Question

Consider the two power systems shown in Figure A below which are initially not interconnected, and are operating in steady state at the same frequency. Separate load flow solutions are computed individually for the two systems, corresponding to this scenario. The bus voltage phasors so obtained are indicated in figure A. These two isolated systems are now interconnected by a short transmission line as shown in figure B, and it is found that $P_1=P_2=Q_1=Q_2=0$.

Figure A
Figure B
The bus voltage phase angular difference between generator bus X and generator bus Y after the interconnection is

• A. ${10}^{\circ }$
• B. ${25}^{\circ }$
• C. $-{30}^{\circ }$
• D. ${30}^{\circ }$

Answer 1

The correct option is A ${10}^{\circ }$

Flow of power in transmission line depends on bus voltage magnitude and phase difference between bus voltages.
After interconnecting the two system by a line there is no power flow in the line. Hence bus voltage magnitude and phase difference between buses will remain same as before interconnecting the two systems.

Phase difference between bus X and bus Y
$=30-20={10}^{\circ }$