Fault calculations in power systems using computer programs typically involve the use of either the Y-Bus or Z-Bus methods. These are commonly used for calculating the fault currents in different types of faults, and they both represent the system in terms of either admittance (Y-Bus) or impedance (Z-Bus) matrices. Both methods are used depending on the type of fault and system configuration.
Thus, the correct answer is Using Y-Bus or Z-Bus.