The FAIL output will be set to a logical one when the following criteria are fulfilled:
• The numerical value of the difference |ΣIphase| – |Iref| is higher than 80% of the numerical
value of the sum |ΣIphase| + |Iref|.
• The numerical value of the current |ΣIphase| – |Iref| is equal to or higher than the set trip value
IMinOp
.
• No phase current has exceeded
Pickup_Block
during the last 10 ms.
• CCSSPVC (87) is enabled by setting
Operation
=
Enabled
.
The FAIL output remains activated 100 ms after the AND-gate resets when being activated for
more than 20 ms. If the FAIL lasts for more than 150 ms an ALARM will be issued. In this case the
FAIL and ALARM will remain activated 1 s after the AND-gate resets. This prevents unwanted
resetting of the blocking function when phase current supervision element(s) trip, for example,
during a fault.
I
A
I
B
I
C
I
ref
+
-
+
+
I>1.054 * IMinOp
+
-
AND
10 ms
OPERATION
100 ms
3000 ms170 ms
40 ms
FAIL
ALARM
I
A
I
B
I
C
I
ref
BLOCK
OR
OR
I>IP>Block
t
ANSI05000463-2-en.vsd
x
0,8
ANSI05000463 V2 EN-US
Figure 388: Simplified logic diagram for Current circuit supervision CCSSPVC (87)
The trip characteristic is percentage restrained, see figure 389.
Slope = 0.8
Slope = 1
Operation
area
I
MinOp
99000068.vsd
phase ref
|
å
I
| - | I |
phase ref
|
å
I
| + | I
|
IEC99000068 V1 EN-US
Figure 389: Trip characteristics
1MRK 502 066-UUS B Section 13
Secondary system supervision
729
Technical manual
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