This seminar presentation discusses symmetrical components in power systems. It introduces symmetrical components and explains their use in power system analysis and protection. Specifically, it covers: 1) The need for symmetrical component analysis to protect generators from overheating during unbalanced loads and to supply sensing voltages for voltage regulators. 2) The mathematical technique of resolving an unbalanced set of phasors into balanced positive, negative, and zero sequence systems. 3) Examples of applying symmetrical component analysis to generators and transformers. 4) The conclusion that symmetrical component analysis improves power system reliability by enabling effective analysis of unbalanced fault systems.

1. Seminar Topic on:-
SYMMETRICAL COMPONENT OF POWER
SYSTEMS
Presented By:-
Devendra Mishra
Branch:- EN-1
Roll No:-1401421020

2. OUTLINE OF THE PRESENTATION
INTRODUCTION
NEED FOR THE SYMMETRICAL
COMPONENET METHOD
TECHINQUES USED TO ANALYSIS
SYMMETRICAL
CONCLUSION

3. INTRODUCTION
A three-phase system is said to be symmetrical when
the system viewed from any phase is similar.
Thus, in a three-phase symmetrical system the
impedances of all the three phases are equal and the
mutual impedances, if any, between the three phases are
the same.
The three phase voltages(or currents) are said to be
balanced if the magnitude of the three voltages(or
currents) are equal and they separated from each other
by 120º(electrical) in phase.
When the system is unbalance the voltages, current and
the phase impedances are in general unequal. Such a
system can be solved by a symmetrical per phase
technique known as the method of symmertical
component.

4. This method was proposed by Fortescue in 1981
and is often called the three-component method.
According to Fortescue, An unbalance set of n
phasors may be resolved in to (n-1) balanced n-
phase system of different phase sequence and one
zero-phase sequence system.
A zero-phase sequence system is one in which all
phasors are of equal magnitude and identical angle,

5. PHASE SEQUENCE
Phase-Sequence of the phasors is the order in which
they pass through a positive maximum.
 Thus, a phase sequence a b c implies that the
maxima occur in order a, b, c.
If a, b, c is taken as the positive phase sequence then
a, c, b represents the negative phase sequence.
It should be noted that for both positive & negative
phase sequence, the direction of rotation of phaser is
taken to be anticlockwise

6. The phasor representation of three phase system

7. Need for the symmetrical
component analysis
Negative sequence relay in generator has helped in
protecting the generator from over heating in the
event of unbalanced loads.
The positive sequence network is used to supply the
sensing voltage to generator voltage regulators
Certain connections of CT and PT develop zero
sequence components that are used in protective
ground relaying scheme

8. Method of adopted for
symmetrical component analysis
Mathematically:
Va= Va0+ Va1+ Va2
Vb= Vb0+ Vb1+ Vb2
Vc= Vc0+ Vc1+ Vc2
 Va Vb Vc are unbalance set of phasor
Va1, VbVc1 are set of positive sequence phasor
Va2, Vb2Vc2 are negative sequence phasor
Va0 Vb0 Vc0 are zero sequence phasor

10. Vp=A Vs
Then Vs=[ adjA÷|A|] Vp

11. Symmetrical components of generator

12. Symmetrical components of
transformer

13. Conclusion
Power system analysis using symmetrical
component is very helpful in improving the
reliability of the power system.
The principle adopted for the analysis of
unbalanced fault system is symmetrical component
method

14. Any query
Thank you