Siemens 7UT51 User Manual

4
Transformer Differential Protection (87T and 87HS)
7UT51 v3
54 PRIM-2330C
Internal Single Phase to Ground Fault with
Io
-
Correction
Refer to Figure 4.8
4.3.7 Using a Ground or Neutral
Current CT
If the protection application includes measuring one or
two ground currents (or neutral currents), relay model
7UT513 must be used. If the relay is ordered with the
optional tank-leakage protection, one of the relay’s two
ground-current inputs measures the absolute ground
current. If instead the relay was ordered with the
ground-differential protection option, both
ground-current inputs measure the ground current as
a multiple of the rated nominal current of the reference
winding of the protected transformer,
I
n
. Addresses
7806 and 7807 tell the relay how the corresponding
ground current input is to be used.
0*
*
0
*
*
*
01
0
0
0
0
∠=
=
=
=
=
N
C
B
A
I
I
I
I
I
Wye-Winding Currents after
I0-Correction:
Wye-Winding
Currents:
Delta-Winding
Currents:
0
1801
01
0
0
01
*
2
*
3
*
0*
1
*
2
*
0*
3
*
1
*
*
3
*
2
0*
1
=−=
∠=−=
∠=−=
=
=
∠=
III
III
III
I
I
I
c
b
a
⎥
⎥
⎥
⎥
⎥
⎦
⎤
⎢
⎢
⎢
⎢
⎢
⎣
⎡
∠
∠
∠
=
⎥
⎥
⎥
⎦
⎤
⎢
⎢
⎢
⎣
⎡
⎥
⎥
⎥
⎦
⎤
⎢
⎢
⎢
⎣
⎡
−
=
⎥
⎥
⎥
⎥
⎦
⎤
⎢
⎢
⎢
⎢
⎣
⎡
0
0
0
*
*
*
*
lim,3
*
lim,2
*
lim,1
180
3
1
180
3
1
0
3
2
1...0....1
1...1....0...
0...1....1...
3
1
c
b
a
E
E
E
I
I
I
I
I
I
Trip !
with
maximum
sensitivity
Differential
Current:
0
0
1
*
lim,3
*
,
*
,
*
lim,2
*
,
*
,
*
lim,1
*
,
*
,
=+=
=+=
=+=
ECorrCCD
ECorrBBD
ECorrAAD
III
III
III
Delta-Winding Currents after I0-Elimination
and Phase-Shift Correction:
0***
,
0***
,
0***
,
0
3
1
3
1
0
3
1
3
1
0
3
1
3
1
∠=+=
∠=+=
∠=+=
NCCorrC
NBCorrB
NACorrA
III
III
III
7806 STAR
-
POINT A (7UT513 only)
7807 STAR
-
POINT B (7UT513 with 87N option only)
What is connected to each ground
-
current input of the relay.
Option Description
NO
ASSIGNMENT
No CT is connected to this
ground
-
current input (default).
SIDE 1 A CT monitoring the ground or neutral
current of Winding 1 of the protected
transformer.
SIDE 2 A CT monitoring the ground or neutral
current of winding 2 of the protected
transformer.
SIDE 3 / V. OBJ A CT monitoring the ground or neutral
current of winding 3 of the principal
protected transformer, or the ground or
neutral current of a separate, additional
protected device (see Chapter 11).

Siemens 7UT51 Specifications

General

Brand	Siemens
Model	7UT51
Category	Relays
Language	English