ABB REG670 - Operation Principle

8.2.7 Operation principle
The Four step phase overcurrent protection OC4PTOC is divided into four different
sub-functions, one for each step. For each step x , where x is step 1, 2, 3 and 4, an
operation mode is set by DirModex: Off/Non-directional/Forward/Reverse.
The protection design can be divided in four parts:
• The direction element
• The harmonic Restraint Blocking function
• The four step over current function
• The mode selection
If VT inputs are not available or not connected, setting parameter
DirModex shall be left to default value, Non-directional.
en05000740-2-en.vsd
Direction
Element
4 step over current
element
One element for each
step
Harmonic
Restraint
Mode Selection
dirPh1Flt
dirPh2Flt
dirPh3Flt
harmRestrBlock
enableDir
enableStep1-4
DirectionalMode1-4
faultState
Element
faultState
I3P
U3P
START
TRIP
IEC05000740 V2 EN
Figure 158: Functional overview of OC4PTOC
1MRK502052-UEN B Section 8
Current protection
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Technical manual