SACE EMAX 2 NEW LOW VOLTAGE POWER C I RCUI T BRE AKERS TO ANS I C37 / UL 1066 / CSA STANDARDS
3/44
— Description of protection functions
Rate of change of frequency (ROCOF – ANSI 81R) : enables both positive and negative frequency variations to be rapidly detected . The protection is constant and is tripped when the frequency variation in Hz/s is greater than the set threshold.
f(Hz)
frequency after failure
failure
50/60Hz
frequency after failure
Time
Second protection against voltage controlled overcurrent protection (S2(V) - ANSI 51V) : available in ad- dition to the protection S(V), enables total selectivity to be achieved in all installations.
t
1
Ks
t21
Ks
t20
I
KsxI20
I21 I20
KsxI21
Second protection against loss of field or reverse reactive power (RQ – ANSI 40 or 32R) : enables the gen- erator’s de-energization curve to be followed very accurately, thereby avoiding any unnecessary disconnec- tion.
Q
kq kq2
P
Q25
Q24
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