Another methods is Symmetrical Components Method in which we break down an unbalanced three phase system into three balanced systems so that we can calculate short circuit currents for any type of fault. Also we have Direct Method which Calculates short circuit current directly from a basic formula using actual values of voltages and impedances.
The formula to calculate the short circuit current in transformers is given by: Isc = KVA rating of the source / Secondary side voltage of the transformer Isc = 30 / 6 Isc = 5 A The short circuit current is 5A. A generator has a generator rated current of 20 A and impedance in the short circuit path is 5 ohms then, find the short circuit current.
Short circuit current is the maximum amount of current that flows through a power system during the fault occurrence. The short circuit current depends on factors like voltage, total impedance and the type of fault. The short circuit current is represented by Isc.
"A Short Circuit current analysis is used to determine the magnitude of the short circuit current which the system is capable of producing and compares the magnitude of the short circuit magnitude with the interrupting rating of the overcurrent protective devices (OCPD)."
Since short circuit current calculations are linear, results for a small to medium sized system can be obtained manually, particularly if the system electrical resistances are neglected, which simplifies the overall complex calculation procedure. Short circuit current calculations are further simplified for radial systems.
The formula for calculating short circuit current in generators is given by: Isc = Generator rated current / Impedance of the short circuit path Isc = 20 / 5 Isc = 4 A The short circuit current is 4A.