Specifications

7SR242 Duobias Applications Guide
Solution 2
Figure 6.4-2 shows use of the ICT Connection settings to correct for the phase shift introduced by the transformer
connection i.e. ICT1 Connection is set to to Yd9, -90° and ICT2 Connection is set to Ydy0, 0°.
ICT1 = Yd9
W1/W2
Yd11 (30
o
)
1718
12
56
910
1413
I
G1
21
65
109
W1 I
L1
W1 I
L2
W1 I
L3
ICT2 = Ydy0
A
1718
I
G2
12
56
910
W2 I
L1
W2 I
L2
W2 I
L3
A
B
NOTES
CTs shown wired
to 1A relay inputs
a
b
c
A
B
C
a
c
b
CB
A
A-N = b-c
B-N = c-a
C-N = a-b
Figure 6-6 AC Connections: Yd9, 90
0
Transformer – Standard Secondary Connections
Notes:
An advantage of the approach above is that ‘standard’ secondary wiring connections are used.
The 7SR24 relay setting correspond to the power system vector relationship i.e. Yd9, 90°.
Relay instruments will indicate ’system’ quantities rather than transformer quantities.
©2010 Siemens Protection Devices Limited Chapter 7 Page 53 of 56