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overcurrent elements NOC1 and NOC2 with independent thresholds output trip signals NOC1
TRIP and NOC2 ALARM through delayed pick-up timers TNC1 and TNC2.
ICD is the inrush current detector ICD, which detects second harmonic inrush current during
transformer energisation, and can block the NOC1D element by the scheme switches [NC1-2F].
See Section 2.1.7.
The tripping and alarming can be disabled by the scheme switches [NC1EN], [NC2EN],
[APPL-CT] or PLC logic signals NOC1 BLOCK and NOC2 BLOCK.
The scheme switch [APPL-CT] is available in which three-phase overcurrent protection can be
selected. The NOC protection is enabled when three-phase current is introduced and [APPL-CT]
is set to "3P".
Note: The [APPL-CT] setting can be set only from the LCD screen because it is concerned in
hardware configuration.
124, 1816
NOC1I
[MNC1]
+
"IEC"
"IEEE"
"US"
"CON"
"DT"
108, 1800
NOC1D
OP. BLOCK
[NC1-2F]
+
&
"BLK"
ICD
[NC1EN]
+
"ON"
[APPL-CT]
+
"3P"
NOC1 BLOCK
1560
Figure 2.1.24
Negative Sequence Overcurrent Protection NOC1 Scheme Logic
109, 1801
NOC2
OP. BLOCK
[NC2-2F]
+
"BLK"
&
ICD
[NC2EN]
+
"ON"
[APPL-CT]
+
"3P"
NOC2 BLOCK
1561
Figure 2.1.25
Negative Sequence Overcurrent Protection NOC2 Scheme Logic
&
&
0.00 - 300.00s
1
&
1
⎯
⎯
34
≥ 1
TNC1
0
t
TNC2
436
t
0
0.00 - 300.00s
6 F 2 S 0 8 4 2
435
NOC1 TRIP
NOC2 TRIP
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