ABB RELION REF615R, Technical Manual

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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 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 54: 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.
Do not set the multiplier setting Pickup value Mult higher than necessary.
If the value is too high, the function may not trip at all during an inrush
followed by a fault, no matter how severe the fault is.
The pickup value multiplication is normally done when the inrush detection function
(INR) is connected to the
ENA_MULT input.
Section 4
1MRS240050-IB C
Protection functions
114 REF615R
Technical Manual