Symmetrical Components Made Easy – Part 2

In the last post we examined and calculated the symmetrical components in a non-faulted, three-phase electrical power system.  This post expands on the same process of using phasor diagrams to describe, illustrate, visualize and calculate the three symmetrical components: Positive Sequence, Negative Sequence and Zero Sequence.  An examination of a phase to neutral (also referred to as phase to ground) fault will be conducted.

Positive Sequence Components B-N Fault

Positive Sequence phase to neutral fault

Thus, there is significant positive sequence in the phase to neutral fault and the positive sequence phasor is lagging the reference phase (phase A).

Negative Sequence Components B-N Fault

negative sequence phase to neutral fault

Thus, there is some negative sequence in the phase to neutral fault and the negative sequence phasor is leading the reference phase (phase A).

Zero Sequence Components B-N Fault

zero sequence phase to neutral fault

 

Thus, there is some zero sequence in the phase to neutral fault.

Conclusion:

  • Sequence components can be calculated and illustrated using phasor diagrams for a phase to neutral fault.
  • There are positive, negative and zero sequence components in a B-N fault; whereas a non-faulted system has only positive sequence – see “Symmetrical Components Made Easy – Part 1

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