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General
requirements for
LV apparatuses
Basics of Standards
Standards guidelines IEC 60947 and
60898
© ABB Group
October 14, 2015 | Slide 1
Contents
§
IEC 60947 Standard, for industrial application
–
Definitions for MCCBs and ACBs
–
Choice criteria based on rated and limit values
§
IEC 60898 Standard, for domestic application
–
Definitions for MCBs
–
Choice criteria based on rated and limit values
§
Comparison between prescription of IEC 60947 and 60898
© ABB Group
October 14, 2015 | Slide 2
Standard for LV apparatus
§
IEC 60947 Standard for industrial application
–
International Standard
IEC 60947
–
European Standard
EN 60947
§
IEC 947-1 Part 1: General rules
§
IEC 947-2 Part 2: Circuit breakers
§
§
§
Ø TIÊU CHUẨN QUỐC GIA TCVN 6592-41:2009 (IEC 60947-4-1 : 2002) VỀ THIẾT BỊ
ĐÓNG CẮT VÀ ĐIỀU KHIỂN HẠ ÁP
Ø TIÊU CHUẨN QUỐC GIA TCVN 64341:2008 (IEC 60898-1 : 2003) VỀ KHÍ CỤ
IEC 947-3 Part 3: Switch disconnectors
ĐIỆN - ÁPTÔMÁT BẢO VỆ QUÁ DÒNG
DÙNG TRONG GIA ĐÌNH VÀ CÁC HỆ
IEC 947-4 Part 4: Contactors
THỐNG LẮP ĐẶT TƯƠNG TỰ
IEC 947-5 Part 5: Control circuit devices
§
IEC 947-6 Part 6: Multifunction devices
§
IEC 947-7 Part 7: Auxiliary materials
© ABB Group
October 14, 2015 | Slide 3
Ø TCVN 7447-5-51: 2010 hoàn toàn
tương đương với IEC 60364-551:2005
Standard for LV apparatus
§
IEC 60947 Standard
The Standards IEC 60947 part 1 and part 2 gives the requirement for
CBs, that are able to be connected in circuits with a rated voltage
< 1000V ac and < 1500V dc
This Standard is applicable whatever may be:
- the rated currents of the CBs;
- the method of construction of the CBs;
- the possible application of the CBs.
IEC 60947-1
The main objects of part 1 are:
definition of electrical parameters;
definition of working, mounting and transport condition.
IEC 60947-2
The main objects of part 2 are referred to the prescription
and parameters for working and test of the CBs
© ABB Group
October 14, 2015 | Slide 4
IEC Standard definitions
© ABB Group
October 14, 2015 | Slide 5
IEC Standard definitions
§
Circuit Breaker - IEC 60947-2
A mechanical switching device capable of breaking, carrying and making
currents under normal circuit conditions and also making, carrying, for a
specified time, and breaking currents under specified abnormal circuit
conditions such as those of short-circuit
§
BREAKING
Breaking Capacity ( Icu, Ics)
§
WITHSTAND
Short time withstand ( Icw)
§
MAKING
Making Capacity (Icm)
Making capacity of a circuit breaker is the maximum current which the
breaker can conduct at the instant of closing. The making capacity is
considered to the peak value of the first cycle when there is an
imaginary short circuit between the phases.
© ABB Group
October 14, 2015 | Slide 6
IEC Standard definitions
§
Switch Disconnector - IEC 60947-3
A mechanical switching device capable of breaking, making and carrying currents
under normal circuit conditions but only making and carrying, for a specified
time, currents under specified abnormal circuit conditions such as those of shortcircuit.
§
BREAKING
Breaking Capacity
§
WITHSTAND
Short time withstand
§
MAKING Capacity
Switch disconnector, Load switch ;
Load Breaker Switch
© ABB Group
October 14, 2015 | Slide 7
IEC Standard definitions
§
Disconnector - IEC 60947-3
A device fulfills the isolating function stipulated under IEC 60947-1 when
in the“Open” position the isolation at a defined withstand voltage is
assured between the open contacts of the main circuit of the switchgear.
According to IEC 60947-3, an isolator must only be able to
make and break a circuit, if either a current of negligible size is
switched on or off, or if during switching no noticeable voltage
difference between the terminals of each pole occurs.
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October 14, 2015 | Slide 8
Changeover Switch
Switch
Switch fuse
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October 14, 2015 | Slide 9
ATS by OTM
IEC Standard definitions
– Air circuit breaker (ACB): a circuit breaker having a supporting housing of
moulding insulating material and a metallic frame, forming an integral part
of the circuit breaker (Emax2)
Electronic trip Unit
IEC 60947 - ACB is Cat B Circuit breaker with
Withstand short circuit current Capacity Icw
© ABB Group
October 14, 2015 | Slide 10
© ABB Group
October 14, 2015 | Slide 11
IEC Standard definitions
§
Circuit breaker type
Moulded case circuit breaker (MCCB): a circuit breaker having a supporting housing of
moulding insulating material, forming an integral part of the circuit breaker (Isomax,
Tmax)
Thermo magnetic trip
Electronic trip Unit
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October 14, 2015 | Slide 12
Thermo magnetic Trip
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October 14, 2015 | Slide 13
© ABB Group
October 14, 2015 | Slide 14
MCCB Electronic trip Unit
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October 14, 2015 | Slide 15
Miniature Circuit Breaker
IEC 60947 defines 5 tripping
characteristics for MCB: B, C, D, K, Z
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October 14, 2015 | Slide 16
Miniature Circuit Breaker
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October 14, 2015 | Slide 17
Current limiting circuit breaker
§
Current limiting circuit breaker (IEC 60947-2 def. 2.3)
A circuit breaker with a break-time short enough to prevent
the short-circuit current from reaching its peak value
A current-limiting circuit
breaker is able to reduce the
stress, both thermal and
dynamic, because is has been
designed to start the opening
operation before the short-circuit
current has reached its first
peak, and to quickly extinguish
the arc between the contacts.
© ABB Group
October 14, 2015 | Slide 18
Current limiting circuit breaker
§
Peak limitation curves
Value of the limited peak
of the short circuit current
according to the value of
the symmetrical short
circuit current Irms
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October 14, 2015 | Slide 19
Current limiting circuit breaker
§
Example
Peak
105kA
100kA
S6L800 In800
54kA
16,8kA
T2L 160 In160
10kA
10kA
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October 14, 2015 | Slide 20
50kA
100kA
Irms
Current limiting circuit breaker
§
Energy limitation
Current
Energy limitation
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October 14, 2015 | Slide 21
Time
Current limiting circuit breaker
n I2t
curves
Value of the let-through
energy according to the
value of the symmetrical
short circuit current Irms
© ABB Group
October 14, 2015 | Slide 22
Current limiting circuit breaker
§
Energy limitation
Protection against short-circuit (IEC 60364)
To protect a cable against short-circuit, the specific let-through energy of
the protective device must be lower or equal to the withstanding energy of
the cable:
Specific let through energy curve LLL
1E3MA²s
100MA ²s
where
– I2 t is the specific let-through energy of
the protective device which can be read on
the curves supplied by the manufacturer;
– S is the cable cross section [mm2]; in the
case of conductors in parallel it is the cross
section of the single conductor;
– k is a factor that depends on the cable
insulating and conducting material.
10MA²s
1MA²s
0.1MA²s
1E-2MA²s
0.1kA
© ABB Group
October 14, 2015 | Slide 23
1kA
10k A
100k A
Choice criteria
In = 1600 A
Iu = 1600 A
Ue = 415 V
Icu= 50 KA
Ics = 50 KA
Ics = 50 KA (1s)
© ABB Group
October 14, 2015 | Slide 24
Choice criteria
§
Rated values (Iu, Ue)
n
Limit values (Icu, Ics, Icw, Icm)
n
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October 14, 2015 | Slide 25
Insulation values (Ui, Uimp)
Rated value Iu
§
Rated uninterrupted current Iu
the rated uninterrupted current of an equipment is a value of
current, stated by the manufacturer, that the equipment can carry
in uninterrupted duty (at 40 °C)
IEC 60947-1 def. 4.3.2.4
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October 14, 2015 | Slide 26
Rated value Iu
The rated uninterrupted current Iu is different from the rated
current In, which is the rated current of the thermomagnetic or
electronic trip unit and is lower or equal to Iu.
§
A new concept
for setting the
current In: the
rating plug
© ABB Group
October 14, 2015 | Slide 27
© ABB Group
October 14, 2015 | Slide 28
Rated value Iu
§
Rated uninterrupted current Iu
Some factors may reduce the Iu of a circuit breaker
T4 320 - Fixed
T4 320 - Plug-in / Withdrawable
© ABB Group
October 14, 2015 | Slide 29
Rated value Iu
§
Rated uninterrupted current Iu
Some factors may reduce the Iu of a circuit breaker
Circuit breakers do not undergo any alterations in their performances up to an
altitude of 2000m. Above this, as the altitude increases, the atmospheric properties
are altered in terms of composition, dielectric resistance, cooling capacity and
pressure; therefore the rated uninterrupted current decreases.
© ABB Group
October 14, 2015 | Slide 30
Rated value Ue
§
Rated operational voltage Ue
the rated operational voltage of an equipment is a value of voltage
which, combined with a rated operational current, determines the
application of the equipment and to which the relevant tests and
the utilization categories are referred.
IEC 60947-1 def. 4.3.1.1
© ABB Group
October 14, 2015 | Slide 31
Choice criteria
§
Rated values (Iu, Ue)
§
Limit values (Icu, Ics, Icw, Icm)
§
© ABB Group
October 14, 2015 | Slide 32
Insulation values (Ui, Uimp)
Limit value Icu
Icu = RATED ULTIMATE SHORT
CIRCUIT BREAKING CAPACITY
IEC 60947-2
def. 4.3.5.2.1
Breaking capacity for which the prescribed conditions
according to a specified test sequence do not include the
capability of the circuit breaker to carry its rated current
continuously
- test sequence: O - 3 min - CO
- dielectric withstand at 2 x Ue
- verification of overload release at 2.5 x I1
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October 14, 2015 | Slide 33
Limit value Ics
Ics = RATED SERVICE SHORT
CIRCUIT BREAKING CAPACITY
IEC 60947-2
def. 4.3.5.2.2
Breaking capacity for which the prescribed conditions
according to a specified test sequence include the capability
of the circuit breaker to carry its rated current continuously
- test sequence: O - 3 min - CO - 3 min – CO
- dielectric withstand at 2 x Ue
- verification of temperature rise at Iu
- verification of overload release at 1.45 x I1
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October 14, 2015 | Slide 34
Rated value Ue
§
Rated operational voltage Ue
Breaking capacity is always referred to the operational voltage; the
breaking capacity decreases when the voltage increases.
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October 14, 2015 | Slide 35
Limit values Icu and Ics
§
Relation between Ics and Icu
This relation is always true!!!
Ics ≤ Icu
The service breaking capacity Ics can be expressed as
a value of breaking current, in kA;
a percentage of Icu, rounded up
to the lowest whole number,
in accordance with the table (for
example Ics = 25% Icu).
Standard ratios between Ics and Icu
© ABB Group
October 14, 2015 | Slide 36
Limit values Icu and Ics
§ Icu and Ics:
selection criteria
Main circuit breakers or circuit breakers for which
a long out-of-service period can not be accepted
(for example naval installation)
Ics
CB selection
based on
Icu
Normal / terminal circuits
and / or economic applications
© ABB Group
October 14, 2015 | Slide 37
Limit value Icw
Icw = RATED SHORT-TIME
WITHSTAND CURRENT
IEC 60947-2
def. 4.3.5.4
Example of use of category B circuit breakers
in electrical plant
The upstream circuit
Trafo 630kVA
breaker can withstand
Ucc%=4%
the fault current up to 1
sec, thus guaranteeing
ACB E1B12
an excellent selectivity
400V
22.7kA
with downstream
MCCB T4
MCCB T3
apparatus
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October 14, 2015 | Slide 38
Limit value Icw
CATEGORY B
CIRCUIT BREAKER
IEC 60947-2
Table 4
Circuit breakers specifically intended for selectivity in short
circuit conditions in relation to other protection devices in
series, that is with an intentional delay (adjustable) applicable
in short circuit conditions.
These circuit breakers have a specified rated short-time
withstand current Icw.
© ABB Group
October 14, 2015 | Slide 39
Limit value Icw
CATEGORY A
CIRCUIT BREAKER
IEC 60947-2
Table 4
Circuit-breakers “not specifically” intended for selectivity under
short circuit conditions with respect to other protection devices
in series on the load side, that is without intentional short-time
delay provided for selectivity under short-circuit conditions.
These circuit-breakers have not a specified rated short-time
withstand current value Icw.
© ABB Group
October 14, 2015 | Slide 40
Limit value Icw
Icw = RATED SHORT-TIME
WITHSTAND CURRENT
IEC 60947-2
Table 3
It is the value of short-time withstand current assigned to the
circuit-breaker by the manufacturer under specified test
conditions. This value is referred to a specified time (usually 1s or 3s).
It must be stated when the circuit-breaker is classified in
category B and its value must be greater than:
§
the highest value between 12 Iu and 5 kA
for CBs with Iu £ 2500A
§
30 kA
for CBs with Iu > 2500A
Circuit breakers without Icw value are classified in category A
© ABB Group
October 14, 2015 | Slide 41
Limit value Icm
Icm = RATED SHORT-CIRCUIT
MAKING CAPACITY
IEC 60947-2
def. 4.3.5.1
Making capacity for which the prescribed conditions according
to a specified test sequence include the capability of the circuit
breaker to make the peak current corresponding to that rated
capacity at the appropriate applied voltage.
It is always necessary to verify that:
Icm ³ Ipeak
© ABB Group
October 14, 2015 | Slide 42
Limit value Icm
§
Short circuit current: how to calculate the peak?
The peak of the short-circuit current Ip is the maximum possible
instantaneous value of the prospective short-circuit current; it
may be calculated by the following formula (IEC 60909-0):
I”k is the short-circuit current (rms value)
at the initial instant of the shortcircuit
The peak is a function of the power factor!!!
© ABB Group
October 14, 2015 | Slide 43
Limit value Icm
§
The Standard hypothesis
Perspective
current IKLLL
10 - 100 kA
10 - 50 kA
6 - 20 kA
0,5 – 4,5 kA
Distance from the
power source
© ABB Group
October 14, 2015 | Slide 44
Limit value Icm
For a.c. the rated short-circuit making
capacity of a circuit-breaker shall be not
less than its rated ultimate short-circuit
breaking capacity, multiplied by the factor
n of the table.
© ABB Group
October 14, 2015 | Slide 45
IEC 60947-2
Table 2
Icm ≥ n x Icu
Limit value Icm
§
SACE product features
If the cosj of the plant is higher than the standard prescribed
value, it is not necessary to take into account the rated shortcircuit making capacity of the circuit-breakers (Icm)
If the cosj of the plant is lower than the standard
prescribed value, usually near to the transformer and/or
generator, it is necessary to verify Icm ³ Ipeak
© ABB Group
October 14, 2015 | Slide 46
Example Icm - Ip
e.g. Short circuit current of the plant is Icc = 75kA ;
the used circuit breaker has an Icu = 75 kA;
according to the table 2, cosjk=0.2 and n=2,2 so Icm = n x Icu = 165 kA
If the cosjk of the plant is equal to 0.16 (lower than the standard prescribed value)
the evaluated Ip=175kA.
Since Ip > Icm the CB selected is not correct. I will use a CB with a greater
value of Icu in order to have an Icm value suitable to the peak current of the plant
© ABB Group
October 14, 2015 | Slide 47
Choice criteria
§
Rated values (Iu, Ue)
§
Limit values (Icu, Ics, Icw, Icm)
§
© ABB Group
October 14, 2015 | Slide 48
Insulation values (Ui, Uimp)
Limit value Ui
IEC 60947-1
def. 4.3.1.2
Ui = RATED INSULATION
VOLTAGE
The rated insulation voltage of an equipment is the value
of voltage to which dielectric tests and creepage
distances are referred
It shall be always verified that:
Ue < Ui
© ABB Group
October 14, 2015 | Slide 49
Limit value Uimp
Uimp = RATED IMPULSE
WITHSTAND VOLTAGE
IEC 60947-1
def. 4.3.1.3
The peak value of an impulse voltage of prescribed form and
polarity (1,2/50ms) which the equipment is capable of withstanding
without failure under specified conditions of test and to which
the values of the clearances are referred.
It shall be always verified that:
Uimp > transient overvoltage in
the plant
© ABB Group
October 14, 2015 | Slide 50
IEC Standard definitions
Miniature Circuit Breakers MCB
International Standard References
IEC 60898
Applicable to circuit-breakers for protection of wiring installation
in buildings and similar applications, and designed for use by
uninstructed persons, and for not being maintained.
Part 1: Circuit-breakers for a.c. operation
Part 2: Circuit-breakers for a.c. and d.c. operation (additional requirements)
© ABB Group
October 14, 2015 | Slide 51
Choice criteria
§
Rated values (In, Ue)
§
© ABB Group
October 14, 2015 | Slide 52
Limit values (Icn, Ics)
Rated value In
Rated uninterrupted current (In):
§the rated uninterrupted current of an equipment is a value of
current, stated by the manufacturer, which the equipment
can carry in uninterrupted duty, at a specified reference
ambient air temperature (30 °C).
§
§The
rated current doesn’t exceed the 125A.
IEC 60898-1 def. 5.2.2
© ABB Group
October 14, 2015 | Slide 53
Rated value Ue
Rated operational voltage (Ue):
The rated operational voltage of a circuit-breaker is the value
of voltage, assigned by the manufacturer, to which its
performances (particularly the short-circuit performance) are
referred.
§
The rated operational voltage doesn’t exceed the 440Vac
220Vdc.
IEC 60898-1 def. 5.2.1.1
© ABB Group
October 14, 2015 | Slide 54
Choice criteria
§
Rated values (In, Ue)
§
© ABB Group
October 14, 2015 | Slide 55
Limit values (Icn, Ics)
Limit value Icn
Icn = RATED SHORT CIRCUIT
CAPACITY
IEC 60898-1
def. 5.2.4
The rated short-circuit capacity is the value of the ultimate
short-circuit breaking capacity for which the prescribed
conditions, according to a specified test sequence, do not
include the capability of the circuit-breaker to carry 0,85 times
its non-tripping current for the conventional time.
test sequence: O - 3 min - CO
- leakage current at 1.1 Ue (< 2 mA)
- dielectric strength test at 900 V
- verification of overload release at 2.8 x In
The rated short circuit capacity doesn’t exceed the
25kA in ac and 10kA in dc
© ABB Group
October 14, 2015 | Slide 56
Limit value Ics
Ics = RATED SERVICE SHORT
CIRCUIT CAPACITY
IEC 60898-1
def. 3.5.5.2
The service short-circuit capacity of a circuit-breaker is the
value of the breaking capacity for which the prescribed
conditions according to a specified test sequence include the
capability of the circuit-breaker to carry 0,85 times its nontripping current for the conventional time.
© ABB Group
October 14, 2015 | Slide 57
Limit value Ics
§
Service Short Circuit capacity (Ics):
- test seq. :
O - 3 min - O - 3 min – CO
O - 3 min - CO - 3 min – CO
(for one or two poles cb)
(for three or four poles cb)
- leakage current at 1.1 Ue (< 2 mA)
- dielectric strength test
- verification of no tripping at 0,85 x In
A circuit-breaker with a rated short-circuit capacity (Icn) has a corresponding service short-circuit
capacity (Ics) as from this table:
The circuit breaker with
Icn < 6000A
6000A < Icn < 10000A
Icn > 10000A
© ABB Group
October 14, 2015 | Slide 58
Ics is equal to 1xIcn
Ics is equal to 0,75xIcn
Ics is equal to 0,5xIcn
Minimum value of Ics is 6000A.
Minimum value of Ics is 7500A.
Tripping Curves
Overload characteristics
The main difference between the overload protection curve of the CBs responding to
IEC 60947 or IEC 60898 are referred to the conventional non tripping current.
The prescibed conditions are given in this table:
© ABB Group
October 14, 2015 | Slide 59
Tripping Curves
Magnetic characteristics
The CBs according to IEC 60947 usually have the instantaneous threshold at 5 or 10 times
the rated current with a tolerance of + 20%.
The CBs according to IEC 60898-1 (ac applications) have different instantaneous
threshold referred to the type B , C , D as indicated in the table below:
© ABB Group
October 14, 2015 | Slide 60
Tripping Curves
© ABB Group
October 14, 2015 | Slide 61
Comparison (summary)
IEC 60947-2
IEC 60898-1
People
Instructed
Uninstructed
Maintenance
Possible
Not possible
< 1000 Vac
< 440 Vac
< 1500 Vdc
< 220 Vdc
40° C
30° C
Rated Voltage
(Ue)
Ambient
Temperature
No limits
Rated Current
(Iu < 6300 A)
Short circuit
breaking current
© ABB Group
October 14, 2015 | Slide 62
No limits for Icu
In = 125 A
Icn = 25 kA (ac)
Icn = 10 kA (dc)
© ABB Group, BU Breakers and Switches
October 14, 2015 | Slide 63