4.1.3.2
Function block
Figure 133: Function block
4.1.3.3
Functionality
The three-phase directional overcurrent protection function DPHxPDOC is used
as one-phase, two-phase or three-phase directional overcurrent and short-circuit
protection for feeders.
DPHxPDOC starts up when the value of the current exceeds the set limit and
directional criterion is fulfilled. The operate time characteristics for low stage
DPHLPDOC and high stage DPHHPDOC 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.
4.1.3.4
Operation principle
The function can be enabled and disabled with the
Operation setting. The
corresponding parameter values are "On" and "Off".
The operation of DPHxPDOC can be described using a module diagram. All the
modules in the diagram are explained in the next sections.
Protection functions
1MRS757644 H
274
620 series
Technical Manual
