Bushing CT Symbol?
Bushing CT Symbol?
(OP)
I use this CT symbol all the time but have not found a reference to what it means. The symbol is used for medium/high voltage power circuit breakers. What I am trying to figure out is why one of the turns is larger than the others?
I looked at the physical construction of one of the CTs and it is one physical torroidal CT. I assume that the manufacturer took a "more common" ratio, say 800:5, and added more turns to make it 1200:5.
What I am trying to figure out is why one of the turns is larger than the others?
I looked at the physical construction of one of the CTs and it is one physical torroidal CT. I assume that the manufacturer took a "more common" ratio, say 800:5, and added more turns to make it 1200:5.
What I am trying to figure out is why one of the turns is larger than the others?






RE: Bushing CT Symbol?
For example, in the 1200:5 multi-ratio CTs that we use you would see that from X1 to X2 is 2/12 of the winding, from X2 to X3 is 1/12 of the secondary, from X3 to X4 is 5/12 of the winding, and from X4 to X5 is 4/12 of the total secondary winding.
I suspect that the symbol is intended to represent via the oversized loop and the bar that it is comprised of different sized tapable sections and is consequently a MR CT. By this putative logic, a single ratio CT would have equally sized loops and no bar.
RE: Bushing CT Symbol?
There are (in the ANSI world, anyway), standard ratios for multi-ratio CTs as well as single ratio CTs.
David Castor
www.cvoes.com
RE: Bushing CT Symbol?