Seg HighTECH MRU3-2, Руководство пользователя

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26 TB MRU3-2 12.00 E
6.4.2 Checking the input circuits and
measuring functions
Apply three voltages of rated value to the voltage in-
put circuits (terminals A3 - A8) of the relay. Check the
measured voltages, frequency and vector surge on the
display by pressing the push button <SELECT/RESET>
repeatedly.
The voltages are indicated on the display in volts, at
Y-connection:
•
Phase-to-neutral voltages: LED L1, L2, L3
Delta-connection:
•
Phase-to-phase voltages: LED L1+L2, L2+L3, L3+L1
Change the voltages around the rated value and
check the measured voltages on the display.
Compare the voltage displayed with the reading at
voltmeter. The deviation for the voltage must not ex-
ceed 1%.
By using an RMS-metering instrument, a greater devia-
tion may be observed if the test voltages contains har-
monics. Because the
MRU1 relay measures only the
fundamental component of the input signals, the har-
monics will be rejected by the internal DFFT-digital fil-
ter. Whereas the RMS-metering instrument measures
the RMS-value of the input signals.
6.4.3 Test of the symmetrical
components values
The following tests describe basically the indicating
values and voltages of the symmetrical components
with which the measuring functions of the
MRU3-2 can
be tested. If simultaneously the tripping function is to
be tested, the corresponding parameter must be set
between the rated voltage and the theoretical value
accept to the table.
Symmetrical measuring voltage system
For this test the relay has to be correctly connected
with all of the three phases and the star point. If the
measuring voltage system is symmetrical, the unit
should indicate the following measuring values:
measuring
value
indication
L1, L2, L3 U
N
U1
≈
U
N
U2
≈
0
U0
≈
0
Table 6.1: Indication at normal rotating field (symmetrical)
The deviation must not exceed some Volts. Exact data
cannot be given here because this depends upon the
actual symmetry of the test voltage system. By an ex-
actly symmetrical system the data must be precisely
within the tolerance of the unit. Also a deviation of the
mains frequency from the set frequency can lead to er-
rors in the measurements. In this case it is better to set
the system frequency to “v = 50 Hz” or “v = 60 Hz”.
Wrong phase sequence
For this test two phases must be reversed to the
MRU3-2 . The third phase and the star point N are
connected as usual. The theoretical indicating values
are:
measuring
value
indication
L1, L2, L3 U
N
U1
≈
0
U2
≈
U
N
U0
≈
0
Table 6.2: Indication during simulated left rotating field
Phase failure
The MRU3-2 is now to be connected with the two
phases L2 and L3 and with the neutral conductor. The
two phases must be assigned correctly. The measuring
input of phase L1 is connected with the star point of
the relay in order to prevent interference voltages at
the input. (This simulation is realistic because in a real
case of failure other relays in parallel or the voltage
transformer itself would cause this "pull down" effect).