This presentation is based on the subject electric power system.Circle diagram of transmission line.In this presentation two topics covered about the circle diagram of transmission line.It is about the medium and long transmission line circle diagram.Receiving-end circle diagram and sending-end circle diagram of the transmission line.This presentation help you to the improve knowledge about the transmission line circle diagram.

1. Gujarat Power Engineering and Research
Institute
B.E. SEM. VI (ELECTRICAL).
PRESENTED BY:
HARSH SONI

3. Circle Diagram
1.Receiving-end Circle Diagram
2.Sending-end Circle Diagram

4. It has been shown above that-the flow of active
and reactive power over a Transmission line can
be handled computationally.
It will now be shown that the Locus of complex
sending- and receiving-end power is a circle.
Since circles are convenient to draw, the circle
diagrams are a useful aid to visualize the load
flow problem over a single transmission.
1. Receiving-end circle diagram

5. The expressions for complex number receiving-
and sending-end powers are Reproduced below
from above Equations.
…(1)
…(2)

6. As per the above equations, and are each
composed of two phasor components-one a
constant phasor and the other a phasor of fixed
magnitude but variable angle.
Rs Ss
The loci for Sr and Ss would therefore be circles
drawn from the tip of constant phasors as
centres
It follows from Eq. (1) that the centre of
receiving-end circle is located at the tip of the
phasor.

7. Horizontal coordinate of the centre
The radius of the receiving-end circle is
Vertical coordinate of the centre

8. Fig.1 Receiving-end circle diagram

9. As per fig.1 the operating point ‘M’ indicates the
receiving end values of , and .
For constant the centre remains fixed. For
varying and constant centre of circles move
along the line
RP RQ 
RV RC
RV SV
ROC

10. In polar coordinates
Similarly for Eq. (2) the centre of sending-end
circle is located at the of the phasor
2. Sending-end circle diagram

11. Horizontal coordinate of the centre
Vertical coordinate of the centre
The radius of the sending-end circle is

12. Fig.2 Sending-end circle diagram

13. The operating point N is located by measuring
the torque angle in the direction indicated from
the reference line.

SV SC
SV RV
SOC
For constant the centre remains fixed.
For varying and constant centre of
circles move along the line