4.2.2.3 Functionality
The earth-fault function DEFxPDEF is used as directional earth-fault protection for
feeders.
The function starts and operates when the operating quantity (current) and
polarizing quantity (voltage) exceed the set limits and the angle between them is
inside the set operating sector. The operate time characteristic for low stage
(DEFLPDEF) and high stage (DEFHPDEF) can be selected to be either definite
time (DT) or inverse definite minimum time (IDMT).
In the DT mode, the function operates after a predefined operate time and resets
when the fault current disappears. The IDMT mode provides current-dependent
timer characteristics.
The function contains a blocking functionality. It is possible to block function
outputs, timers or the function itself, if desired.
4.2.2.4 Operation principle
The function can be enabled and disabled with the Operation setting. The
corresponding parameter values are "On" and "Off".
The operation of directional earth-fault protection can be described using a module
diagram. All the modules in the diagram are explained in the next sections.
A070438 V3 EN
Figure 134: Functional module diagram. Io and Uo represent the residual
current and residual voltage. I
2
and U
2
represent the negative
sequence components for current and voltage.
Level detector
The operating quantity (residual current) can be selected with the setting Io signal
Sel. The selectable options are "Measured Io" and "Calculated Io" respectively. The
polarizing quantity can be selected with the setting Pol signal Sel. The selectable
options are "Measured Uo", "Calculated Uo" and "Neg. seq. volt". The magnitude
of the operating quantity is compared to the set Start value and the magnitude of
Section 4 1YHT530004D05 D
Protection functions
274 615 series
Technical Manual
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