k
am,b
=
I
nom,b
I
ref ,b
k
am,c
=
I
nom,c
I
ref ,c
k
am,d
=
I
nom,d
I
ref ,d
with
k
am,a...d
: amplitude matching factor of end a, b, c or d
I
nom,a...d
: primary nominal currents of the system transformers
Reference currents and matching factors are displayed at the P634.
The P634 checks that the reference currents and matching factors are within
their permissible ranges. The matching factors must satisfy the following
conditions:
●
The matching factors must always be ≤ 16.
●
The value for the second highest matching factor (k
am,mid
) must always be
≥ 0.5.
In three- or four-end protection, the “weakest“ end, that is the end with the
smallest primary nominal transformer current, is thus not under any restrictions
pertaining to the settings for the amplitude matching.
Should the P634 calculate reference currents or matching factors not satisfying
the above conditions then an alarm will be issued and the P634 will be blocked
automatically.
The measured values of the phase currents of the windings of the protected
object 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 currents rather than to the
transformer nominal currents or the nominal currents of the device.
3 Operation P634
P634/EN M/R-42-A // P634‑311‑653 3-125
To Next Page
Loading...
