Apidays Singapore 2024 - Modernizing Securities Finance by Madhu Subbu
Power Flow in a Transmission line
1. Power Flow in Transmission Line
Presented by
T.S.L.V.Ayyarao
Assistant Professor
GMRIT
2. Power Flow in Transmission Line
Fig 1: A Simple two-machine System
E1 and E2 are the magnitude of the bus voltages,δ the
angle between two and X the line reactance
The driving voltage drop EL is phasor difference E1-E2
The line current I = EL/X and lags EL by 900
The current flow in the line can be controlled by
controlling EL or X or δ
3. Power Flow in Transmission Line
The rating of series controller would be a fraction of the
rating of the line
If the angle δ is small, the current flow
largely represents the active power
Increase or decrease of line
reactance X will greatly affect Fig 2. Phasor diagram
the active power flow
It is the cost effective means of controlling the power
The active power at E1 end is P1 = E1E2 sin δ/X
Reactive power at E1 end is Q1 = E1(E1-E2 cos δ)/X
4. Power Flow in Transmission Line
The active power at E2 end is P2 = E1E2 sin δ/X
Reactive power at E1 end is Q1 = E2(E2-E1 cos δ)/X
Active power flow increases
up to δ = 900 and then falls to 0
Control is possible well below
δ = 900
Sufficient margin is required
for transient and dynamic
stability
Increase or decrease of X will
raise or lower the curves Fig 3. power angle curves for
different X
5. Power Flow in Transmission Line
Power flow can be controlled by regulating the
magnitude of E1 or E2
The driving voltage EL doesn’t
vary by much but its phase
angle does
The change of magnitude
Fig 4. regulating the magnitudes
has much effect on of voltages
the reactive power than
the active power flow
6. Power Flow in Transmission Line
Fig. 5 (a) quadrature (b) with phase angle
Current and hence power flow can be controlled by
injecting a voltage in series of the line
By varying the magnitude and phase angle of the
injected voltage, active and reactive power flow can be
controlled.