See Also
The Line Per Unit Impedance Calculator Dialog allows to convert actual impedance and current limit values to per unit impedance and MVA limit values, and vice versa.
The dialog has the following elements:
Actual Impedance and Current Limits
This part of the dialog shows all the impedance related values in Ohms/length-unit as well as the transmission line limits specified in Amps. If any of these values is modified, the corresponding per unit or MVA value will be changed accordingly, taking into consideration the current line length, length units, and system base values.
Line Length
This value indicates the length of the line in miles or kilometers, depending on the units selected in Length Units. The option When changing convert is used to convert the values when the length value is modified. The option PU/MVA --> indicates that the actual impedance and current limits will be converted to per unit impedance and MVA limits when the length value is changes. The option <-- Electrical specifies that the per unit impedance and MVA limits will be converted to actual impedance and current limits when the length value is modified.
Length Units
This option indicates the length units. Choices are miles and kilometers. When this parameter is changed, the user will be prompted to confirm to convert the actual impedance and current limits, as well as the line length values, from the old units to the new units. If the answer is positive, then the actual impedance and current limits, and the line length will be the same but they will be expressed in the new units selected. If the answer is negative, the values will not change numerically but they still will be expressed in the new units selected.
System Base Values
The system base values show the power base, the voltage base, and the impedance base. These values can not be modified in this dialog.
Per Unit Impedance and MVA Limits
This part of the dialog shows all the impedance related values in per unit as well as the transmission line limits specified in MVA. If any of these values is modified, the corresponding actual or Amps value will be changed accordingly, taking into consideration the current line length, length units, and system base values.
Conductor Type
Shows the conductor type selected to compute the per unit impedances in the Transmission Line Parameter Calculator dialog. It will be blank if there isn’t any.
Tower Configuration
Shows the tower configuration selected to compute the per unit impedances in the Transmission Line Parameter Calculator dialog. It will be blank if there isn’t any.
Calculate PU Impedances From Conductor Type and Tower Configuration
Clicking this button will open the Transmission Line Parameter Calculator form.