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Technical Data
4.3 Inverse-Time Overcurrent Protection 51(N)
SIPROTEC, 7SJ61, Manual
C53000-G1140-C210-1, Release date 02.2008
320
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 current 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 current 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 I
p
, I
Ep
for IEC characteristics 0.05 s to 3.20 s or
∞
(disabled) Increments 0.01 s
Time multiplier T for I
p
, I
Ep
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 Figure 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 3 I 0p instead of I
p
and T
3
I
0p
instead of T
p
;
for ground fault read
I
Ep
instead of
I
p
and T
I Ep
instead of T
p
Pickup Threshold approx. 1.10 ·
I
p