MV design gu

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at the rated operating sequence
# ANSI specifies 50% asymmetry and IEC 30%. In 95% of applications,
30% is sufficient. When 30% is too low, there are specific cases (proximity
of generators) for which the asymmetry may be greater than 50%.
# For both standard systems, the designer has to check the circuit
breaker breaking capacity. The difference is not important because
without taking account of the asymmetry factor "S", it is equal to 10%.
ANSI: Iasym = Isym (1 + 2A2) = 1.22 Isym (A = 50%)
IEC: Iasym = Isym (1 + 2A2) = 1.08 Isym (A = 30%)
According to IEC
# Short-circuit breaking tests must meet the following 5 test sequences:
Sequence n� % Isym % aperiodic component
110 d" 20
220 d" 20
360 d" 20
4 100 d" 20
5* 100 30
* for circuit breakers opening at least 80 ms
Schneider Electric
Gamme AMTED300014EN_070_08
Standards
0CEI - ANSI comparison
According to ANSI
# The circuit breaker must be able to break:
5 the rated short circuit current at the rated maximum voltage
5 K times the rated short-circuit current (maxi symmetrical interrupting
capability with K: voltage range factor) at the operating voltage (maximum
voltage/K)
5 between the two currents obtained by the equation:
ma--i symetrical current r-----------d-- maxi voltage
------------x------------------------------------------------------ = -ate-- ---------------------------------- = K
rated short-circuit current rated voltage
We therefore have a constant breaking power (in MVA) over a given
voltage range. Moreover, the asymmetrical current will be a function of the
following table taking S = 1.1 for Merlin Gerin circuit breakers.
ratio S
1.8
Asymmetrical interrupting capability = S x symetrical interrupting capability.
1.7
Both at specified operating voltage
1.6
1.5
1.4
1.3
Symetrical interrupting capability at
1.2 specified operating voltage = 1.0
1.1
1
0 0.5 1234 cycles
0 0.006 0.017 0.033 0.050 0.067
seconds
# Rated short-circuit breaking capacity (kA)
Sequence n� current broken % aperiodic component
1 10 50 - 100
Example:
230
# Isc = 40 kA
3 60 50 - 100
# % asymmetry = 50% 4 100
5 KI to V/K
# Iasym = 1.1 " 40 = 44 kA
44 44 6 SI to V 50 - 100
-----------------------------------= ----------= 36 kA
-
# Isym =
7 KSI to V/K 50 - 100
1 + 2(50%)2 1,22
8 electrical endurance
Sequence 6 will therefore be tested at
9/10 reclosing cycle at ASI and AKSI
36 kA + 50% asymmetry,
11 C - 2 s - O at KI
this being 44 kA of total current.
12 rated Isc duration = KI for 3 s
13/14 single phase testing at KI and KSI (0.58 V)
Short-circuit breaking testing must comply with the
14 test sequences above, with:
I : symmetrical breaking capacity at maximum voltage
R : reclosing cycle coefficient
(Reclosing factor)
K : voltage range factor: K =Vmax--
-----------
Vmin
I----------=
asym
S : asymmetrical factor: -- 1.1
Isym
for Merlin Gerin circuit breakers
V : maximum rated voltage
Schneider Electric
TED300014EN_070_081. Gamme
Standards
00CEI - ANSI comparison
Coordination of rated values
According to IEC
Rated Rated short-circuit Rated operating current
voltage breaking current
r sc r
U (kV) I (kA) I (A)
3.6 10 400
630 1250
16
25 1250 1600 2500
40 1250 1600 2500
3150
7.2 8 400
400 630 1250
12.5
16 630 1250 1600
25 630 1250 1600 2500
40 1250 1600 2500
3150
12 8
400
400 630 1250
12.5
16 630 1250 1600
25 630 1250 1600 2500
40 1250 1600 2500
3150
50 1250 1600 2500
3150
17.5 400 630 1250
8
12.5 630 1250
16 630 1250
1250
25
40 1250 1600 2500
3150
24 400 630 1250
8
630 1250
12.5
16 630 1250
1250 1600 2500
25
40 1250 1600 2500
3150
36 8 630
12.5 630 1250
630 1250 1600
16
25 1250 1600 2500
40 1250 1600 2500
3150
According to ANSI
Maximum Rated Minimum Rated Rated
rated short-circuit rated short-circuit operating
voltage breaking current breaking current
voltage
current
at Umin
at Umax
Umax (kV) Isc (kA) (kV) Isc (kA) Ir (A)
4.76 18 3.5 24 1200
29 3.85 36 1200 2000
41 4 49 1200 3000
8.25 7 2.3 25 600 1200 2000
17 4.6 30 1200
33 6.6 41 1200 2000
15 9.3 6.6 21 1200
9.8 4 37 1200
18 11.5 23 1200 2000
19 6.6 43 1200 2000
28 11.5 36 1200 2000
37 11.5 48 1200 3000
15.5 8.9 5.8 24 600
18 12 23 1200
35 12 45 1200
56 12 73 2000 3000 4000
25.8 5.4 12 12 600
11 12 24 1200
38 22 23 36 1200 3000
36 24 57 1200
Schneider Electric
Gamme AMTED300014EN_070_08
Standards
0CEI - ANSI comparison
Derating
According to IEC
# Refer to "Switchgear definition/Derating" chapter.
According to ANSI
# The ANSI standard C37 04 gives for altitudes greater than 1 000 metres:
5 a correction factor for the applicable voltage on the rated insulation level
and on the rated maximum voltage,
5 a correction factor for the rated operating current.
The table of correction factors according to altitude [ Pobierz całość w formacie PDF ]

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