ABB REG316 4 Series - Page 83

REG 316*4 1MRB520049-Uen / Rev. F ABB Switzerland Ltd
3-45
Compensation for group of connection
Phase-to-phase currents are measured in order to compare pri-
mary and secondary currents without regard to the circuit of the
transformer. The combination of these currents internally in the
protection takes account, however, of their phase relationships.
The relationships between the current vectors for different
groups of connection can be seen from the following illustrations.
For example, for a Yd5 connected transformer
R
S
T
R
S
T
I
1R
I
I
1R
1S
1T
2R
2S
2T
150°
I
I
I
I
I
HEST 905 005 C
· Star-connected primary
· Delta-connected secondary
· Phase-angle between the currents of
the same phase on both sides
5 x 30° = 150°
I
I
1r (compensated) 1R 1S
2r (compensated) 2R
1/ 3 ( I I )
I
=-+
=
ì
í
ï
î
ï
R
S
T
R
S
T
R
S
T
R
S
T
R
S
T
R
S
T
I
1R
2R
I
R
S
T
R
S
T
Yy0
Yy6
Yd1
Yd5
1
2
I
1R 2R
I
12
I
1R
2R
I
2
I
1R
2R
I
2
R
S
T
R
S
T
R
S
T
R
S
T
2 2
Yd7 Yd11
I
1R
2R
I
I
1R
2R
I
HEST 905 006 C
1
1
1
1