Module 7 : Out of Step
Protection
Lecture 24 : Power Swings and Distance Relaying
Review Questions
1.
Define a power swing and elaborate its consequences on distance relaying performance.
2.
Derive the expressions for apparent impedance seen by a relay in a two area system as function of angle of separation
. Show that the locus is a straight line if |E
A
| = |E
B
| and a circle if |E
A
|
|E
B
|.
3.
What are assumptions made on the system behaviour in above derivation?
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11
. Show that the locus is a straight line if |EA| = |EB| and a circle if |EA|
|EB|. 
