Seg HighTECH Line MRI1IU, Manual, Page: 14 / 22

14 TD_MRI1-IU_05.04_GB
6.4.4 Checking the operating and
resetting values of the relay under
normal and low voltage
Apply three phase voltages 5% above the undervolt-
age set value and inject a current which is less than
the relay low set current at low voltage condition in
phase 1 of the relay. Gradually increase the current
until the relay starts, i.e. at the moment when the LED
I> and L1 light up or the alarm output relay I> is acti-
vated. Read the operating current indicated by the
ammeter. The deviation must not exceed 5% of the
pickup current at nominal voltage condition.
Furthermore, gradually decrease the current until the re-
lay resets, i.e. the alarm output relay I> is disengaged.
Check that the resetting current is smaller than 0.97
times the operating current.
Apply three phase voltages 5% below the undervolt-
age set value. Do the same test as above mentioned
and check the relay operating current value and reset-
ting value at low voltage condition.
Repeat the test on phase 2, phase 3 in the same man-
ner.
6.4.5 Checking the relay operating time
To check the relay operating time, a timer must be
connected to the trip output relay contact. The timer
should be started simultaneously with the current injec-
tion in the current input circuit and stopped by the trip
relay contact. Set the current to a value corresponding
to twice the operating value and inject the current in-
stantaneously. The operating time measured by the
timer should have a deviation of less than 3% of the set
value or
±
10 ms (DEFT). Accuracy for inverse time
characteristics refer to IEC 255-3.
Repeat the test on the other phases or with the inverse
time characteristics in the similar manner.
In case of inverse time characteristics the injected cur-
rent should be selected according to the characteristic
curve, e.g. two times I
S
. The tripping time may be red
from the characteristic curve diagram or calculated
with the equations given under "technical data".
Please observe that during the secondary injection test
the test current must be very stable, not deviating more
than 1%. Otherwise the test results may be wrong.
6.4.6 Checking the high set element
of the relay
Set a current above the set operating value of I>>. In-
ject the current instantaneously and check that the
alarm output relay I>> (contact terminals D5/E5) op-
erates. Check the tripping time of the high set element
according chapter 6.4.5.
Check the accuracy of the operating current setting by
gradually increasing the injected current until the I>>
element picks up. Read the current value form the am-
meter and compare with the desired setting.
Repeat the entire test on other phases in the same
manner.
Note !
Where test currents >4 x I
N
are used, the thermal with-
stand capability of the current paths has to be consid-
ered (see technical data, chapter 7.1).
6.4.7 Checking the external blocking and
reset functions
The external blocking input inhibits e. g. the function of
the high set element of the phase current. To test the
blocking function apply auxiliary supply voltage to the
external blocking input of the relay (terminals E8/D8).
The time delay t
I>
should be set to EXIT for this test. In-
ject a test current which could cause a high set (I>>)
tripping. Observe that there is no trip and alarm for the
high set element.
Remove the auxiliary supply voltage from the blocking
input. Inject a test current to trip the relay (message
„TRIP“ on the display). Interrupt the test current and ap-
ply auxiliary supply voltage to the external reset input
of the relay (terminals C8/D8). The display and LED
indications should be reset immediately.