  An important task in grid planning is to ensure that faults in the grid are
detected and cut off without damage in any grid element. Calculating short
circuit currents is therefore a vital grid analysis functionality for grid
planning applications. The standard IEC 60909 provides guidelines for short
circuit calculations and is routinely applied in grid planning applications.
This paper presents a method for the vectorized calculation of short circuit
currents according to IEC 60909. Distributed generation units are considered
according to the latest revision of the standard. The method is implemented in
the python based open source tool pandapower and validated against commercial
software and examples from literature. The implementation presented in this
paper is the first comprehensive implementation of the IEC 60909 standard which
is available under an open source license. It can be used to evaluate fault
currents in grid studies with a high degree of automation and is shown to scale
well for large grids. Its practical applicability is shown in a case study with
a real MV grid with a high degree of DG penetration.
