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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