20
TB MRF3 04.01 E
5.8
Measuring values
5.8.1
Instantaneous values
The indication of the instantaneous measuring values is
described in the general description "
MR
- Digital Mul-
tifunctional Relays", chapter 4.1.
5.8.2
Tripping memory
The indication of the measuring values in case of a trip
is described in the general description "
MR
- Digital
Multifunctional Relay“, chapter 4.5.2.
5.8.3
Display of measuring values
During normal operation the following measuring val-
ues can be displayed:
Displayed measuring values:
U:
System voltage in Volt
f:
System frequency in Hz
df:
Frequency gradient in Hz/s
f
min/max
: Min. and Max. value of systemfrequency in Hz
df
min/max
: Min. and Max. value of frequency gradient
in Hz/s
5.8.4
Unit of the measuring values
displayed
The measuring values can optionally be shown in the
display as a multiple of the "sec" rated value (x ln) or
as primary current (A). According to this the units of the
display change as follows:
Indication as
Range
Unit
sec. voltage
000V - 999V
V
primary voltage .00V – 999V
1k00 – 9k99
10k0 – 99k0
100k – 999k
1M00 –- 3M00
V
kV
kV
kV
MV
Table 5.4: Units of the display
5.8.5
Minimum and maximum values
The
MRF3
offers a minimum/maximum storage each
for the measuring values of the frequency gradient.
These min./max. values are mainly used to appraise
the system quality. Always the highest and lowest val-
ues of
each cycle
are measured and stored until the
next reset.
Min.-/max. measurement of the frequency:
Unit
MRF3
calculates from each cycle of the mains
voltage the instantaneous frequency. These measuring
values are written into the min.-/max.-storage. Hereby
only a new minimum- or maximum value overwrites
older stored values. According to the setting of T and
the tripping delay it can happen that the stored min.-
/max.-values are far above the tripping thresholds, but
tripping does not occur. This is established by the stor-
age of
instantaneous values
.
Min.-/max.-measurement of the frequency gradient
The before described is valid in the same way for
storage of min.-/max. values of the df/dt measure-
ment. Because every instananeous df/dt value is
stored, high values can occur which however do not
lead to tripping. This can for instance occur due to
switching transients where high positive and negative
df/dt values occur. Because of the special measuring
procedure the relay does not trip.
Very helpful are the min.-/max.- measurements for long
time study of the mains quality.
Operation:
At each reset (see chapter 5.4) the stored min.-/max.-
values are deleted. From this time the min.-/max.-
storage runs without time limitation until the next reset.
The measuring values of the min.-/max.-storage can
be called by pressing push button <SELECT> several
times. Simultaneously the respective LEDs light up, for
instance LEDs "f"and "min" light up at the indication of
the minimum frequency.
5.9
Fault memory
When the relay is energized or is energized or trips,
all fault data and times are stored in a non-volatile
memory manner. The
MRF3
is provided with a fault
value recorder for max. five fault occurrences. In the
event of additional trippings always the oldest data set
is written over.
For fault indication not only the trip values are re-
corded but also the status of LEDs. Fault values are in-
dicated when push buttons <-> or <+> are pressed
during normal measuring value indication.
Содержание MRF3
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