Fault Analysis Lab

How this is built: symmetrical- components fault analysis (Fortescue transform + sequence networks) — the same closed- form method used in fault studies and relay-testing tools, not an iterative power flow. Positive- and negative-sequence impedances are treated as equal throughout; the transformer's zero-sequence impedance is assumed equal to its positive-sequence impedance; pre-fault load current is neglected (standard practice for a maximum fault- current study — it's also why MP2, downstream of the fault, reads ~0 current here). The transformer is assumed Dyn, so the grid source never enters the zero-sequence path — only the transformer and its grounding impedance do. Line and cable shunt capacitance is neglected: that is fine for solidly or low-impedance earthed networks, but in isolated or resonant-earthed (Petersen-coil) networks — common in German medium-voltage grids — the earth-fault current is set mainly by that capacitance, so treat single line-to-ground results there as the inductive part only. Per-unit values referred to a fixed 100 MVA system base internally; every result shown is scaled back to real kV/kA, so the choice of base has no effect on any number above.