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Electrical Power Systems

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= | Vo|<br />

| Vo|<br />

| Z|<br />

´ × (MVA) Base<br />

2<br />

= () 1<br />

01727 .<br />

50 ´ = 289.5 MVA Ans.<br />

Symmetrical ault 193<br />

Example 8.4: A 4 bus sample power system is shown in ig. 8.6. Perform the short circuit<br />

analysis for a three phase solid fault on bus 4. Data are given below:<br />

G1 : 11.2 KV, 100 MVA, x¢ g1 = 0.08 pu<br />

G2 : 11.2 KV, 100 MVA, x¢ g2 = 0.08 pu<br />

T1 : 11/110 KV, 100 MVA, xT 1 = 0.06 pu<br />

T2 : 11/110 KV, 100 MVA, xT 2 = 0.06 pu.<br />

Assume prefault voltages 1.0 pu and prefault currents to be zero.<br />

Solution: Circuit model for fault calculation is<br />

shown in ig. 8.6 (a)<br />

Now<br />

If = V 1 0º<br />

40<br />

=<br />

Z j012<br />

.<br />

I 1f = I 2f = –j8.33 ×<br />

=–j4.165 pu.<br />

0<br />

g11f E - V<br />

j 014 .<br />

= –j8.33 pu<br />

= I 1f = –j4.165<br />

ig. 8.6: 4 bus power system.<br />

j0.<br />

1775<br />

j(.<br />

0 1775 + 0. 1775)<br />

ig. 8.5(e)<br />

ig. 8.6(a)

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