ABB RED650 Technical Manual page 178

Section 8
Current protection
172
• The direction element
• The harmonic restraint blocking function
• The four step overcurrent function
• The mode selection
If VT inputs are not available or not connected, setting parameter
DirModex shall be left to default value, Non-directional.
Direction
faultState
Element
I3P
U3P
Harmonic
Restraint
Element
Mode Selection
IEC05000740 V3 EN-US
Figure 75: Functional overview of OC4PTOC
A common setting for all steps, StartPhSel, is used to specify the number of phase
currents to be high to enable operation. These settings can be chosen: 1 out of 3, 2
out of 3 or 3 out of 3.
Using a parameter setting MeasType within the general settings for the function
OC4PTOC, it is possible to select the type of the measurement used for all
overcurrent stages. Either discrete Fourier filter (DFT) or true RMS filter (RMS)
can be selected.
If the DFT option is selected, only the RMS value of the fundamental frequency
component of each phase current is derived. The influence of the DC current
component and higher harmonic current components are almost completely
suppressed. If the RMS option is selected, then the true RMS value is used. The
true RMS value includes the contribution from the current DC component as well
as from the higher current harmonic in addition to the fundamental frequency
component.
4 step overcurrent
dirPh1Flt
One element for each
dirPh2Flt
dirPh3Flt
harmRestrBlock
enableDir
enableStep1-4
DirectionalMode1-4
Line differential protection RED650 2.2 IEC
1MRK 505 394-UEN A
element
faultState
step
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IEC05000740-3-en.vsdx
M12883-16 v11
Technical manual