arrehman1
Member
- Location
- Seattle, WA
While doodling delta connected CTs on engineering paper, I realized that the CT secondary line current which is going into the relay input terminal has no return path back to the CT secondary winding... for example, line current a goes through the terminal input A on the relay... it then gets added to line current B... then line current B gets added to line current C... IL,A + IL,B + IL,C essentially goes to ground. I understand that during balanced conditions, we'll have no (line) current flowing to ground.... but there is also no circulation of line current... Is this a correct way of thinking about it?
http://files.engineering.com/downlo...e2f-f1622e9f3752&file=delta_connected_Cts.pdf
Just as a comparison, for WYE connected CTs, we'll often see the non polarity side (X2 bushings) of the CT connected together which is also connected to the non-polarity side of the relay input terminal... and grounded in only one location of the secondary circuit. We can easily see the circulating path for secondary phase current.... even during unbalanced conditions, the phase currents circulate back to the CT secondary windings.
http://files.engineering.com/downlo...e2f-f1622e9f3752&file=delta_connected_Cts.pdf
Just as a comparison, for WYE connected CTs, we'll often see the non polarity side (X2 bushings) of the CT connected together which is also connected to the non-polarity side of the relay input terminal... and grounded in only one location of the secondary circuit. We can easily see the circulating path for secondary phase current.... even during unbalanced conditions, the phase currents circulate back to the CT secondary windings.