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2 Version : 2.5 25/09/2015 CA908025E.indd
DB
1257
68D
B12
5767
Technical Advice Short-circuit current limiting
DefinitionThe limiting capacity of a circuit breaker is its ability to lessen the effects of a short circuit on an electrical installation by reducing the current amplitude and the dissipated power.
Benefits of limitingLong installation service lifeThermal effectsLower temperature rise at the conductor level, hence increased service life for cables and all components that are not self-protected (e.g. switches, contactors, etc.)Mechanical effectsLower electrodynamic repulsion forces, hence less risk of deformation or breakage of electrical contacts and busbars.Electromagnetic effectsLess interference on sensitive equipment located in the vicinity of an electric circuit.
Savings through cascadingCascading is a technique derived directly from current limiting: downstream of a current-limiting circuit breaker it is possible to use circuit breakers of breaking capacity lower than the prospective short-circuit current (in line with the cascading tables). The breaking capacity is heightened thanks to current limiting by the upstream device. Substantial savings can be achieved in this way on switchgear and enclosures.
Discrimination of protection devicesThe circuit breakers' current limiting capacity improves discrimination with the protection devices located upstream: this is because the required energy passing through the upstream protection device is greatly reduced and can be not enough to cause it to trip. Discrimination can thus be natural without having to install a time-delayed protection device upstream.
Acti 9 circuit breaker current limitingProfiting from Schneider Electric's experience and expertise in the field of short-circuit current breaking, the circuit breakers of the Acti 9 range have a top-level current limiting characteristic for modular devices. This assures them of optimal protection of the entire power distribution system.
I²sc
A²Prospective energy100%
Limited energy100%
t
IscProspective peak Isc
Limited peak Isc
Limited Isc
Prospective Isc
ttc
Prospective current and real limit current.
3Version : 2.5 25/09/2015CA908025E.indd
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Technical Advice Short-circuit current limiting (cont.)
Representation: Current limiting curvesThe current limiting capacity of a circuit breaker is reflected by 2 curves which give, as a function of the prospective short-circuit current (current which would flow in the absence of a protection device):
b the real peak current (limited) b the thermal stress (in A²s), this value, multiplied by the resistance of any element
through which the short-circuit current passes, gives the power dissipated by this element.
The straight line "10 ms" representing the energy A²s of a prospective short-circuit current of a half-period (10 ms) indicates the energy that would be dissipated by the short-circuit current in the absence of limiting by the protection device (see example).
Example What is the energy limited by an iC60N 25 A circuit breaker for a prospective short-circuit current of 10 kA rms. What is the quality of current limiting?> as shown in the graph opposite: b this short-circuit current (10 kA rms) is likely to dissipate up to 1,000 kA2s b the iC60N circuit breaker reduces this thermal stress to: 35 kA2s, which is 22 times less.
Example of use: Stresses acceptable by the cablesThe following table shows the thermal stresses acceptable by the cables depending on their insulation, their composition (Cu or Al) and their cross section. Cross-section values are expressed in mm² and stresses in A²s.S (mm²) 1.5 2.5 4 6 10PVC Cu 2.97 x 104 8.26 x 104 2.12 x 105 4.76 x 105 1.32 x 106
Al 5.41 x 105
PRC Cu 4.10 x 104 1.39 x 105 2.92 x 105 6.56 x 105 1.82 x 106
Al 7.52 x 105
S (mm²) 16 25 35 50PVC Cu 3.4 x 106 8.26 x 106 1.62 x 107 3.21 x 107
Al 1.39 x 106 3.38 x 106 6.64 x 106 1.35 x 107
PRC Cu 4.69 x 106 1.39 x 107 2.23 x 107 4.56 x 107
Al 1.93 x 106 4.70 x 106 9.23 x 106 1.88 x 107
ExampleIs a Cu/PVC cable of cross section 10 mm² protected by a NG125L device?The above table shows that the acceptable stress is 1.32 x 106 A²s. Any short-circuit current at the point where a NG125L device (Icu = 25 kA) is installed will be limited, with a thermal stress of less than 2.2 x 105 A²s. (Curve on page 10).The cable is therefore always protected up to the breaking capacity of the circuit breaker.
10000
100000
1000000
100
1000
1001010,10,01
≤1
468 -101620 -2532 -4050 -63
2 -3
10 ms
400
3
Lim
ited
ener
gy (A
²s)
Prospective current (kA rms)
4 Version : 2.5 25/09/2015 CA908025E.indd
DPN (MCB and RCBO)1P+N / 3P / 3P+NPeak current Thermal stress
DB
1242
67
Pea
k cu
rren
t (kA
)
Prospective short-circuit current (kA eff.)
0,1
1
10
100
1010,10,01
1
23 - 4
1016 - 2532 - 40
DB
1242
65
Ther
mal
stre
ss (
A²s
)
Prospective short-circuit current (kA eff.)
100
1 000
10 000
100 000
1 000 000
0,01 0,1 1 10
1
2
10
10 ms
3 - 4
16 - 2532 - 40
DPN N (MCB and RCBO)1P+N / 3P / 3P+NPeak current Thermal stress
DB
1242
64
0,1
1
10
100
1010,10,01
1
2
10
3 - 4
16 - 2532 - 40
Pea
k cu
rren
t (kA
)
Prospective short-circuit current (kA eff.)
DB
1242
66
100
1 000
10 000
100 000
1 000 000
0,01 0,1 1 10
1
2
10
10 ms
3 - 4
16 - 2532 - 40
Prospective short-circuit current (kA eff.)
Ther
mal
stre
ss (A
²s)
Limitation curves for network Ue: 380-415 V AC (Ph/N 220-240 V AC)
Technical Advice Short-circuit current limiting (cont.)
5Version : 2.5 25/09/2015CA908025E.indd
Technical Advice Short-circuit current limiting (cont.)
iC60N1P / 1P+N / 2P / 3P / 4PPeak current Thermal stress
DB
1242
80
Pea
k cu
rren
t (kA
)
Prospective short-circuit current (kA eff.)
0,1
1
10
100
1001010,10,01
y1
46
8 - 101620 - 25
32 - 4050 - 63
2 - 3D
B12
4281
Prospective short-circuit current (kA eff.)
Ther
mal
stre
ss (A
²s)
10000
100000
1000000
100
1000
1001010,10,01
y1
468 -101620 -2532 -40
50 -63
2 -3
10 ms
iC60H1P / 1P+N / 2P / 3P / 4PPeak current Thermal stress
DB
1242
84
Pea
k cu
rren
t (kA
)
Prospective short-circuit current (kA eff.)
0,1
1
10
100
10 10010,10,01
y1
46
8 - 101620 - 25
32 - 4050 - 63
2 - 3
DB
1242
85
Prospective short-circuit current (kA eff.)
Ther
mal
stre
ss (A
²s)
10000
100000
1000000
100
1000
1001010,10,01
y1
468 -101620 -25
32 -4050 -63
2 -3
10 ms
Limitation curves for network Ue: 380-415 V AC (Ph/N 220-240 V AC)
6 Version : 2.5 25/09/2015 CA908025E.indd
Technical Advice Short-circuit current limiting (cont.)
iC60L1P / 2P / 3P / 4PPeak current Thermal stress
DB
1242
88
Prospective short-circuit current (kA eff.)
Pea
k cu
rren
t (kA
)
0,1
1
10
100
1001010,10,01
y1
468 - 101620 - 25
32 - 4050 - 63
2 - 3
DB
1242
89
Prospective short-circuit current (kA eff.)
Ther
mal
stre
ss (A
²s)
10000
100000
1000000
100
1000
1001010,10,01
y1
468 -101620 -25
32 -4050 -63
2 -3
10 ms
Limitation curves for network Ue: 380-415 V AC (Ph/N 220-240 V AC)
7Version : 2.5 25/09/2015CA908025E.indd
Technical Advice Short-circuit current limiting (cont.)
C60a1P / 2P / 3P / 3P+N / 4PPeak current Thermal stress
DB
4057
16
100
10
1100101
461016 - 254063
DB
4057
12
10000
100000
1000000
100
10
1000
1001010.10.01
10 ms
0.5
0.75
1
234
6
10 - 16
20 - 2532 - 4050 - 63
C60N1P / 1P+N / 2P / 3P / 3P+N / 4PPeak current Thermal stress
DB
4057
19
100
10
1100101
46
1016 - 254063
DB
4057
15
10000
100000
1000000
100
10
1000
1001010.10.01
10 ms
0.5
0.75
1
234
6
10 - 1620 - 2532 - 4050 - 63
Limitation curves for network Ue: 380-415 V AC (Ph/N 220-240 V AC)
Prospective short-circuit current (kA eff.)
Prospective short-circuit current (kA eff.)
Pea
k cu
rren
t (kA
)P
eak
curr
ent (
kA)
Prospective short-circuit current (kA eff.)
Prospective short-circuit current (kA eff.)
Ther
mal
stre
ss (A
²s)
Ther
mal
stre
ss (A
²s)
8 Version : 2.5 25/09/2015 CA908025E.indd
C60H1P / 1P+N / 2P / 3P / 3P+N / 4PPeak current Thermal stress
DB
4057
17
100
10
1100101
46
1016 - 254063
DB
4057
13
10000
100000
1000000
100
10
1000
1001010.10.01
10 ms
0.5
0.75
1
234
6
10 - 16
20 - 2532 - 4050 - 63
C60L1P / 2P / 3P / 4PPeak current Thermal stress
DB
4057
18
100
10
1100101
46
10
16 - 254063
DB
4057
14
10000
100000
1000000
100
10
1000
1001010.10.01
10 ms
0.5
0.75
1
234
6
10 - 1620 - 25
32 - 4050 - 63
Limitation curves for network Ue: 380-415 V AC (Ph/N 220-240 V AC)
Prospective short-circuit current (kA eff.)
Prospective short-circuit current (kA eff.)
Pea
k cu
rren
t (kA
)P
eak
curr
ent (
kA)
Prospective short-circuit current (kA eff.)
Prospective short-circuit current (kA eff.)
Ther
mal
stre
ss (A
²s)
Ther
mal
stre
ss (A
²s)
Technical Advice Short-circuit current limiting (cont.)
9Version : 2.5 25/09/2015CA908025E.indd
C120N, H1P / 2P / 3P / 4PPeak current
DB
1242
93
1 2 101
2
4
10
3
5
8
67
9
20
5 6 7 8 943 15 20
15
30
2
91
cos phi = 0.3
= 0.5
= 0.8
= 0.9
= 0.95
87
6
5
= 0.7
Prospective short-circuit current (kA eff.)
Pea
k cu
rren
t (kA
)
b Circuit breaker type in accordance with the mark: v 1: C120N v 2: C120H v 5: 10-16 A v 6: 20-25 A v 7: 32-40 A v 8: 50-63 A v 9: 80-125 A
Thermal stress
DB
4056
04
10
10
10
10
10
6
5
2
4
3
0.1 1 10 1005
5
5
5
5
21
16A
25A32A
50A
125A100A
63A
10A
20A
40A
80A
10ms
Prospective short-circuit current (kA eff.)
Ther
mal
stre
ss (A
²s)
b Circuit breaker type in accordance with the mark: v 1: C120N v 2: C120H
Limitation curves for network Ue: 380-415 V AC (Ph/N 220-240 V AC)
Technical Advice Short-circuit current limiting (cont.)
10 Version : 2.5 25/09/2015 CA908025E.indd
NG125a, N, H, L1P / 2P / 3P / 4PPeak current
DB
1242
99
Prospective short-circuit current (kA eff.)
Pea
k cu
rren
t (kA
)
1 2 101
2
4
10
3
5
8
6
7
9
20
5 6 7 8 943 10050403020
15
4
2
6
5
7
89
1
3
cos phi = 0.3
= 0.5
= 0.7
= 0.8
= 0.9
= 0.95
b Circuit breaker type in accordance with the mark: v 1: NG125a v 2: NG125N v 3: NG125H v 4: NG125L v 5: 10 -16 A v 6: 20-25 A v 7: 32-40 A v 8: 50-63 A v 9: 80-125 A
Thermal stress
DB
4056
07
Prospective short-circuit current (kA eff.)
Ther
mal
stre
ss (A
²s)
10A16A20A25A32A40A50A
80A
125A100A
63A
10ms
1
2
3
4
10
10
10
10
10
6
5
2
4
3
0.1 1 10 1005
5
5
5
5
b Circuit breaker type in accordance with the mark: v 1: NG125a 80-100-125 A v 2: NG125N v 3: NG125H v 4: NG125L
Limitation curves for network Ue: 380-415 V AC (Ph/N 220-240 V AC)
Technical Advice Short-circuit current limiting (cont.)
11Version : 2.5 25/09/2015CA908025E.indd
C60N2P / 3P / 4PPeak current Thermal stress
DB
4057
27
100
10
1100101
461016 - 254063
DB
4057
23
10000
100000
1000000
100
10
1000
1001010.10.01
0.5
0.75
1
2
3
4
6
10 - 1620 - 2532 - 40
50 - 63
10 ms
Limitation curves for network Ue: 440 V AC
Prospective short-circuit current (kA eff.)
Pea
k cu
rren
t (kA
)
Prospective short-circuit current (kA eff.)
Ther
mal
stre
ss (A
²s)
Technical Advice Short-circuit current limiting (cont.)
12 Version : 2.5 25/09/2015 CA908025E.indd
C60H2P / 3P / 4PPeak current Thermal stress
DB
4057
25
100
10
1100101
4
6016 - 254063
DB
4057
21
10000
100000
1000000
100
10
1000
1001010.10.01
0.5
0.75
1
2
3
4
6
10 - 16
20 - 2532 - 40
50 - 63
10 ms
C60L2P / 3P / 4PPeak current Thermal stress
DB
4057
26
100
10
1100101
4
610
16 - 254063
DB
4057
22
10000
100000
1000000
100
10
1000
1001010.10.01
0.5
0.75
1
2
3
4
610 - 16
20 - 2532 - 40
50 - 63
10 ms
Limitation curves for network Ue: 440 V AC
Prospective short-circuit current (kA eff.)
Prospective short-circuit current (kA eff.)
Pea
k cu
rren
t (kA
)P
eak
curr
ent (
kA)
Prospective short-circuit current (kA eff.)
Prospective short-circuit current (kA eff.)
Ther
mal
stre
ss (A
²s)
Ther
mal
stre
ss (A
²s)
Technical Advice Short-circuit current limiting (cont.)
13Version : 2.5 25/09/2015CA908025E.indd
C120N, H2P / 3P / 4PPeak current
DB
1242
94
Prospective short-circuit current (kA eff.)
Pea
k cu
rren
t (kA
)
1 2 101
2
4
10
3
5
8
6
7
9
20
5 6 7 8 943 15 20
15
30
2
7
cos phi = 0.3
= 0.5
= 0.8
= 0.9
= 0.95
6
5
4
3
= 0.7
1
b Circuit breaker type in accordance with the mark: v 1: C120N v 2: C120H v 3: 0-16 A v 4: 20-25 A v 5: 32-40 A v 6: 50-63 A v 7: 80-125 A
Thermal stress
DB
4056
05
Prospective short-circuit current (kA eff.)
Ther
mal
stre
ss (A
²s)
2
16A
25A32A
50A
125A100A
63A
10A
20A
40A
80A
1
10ms10
10
10
10
10
6
5
2
4
3
0.1 1 10 1005
5
5
5
5
b Circuit breaker type in accordance with the mark: v 1: C120N v 2: C120H
Limitation curves for network Ue: 440 V AC
Technical Advice Short-circuit current limiting (cont.)
14 Version : 2.5 25/09/2015 CA908025E.indd
NG125a, N, H, L2P / 3P / 4PPeak current
DB
1243
00
Prospective short-circuit current (kA eff.)
Pea
k cu
rren
t (kA
)
1 2 101
2
4
10
3
5
8
6
7
9
20
5 6 7 8 943 10050403020
15
2
9
8
101
3
cos phi = 0.3
= 0.5
= 0.7
= 0.8
= 0.9
= 0.95
6
4
11
12
57
b Circuit breaker type in accordance with the mark: v 1: NG125a 3, 4P v 2: NG125N 2, 3, 4P v 3: NG125H 3, 4P v 4-5: NG125H 2P/NG125L 3, 4P v 6: NG125L 2P v 7: NG125 LMA 2, 3, 4P v 8: 10 -16 A v 9: 20-25 A v 10: 32-40 A v 11: 50-63 A v 12: 80-125 A
Thermal stress
DB
4056
08
Prospective short-circuit current (kA eff.)
Ther
mal
stre
ss (A
²s)
10A16A20A25A32A40A50A
125A2
3 6
100A
63A1
754
80A
10ms10
10
10
10
10
6
5
2
4
3
0.1 1 10 1005
5
5
5
5
b Circuit breaker type in accordance with the mark: v 1: NG125a 3, 4P v 2: NG125N 2, 3, 4P v 3: NG125H 3, 4P v 4-5: NG125H 2P/NG125L 3, 4P v 6: NG125L 2P v 7: NG125LMA 2, 3, 4P
Limitation curves for networkUe: 550 V AC
Technical Advice Short-circuit current limiting (cont.)
15Version : 2.5 25/09/2015CA908025E.indd
C60a1P / 2P / 3P / 3P+N / 4PPeak current Thermal stress
DB
4057
06
100
10
1100101
4
61016 - 254063
DB
4057
02
10 ms
0.5
0.75
1
234
610
1620 - 2532 - 4050 - 63
10000
100000
1000000
100
10
1000
1001010.10.01
C60N1P / 1P+N / 2P / 3P / 3P+N / 4PPeak current Thermal stress
DB
4057
09
100
10
1100101
4
61016 - 254063
DB
4057
05
10000
100000
1000000
100
10
1000
1001010.10.01
10 ms
0.5
0.75
1
234
610
16
20 - 2532 - 4050 - 63
Limitation curves for network Ue: 220-240 V AC (Ph/N 110-130 V AC)
Prospective short-circuit current (kA eff.)
Prospective short-circuit current (kA eff.)
Pea
k cu
rren
t (kA
)P
eak
curr
ent (
kA)
Prospective short-circuit current (kA eff.)
Prospective short-circuit current (kA eff.)
Ther
mal
stre
ss (A
²s)
Ther
mal
stre
ss (A
²s)
Technical Advice Short-circuit current limiting (cont.)
16 Version : 2.5 25/09/2015 CA908025E.indd
C60H1P / 1P+N / 2P / 3P / 3P+N / 4PPeak current Thermal stress
DB
4057
07
100
10
1100101
04
61016 - 254063
DB
4057
03
10000
100000
1000000
100
10
1000
1001010.10.01
10 ms
0.5
0.75
1
234
610
1620 - 2532 - 4050 - 63
C60L1P / 2P / 3P / 4PPeak current Thermal stress
DB
4057
08
100
10
1100101
4
610164063
DB
4057
04
10000
100000
1000000
100
10
1000
1001010.10.01
10 ms
0.5
0.75
01
234
610
1620 - 25
32 - 4050 - 63
Technical Advice Short-circuit current limiting (cont.)
Limitation curves for network Ue: 220-240 V AC (Ph/N 110-130 V AC)
Prospective short-circuit current (kA eff.)
Prospective short-circuit current (kA eff.)
Pea
k cu
rren
t (kA
)P
eak
curr
ent (
kA)
Prospective short-circuit current (kA eff.)
Prospective short-circuit current (kA eff.)
Ther
mal
stre
ss (A
²s)
Ther
mal
stre
ss (A
²s)
17Version : 2.5 25/09/2015CA908025E.indd
Technical Advice Short-circuit current limiting (cont.)
C120N, H1P / 2P / 3P / 4PPeak current
DB
1242
92
Prospective short-circuit current (kA eff.)
Pea
k cu
rren
t (kA
)
1 2 101
2
4
10
3
5
8
67
9
20
5 6 7 8 943 15 20
15
30
2
9
1
cos phi = 0.3
= 0.5
= 0.8
= 0.9
= 0.95
8
7
6
5
= 0.7
b Circuit breaker type in accordance with the mark: v 1: C120N v 2: C120H v 5: 10-16 A v 6: 20-25 A v 7: 32-40 A v 8: 50-63 A v 9: 80-125 A
Thermal stress
DB
4056
03
Prospective short-circuit current (kA eff.)
Ther
mal
stre
ss (A
²s)
210ms
1
16A
25A32A
50A
125A100A
63A
10A
20A
40A
80A
10
10
10
10
10
6
5
2
4
3
0.1 1 10 1005
5
5
5
5
b Circuit breaker type in accordance with the mark: v 1: C120N v 2: C120H
Limitation curves for network Ue: 220-240 V AC (Ph/N 110-130 V AC)
18 Version : 2.5 25/09/2015 CA908025E.indd
Technical Advice Short-circuit current limiting (cont.)
NG125a, N, H, L1P / 2P / 3P / 4PPeak current
DB
1242
98
Prospective short-circuit current (kA eff.)
Pea
k cu
rren
t (kA
)
1 2 101
2
4
10
3
5
8
6
7
9
20
5 6 7 8 943 10050403020
15 43
2
6
5
7
8
9
1
cos phi = 0.3
= 0.5
= 0.7
= 0.8
= 0.9
= 0.95
b Circuit breaker type in accordance with the mark: v 1: NG125a v 2: NG125N v 3: NG125H v 4: NG125L v 5: 10-16 A v 6: 20-25 A v 7: 32-40 A v 8: 50-63 A v 9: 80-125 A
Thermal stress
DB
4056
06
Prospective short-circuit current (kA eff.)
Ther
mal
stre
ss (A
²s)
1
2
3
4
10A16A
40A
125A100A80A63A50A
32A25A20A
10ms10
10
10
10
10
6
5
2
4
3
0.1 1 10 1005
5
5
5
5
b Circuit breaker type in accordance with the mark: v 1: NG125a 80-100-125 A v 2: NG125N v 3: NG125H v 4: NG125L
Limitation curves for network Ue: 220-240 V AC (Ph/N 110-130 V AC)
19Version : 2.5 25/09/2015CA908025E.indd
Technical Advice Short-circuit current limiting (cont.)
C60H-DC curve C1P (220 V) - 2P (440 V)Peak current Thermal stress
DB
1235
88
0.1
1
10
100
1001010.10.01
≤ 1
23461016
20 - 2532 - 4050 - 63
Prospective short-circuit current (kA eff.)
Pea
k cu
rren
t (kA
)
DB
1235
9110000
100000
1000000
100
1000
1001010.10.01
0.5 - 23
4
6
10
1620 - 2532 - 40
50 - 63
10 ms
Prospective short-circuit current (kA eff.)
Ther
mal
stre
ss (A
²s)
Limitation curves for direct current network
C60H-DC curve C1P (250 V DC) - 2P (500 V DC)Peak current Thermal stress
DB
1235
89
0.1
1
10
100
1001010.10.01
≤ 1
23461016
20 - 2532 - 4050 - 63
Prospective short-circuit current (kA eff.)
Pea
k cu
rren
t (kA
)
DB
1243
06
10000
100000
1000000
100
1000
1001010.10.01
0.5 - 23
461016
10 ms
50 - 63 32 - 40
20 - 25
Prospective short-circuit current (kA eff.)
Ther
mal
stre
ss (A
²s)
20 Version : 2.5 25/09/2015 CA908025E.indd
Technical Advice Short-circuit current limiting (cont.)
Evolutions
This page must be removed before publishing
2.5 29/07/2013 in thermal stress graphs change "peak current" by "thermal stress" JPM2.4 17/07/2012 Changed number of poles and pages order Sedoc2.3 13/07/2012 Add C60 curves Sedoc2.2 4/07/2012 Deleted iDPN, iK60 curves Sedoc2.1 06/06/2012 Change texts and curves Sedoc2.0 21/06/2011 InDesign CS5 - Add C60H-DC, C120 and NG125 curves Sedoc1.0 22/11/2010 Creation SedocIndice Date Modification Name