TD_MRN3-3_08.06_GB
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6.5.4 Checking the operating and reset
ting values of the over-/underfre-
quency
functions
Note:
Due to frequency changes, vector surge or df/dt - trip-
ping can occur during frequency tests. In order to en-
sure a trouble-free test procedure, the vector surge
df/dt function of the relay have to be blocked before
tests are started.
During frequency tests, each of the frequency elements
should be tested separately. This makes it necessary
that the other frequency elements of the relay have to
be blocked by setting the frequency pickup values
f
1
- f
3
to "EXIT". For testing the pickup and dropout to
pickup values, the test frequency has to be increased
(decreased) until the relay is energised. This is indi-
cated by lighting up of LEDs f
1
- f
3
.
When comparing the values displayed with those of
the frequency meter, the deviation must not exceed
0.01 Hz. The dropout to pickup values are ascer-
tained by increasing (decreasing) the test frequency
slowly until the output relay releases.
The dropout to pickup value for overfrequency must be
>0.99, and for underfrequency <1.01.
6.5.5 Checking the tripping delay of the
over-/underfrequency
functions
The tripping delay of the over/underfrequency func-
tions can be tested in the similar manner as in chapter
6.5.3 for over/undervoltage functions.