The fault study mode works differently:

  1. The system Y matrix is built including all loads as admittances.
  2. All generators are converted to their dynamic model (or Thevinen equivalent).
  3. All Fault objects are disabled (removed from the circuit).
  4. A direct solution of the Y matrix equations is performed including source injections and generator injections. The resulting open-circuit voltage Voc is stored for future use.
  5. The Thevinen short circuit impedance matrix Zsc  at each bus is computed. The inverse is also computed. Both become part of the Bus object. Note that the Zsc and Zsc10 commands will return this matrix.
  6. The short circuit currents for a variety of fault conditions are computed for each bus using the Thevinen model. Only the "all-phase" short circuit current is computed at the time the Solve command is issued. The remainder are computed when the Show Faults command is issued.

Note that many distribution system analysis programs do not include Load elements or Capacitors. If you are making comparisions, you might remove these elements. Generators and Induction machines may also be omitted from other programs. OpenDSS performs the fault analysis with all elements in the circuit as defined in the DSS files.