TB XRI1-IR 02.00 E
25
7.4.3
Checking the input circuits and
measured values
Inject a current in phase 1 (terminals 1S1/1S2),
which is less than the relay pickup current set values,
and check the measured current on the display by
pressing the push button <SELECT>. For a relay with
rated current In = 5 A, for example, a secondary cur-
rent injection of 1 A should be indicated on the dis-
play with about 0.2 (0.2 x In). The current can be also
injected into the other current input circuits (Phase 2:
terminals 2S1/2S2, Phase 3: terminals 3S1/3S2).
Compare the displayed current value with the reading
of the ammeter. The deviation must not exceed 3% or
1% In. By using an RMS-metering instrument, a greater
deviation may be observed if the test current contains
harmonics. Because the
XRI1-IR
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.
7.4.4
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 3% of the set
operating value or 1% In.
Furthermore, gradually decrease the current until the re-
lay resets, i.e. the alarm output relay I> is de-ener-
gized. Check that the resetting current is smaller than
0.97 times the operating current.
This procedure has also to be used for the other
phases.
7.4.5
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.
7.4.6
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>> operates. Check the tripping
time of the high set element according chapter 7.4.5.
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 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 8.1).
