SEG Electronics GmbH
Manual MRG3
64
DOK-TD-MRG3, Rev. D
6.4.3 Checking of the input circuits and measuring functions
Apply three voltages of rated value to the voltage input circuits (terminals A3 - A8) of the relay.
Check the measured voltages, frequency and vector surge on the display by pressing the push but-
ton <SELECT/RESET> repeatedly.
The displayed measuring voltages (shown in Volt) are dependent on the wiring of the input voltage
converters und and the settings of rated primary and secondary transformer voltage.
The voltages are indicated on the display in volts.
At Y-connection:
Phase-to-neutral voltages: LEDs U and L1, L2 or L3 At Delta-connection:
Phase-to-phase voltages: LEDs U and L1+L2, L2+L3 or L1+L3
The frequency is indicated on the display in Hz: LED f (system frequency = 50.01Hz, Indication =
5001) The vector surge angle is indicated on the display in degrees LEDs
/df (Indication in °)
plus L1, L2 or L3. The rate of change of frequency (LED
/df) is indicated on the display in Hz/s.
Example: 3.1 = 3.1 Hz/s.
Change the voltages around the rated value and check the measured voltages on the display.
Change the system frequency around the rated frequency and check the measured frequency on
the display.
When comparing the values indicated on the display with the indication of the measuring instru-
ments, the voltage deviation must not exceed 1% or 0.3%/Un. and the frequency shall not deviate
by more than 0.01 Hz.
By using an RMS-metering instrument, a greater deviation may be observed if the test voltage con-
tains harmonics. Because the MRG3 relay measures only the fundamental component of the input
signals, the harmonics will be rejected by the internal DFFT-digital filter. Whereas the RMS-
metering instrument measures the RMS-value of the input signals.
6.4.4 Checking the pick-up and release values for over/under voltage
Note!
When the measuring voltage is connected or disconnected, vector surge tripping or df/dt tripping
can occur. In order to ensure a trouble-free test procedure, the vector surge function or df/dt func-
tion of the relay have to be blocked before tests are started. Furthermore, attention must be paid
that relays which are used for the alarm function, are assigned to the correct position (see chapter
5.9.1)
For the testing of response and release values, the test voltage has to be increased (decreased)
until the relay is excited.
This is signalized by flashing of the LEDs U + 1(2) + <(>). The assigned alarm relay (e.g. contacts
D4/E4) simultaneously picks up.
When comparing the values shown on the display to voltmeter values, the deviation must not be
more than 1% of the measured value or 0.3% U
N
.
Disengaging values can be detected by slowly in-creasing (decreasing) the test voltage until the
output relay of U< (U>) drops.
Check that the dropout to pickup ratio for voltage is greater than 0.97 (for overvoltage function) or
smaller than 1.03 (for under voltage).
6.4.5 Checking of the tripping delay time for over/under voltage
To check the relay's operating time, a timer must be connected to the trip output relay contact
(Contact terminals D1/E1). The timer should be started simultaneously with the voltage change
from sound condition to a faulty condition and stopped by the trip relay contact. The operating time
measured by timer should have a deviation about 1%, of the set value or <20 ms.