ABB REO 517, Applications Manual

Page: 110 / 440

100
Sudden current change function (SCC)
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If the input signal SCC-RELEASE is activated and the setting Operation=Backup is se-
lected, the signal SCC-TRIP is activated simultaneously with the signal SCC-START.
The function is disabled (blocked) if:
• The terminal is in TEST mode (TEST-ACTIVE is high) and the function has been
blocked from the HMI (BlockSCC=Yes).
• The input signal SCC--BLOCK is high.
The SCC--BLOCK blocking signal can be connected to a binary input of the terminal
in order to receive a block command from external devices or can be software connect-
ed to other internal functions of the terminal itself in order to receive a block command
from internal functions. Through an OR gate it can be connected to both binary inputs
and internal functions outputs.
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The output signal SCC-START and the start signal ZnRW-START from the impedance
function should be configured to an AND-gate for the release of a trip signal to the line-
breaker. An example of the tripping logic for the impedance protection and the func-
tions SCC and SVC (Sudden voltage change function) is shown in figure 46.
en02000534.v sd
TEST-ACTIVE
BlockSCC = Yes
&
TEST
SCC-RELEASE
&
IL1
≥
1
&
Backup
SCC-BLOCK
SCC-TRIP
t
di
dt
≥
1
di
dt
SCC-START
IL2