The function is based on the asymmetic differential current. If the content of asymmetry of two phases
exceeds the allowed degree of asymmetry, differential protection will be blocked. In order to prevent a mal-
function under single phase earthed fault, another degree of asymmetry the max phase criterion is used to
unblock this logic.
The restraint with harmonics does not influence the stage
I-DIFF>>
.
See following logic diagram for the details:
[lo_cwa-7utx, 1, en_GB]
Figure 2-51
Logic Current Waveform Analysis Restraint (CWA)
i
i
NOTE
The current values
Ι
/
Ι
NO
in the settings overview below always refer to the rated current of the main
protected object. The current values
Ι
/
Ι
NS
always refer to the rated current of the relevant side of the main
protected object.
Settings
Addresses which have an appended “A” can only be changed with DIGSI, under “Additional Settings”.
Addr.
Parameter
Setting Options
Default Setting
Comments
1201
DIFF. PROT.
OFF
ON
Block relay
OFF
Differential Protection
1205
INC.CHAR.START
OFF
ON
OFF
Increase of Trip Char. During Start
1206
INRUSH 2.HARM.
OFF
ON
ON
Inrush with 2. Harmonic Restraint
1207
RESTR. n.HARM.
OFF
3. Harmonic
5. Harmonic
OFF
n-th Harmonic Restraint
1208
I-DIFF> MON.
OFF
ON
ON
Differential Current monitoring
1210
I> CURR. GUARD
0.20 .. 2.00 I/InS; 0
0.00 I/InS
I> for Current Guard
1211A
DIFFw.IE1-MEAS
NO
YES
NO
Diff-Prot. with meas. Earth Current
S1
1212A
DIFFw.IE2-MEAS
NO
YES
NO
Diff-Prot. with meas. Earth Current
S2
2.2.8
Functions
2.2 Differential Protection
SIPROTEC 4, 7UT6x, Manual
121
C53000-G1176-C230-5, Edition 09.2016
Summary of Contents for SIPROTEC 4 7UT6 Series
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