symmetrical component of power system
TRANSCRIPT
Seminar Topic on:-
SYMMETRICAL COMPONENT OF POWER SYSTEMS
Presented By:- Devendra Mishra
Branch:- EN-1 Roll No:-1401421020
OUTLINE OF THE PRESENTATIONINTRODUCTION
NEED FOR THE SYMMETRICAL COMPONENET METHOD
TECHINQUES USED TO ANALYSIS SYMMETRICAL
CONCLUSION
INTRODUCTIONA 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.
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,
PHASE SEQUENCEPhase-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
The phasor representation of three phase system
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
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
Vp=A VsThen Vs=[ adjA÷|A|] Vp
Symmetrical components of generator
Symmetrical components of transformer
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
Any query
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