TD_MRN3-3_08.06_GB
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5.8 Indication of measuring and fault
values
5.8.1 Measuring
indication
In normal operation the following measuring values
can be displayed.
•
Voltages (LED L1, L2, L3 green)
•
All phase-to-neutral voltages in star connection
•
All phase-to-phase voltages in delta connection
•
Frequency (LED f green)
•
Vector surge in all three phases (LED
∆Θ
/df green +
L1, L2, or L3 green) or
•
Frequency change df/dt (LED df green)
Min. and max. values prior to the last reset:
•
Frequency (LED f + min or f + max)
•
Vector surge(LED
∆Θ
/df + min or df/
∆Θ
+ max) or
•
Frequency change(LED
∆Θ
/df + min
or
∆Θ
/df + max).
5.8.2 Min./Max.-
values
The
MRN3-3
offers a minimum/maximum storage
each for the measuring values of the vector surge as
well as the frequency gradient. These min./max. val-
ues are mainly used to appraise the mains quality. Al-
ways the highest and lowest values of
each cycle
are
measured and stored until the next reset.
Min./max. frequency measuring:
The
MRN3-3
ascertains the actual frequency from
each cycle of the system voltage. These measuring
values are entered into the min./max. storage. The
latest entered min./max. values replace the previously
stored values.
Dependent on the adjustment of T 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.
* Reset function see chapter 5.9.1
Min./Max. measuring of the frequency gradient:
The procedure described above applies also to stor-
age 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.
These min./max. measurements are of great advan-
tage for long-time analysis of the grid quality.
Min./max. vector surge measuring :
The procedure described above applies also to stor-
age of min./max. values of vector surge measuring.
Since each instantaneous
∆Θ
value is stored, also
here high values are possible which, however, do not
cause any tripping.
These min./max. measurements are of great advan-
tage for long-time analysis of the grid quality.
As to operation :
After each reset (ref. 5.9.1) the min./max. storage
units 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 "min" light up.
5.8.3 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 .000 – 999V
1K00 – 9K99
10K0 – 99K9
100K – 999K
1M00 – 3M00
V
KV
KV
KV
MV
Table 5.5: Displayed units
5.8.4 Indication of fault data
All faults detected by the relay are indicated on the
front plate optically. For this purpose, the four LEDs (L1,
L2, L3, f) and the four function LEDs (U1,U2,U3, f1,
f2, f3 und df/dt) are equipped at
MRN3-3
. Not only
fault messages are transmitted, the display also indi-
cates the tripped protection function. If, for example an
overcurrent occurs, first the respective phase LED will
light up and also, for example LED U1, provided, this
step was previously parameterised as over voltage
function. After tripping the LEDs are lit permanently.
