Symmetrical Components and Fault Calculation
INTRODUCTION
SYMMETRICAL FAULT
A fault involving all the three phases is known symmetrical fault.
Remember :
Assumptions:
This means that the system voltage is at its nominal value and the system is operating on no load at the time of fault. The effect of this is that all generators can be replaced by a single generator since all emfs are equal and in phase.
Steps in Calculation
Consideration of Pre-Fault Load Current
Steps
Remember:
SYMMETRICAL COMPONENTS
General Principles
Any set of unbalanced 3-phase voltages (or current) can be transformed into 3 balanced into 3 balanced sets these are :
Operator ‘a’
Properties of Operator ‘a’ 1 + a + a2 = 0
Remember:
1 + a2 = 1Ж60° = 0.5 – j0.866
1 + a = 1Ð60° 0.5+ j0.866
Relation Between Phase Voltages and Symmetrical Component Voltages
Where [A] is known as operator matrix
Where
Note:
Effect on 3-f Power
Observations:
Effect on Impedance Matrix
Conclusions:
Two Conductors Open
va1 = va2 - Va0'=0
Conclusions:
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1. What are symmetrical components in electrical engineering? |
2. How are symmetrical components used in fault calculations? |
3. What are the advantages of using symmetrical components in fault analysis? |
4. How can symmetrical components help in identifying the type of fault in a power system? |
5. Are symmetrical components only applicable to three-phase systems? |
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