Voltage Transformer Ratio
Voltage Transformer Ratio
(OP)
Hi Fellow Professionals,
Usually the VT ratio is given as for e.g 11kv/110V. But I've seen a different representation like 11kV/√3 / 110V/√3. Schneider's instrument transformer catalogue explains the first ratio representation is when primary voltage is connected between phases and the second representation is when the primary voltage is connected between phase and earth. How do we choose to connect the VT between phases or between phase and earth? Is there any specific requirement for that?
This is my first post. Please let me know if the question is not clear or additional information required.






RE: Voltage Transformer Ratio
RE: Voltage Transformer Ratio
RE: Voltage Transformer Ratio
Something in your post caught my attention.
You said you use VTs rated for 12470V systems (7200:120V) on your 13200V system. Given that the typical overvoltage factor is 1.1 continuous (could be 1.05 depending on the class per IEEE C57.13), that doesn't give you much head-room.
12470 * 1.1 = 13717V
13717/13200 = 1.039
Does your 13200V system have an overvoltage limitation of less than 4%?
RE: Voltage Transformer Ratio