See Also
Line fields are often placed close to transformers on the oneline to indicate the power flow through the device. Transformer fields are often placed close to transformers on the oneline to indicate and control their tap positions. See Transformer Modeling for details on modeling either LTC or phase shifting transformers.
Run Mode
Simulator's animation feature can be used to indicate the magnitude of the flow through the transmission line, either in MW or in terms of the transformer's percentage loading. You can customize the line flow animation using the Animated Flows Options on the Oneline Display Options Dialog.
Right-clicking on a transformer displays the line's local menu, from which you can choose to inspect the Branch Information Dialog.
Edit Mode
New transformers are inserted in much the same way as transmission lines. To add a new transformer to the case, first select Network > Transformer from the Individual Insert ribbon group on the Draw ribbon tab. Then place the cursor on the first bus for the transformer (the from bus) and click the left mouse button. Add more segments to the transformer by moving the cursor and clicking with the left mouse button. To complete the new transformer, place the cursor on the transformer's other terminal (the to bus) and double-click with the left mouse button. This calls up the Branch Options dialog. The from and to bus numbers for the transformer should have been set automatically. If there is just one transformer between the buses, the circuit number should be "1." For multiple transformers between buses, you must give each a unique circuit number. Enter the thickness of the lines [in pixels] used to display the transformer, the number of the line segment in which you would like the transformer symbol drawn, and the size of the transformer symbol.
Enter the per unit (100 MVA base by default) resistance, reactance and charging susceptance for the transformer, and an MVA rating. Enter the off-nominal tap ratio and the phase shift angle in degrees. (For a transformer without tap or phase control, the off-nominal tap should be 1.0 and the phase shift angle should be 0 degrees.)
Select the appropriate Automatic Control Option. If the transformer does not have tap control, select No Automatic Control (this is the default). Select AVR (Automatic Voltage Regulation) if the transformer changes its tap ratio to control the voltage at user specified regulation bus. Select Reactive Power Control if the transformer changes its tap ratio to control the reactive power through the transformer. Finally, select Phase Shift Control if the transformer changes its phase shift to control the MW flow through the transformer. If you need any of the last three options, select the Automatic Control Options button to set the parameters associated with the automatic control. When the transformer is in automatic control an automatic control symbol is drawn when drawing transformer symbol using circles.
For AVR control, enter the number of the bus whose voltage is to be controlled, the allowable range for the controlled voltage (in per unit), the minimum and maximum tap ratios (typical values are 0.9 and 1.1), and the step size for the discrete changes in the tap ratio (typical value is 0.00625).
For reactive power control, the control variable is always the reactive power measured at the from bus (i.e., the tapped side) of the transformer. Positive flow is assumed to be going through the transformer to the to bus. Enter the minimum and maximum allowable flows, the minimum and maximum tap ratios (typical values are 0.9 and 1.1), and the step size for the discrete changes in the tap ratio (typical value is 0.00625).
For phase shift control, the MW flow through the transformer is the controlled value. Enter the bus number of the terminal whose flow is controlled, the allowable range for the controlled flow (positive flow is assumed to be into the transformer at the terminal entered in the previous field), the minimum and maximum phase angles (typical values are -30° and 30°), and the step size in degrees (typical values are between 1° and 2°).
Select OK to save the values and return to the Transformer Options Dialog; otherwise select Cancel.
If you would like the transformer to be initially modeled as being on automatic control at the start of the case, select the Automatic Control Active checkbox.
If you do not want to add the transformer to the case, select Cancel.
To modify the parameters for an existing transformer, position the cursor anywhere on the device and right-click. This brings up the local menu from which you can choose to view the Line Information Dialog. This will open the Branch Options dialog. Use this dialog to adjust many of the transformer's electrical properties. The Formatting ribbon group provides tools to change the transformer's color and/or line thickness.
See Transformer Modeling for details on modeling either LTC or phase shifting transformers.