The function starts when the current exceeds the set limit. Each phase has its own
timer. The operating time characteristics for low-stage PH3LPTOC and high-stage
PH3HPTOC can be selected to be either definite time (DT) or inverse definite
minimum time (IDMT). The instantaneous stage PH3IPTOC always operates with
the DT characteristic.
In the DT mode, the function operates after a predefined operating 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".
The three-phase overcurrent protection 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 the three-phase overcurrent protection function can be described
using a module diagram. All the modules in the diagram are explained in the next
sections.
Section 4 1YHT530004D05 D
Protection functions
158 615 series
Technical Manual
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