inverse definite minimum time (IDMT). The instantaneous stage 50P-3 always trips with
the DT characteristic.
In the DT mode, the function trips after a predefined trip 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.
4.1.1.4 Operation principle
The function can be enabled and disabled with the Operation setting. The corresponding
parameter values are “Enable” and “Disable”.
The operation of 51P, 50P, 50P-3 can be described by using a module diagram. All the
modules in the diagram are explained in the next sections.
A070552-ANSI V1 EN
Figure 105: Functional module diagram
Level detector
The measured phase currents are compared phasewise to the set Pickup value. If the
measured value exceeds the set Pickup value, the level detector reports the exceeding of
the value to the phase selection logic. If the ENA_MULT input is active, the Pickup value
setting is multiplied by the Pickup value Mult setting.
The protection relay does not accept the Pickup value or Pickup value
Mult setting if the product of these settings exceeds the Pickup value
setting range.
The pickup value multiplication is normally done when the inrush detection function
(INR) is connected to the ENA_MULT input.
Section 4 1MAC059074-MB A
Protection functions
212 615 series ANSI
Technical Manual
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