Areva MiCOM P921 - Page 130

P92x/EN FT/E11 Technical Guide
User Guide
Page 52/110 MiCOM P921-P922-P923
10.7.2 df/dt functionning
32
32
2
/
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- -
-
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=
ii
ii
i
tt
ff
dtdf
32- - ii
21
21
1
/
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- -
-
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=
ii
ii
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dtdf
f
i-1
1
1
/
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ii
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dtdf
f
i
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i-2
ii
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dtdf
P0399ENa
-
-
=
+
+
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1
1
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/
f
i+1
FIGURE 2
The rates of change of frequency are calculated every cycle based upon the frequency
values being insensitives to vector shifts, phase jumps and harmonics.
NOTE: To be insensitive to the phase shift and vector jumps, we reject
all measuements of df/dt greater than 20Hz/s .