F< Threshold And Drop-Off - ISA T1000 PLUS User Manual

DOC. MIE91093 Rev. 1.34 Page 51 of 145
frequency should be changed quite slowly. If threshold
measurement was not good because you were moving too
fast, do not confirm test results and repeat the test.
Next, we find the drop-off threshold for F>. From the
frequency above, slowly decrease it; as the relay resets,
confirm save results pressing the multi-function knob, and
proceed.
NOTE: stored value is the frequency as the relay resets. This
corresponds to the relay drop-off only if the frequency did not
change very much while the relay timing elapsed; however,
reset timing is usually very short, so the frequency does not
change very much at release, and the measurement is
accurate.
1.6.4. F< Threshold and drop-off
Now we find the threshold F<. Remaining ON from the above
test, slowly decrease the auxiliary AC frequency. As the relay
trips, confirm save results pressing the multi-function knob,
and proceed.
Next, we find the drop-off threshold for F<. From the
frequency above, slowly increase it; as the relay resets,
confirm save results pressing the multi-function knob, and
proceed.
1.6.5. F>> Threshold and drop-off
The second session is finding threshold F>>. The problem is
that the test result criterion is no more to find the limit
between no trip and trip; it is instead to find the limit between
two different timings: what we have shown as T1, for
frequencies less than F>>, and T2, for frequencies more than
F>>. There are many ways to perform the test; we suggest
taking advantage of the Timed generation option, as follows.
Set the "Don't save" function, as follows.
Test control > Save > Don't save ESC
Start from a frequency more than F>; select ON+TIME, and
check for time response. Increase the test current, repeat the
test until the relay trips with a delay T2. Reduce the