VT Secondary winding voltage rating
VT Secondary winding voltage rating
(OP)
Hi
Could someone please explain the following from a VT spec.
Voltage ratio = (11kV/1.732):110V/1.732 : 110/3
There are two secondary windings. I understand that the primary has 11kV line-to-line volts and the 1st secondary winding has 110V line to line and 63.5V line to neutral. What puzzles me is why the 2nd winding (a broken delta one) is given as 110/3? does this mean the line to neutral volts = 36.67V?
I understand that the voltage at the broken delta would be 3V0 but am really puzzled by the 110/3.![[ponder] ponder](https://www.tipmaster.com/images/ponder.gif)
Thanks.
Could someone please explain the following from a VT spec.
Voltage ratio = (11kV/1.732):110V/1.732 : 110/3
There are two secondary windings. I understand that the primary has 11kV line-to-line volts and the 1st secondary winding has 110V line to line and 63.5V line to neutral. What puzzles me is why the 2nd winding (a broken delta one) is given as 110/3? does this mean the line to neutral volts = 36.67V?
I understand that the voltage at the broken delta would be 3V0 but am really puzzled by the 110/3.
![[ponder] ponder](https://www.tipmaster.com/images/ponder.gif)
Thanks.






RE: VT Secondary winding voltage rating
RE: VT Secondary winding voltage rating
RE: VT Secondary winding voltage rating
I hear what you say but I still do not get it. The way I see it, the "broken delta" voltage is 3V0 = Va + VB + VC. Each phase voltage is 110/3 = 36.67V and 120degrees apart under normal healthy conditions.
With an earthfault, let's say VA is reduced to 0. Then 3V0 = VB + VC = 36.67<-120 + VC<120 = 36.67<180V which is a long way off from 110V???
What am I missing?
Thanks.
RE: VT Secondary winding voltage rating
RE: VT Secondary winding voltage rating
CODE
= -------------- = 173.2
110/3
CODE
VBD = ----------------------------------
turns ratio
= (3 X 11,000/1.732)/ 173.2 = 110 volts
RE: VT Secondary winding voltage rating
With solid earthing there is no appreciable neutral shift under earthfault conditions and so the delta voltages can be the conventional 110/1.732 to give a delta output of 63.5 during an earthfault.
If the latter delta was used for high resistance earthing the delta output could be as high as 1.732 * 110V during an earthfault.
Thanks again and regards.