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.
4.1.2.4 Operation principle
The function can be enabled and disabled with the
Operation
setting. The
corresponding parameter values are "On" and "Off".
PH3xPTOC is used as single-phase and three-phase non-directional overcurrent and
short circuit protection. The phase operation mode is selected with the
Operation
curve type
setting. The operation is further specified with the
Num of start phases
setting, which sets the number of phases in which the current must exceed the
set current start value before the corresponding start and operating signals can be
activated.
The operation of PH3xPTOC can be described by using a module diagram. All the
modules in the diagram are explained in the next sections.
Figure 126: Functional module diagram
Level detector
The measured phase currents are compared phasewise to the set
Start value
. If the
measured value exceeds the set
Start value
, the level detector reports the exceeding
1MRS757644 H
Protection functions
620 series
Technical Manual
257
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