DOC. MIE91093 Rev. 1.34
Page 123 of 145
1.15.7
Connections for different transformers
Here below the connections for the most common situations.
Beware of the following.
When you test relays for Yd or Dy Transformers, since
the test is performed in single phase mode, a √3 =
1.732 coefficient is to be applied on the current flowing
in the Y connected pole. For a Yd transformer, the
Restraint and Differential Currents formulas are the
following:
o
Restraint Current:
2
)
(
3
2
3
2
1
1
I
I
I
I
I
I
B
A
R
o
Differential Current:
