1. Prepared By:- Nisarg Amin
Topic:- Symmetrical Component Method For 3
Phase Power Representation

2. INTRODUCTION
The normal operating conditions of an electric
power system are occasionally disrupted because of
faults.
Analysis of power systems usually implies the
computation of network voltages and currents
under a given set of conditions.
Under many circumstances we tend to ignore the
unbalanced operation in the system and
unbalanced operation is always present.
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3. 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 segregating 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.
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4. Mathematically
Va= Va1+Va2+Va3+----------Van
Vb= Vb1+Vb2+Vb3+----------Vbn
Vn= Vn1+Vn2+Vn3+----------Vnn
Va,Vb…….Vnareunbalancedsetofphosors
Va1,Vb1……Vn1 firstsetofnbalancedphasorswithanangle2pi/nbetweencomponentsa,b,…..n.
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5. Va2,Vb2……Vn2secondsetofnbalancedphasorswithanangle4pi/nbetweencomponentsa,b………,n
Va(n-1),Vb(n-1)……Vn(n-1)are (n-1)thsetofnbalancedphasorswithanangle2pi(n-1)/nbetweencomponentsa,b………,…..n
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6. Equation in matrix form
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7. Symmetrical components for three Phase
system
The n-phase system presented above is of
academic interest only and only the practical three
phase system will be emphasised.
Power is generated, transmitted and consumed
mostly in three phase only.
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8. The phasor representation of three phase
system
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9. The positive sequence set consisting of three
components of equal magnitude, displaced by 120 &
240o
respectively and having the phase sequence of
abca.
The negative sequence set consisting of three
components of equal magnitude displaced by 240 &
120o
respectively, having phase sequence of acba.
The zero sequence set of the component of which
being equal both in magnitude and and phase.
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10. Relations of voltage components in matrix form
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11. Symmetrical components of generator
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12. Thank You
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