TB MRI3-ITE(R) 12.00 E
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6.4.5
Checking the operating and
resetting values of the relay
Inject a current which is less than the relay set values in
phase 1 of the relay and gradually increase the cur-
rent until the relay starts, i.e. at the moment when the
LED I> and L1 light up or the alarm output relay I> is
activated. Read the operating current indicated by the
ammeter. The deviation must not exceed 5% of the set
operating value.
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 not smaller than
0.97 times the operating current.
Repeat the test on phase 2, phase 3 and earth current
input circuits in the same manner.
6.4.6
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 <20 ms.
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. Otherwise the test
results may be wrong. This espacially applies for cur-
rents smaller than 2 x I
S
, where the trip delays are in
the steep range of the inverse curves.
6.4.7
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>> operates. Check the tripping
time of the high set element according chapter 6.4.6
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 and earth current
input circuits 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
6.4.8
Checking the external blocking and
reset functions
By means of the external blocking input, it is possible
to block all protective functions. To give an example,
the blocking function of the phase current high set ele-
ment is described.
This can be tested by first setting the parameter for the
phase current high set element to „BLOC“ and then
connecting the auxiliary voltage to terminals E8/D8.
The phase current low set element I> should be set to
EXIT for this test. Inject a test current which could cause
a high set (I>>) tripping. Observe that there is no trip
of any assigned output relay of the high set or low 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.
