Describing The Transformer - Siemens 7UT51 Instruction Manual

7UT51 v3
Figure 4.5 Typical CT Wiring for a Three
4.2 Describing the
Transformer
This section describes the addresses used to provide
the relay with information about the protected
transformer, including:
• The number of windings the transformer has
• The rated frequency of the protected transformer
• The rated phase-to-phase voltage (V
winding of the protected transformer
PRIM-2330C
Prim ary
A
C B
c b
Secondary
c' b ' a '
Tertiary
-
Winding, Delta
) of each
n
Transformer Differential Protection (87T and 87HS)
I
3 A 1
A
I
2 A 1
B
I
1 A 1
C
I
3 B 1
a
I
2 B 1
b
I
a
1 B 1
c
I
3 D 1
a'
I
2 C 1
b'
I
1 C 1
c '
- -
Wye Delta Transformer
• The rated apparent power (VA) of each winding of
the protected transformer
• The phase shift (lag angle relative to Winding 1) of
winding 2 (and, if applicable, of winding 3) of the
protected transformer
In the following discussion, "Winding 1" is the
reference winding, which is usually the high-side
winding of the protected transformer. If a CT is
installed in the ground lead of a grounded wye
connected transformer, that winding must be used as
the reference winding in order to ensure increased
ground-fault sensitivity by correction of the zero
sequence current.
3 A 2
2 A 2
1 A 2
3 B 2
2 B 2
1 B 2
3 D 2
2 C 2
1 C 2
7UT513
4
43