If the operating mode is set to “Low imped. / IP,max”, the formula to calculate
the restraining current remains unchanged from the application for a single end.
But now the highest phase current is calculated from the amplitude-matched
sum of the currents on the relevant phase of all ends involved.
I
R,N
= 0.5·(max{|I
A
|,|I
B
|,|I
C
|} + k
am,Y
·|I
a,Y
|) (unchanged)
with I
x
= k
am,a
·I
x,a
+ k
am,b
·I
x,b
+ k
am,c
·I
x,c
+ k
am,d
·I
x,d
for x = A, B or C
The value pairs ( I
d,N
/ I
R,N
) calculated with the above formula are then compared
with the already identified tripping characteristics of the ground differential
protection function.
3 Operation P634
P634/EN M/R-42-A // P634‑311‑653 3-151
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