Figure 3.2-2 The initiation logic diagram for 51P
The measured phase currents are compared phase wise to the set 51P_Cur_Str. If the measured
value exceeds the set 51P_Cur_Str, the level detector reports the exceeding of the value to the
phase selection logic. If the 51P_Ena_Mult input is active, the 51P_Cur_Str value setting is
multiplied by the 51P_Mult_Cur_Str setting.
If the fault criteria are fulfilled in the level detector, the phase selection logic detects the phase or
phases in which the measured current exceeds the setting. If the phase information is equal to or
more than the 51P_Str_Ph_Num setting, the phase selection logic activates the “Initiation” signal.
Where:
51P_Cur_Str is the 51P start value.
51P_Mult_Cur_Str is the multiplier for scaling the start value.
51P_Op_Ph_Num is the Number of phases required for operate activation.
NOTICE!
Do not set the multiplier setting 51P_Mult_Cur_Str higher than necessary. If the value is
too high, the function may not operate at all during an inrush followed by a fault, no
matter how severe the fault is.
The start value multiplication is normally done when the inrush detection function
(OCR_INR) is connected to the Ena_Mult input by Three phase inrush function
OCR_INR.
Timer element
The functional module diagram is shown as below:
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