Question

A generator is connected to a transformer which feeds another transformer through a short feeder.

The zero sequence impendance values are expressed in p.u. on a common base and are indicated in figure.The Thevenin equivalent zero sequence impendance at point B (in p.u.) is

• A. 0.8 + j0.6
• B. 0.75 + j0.22
• C. 0.75 + j0.25
• D. 1.5 + j0.25

Answer 1

The correct option is B 0.75 + j0.22

Per unit zero sequence reactance diagram of the given single line diagram is shown below.
Hence, Thevenin's equivalent impedance at B is
$Z_{Th}=j0.1+j0.05+j0.07+0.75$
$=0.75+j0.22$