Handbook of Electrical Engineering

270 HANDBOOK OF ELECTRICAL ENGINEERING

Figure 11.1 One-line diagram of faulted high voltage system.

Figure 11.2 Equivalent circuit of faulted high voltage system.

The base MVA rating chosen for this system is 100 MVA. The impedance data is given in Table 11.1.

Hence the total series per unit impedance isR= 0 .069 pu,X= 1 .021 pu. The short-circuit
current is therefore:

If=

V

R+jX

=

1. 0

0. 069 +jl. 02. 1

= 0 .9775 pu

Therefore the fault MVA is 0. 9775 × 100 = 97 .75 MVA.