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6.8.7
Operation principle
The sampled analog phase currents are pre-processed in a discrete Fourier filter (DFT)
block. From the fundamental frequency components of each phase current the RMS value
of each phase current is derived. These phase current values are fed to a comparator in the
stub protection function STBPTOC (50STB). In a comparator the RMS values are
compared to the set operating current value of the function
IPickup
.
If a phase current is larger than the set operating current the signal from the comparator for
this phase is activated. If the fault current remains during the timer delay
t
, the TRIP output
signal is activated. The function can be blocked by activation of the BLOCK input.
BLOCK
TRIP
STUB PROTECTION FUNCTION
PU_A
PU_B
PU_C
OR
AND
ENABLE
en05000731_ansi.vsd
ANSI05000731 V1 EN
Figure 58:
Simplified logic diagram for Stub protection (50STB)
6.8.8
Technical data
Table 78:
STBPTOC (50STB) technical data
Function
Range or value
Accuracy
Operating current
(1-2500)% of
IBase
±
1.0% of I
n
at I
£
I
n
±
1.0% of I at I > I
n
Reset ratio
> 95%
-
Operate time
20 ms typically at 0 to 2 x I
set
-
Reset time
30 ms typically at 2 to 0 x I
set
-
Critical impulse time
10 ms typically at 0 to 2 x I
set
-
Impulse margin time
15 ms typically
-
Section 6
1MRK 511 287-UUS A
Current protection
144
Technical manual
Содержание REC650 ANSI
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