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TB XRW1-4 04.01 E
6.3
Indication of measuring values
In normal operation the following measuring values can
be displayed:
Voltages (LED L1, L2, L3 green)
•
In star connection all phase-to-neutral voltages
•
In delta connection all phase-to-phase voltages
Frequency (LED f green + L1, L2 or L3 green;
Frequency gradient df/dt (LED df green)
Min. and max. values since the last reset :
•
Frequency (LED f + min or f + max)
•
Frequency gradient (LED df + min or df + max)
6.3.1
Min./Max.- values
The
XRW1-4
offers a minimum/maximum storage for
the measuring values of the frequency gradient. These
min./max. values are mainly used to appraise the sys-
tem quality. Always the highest and lowest values of
each cycle
are measured and stored until the next re-
set.
Min./max. frequency measuring :
The
XRW1-4
ascertains the actual frequency from each
cycle of the system voltage. These measuring values
are entered into the min./max. storage. The latest en-
tered min./max. values replace the previously stored
values.
Dependent on the adjustment of dt and tripping delay,
it is possible that the stored min./max. values are
higher than the tripping threshold without causing a
trip. The reason for this is storage of instantaneous val-
ues.
Min./Max. measuring of the frequency gradient :
The procedure described above applies also to storage
of min./max. values of df/dt measurement. Since each
instantaneous df/dt value is stored, high values can
occur which, however, do not cause any tripping.
This can for instance happen during switching proce-
dures where high positive and negative df/dt values
occur, but they do not cause any tripping due to the
special measuring method.
As to operation :
After each reset (ref. 6.4) the min./max. storages are
cleared. As from this instant there is no time limit for the
min./max. storage until the next reset.
By repeatedly pressing the <SELECT/RESET> push but-
ton, the measuring values of the min./max. storage
can be queried. The respective LEDs light up at the
same time; e.g. during minimum frequency is dis-
played, LEDs "f" and "<" light up.
