ABB Relion 670 series - Page 494

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
2
N
D
H
A
R
M
D
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-US
Figure 257: Simplified logic diagram for 2nd harmonic blocking feature and Block for Parallel Transformers
feature
8.4.7.10 Switch on to fault feature
M13941-211 v4
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 change in circuit breaker
position or from circuit breaker close command pulse. The setting parameter
SOTFSel can be set
for activation of CB position open change, CB position closed change or CB close command. In
case of a residual current pickup from step 2 or 3 (dependent on setting) the function will give a
trip after a set delay
tSOTF . This delay is normally set to a short time (default 200 ms).
Section 8 1MRK 502 066-UUS B
Current protection
488
Technical manual