Zero -Sequence Currents

[electrics]

İs this current flowing out of three phase system or any neutral imbalance is counted as zero-sequence current? The only way for this current to appear is grounded wye?

 

[roger]

In any system, be it single phase or three phase the current flowing in the conductors should equal zero, if for some reason the current going and coming on the system conductors does not equal zero, there is another path other than the conductors.

Roger

 

[al hildenbrand]

The term "zero sequence current" comes from the method of Symmetrical Components used to simplify analysis of, in modern power systems, the vector representation of 60 cycle current (a phasor) when the currents are not equal in magnitude and are not exactly 120? apart.

So, given a three wire three ? system, three non symmetrical current phasors can be represented by three sets of symmetrical phasors, the positive sequence, negative sequence and the zero sequence. The more non symmetrical the current phasors are the larger the zero sequence becomes. When the current phasors become symmetrical, the zero sequence phasors go to zero.

I only link to Wikipedia above, but a good electrical engineering handbook or site will carry this further.

 

[charlie b]

The only way for this current to appear is grounded wye?

I seem to recall that a delta connection cannot have any zero sequence currents. But I might have that wrong. I am not in the office, but my textbook is, so I will check later.

 

[richxtlc]

Zero sequence currents are only found during a fault or an imbalance between phases. There are three types of current, positive sequence, the normal rotation A followed by B followed by C, negative sequence of C followed by B followed by A, and zero sequence.