Page 64 - Sace Emax 2 Catalogue

3/40 SACE EMA X 2 LOW VOLTAGE AIR CIRCUIT-BRE AKERS

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Description of protection functions

Rate of change of frequency (ROCOF – ANSI 81R): enables both positive and negative frequency varia-
f(Hz) frequency
after failure tions to be rapidly detected . The protection is constant and is tripped when the frequency variation in
failure
Hz/s is greater than the set threshold.
50/60Hz
frequency
after failure
Time

Second protection against voltage controlled overcurrent protection (S2(V) - ANSI 51V): available in
t 1
Ks addition to the protection S(V), enables total selectivity to be achieved in all installations.
t21
Ks
t20
I
KsxI20 I20 I21
KsxI21

Second protection against loss of field or reverse reactive power (RQ – ANSI 40 or 32R): enables the
Q
generator’s de-energization curve to be followed very accurately, thereby avoiding any unnecessary dis-
kq kq2
connection.
P
Q25
Q24