- #1
KraakeCrest
- 18
- 2
Hey,
I have some questions regarding zero sequence current flow in a multi phase system I was hoping some kind soul could help me with.
Imagine the following scenario illustrated in my bad paint drawing below:
A delta-wye(n) transformer are supplying a non linear load producing 3rd harmonics. These harmonics are being added and flow back in the neutral due to being in phase with each other.
Ok, fine so far.
Then the currents on the secondary side are being reflected on the primary delta side of the transformer, and from what I've read in this forum and literature they circulate inside the delta triangle.
Why do they circulate inside the delta, ok, let's see. Let's say a zero sequence current is flowing from a-c, how does it get back to a? Well, it could go a -> c -> b and back to a, and it could go a -> c -> C -> A and back to a.
1. So could one confirm if my way of thinking is correct, so I know if I fully understand this or not.
The reason the current goes a-c-b-a, is because it offers much lower impedance then a-c-C-A-a. The path a-c-b-a is essentially just the winding resistance of the transformer, while the path a-c-C-A-a is several miles of power lines + the internal impedance of the generator or supply transformer.
This is basically just based on threads posted here on the forum, and I made this post to see if someone could point to me if I understand this or not.2. Also one final thing, is my way of drawing the schematic above correct? I mean, I've not added any voltage source in the wye connection to the left, the reason is that I assumed that there is no supply of zero sequence voltage.Hope I made myself clear enough, if not, please do not hesitate to ask me.
-Kraake
I have some questions regarding zero sequence current flow in a multi phase system I was hoping some kind soul could help me with.
Imagine the following scenario illustrated in my bad paint drawing below:
A delta-wye(n) transformer are supplying a non linear load producing 3rd harmonics. These harmonics are being added and flow back in the neutral due to being in phase with each other.
Ok, fine so far.
Then the currents on the secondary side are being reflected on the primary delta side of the transformer, and from what I've read in this forum and literature they circulate inside the delta triangle.
Why do they circulate inside the delta, ok, let's see. Let's say a zero sequence current is flowing from a-c, how does it get back to a? Well, it could go a -> c -> b and back to a, and it could go a -> c -> C -> A and back to a.
1. So could one confirm if my way of thinking is correct, so I know if I fully understand this or not.
The reason the current goes a-c-b-a, is because it offers much lower impedance then a-c-C-A-a. The path a-c-b-a is essentially just the winding resistance of the transformer, while the path a-c-C-A-a is several miles of power lines + the internal impedance of the generator or supply transformer.
This is basically just based on threads posted here on the forum, and I made this post to see if someone could point to me if I understand this or not.2. Also one final thing, is my way of drawing the schematic above correct? I mean, I've not added any voltage source in the wye connection to the left, the reason is that I assumed that there is no supply of zero sequence voltage.Hope I made myself clear enough, if not, please do not hesitate to ask me.
-Kraake