ABB RET670 - Page 63

L1
(A)
L2
(B)
L3
(C)
Protected Object
CT 1500/5
Star/Wye
Connected
7
8
9
10
11
12
1
2
3
4
5
6
AI01 (I)
AI02 (I)
AI03 (I)
AI04 (I)
AI05 (I)
AI06 (I)
6
7
8
IED
X1
R
1
1
2
4 5
U
R
2
1
3
4
2
1 2 3
N
1-Ph Plate with Metrosil and Resistor
2
3
5
4
9
N
L1
(A)
L2
(B)
L3
(C)
C
T
1
5
0
0
/
5
1
IEC07000194_2_en.vsd
AI3P
AI1
AI2
AI3
AI4
AIN
SMAI2
BLOCK
^GRP2L1
^GRP2L2
^GRP2L3
^GRP2N
TYPE
IEC07000194 V2 EN
Figure 29: CT connections for restricted earth fault protection
Pos Description
1 Scheme earthing point
Note that it is of outmost importance to insure that only one earthing point
exist in such scheme.
2 One-phase plate with setting resistor and metrosil.
3 Necessary connection for the metrosil. Shown connections are applicable for both types of one-
phase plate.
4 Position of optional test switch for secondary injection into the high impedance differential IED.
5 Necessary connection for setting resistor. Shown connections are applicable for both types of
one-phase plate.
6 How to connect REFPDIF high impedance scheme to one CT input in IED.
7 Transformer input module where this current input is located.
Note that the CT ratio for high impedance differential protection application
must be set as one.
• For main CTs with 1A secondary rating the following setting values shall be entered:
CTprim = 1A and CTsec = 1A
• For main CTs with 5A secondary rating the following setting values shall be entered:
CTprim = 5A and CTsec = 5A
• The parameter CTStarPoint shall always be left to the default value ToObject
1MRK 504 088-UEN C Section 5
Installing the IED
57
Installation and commissioning manual