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TD_MRN3-3_08.06_GB
5.3.3 Setting of nominal frequency
For proper functioning it is necessary to first adjust the
rated frequency (50 or 60 Hz).
For this a distinction has to be made between the set-
tings v = 50 Hz/f = 50 Hz or v = 60 Hz/f = 60 Hz
The difference lies in the method of voltage measuring.
With the setting "v“ = 50/60 Hz voltage measuring is
independent of the existing frequency. This means, the
voltage value can be correctly measured between 30
Hz and 80 Hz without adverse effects from the fre-
quency.
With the setting "f“ = 50/60 Hz the measured volt-
age value is influenced by the frequency (see table
5.2).
Deviation of measuring value at 50Hz
97,5
98,0
98,5
99,0
99,5
100,0
100,5
44
46
48
50
52
54
56
[%]
[Hz]
Figure 5.1: Median influence at f = 50 Hz
Deviation of measuring value at 60Hz
97,5
98,0
98,5
99,0
99,5
100,0
100,5
54
56
58
60
62
64
66
[%]
[Hz]
Figure 5.2: Median influence at f = 60 Hz
This difference in settings is required for the fault re-
corder. If the fault recorder is to be used, the setting
must be f = 50 Hz or f = 60 Hz.
The different designations "f“ or "v“ have no influence
on any of the other functions.
All frequency functions are determined by setting the
nominal frequency, i.e. whether the set frequency
thresholds are evaluated as over- or underfrequency
(see also chapter 5.4.4). Also the cycle duration
(20 ms at 50 Hz and 16.67 ms at 60 Hz) derives
from this setting which determines the minimum tripping
delay for frequency elements f
1
- f
3
with an adjustable
multiplier (see also chapter 5.4.5).
During setting of the nominal frequency a value in Hz
is shown on the display.
Setting
v = 50
f = 50
v = 60
f = 60
Rated frequency
50 Hz
50 Hz
60 Hz
60 Hz
Influence on voltage
measurement
none 0.5..1%/Hz
(see figure 5.1)
none 0.5..1%/Hz
(see figure 5.2)
Fault recorder
Recording
distorted**
Recording
correct***
Recording
distorted**
Recording
correct***
Influence on all other
functions
none none none none
Table 5.2: Deviation of measured value at 50 Hz or 60 Hz
* Setting is important for differentiation between over- and underfrequency
** Sample rate is variably adjusted to the momentarily measured frequency. 16 samples are always measured in one period.
*** Sample rate setting is fixed to 50 Hz or 60 Hz. 16 samples per 20 ms or 16.67 ms are always measured.
