ABB COM600 series, User'S & Technical Manual, Page: 14 / 60

functional_module_diagram.png
Figure 4.3-1 Functional module diagram
Fault loop indication (PSL)
The fault distance calculation is done in two steps. The fault type is determined with the
inbuilt Phase Selection Logic (PSL) and then the fault distance is calculated.
As a fundamental operation criterion, it is required that the phase current and voltage
magnitudes must exceed the threshold values of 2% Ir and 3% Ur, respectively.
For cases where positive-sequence components or phase-to-phase signals are used for
fault distance indication, the corresponding threshold values are scaled, accordingly, to
the one-third or one-to-square-root-three of the phase signal limits.
If the zero-clamping condition is not met, the output and monitored data of the function
is reset.
Fault type selection
The identification of the faulty phases is compulsory for the correct operation of SCE-
FRFLO. This is because only one of the impedance-measuring elements (fault loops)
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1MRS758734 COM600 series 5.1
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