5 Necessary connection for setting resistors.
6 Factory-made star point on a three-phase setting resistor set.
The star point connector must be removed for installations with 670 series IEDs.
This star point is required for RADHA schemes only.
7 Connections of three individual phase currents for high impedance scheme to three CT inputs in the
IED.
6.1.3.2 Connections for 1Ph High impedance differential protection HZPDIF
GUID-D68A237F-610C-4AF0-870F-273117F64D92 v10
Restricted earth fault protection is a typical application for 1Ph High impedance differential
protection HZPDIF. Typical CT connections for the high impedance based protection scheme
are shown in figure 35.
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
X1
R1
1
2
4 5
U
R2
1
3
4
2
1 2 3
N
1-Ph Plate with Metrosil and Resistor
2
3
5
4
N
L1
(A)
L2
(B)
L3
(C)
CT 1500/5
1
IEC07000194_4_en.vsd
AI3P
AI1
AI2
AI3
AI4
AIN
SMAI2
BLOCK
^GRP2L1
^GRP2L2
^GRP2L3
^GRP2N
TYPE
IEC07000194 V4 EN-US
Figure 35: CT connections for restricted earth fault protection
Pos Description
1 Scheme earthing point
Ensure that only one earthing point exists in this scheme.
2 One-phase plate with stabilizing resistor and metrosil. Protective earth is a separate 4 mm screw
terminal on the plate.
3 Necessary connection for the metrosil.
4 Position of optional test switch for secondary injection into the high impedance differential IED.
5 Necessary connection for stabilizing resistor.
6 How to connect the high impedance restricted earth fault protection scheme to one CT input in IED.
1MRK 511 358-UEN A Section 6
Differential protection
93
Application manual
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