DOC. MIE91093 Rev. 1.34 Page 57 of 145
V pre-fault = VN/1.73
Standard values are: 57.8 V for VN = 100 V; 63.5 V for VN =
110 V.
After this adjustment the pre-fault voltage is generated prior
to all tests, as the unit is OFF. Select ON: as the test is
started, the voltage goes to the fault value, that is adjusted by
the knob (20). Adjust the fault value at the same value as the
pre-fault.
. Connect the relay to the auxiliary voltage output sockets
(62).
. Set the “Automatic save at trip” function, as follows.
Test control > Save > Confirm at trip > ESC
NOTE: for other selections see the pop-up menu chapter.
. Set the timer with the following selections:
Timer start/stop > START > INT (RET)
STOP > EXT > Clean (Voltage) (RET)
Edge ESC
NOTE: stop clean or voltage according to the relay trip contact
connections.
1.7.3. MXROC Threshold
The first session is finding the MXROC threshold; we will start
testing the positive ROC. The ROC threshold cannot be found
as usual, modifying the ROC until the relay trips: as we do, the
frequency changes, and the relay would trip because of
thresholds F>> or F<<. The following session is therefore a
series of trip tests performed at different values of ROC. The
threshold is found when we have two values of ROC, ROC(31)
and ROC(32), ROC(31) < ROC(32), where:
. For ROC(31) the relay does not trip;
. For ROC(32) the relay trips;
. The difference ROC(32) – ROC(31) is small enough for the
desired test accuracy.
First of all, set the maximum test time as 1.5 * T1, so that we
do not waste time:
Test control > Fault injection > Timed > 1.5*T1 (RET)
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