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1MRK 505 288-UEN A
7.2.2
7.2.3
Technical manual
Functionality
The four step residual overcurrent protection, zero or negative sequence direction
(EF4PTOC) has a settable inverse or definite time delay independent for step 1 and 4
separately. Step 2 and 3 are always definite time delayed.
All IEC and ANSI inverse time characteristics are available.
EF4PTOC can be set directional or non-directional independently for each of the
steps.
The directional part of the function can be set to operate on following combinations:
•
Directional current (I3PDir) versus Polarizing voltage (U3PPol)
•
Directional current (I3PDir) versus Polarizing current (I3PPol)
•
Directional current (I3PDir) versus Dual polarizing (UPol+ZPol x IPol) where
ZPol = RPol + jXPol
IDir, UPol and IPol can be independently selected to be either zero sequence or
negative sequence.
Other setting combinations are possible, but not recommended.
Second harmonic blocking level can be set for the function and can be used to block
each step individually.
Function block
EF4PTOC
I3P*
TRIP
U3P*
TR1
I3PPOL*
TR2
I3PDIR*
TR3
BLOCK
TR4
BLKST1
START
BLKST2
ST1
BLKST3
ST2
BLKST4
ST3
ST4
STFW
STRV
2NDHARMD
IEC08000004-2-en.vsd
IEC08000004 V2 EN
Figure 36:
EF4PTOC function block
Section 7
Current protection
89
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