The figure below shows the single-line diagram of an electrical power system,
which contains the data of its main electrical equipment. Consider that the
system operates in steady state at rated voltage and that the load currents
in this condition are negligible against short circuit currents.
Assume that the positive, negative and zero sequence reactances of each
device are the same and that the resistances of the devices
(generator and transformer) are negligible.
The line impedance has only a resistive component of 40ohms.
Considering the above information, 100 MVA base power and 13.8 kV
base voltage, find:
1- The three-phase short-circuit current in the middle of the transmission line;
2-The short-circuit AC and DC component;
3-The worst value for the initial short circuit angle d) The highest value for the initial short circuit current