Technical Data
4.3 Inverse-Time Overcurrent Protection 51(N)
SIPROTEC, 7SK80, Manual
E50417-G1140-C344-A4, Release date 08.2010
347
4.3 Inverse-Time Overcurrent Protection 51(N)
Operating Modes
Measuring Technique
Setting Ranges / Increments
Trip Time Curves acc. to IEC
Three-phase Standard
Two-phase Phases A and C
All elements First harmonic, rms value (true rms)
Pickup currents 51 (phases) for I
Nom
= 1 A 0.10 A to 4.00 A Increments 0.01 A
for I
Nom
= 5 A 0.50 A to 20.00 A
Pickup currents 51N
(ground)
for I
Nom
= 1 A 0.05 A to 4.00 A Increments 0.01 A
for I
Nom
= 5 A 0.25 A to 20.00 A
Time multiplier T for 51, 51N
for IEC characteristics
0.05 s to 3.20 s or ∞
(disabled)
Increments 0.01 s
Time multiplier T for 51, 51N
for ANSI characteristics
0.50 s to 15.00 s or ∞
(disabled)
Increments 0.01 s
Acc. to IEC 60255-3 or BS 142, Section 3.5.2 (see also Figures 4-1 and 4-2)
The tripping times for I/I
p
≥ 20 are identical with those for I/I
p
= 20
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
Pickup threshold approx. 1.10 · I
p
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