4.3.3.2 Function block
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Figure 223: Function block
4.3.3.3 Functionality
The stabilized restricted low-impedance earth-fault protection LREFPNDF for a two-
winding transformer is based on the numerically stabilized differential current
principle. No external stabilizing resistor or non-linear resistor are required.
The fundamental components of the currents are used for calculating the residual
current of the phase currents, the neutral current, differential currents and
stabilizing currents. The operating characteristics are according to the definite time.
LREFPNDF contains a blocking functionality. The neutral current second
harmonic is used for blocking during the transformer inrush situation. It is also
possible to block function outputs, timers or the function itself, if desired.
4.3.3.4 Operation principle
The function can be enabled and disabled with the Operation setting. The
corresponding parameter values are "On" and "Off".
The operation of the stabilized restricted low-impedance earth-fault protection can
be described using a module diagram. All the modules in the diagram are explained
in the next sections.
GUID-079EB39A-B62C-47DF-9B53-9432AB24A9CE V2 EN
Figure 224: Functional module diagram
1YHT530004D05 D Section 4
Protection functions
615 series 423
Technical Manual
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