Siemens SIPROTEC 7SK80 - Page 352

Technical Data
4.3 Inverse-Time Overcurrent Protection 51(N)
SIPROTEC, 7SK80, Manual
E50417-G1140-C344-A4, Release date 08.2010
352
Dropout Time Characteristics with Disk Emulation acc. to ANSI/IEEE
Dropout Setting
Tolerances
Acc. to ANSI/IEEE (see also Figures 4-3 to 4-6)
The dropout time curves apply to (I/Ip) ≤ 0.90
For zero sequence current read 3I0p instead of I
p
and T
3I0p
instead of T
p
;
for ground fault read I
Ep
instead of I
p
and T
IEp
instead of T
p
ANSI without Disk Emulation approx. 1.05 · setting value I
p
for I
p
/I
N
≥ 0.3; this corresponds to approx.
0.95 · pickup value
ANSI with Disk Emulation approx. 0.90 · I
p
setting value
Pickup/dropout thresholds I
p
, I
Ep
3 % of setting value or 15 mA for I
N
= 1 A, or 75 mA for I
N
= 5 A
Trip time for 2 ≤ I/I
p
≤ 20 5 % of reference (calculated) value +2 % current tolerance, or 30 ms
Dropout time for I/Ip ≤ 0.90 5 % of reference (calculated) value +2 % current tolerance, or 30 ms