43
Siemens · 10/2015
Miniature Circuit Breakers
Configuration and dimensioning
Selectivity of miniature circuit breakers/fuses
Distribution systems are usually set up as radial networks. An
overcurrent protection device is required for each reduction of
the conductor cross-section. This produces a series connection
staggered according to rated currents, which should, if possible,
be "selective".
Selectivity means that, in the event of a fault, only the protective
device that is directly next to the fault in the current circuit is
tripped. This means that current paths in parallel can maintain a
power flow.
In the case of miniature circuit breakers with upstream fuses, the
selectivity limit depends largely on the current limitation and
tripping characteristics of the miniature circuit breaker and the
melting I2t value of the fuse.
This produces different selectivity limits for miniature circuit
breakers with different characteristics and rated breaking
capacity.
The following tables provide information on the short-circuit
currents up to which selectivity exists between miniature circuit
breakers and upstream fuses according to DIN VDE 0636-2. The
values specified in kA are limit values that were determined
under unfavorable test conditions. Under normal practical
conditions, you can often expect considerably better values,
depending on the upstream fuses.
In the event of a short-circuit, there is selectivity between the
5SY4, 5SY7, 5SP4, 5SJ4...-.HG.. miniature circuit breakers and
melting fuses according to DIN VDE 0636-2 up to the specified
values in kA.
Selectivity limit values of 3NA miniature circuit breakers/fuses in kA, operational class gG
Downstream miniature circuit
breakers
Upstream fuses
I
n
[A]
1)
16 A 20 A 25 A 35 A 50 A 63 A 80 A 100 A 125 A
5SY6 (without 5SY60)
Characteristic B 6 0.3 0.4 0.7 1.2 3.0 3.2 T T --
10 -- 0.4 0.6 1.0 2.2 3.0 5.0 T--
13 -- -- 0.5 1.0 2.2 3.0 5.0 T--
16 -- -- -- 1.0 2.0 2.4 4.0 T--
20 -- -- -- -- 2.0 2.4 4.0 T--
25 -- -- -- -- -- 2.0 3.5 T--
32 -- -- -- -- -- 1.7 2.0 T--
40 -- -- -- -- -- -- 2.0 4.0 --
50 -- -- -- -- -- -- -- 4.0 --
Characteristic C ≤ 2 0.3 0.5 1.2 1.7 T T T T --
30.3 0.4 0.8 1.4 4.0 5.0 T T --
40.3 0.4 0.6 1.1 3.0 4.0 T T --
6-- 0.4 0.6 1.0 2.4 3.2 T T --
8-- -- 0.5 0.9 1.4 2.6 3.1 T--
10 -- -- 0.5 0.9 1.4 2.1 3.1 T--
13 -- -- -- 0.8 1.3 2.0 3.0 T--
16 -- -- -- 0.8 1.3 2.0 3.0 T--
20 -- -- -- -- 1.3 2.0 2.7 T--
25 -- -- -- -- -- 2.0 2.4 5.0 --
32 -- -- -- -- -- -- 2.2 4.0 --
40 -- -- -- -- -- -- -- 3.5 --
50 -- -- -- -- -- -- -- 3.0 --
63 -- -- -- -- -- -- -- 3.0 --
5SY4...-5, -6, 5SY7...-6, 5SJ4...-6HG40
2)
Characteristic A, B 6 0.3 0.4 0.8 1.4 3.2 4.5 9.0 T T
10 -- 0.4 0.7 1.2 2.5 3.5 5.0 T T
13 -- -- 0.7 1.2 2.5 3.5 5.0 T T
16 -- -- -- 1.0 2.0 2.8 4.2 9.0 T
20 -- -- -- 1.0 2.0 2.6 4.2 9.0 T
25 -- -- -- -- 1.7 2.2 3.7 7.0 T
32 -- -- -- -- 1.7 2.2 3.7 7.0 6.0
40 -- -- -- -- -- 1.6 2.2 4.0 6.0
50 -- -- -- -- -- -- 2.2 4.0 6.0
63 -- -- -- -- -- -- -- 3.0 5.0
5SY4...-7, 5SY7...-7, 5SJ4...-7HG..
2)
Characteristic C ≤ 2 0.3 0.5 1.5 2.0 9.0 T T T T
30.3 0.4 1.1 1.6 5.0 6.0 T T T
40.3 0.4 0.9 1.4 3.5 5.0 9.0 T T
6-- 0.4 0.8 1.4 2.7 4.5 6.0 T T
8-- -- 0.6 1.2 2.2 3.5 5.0 7.0 T
10 -- -- 0.5 1.2 2.0 3.0 4.2 7.0 T
13 -- -- -- 1.0 1.6 2.4 3.4 6.0 T
16 -- -- -- 1.0 1.5 2.2 3.0 6.0 T
20 -- -- -- -- 1.3 2.2 3.0 6.0 T
25 -- -- -- -- -- 2.2 2.9 5.0 9.0
32 -- -- -- -- -- -- 2.4 4.0 7.0
40 -- -- -- -- -- -- 2.0 3.5 4.0
50 -- -- -- -- -- -- -- 3.0 4.0
63 -- -- -- -- -- -- -- 3.0 3.5
T r full selectivity up to rated breaking capacity I
cn
of the downstream protective device.
1)
In 240/415 V, 50 Hz systems, the selectivity limits are reduced by 10 %. The selectivity limits for adjustable releases apply to the maximum value,
I
n
= rated current. I
i
r tripping current.
2)
The values specified for 5SJ4...-.HG.. are not according to UL but are the manufacturer's specifications according to EN 60947-2 and apply for
voltage U
e
= 230 V ~. For available rated currents, see Catalog LV 10.
PH_03.book Seite 43 Dienstag, 12. Januar 2016 9:28 09
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