P92x/EN FT/E11 Technical Guide
User Guide
Page 48/110 MiCOM P921-P922-P923
10.6 Frequency protection (MiCOM P922 and P923)
10.6.1 Description
The principle of measurement of frequency is based in general on the measurement
of time every cycle, thus a new measurement is started at each voltage zero crossing.
Numerical filters are used to minimize the harmonics influence.
Precautions have been made to make this mode of calculation insensitive to the
vector shifts and phases jumps.
This function will be inhibited if the voltage level for each phase is below the blocking
minimum voltage. This voltage is settable (P923) in the CONFIGURATION menu (5
to 130V for range 1 and 20 to 480V for range 2).
The information “Freq. Out Of Range” will be generated :
· in the above mentioned application,
· if the frequency is out of the range : f
measured
> fn+20Hz or f
measured
< fn–20Hz
with fn=50Hz or 60Hz according to the settings of the relay.
10.6.2 HMI description
To gain access to the “FREQUENCY” sub-menu from the default display, press 2
once, 6 4 times, 2 once and 4 once (P922) or 4 twice (P923).
[81] FREQUENCY
Heading of the “FREQUENCY” sub-menu
[81] F1=
NO
Description : configuration of the 1
er
stage
Range : NO / 81> / 81<
[81] F1=
50.0 Hz
Description : setting of the 1
er
stage
Range : from "fn – 10Hz" to "fn + 10Hz"
[81] tF1=
0 ms
Description : time delay setting
Range : from 0 to 599s, step = 0.01s
[81] F2=
NO
Description : configuration of the 2
nd
stage
Range : NO / 81> / 81<
[81] F2=
50.0 Hz
Description : setting of the 2
nd
stage
Range : from "fn – 10Hz" to "fn + 10Hz"
[81] tF2=
0 ms
Description : time delay setting
Range : from 0 to 599s, step = 0.01s
[81] F3=
NO
Description : configuration of the 3
rd
stage
Range : NO / 81> / 81<
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