ABB Relion 670 series, Technical Reference Manual

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a
b
a>b
BLOCK
AND
I
OP
Extract second
harmonic current
component
Extract
fundamental
current component
X
2ndHarmStab
a
b
a>b
a
b
a>b
0.07*IBase
ANSI13000015-1-en.vsd
2NDHARMD
Use_PUValue
Pickup1>
Pickup2>
Pickup3>
Pickup4>
a
b
a>b
|I
OP
|
OR
AND
BlkParTransf=On
q
-1
OR 2ndH_BLOCK_Int
0-70ms
0
ANSI13000015 V1 EN
Figure 209: Simplified logic diagram for 2nd harmonic blocking feature and Block for Parallel Transformers feature
7.4.2.9 Switch on to fault feature
Integrated in the four step residual overcurrent protection are Switch on to fault logic
(SOTF) and Under-Time logic. The setting parameter
SOTF is set to activate either
SOTF or Under-Time logic or both. When the circuit breaker is closing there is a risk
to close it onto a permanent fault, for example during an autoreclosing sequence. The
SOTF logic will enable fast fault clearance during such situations. The time during
which SOTF and Under-Time logics will be active after activation is defined by the
setting parameter
t4U .
The SOTF logic uses the pickup signal from step 2 or step 3 for its operation, selected
by setting parameter
StepForSOTF . The SOTF logic can be activated either from
Section 7
1MRK505222-UUS C
Current protection
410
Technical reference manual