Symmetrical Components Calculations

This calculation works for phasors such as current and voltage, and for vectors such as impedance. The calculations assume system phase sequence of 1-2-3.

To find positive sequence (subscript 1):

1. Rotate phase 2 by 120 degrees counter clockwise.

2. Rotate phase 3 by 240 degrees counter clockwise.

3. Convert all three phases to their rectangular coordinate equivalents.

4. Sum all three horizontal components.

5. Sum all three vertical components.

6. Convert resultant rectangular coordinates to their polar coordnate equivalent.

7. Value is positive sequence component of phase 1.

8. Phase 2 positive sequence is equal in magnitude to phase 1. Phase 2 positive sequence angle is equal to phase 1 positive sequence angle with an added 120 degree rotation in a clockwise direction.

9. Phase 3 positive sequence is equal in magnitude to phase 1. Phase 3 positive sequence angle is equal to phase 1 positive sequence angle with an added 240 degree rotation in a clockwise direction.



To find negative sequence (subscript 2):

1. Rotate phase 2 by 240 degrees counter clockwise.

2. Rotate phase 3 by 120 degrees counter clockwise.

3. Convert all three phases to their rectangular coordinate equivalents.

4. Sum all three horizontal components.

5. Sum all three vertical components.

6. Convert resultant rectangular coordinates to their polar coordnate equivalent.

7. Value is negative sequence component of phase 1.

8. Phase 2 negative sequence is equal in magnitude to phase 1. Phase 2 negative sequence angle is equal to phase 1 negative sequence angle with an added 240 degree rotation in a clockwise direction.

9. Phase 3 negative sequence is equal in magnitude to phase 1. Phase 3 negative sequence angle is equal to phase 1 negative sequence angle with an added 120 degree rotation in a clockwise direction.



To find zero sequence (subscript 0):

1. Convert all three phases to their rectangular coordinate equivalents.

2. Sum all three horizontal components.

3. Sum all three vertical components.

4. Convert resultant rectangular coordinates to their polar coordnate equivalent.

5. Value is 100% residual component of 3-phase system.

6. Zero sequence is found by dividing residual value by 3.

7. Value is zero sequence component of any one of the three phases. (All three phases' zero sequence components are equal in magnitude and in their anglular displacement.)