On a 100 MVA system base, the cente

On a 100 MVA system base, the center of the steady-state stability limit circle is located at (0,595) MVA and the radius of the circle is 1071 MVA. In the R – X plane, the center of the circle is located atandR0 = 0, X0 = −(0.21 − 0.06)/2 = −0.075 puZ0 = (0.21 + 0.06)/2 = 0.135 puThe base impedance on the 100 MVA base is (34.52/100) = 11.902 Q. Thus, in terms of pri- mary ohms, the coordinates of the center of the R – X circle are (0, −0.892) Q and its radius is 1.607 Q. If a distance relay is connected at the terminals of the generator, its settings must be made in terms of the secondary ohms. If we assume a CT ratio of 20 000:5 (i.e. 4000:1), we√ would have the full-load generator current of 1000 × 103/(3 34.5), or 16 735 A produce a√secondary current of approximately 4.18 A. The VT ratio is 34.5 × 103/(3 × 69.3) = 287.4 : 1.Hence, the impedance conversion factor is ni/ne = 4000/287.4 = 13.92. Thus, the distance relay zone for detecting the steady-state stability limit would be a circle, with its center at (0, −12.41) Q secondary, and the radius of the circle should be 22.37 Q secondary.

On a 100 MVA system base, the center of the steady-state stability limit circle is located at (0,
595) MVA and the radius of the circle is 1071 MVA. In the R – X plane, the center of the circle is
located at








and






R0 = 0, X0 = −(0.21 − 0.06)/2 = −0.075 pu



Z0 = (0.21 0.06)/2 = 0.135 pu












The base impedance on the 100 MVA base is (34.52/100) = 11.902 Q. Thus, in terms of pri- mary ohms,
the coordinates of the center of the R – X circle are (0, −0.892) Q and its radius is 1.607 Q. If a
distance relay is connected at the terminals of the generator, its settings must be made in terms
of the secondary ohms. If we assume a CT ratio of 20 000:5 (i.e. 4000:1), we
√

















would have the full-load generator current of 1000 × 103/(

















3 34.5), or 16 735 A produce a
√


















secondary current of approximately 4.18 A. The VT ratio is 34.5 × 103/(


















3 × 69.3) = 287.4 : 1.



















Hence, the impedance conversion factor is ni/ne = 4000/287.4 = 13.92. Thus, the distance relay zone
for detecting the steady-state stability limit would be a circle, with its center at (0, −12.41) Q
secondary, and the radius of the circle should be 22.37 Q secondary.