k
am,N ,a
=
I
nom,a
I
ref ,N,a
k
am,Y ,a
=
I
nom,Y ,a
I
ref ,N,a
with
am: amplitude-matched
I
nom,a
: primary nominal current of the main current transformer
I
nom,Y ,a
: primary nominal current of current transformer in the neutral-point-to-
ground connection
Reference currents and matching factors are displayed at the P634.
The P634 checks that the reference current and matching factor are within their
permissible ranges. The acceptable range for the reference current can be read
out from the operating program. The following applies to the matching factors:
●
The matching factor must always be ≤ 16.
●
The value for the smaller matching factor (k
am,min
) must always be ≥ 0.5.
Should the P634 calculate a reference current or matching factors not meeting
the above conditions then an alarm will be issued and the P634 will be blocked
automatically.
The measured values are multiplied by the relevant matching factors and are
then available for further processing. Consequently, all threshold values and
measured values always refer back to the relevant reference current rather than
to the transformer nominal current or the nominal current of the device.
3 Operation P634
P634/EN M/R-42-A // P634‑311‑653 3-143
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