usage Generation at RRN = (Generation - Auxiliary Usage) × Marginal Loss Factor

The auxiliary use is set by the inputs Aux Incr, Aux Base, and Aux Fixed. These can be used in any combination.

Example:

Generator	Property	Value	Units
BOB	Units	2	-
BOB	Max Capacity	250	MW
BOB	Aux Fixed	0.5	MW
BOB	Aux Base	3	MW
BOB	Aux Incr	3	%

Here there is a constant station load of 0.5 MW per installed unit. Each unit that is running incurs a load of 3 MW and loses 3% of its raw generation to auxiliaries. Thus with one unit generating at total of 250 MW the power station consumes 0.5 x 2 + 3 x 1 + 0.03 x 250 = 11.5 MW. The sent out generation is 250 - 11.5 = 238.5 MW.

Note that if you do not define auxiliary losses then generator heat rate functions must be entered on a sent-out basis.

How auxiliary loads affect the load and hence the dispatch is controlled by the setting Region Load Metering Point. By default auxiliary loads are assumed to be captured in the input load and thus are only calculated after the dispatch.