Lines may be added, deleted, or given impedance changes through the use of convenient dialog boxes, without actually altering the underlying (necessarily very large and cumbersome) data base. A list of all such changes that the user has made is available from the main menu, and any change may be readily "undone," or if desired, changed further.

In addition, there are four network alterations which can be made immediately, do not appear in the list of changes, and are automatically reversed when subsequent faults are requested:

1. Any line connected to the faulted bus can be opened at the end away from the fault by a simple check-box click.
2. The fault can then be located anywhere along the opened line by another check-box click together with an edit box distance entry.
   (These effects can be easily reversed by re-clicking the respective check boxes.)

   There are two methods provided to fault lines anywhere along their lengths while each end remains normally connected:

3. A dialog box is displayed that allows the user to vary the fault point along a line through the use of a slider control. This option is not available for phase shifters, mutually-coupled lines, or sub-groups of parallel lines.
4. A fault can be located anywhere along the length of any line (including all those excluded in item 3) by entering the desired percentage of the line's length in an edit box and clicking a push button.

The program's user interface screen is divided into a graphics section, which shows network connectivity, and a control-results dialog box containing standard Windows input and output controls. (Selected segments of an actual screen are currently being displayed at left.)

Fault currents can be displayed in the graphics section for all lines up to two buses away from any bus, for a fault on any bus. These currents can be suppressed to decrease clutter if the network configuration is of primary concern.

The program uses the Philadelphia Electric Version 2 data base format with a couple of new fields for phase-shifter angles, and additional mutual coupling information (optional).
Solutions are obtained using sparse admittance matrix, optimal bus ordering, and upper-lower triangular factorization techniques. While several data files are used by the program, the user is only responsible for the Philadelphia Electric data base, and the rest of the files are generated automatically.