Reflection of harmonics through Y-d, D-d and D-y transformers

[powereng91]

Can anyone clarify for me which order harmonics can be reflected through these different transformer configurations? I understand that the 3rd harmonic can not be reflected through a Y-d or D-y transformer but other order harmonics can. Will all harmonics be reflected through a delta-delta transformer? What are the implications of these harmonics being reflected back to the a generator source and how do I determine which harmonics may cause issues for the generators. Thanks.

 

[davidbeach]

Define "reflected". I have one idea about what you might mean, but can easily come up with a completely different definition also.

 

[powereng91]

Will these harmonic components be seen on the other side of the transformer (reflected).

 

[davidbeach]

I thought that's what you might mean, but it could have had the optics meaning of reflected instead.

1st harmonic (fundamental) is positive sequence.

2nd harmonic is negative sequence.

3rd harmonic is zero sequence.

4th harmonic is positive sequence.

etc.


The way that those sequences pass through the transformer is how those harmonics will. Remember that the phase shift for positive and negative sequences are not the same.

 

[sibeen]

Have a think about what a zero sequence harmonic voltage will do across a coil. A 2V, on all three phases, appearing at a delta coil. What is the PD across the coil = 0. Across a Y configuration, a totally different result