Simulator 16 User Guide - PowerWorld

Transformer Mvar Control Dialog
The Transformer Mvar Control dialog is used to view the control parameters associated with load-tapchanging
(LTC) transformers that are used to control the Mvar flow through the transformer. To view
this dialog, click on the Change Automatic Control Options button found with the Transformer
Control options, provided that the Reactive Power Control option is chosen from the Automatic
Control Type group.
When used to control reactive power, the LTC transformer always controls the reactive power flow at
the from end of the transformer (i.e., the tapped side), with positive flow assumed to be going
through the transformer to the to bus. Therefore the regulated bus field is not used.
The Common Options tab of this dialog has the following fields:
Automatic Control Type
This section is only visible on the dialog in edit mode. The control type of the transformer can be
changed between no control, voltage regulation, reactive power control, or phase shifter control.
Changing the control type will update the dialog to reflect the type of control that is selected.
Mvar Flow at From Bus
The current Mvar flow as measured at the from end of the line. This is the parameter the
transformer tries to control.
Mvar Error
If the Mvar flow at the from end violates the limits defined by the Regulation Minimum Mvar
Flow and Regulation Maximum Mvar Flow fields, the Mvar Error field indicates by how
much the flow falls outside the control range.
Regulation Minimum Mvar Flow, Regulation Maximum Mvar Flow
Minimum and maximum allowable reactive power flow as measured at the from bus. The
transformer attempts to regulate the reactive flow to fall within this range.
Regulation Target Type
As long as the regulated Mvar flow is inside the regulation minimum and maximum, the
transformer will not change its tap ratio. When the regulated Mvar flow moves outside of this
regulation range, Simulator will calculate a new tap ratio in an attempt to bring the regulated
Mvar flow back inside of its range. The Regulation Target Type determines what value is used
as a target when calculating this change in tap ratio. Middle is the default and means that the
target is the average of the regulation minimum and maximum regardless of whether the Mvar
flow is high or low. Max/Min means that the regulation maximum is used as the target when
the regulated Mvar flow is above the maximum, and regulation minimum is used as the target
value when the regulated Mvar flow is below the minimum.
Present Tap Ratio
The transformer's present off-nominal turns ratio.
Minimum Tap Ratio, Maximum Tap Ratio
Minimum and maximum allowable off-nominal tap ratios for the LTC transformer. Typical values
are 0.9 and 1.1.
Tap Step Size
Transformer off-nominal turns ratio increment. The off-nominal turns ratio is either incremented
or decremented from 1.0 in integer multiples of this value. Default value is 0.00625.
Mvar to Tap Sensitivity
©2011 PowerWorld Corporation
410