A flexible alternating current transmission system (FACTS) is a system composed of static equipment used for the AC transmission of electrical energy. It is meant to enhance controllability and increase power transfer capability of the network. It is generally a power electronics-based system. In conventional AC transmission system, the ability to transfer AC power is limited by several factors like thermal limits, transient stability limit, voltage limit, short circuit current limit etc. These limits define the maximum electric power which can be efficiently transmitted through the transmission line without causing any damage to the electrical equipments and the transmission lines. This is normally achieved by bringing changes in the power system layout. However this is not feasible and another way of achieving maximum power transfer capability without any changes in the power system layout. Also with the introduction of variable impedance devices like capacitors and inductors, whole of the energy or power from the source is not transferred to the load, but a part is stored in these devices as reactive power and returned back to the source. Thus the actual amount of power transferred to the load or the active power is always less than the apparent power or the net power. For ideal transmission the active power should be equal to the apparent power. In other words, the power factor (the ratio of active power to apparent power) should be unity. This is where the role of Flexible AC transmission System comes.

1. FLEXIBLE AC
TRANSMISSION SYSTEM
GANESH BEHERA
ELECTRICAL & ELECTRONICS ENGINEERING
RAGHU INSTITIUTE OF TECHNOLOGY

2. CERTIFICATE
This is to certify that the work entitled on “FACTS” is the bonafide work done by
GANESH BEHERA (163J1A0206) and submitted in partial fulfilment for the award of
the degree of BACHELOR OF TECHNOLOGY in ELECTRICAL AND ELECTRONICS
ENGINEERING FROM RAGHU INSTITUTE OF TECHNOLOGY affiliated to JNTUK,
KAKINADA.
PROJECT GUIDE HEAD OF THE DEPARTMENT
K. SHIVA SHANKAR Dr.G.JOGA RAO ,Ph.D.
Assistant Professor Associate professor & HOD
Department of EEE Department of EEE
RAGHU INSTITUTE OF TECHNOLOGY
(AUTONOMOUS)
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
M .tech

3. CONTENTS
Acknowledgement
Abstract
Introduction
Why FACTS
Basic principles
Power System Stability
Transmission line model
Variation of P Q V with δ
Power Transfer
Shunt Compensation
Series Compensation

4. Acknowledgement
I articulate our profound gratitude to K.Shiva Shankar ,Assistant Professor and our guide ,
Dr . G . Joga Rao , Ph.D Associate Professor & HOD. Department of EEE for his
indispensable encouragement with salient guidelines and suggestions throughout the work.
He helped us in various difficulties and challenges that raised at various stages of this report.
I would like to thank all teaching and non teaching staff for their valuable suggestions and
guidance in successfully completing this project. Finally we express indebtedness to everyone
even remotely involved in the successful completion of our report .
I convey our special thanks to our beloved and honorable Principal, Prof.
S.Satyanarayana, Vice principal Dr. P.S.R.Chowdhary and Management for
providing excellent teaching for the completion of this report.
I thank my parents who nurtured me and were always there when i needed them and I
heartily thank my friends who supported and encouraged me in making this report.
GANESH BEHERA

5. ABSTRACT :
Presently the increasing industrialization, urbanization of life
style has lead to more dependency on the electrical energy.
However, the cost of transmission lines and losses, as well as
difficulties encountered in building new transmission lines, would
often limit the capacity of lines. As power transfers grow,
degree of complexity in power system increases and leads to the
reduction in security level of the system. In addition, it may
lead to large power flows with inadequate control, excessive
reactive power in various parts of the system, large dynamic
swings between different parts of the system and other
bottlenecks. Thus, the full potential of transmission
interconnections cannot be utilized
Finally using conventional and heuristics methods for location of
FACTS devices, the stability of the system has been improved
and congestion in the overloaded lines has also been reduced,
which in turn improved stability of the power system.

6. INTRODUCTION
A Flexible AC Transmission System can be defined as the
system consisting of fast acting power electronic controllers
along with power devices to increase the controllability and
stability of transmission system along with increase in
power transfer capabilities of the existing system.
Power transfer between two points is given by
P =
.

7. Why FACTS ?
● In conventional AC transmission system the ability to
transfer the AC power is limited by several factors like
thermal limits , transient stability limit , voltage limit ,
short circuit current limit etc.
● These limits actually determine the maximum power
which can be transmitted through the transmission line
without causing any damage to the electrical equipments
and the transmission lines.
● This can be obtained by variables devices like capacitor
and inductors.
● In ideal transmission system the power factor should be
unity.

8. Basic principles of FACTS
⚫ Dynamic limitations of power transmission
⚫ FACTS and Reactive power
⚫ Power transfer in a simple two machine system
⚫ Variation of P , Q , .
⚫ Different compensation techniques to increase the
transmittable power

9. Dynamic limitation of power transmission system :

10. Contd…
Power systems are usually interconnected and forms a
energy pool in which energy can be transmitted
between and among the systems.
The main objective of power grid :
⚫ To provide good quality power to the consumers .
⚫ maintain the stability of the network.
Limitations of power transmission system :
⚫ The power system take on rotating synchronous machines
for generation of power.
⚫ All synchronous system in the system must operate.

11. POWER SYSTEM STABILITY
Here the power system stability
• The power system capability of recovering from an
adverse situation created due to disturbances and
regains the original condition under stipulated
contingencies is called the power system stability .
The power system stability is divided into two parts :
⚫ Transient stability
⚫ Steady state stability

12. POWER SYSTEM STABILITY

13. Contd…
⚫ If following a small and gradual disturbance the
power system reaches a steady state operation
then it is called a steady state stability.
⚫ If the power system reaches maintains synchronism
under severe and sudden disturbance then it is called
as transient stability .

14. Contd….
We know that advanced technologies are paramount for reliable
and secure operations of power system .
For achieving both operational reliability and financial profitability
we require more efficient utilization and control of existing
transmission system with power electronics based equipments and
FACTS .
The concept of FACTS implies the use of high power electronic
devices in order to control the power flow in a transmission
network there by allowing the transmission lines to be loaded to
their full capacity.
FACTS technology can boost power transfer capability by 20-30%.

15. Contd….
⚫ FACTS devices are high reactive power compensators
and therefore it helps to restore the stability and voltage
to the grid in order to prevent the voltage collapse.
Reactive power enhances the maximum transmission of
useful reactive power .
Voltage will sag if reactive power is less and swell if reactive
power is more .
Therefore we an say that reactive power maintains the
voltage profile in the system.
The task of FACTS device as a reactive power compensator is
to have reactive power in the right place and in right
amount .

16. SIMPLE TRANSMISSION LINE
MODEL

17. TRANSMISSION LINE MODEL

18. Contd…
⚫ An approximate form of power transmitted now
becomes :
⚫ The sending end and receiving end voltages are
given as :

19. Contd…
Thus transmission line is purely inductive with zero
shunt capacitance .
Mid point voltage :

20. Contd…..

21. Variation of P , Q , V with δ

22. Contd…
⚫ Hence the product of midpoint voltage and line
current is the transmitted power .
⚫ so δ will progressively not increase the power .
⚫ For δ >90‧
the mid point voltage will decrease rapidly and line
current will increase .
Consequently their product will decrease from its
maximum value and reaches to zero at δ = 180.
Variation of in phase and quadrature component of line
current w . r . t. receiving end voltage as δ reaches (0-
180)

26. POWER TRANSFER

27. Shunt compensation

28. Contd ….

29. Series compensation

30. series compensation :

31. contd..

32. CONTD…..

33. contd...

34. contd..
series capacitance have been used extensively in the last
50 years throughout the world for the compensation of
long transmission line .

35. References
https://people.qatar.tamu.edu/shehab.ahmed/ecen_459/FACTS.pdf
https://en.wikipedia.org/wiki/Flexible_AC_transmission_system
https://www.elprocus.com/flexible-ac-transmission-system-need-definition-types/
https://www.electrical4u.com/facts-on-facts-theory-and-applications/
https://people.qatar.tamu.edu/shehab.ahmed/ecen_459/FACTS.pdf

36. Thank you