62271-200 IEC:2011 – 65 –
Annex AA
(normative)
Internal arc fault –
Method to verify the internal arc classification (IAC)
AA.1 Room simulation
AA.1.1 Room simulation for indoor switchgear and controlgear
The room shall be represented by a floor, ceiling and two walls perpendicular to each other.
Where appropriate, simulated cable access ways and/or exhaust ducts shall also be built.
NOTE 1 The dimensions of the room simulation establish defined test condition, however real installation
conditions generally deviate, refer to 10.2.
Ceiling
The test shall be performed at a ceiling height as specified by the manufacturer.
The ceiling height is always stated from the floor or false floor level where the switchgear is
actually placed. This is also the level where the indicator racks are placed during the IAC test,
refer to Figure AA.8.
However, the ceiling shall be located as a minimum:
– at a distance not less than 200 mm (± 50 mm) above the height of the test specimen
and
– at a distance of 2 000 mm (± 50 mm) from the floor or false floor, if the height of the
test specimen is less than 1 800 mm.
The height of the test specimen is determined by its most upper part that influences the gas
flow, including pressure relief flaps in the highest open position by design and construction.
The pressure relief flaps shall not strike the ceiling during opening.
The test results performed with these conditions are valid for all distances between test
specimen and ceiling larger than the tested ones.
EXAMPLE A test performed with a distance between test specimen and ceiling of 600 mm is valid for this and all
higher distances.
If the manufacturer states a distance between ceiling and the height of the test specimen
between 0 mm and 200 mm, the test results are only valid for this ceiling distance and this
distance may be declared as admissible for the installation instructions.
Lateral wall
The lateral wall shall be placed at 100 mm (± 30 mm) from the left or right lateral side of the
test specimen. A lower distance can be chosen provided that it can be demonstrated that any
permanent deformation of the lateral side of the test specimen is not interfered with or limited
by the wall.
The test results performed with these conditions are valid for all distances between test
specimen and lateral wall larger than the tested ones, provided that the gases are not
directed to the walls.
– 66 – 62271-200 IEC:2011
Rear wall
The test specimen shall be placed at a distance to the rear wall depending on the accessibility
of the rear side of the switchgear and controlgear. Test specimens consisting of functional
units with various depths shall have the required distances at the unit with the biggest depth.
In all cases the distance from the rear wall to the switchgear and controlgear is measured
from the surface of the enclosure, disregarding protruding elements not expected to influence
the evacuation of hot gases (e.g. handles).
Non-accessible rear side
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Unless the manufacturer states a larger minimum clearance, the wall shall allow a clearance
to the rear of the test specimen of 100 mm (± 30 mm). A lower clearance can be chosen
provided that it can be demonstrated that any permanent deformation of the rear side of the
test specimen is not interfered with or limited by the wall.
This test arrangement is deemed valid for an installation mounted closer to the wall than the
test arrangement, provided that two additional conditions are met (refer to 6.106.5, Criterion
No. 1).
If these conditions cannot be demonstrated, or the manufacturer requires direct qualification
of a wall-mounted design, a specific test without clearance to the rear wall shall be carried
out. However, the validity of such a test shall not be extended to any other installation
condition.
When the test is carried out at any larger clearance to the rear wall, as stated by the
manufacturer, this clearance shall be declared as a minimum admissible for the installation
instructions. The instructions shall also include guidance on the obligation to adopt measures
preventing persons to enter that area.
Accessible rear side
+100
The rear wall shall leave a standard clearance of 800 mm ( mm) from the rear side of the
0
test specimen.
The test is also valid for non-accessible rear side with a distance to the wall of 300 mm and
more, in case of accessibility type A has been tested or 100 mm and more in case of
accessibility type B has been tested.
When the test is carried out at any larger clearance to the rear wall, as stated by the
manufacturer, this clearance may be declared as a minimum admissible for the installation
instructions.
Special case, use of exhausting ducts
If the manufacturer claims that the design requires that cable access way and/or any other
exhausting duct need to be used to evacuate gases generated during the internal arc, their
minimum cross-section dimensions, location and output features (flaps or grid, with their
characteristics) shall be stated by the manufacturer. The test shall be carried out with
simulation of such exhausting ducts. The output end of the exhausting ducts shall be at least
2 000 mm (± 50 mm) away from the switchgear and controlgear tested.
For tests performed with an exhausting duct, the absolute ceiling height is not relevant. If the
exhausting duct is installed on top of the specimen, a minimum distance of the test specimen
62271-200 IEC:2011 – 67 –
to the ceiling of 100 mm shall be ensured to document permanent deformations of the
exhausting duct. If such a test is performed for accessible rear side, the test arrangement is
deemed valid for an installation for non-accessible rear side at any distance to the wall, if two
additional conditions are met, refer to 6.106.5, Criterion No. 1.
NOTE 2 The possible effects of hot gases at the end and around the exhausting duct beyond the indicators, are
not covered by the tests in this standard.
AA.1.2 Room simulation for outdoor switchgear and controlgear
Neither ceiling nor walls are required if accessibility is stated for all sides (F, L, R). Simulation
of cable access ways shall be constructed, if necessary, as indicated above.
From the point of view of internal arc, a metal-enclosed switchgear and controlgear passing
the test for indoor application is considered to be valid for outdoor application with the same
accessibility requirements.
In cases where switchgear and controlgear for outdoor application are intended to be placed
under a shelter (for example, for protection against rain) which lowest part is less than
1 500 mm above the switchgear and controlgear, a corresponding ceiling should be
considered.
AA.2 Indicators (for assessing the thermal effects of the gases)
AA.2.1 General
Indicators are pieces of black cotton cloth so arranged that their cut edges do not point
toward the test specimen.
Black cretonne (cotton fabric approximately 150 g/m 2 ) or black cotton-interlining lawn
(approximately 40 g/m 2 ) shall be used for indicators, depending on the accessibility condition.
Care shall be taken to see that the vertical indicators can not ignite each other. This is
0
achieved by fitting them in a frame of steel sheet, with a depth of 2 × 30 mm ( mm) (refer to
−3
Figure AA.1).
With the horizontal indicators, care shall be taken that glowing particles do not accumulate.
This is achieved if the indicators are mounted without frame (refer to Figure AA.2).
+15
The indicator dimensions shall be 150 mm × 150 mm ( mm).
0
AA.2.2 Arrangement of indicators
Indicators shall be placed at each classified side on a mounting rack, at distances depending
on the type of accessibility.
The length of the mounting rack shall be larger than the test specimen to take into account
the possibility of hot gases escaping at angles of up to 45º, from the surface under test. This
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means that the mounting frame on each side – if applicable – shall be at least 100 mm longer
than the unit under test in case of accessibility type B, or at least 300 mm in case of
accessibility type A, provided that the position of the wall in the arrangement of the room
simulation does not limit this extension.
The distance from the indicators fitted vertically to the switchgear and controlgear is
measured from the surface of the enclosure, disregarding protruding elements not expected to
– 68 – 62271-200 IEC:2011
influence the evacuation of hot gases (e.g. handles). If the surface of the switchgear and
controlgear is not regular, the indicators should be placed to simulate as realistically as
possible the position that a person usually may adopt in front of the equipment, at the
specified distance, according to type of accessibility.
a) Accessibility type A (authorized personnel)
Black cretonne (cotton fabric approximately 150 g/m 2 ) shall be used for the indicators.
Indicators shall be fitted vertically at all classified sides of the metal-enclosed switchgear
and controlgear up to a height of 2 000 mm (± 50 mm) evenly distributed, arranged in a
checkerboard pattern, covering 40 % to 50 % of the area (refer to Figures AA.3 and AA.4).
The distance from the indicators to the switchgear and controlgear shall be 300 mm
(± 15 mm).
Indicators shall also be arranged horizontally at a height of 2 000 mm (± 50 mm) above
the floor as described in Figures AA.3 and AA.4 and covering the whole area between
300 mm (± 30 mm) and 800 mm (± 30 mm) from the metal-enclosed switchgear and
controlgear. When the ceiling is placed at a height of 2 000 mm (± 50 mm) above the floor
(refer to AA.1.1) no horizontal indicators are required. The indicators shall be evenly
distributed, arranged in a checkerboard pattern, covering 40 % to 50 % of the area (refer
to Figures AA.3 and AA.4).
Special accessibility condition:
– where normal operation requires persons to stand or walk upon the equipment,
horizontal indicators shall be placed above the upper accessible surface, as described
in Figure AA.6, whatever the height of the switchgear and controlgear;
– black cotton-interlining lawn (approximately 40 g/m 2 ) shall be used for the indicators.
b) Accessibility type B (general public)
Black cotton-interlining lawn (approximately 40 g/m 2 ) shall be used for indicators.
Indicators shall be fitted vertically at all classified sides for the metal enclosed switchgear
and controlgear up to 2 000 mm (± 50 mm) above the floor. If the actual height of the
specimen is lower than 1 900 mm, vertical indicators shall be fitted up to a height 100 mm
(± 50 mm) higher than the test specimen.
The indicators shall be evenly distributed, arranged in a checkerboard pattern, covering
40 % -50 % of the area (refer to Figures AA.3 and AA.5).
The distance from the indicators to the switchgear and controlgear shall be 100 mm
(± 5 mm).
Indicators shall also be arranged horizontally at a height above the floor, as described in
Figure AA.5, and covering the whole area between 100 mm (± 5 mm) and 800 mm
(± 50 mm) from the metal-enclosed switchgear and controlgear. If the test specimen is
lower than 1 900 mm, indicators shall be placed directly on the top covers as for classified
sides, at a distance of 100 mm (± 5 mm) (refer to Figure AA.6). They shall be evenly
distributed, arranged in a checkerboard pattern, covering 40 % to 50 % of the area (refer
to Figures AA.5 and AA.6).
c) Accessibility type C – Pole-mounted equipment (authorized personnel / general public)
Black cotton-interlining lawn (approximately 40 g/m 2 ) shall be used for indicators.
Indicators shall be arranged horizontally, at a distance to be declared by the manufacturer
as the minimum approach distance (± 50 mm) below the test specimen. The indicators
shall cover the whole area of a 3 m × 3 m square frame centred about the pole. They shall
be evenly distributed, arranged in a checkerboard pattern, covering 40 % to 50 % of the
area (refer to Figure AA.7).
The indicators may be at a convenient height above the ground allowing for the control
box and/or electrical/mechanical linkages if applicable.
NOTE 1 This test covers the verification of the protection of both authorized personnel and general public.
62271-200 IEC:2011 – 69 –
NOTE 2 Black cretonne (cotton fabric approximately 150 g/m2) is considered to represent workman’s clothes,
whereas cotton-interlining lawn (approximately 40 g/m2) is considered to represent light summer wear of the
general public.
AA.3 Tolerances for geometrical dimensions of test arrangements
Summary of tolerances for geometrical dimensions of test arrangements as given in the text
(the values given there in brackets are tolerances only for the actual test arrangement and do
not extend the required values):
Distance between test specimen and ceiling: ± 50 mm
Distance between test specimen and lateral wall: ± 30 mm
Distance between test specimen and rear wall (non-accessible): ± 30 mm
Distance between test specimen and rear wall (accessible): 0/+100 mm
Indicator dimensions: 0/+15 mm
Depth of the steel frame for indicators: -3/0 mm
Height of indicators ± 50 mm
Distance between test specimen and indicators
Accessibility type A ± 30 mm
Accessibility type B ± 5 mm
Accessibility type C ± 50 mm
AA.4 Test parameters
AA.4.1 General
A test performed at a given voltage, current and duration is generally valid for all lower values
of current, voltage and duration.
NOTE Lower current level may influence the behaviour of the pressure relief devices and the burn through
performance. For short-circuit current levels lower than tested, care should be taken in the interpretation of the
results.
AA.4.2 Voltage
The test shall be performed at any suitable voltage up to and including the rated voltage. If a
voltage lower than the rated voltage is chosen, the following conditions shall be met.
a) the average r.m.s. current value during the test as computed by a digital recording device
complies with current requirements of AA.4.3.1;
b) the arc is not extinguished prematurely in any of the phases in which it has been initiated
Temporary single-phase extinguishing is permitted, as long as the cumulated duration of
the intervals without current does not exceed 2 % of the test duration and the single
events last not longer than to the next prospective current zero, provided that the integral
of the a.c. component of the current equals at least the value specified in AA.4.3.1 in the
relevant phase.
AA.4.3 Current
AA.4.3.1 AC component
The test current shall be set within a ±5 % tolerance of the rated arc fault current (I A or I Ae ). If
the applied voltage is equal to the rated voltage, this tolerance applies only to the prospective
current.
The current should remain constant. If the capability of the test plant does not permit this, the
test shall be extended until the integral of the a.c. component of the current (I*t) equals the
– 70 – 62271-200 IEC:2011
+10
value specified within a tolerance of ( %). In this case, the current shall be equal to the
0
specified value at least during the first three half-cycles and shall not be less than 50 % of the
specified value at the end of the test.
NOTE Information about the relationship between type of neutral earthing and the single phase-to-earth arc fault
current is provided in 8.104.6.
AA.4.3.2 Peak current
The instant of closing shall be chosen so that the peak current is flowing in one of the outer
phases, and a major loop also occurs in the other outer phase.
If the applied voltage is equal to the rated voltage, the peak value of the prospective current
shall be set to 2,5 times (for frequencies up to 50 Hz) or 2,6 times (for 60 Hz) the r.m.s. value
+5
of the a.c. component defined in AA.4.3.1 with a tolerance of %.
0
If the voltage is lower than the rated voltage, the peak value of the prospective current is
irrelevant, but the peak value of the short-circuit current for the metal-enclosed switchgear
and controlgear under test shall not drop below 90 % of the rated peak value.
NOTE For other, higher, d.c. time constants of the feeding network, a uniform value of 2,7 times the r.m.s. value
of the a.c. component should be used as a rated value for both 50 Hz and 60 Hz applications.
In case of two-phase initiating of the arc, the instant of closing shall be chosen to provide the
maximum possible d.c. component.
AA.4.4 Frequency
At a rated frequency of 50 Hz or 60 Hz, the frequency at the beginning of the test shall be
between 48 Hz and 62 Hz. At other frequencies it shall not deviate from the rated value by
more than ±10 %.
AA.5 Test procedure
AA.5.1 Supply circuit
AA.5.1.1 Three phase tests
The supply circuit shall be three-phase and all three phases of the switchgear and controlgear
shall be energised. The neutral point of the supply circuit may be either isolated or earthed
through an impedance, in such a way that the maximum earth current is less than 100 A. In
this situation, the arrangement covers all situations of neutral treatment.
AA.5.1.2 Single phase tests
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One terminal of the supply circuit shall be connected to the earthing point provided on the
switchgear and controlgear, the other to the phase under test.
The two remaining phases of the test specimen shall be energised at rated voltage, unless
mutual influence between the phases is unlikely.
If one of the remaining phases ignites, the test shall be repeated as a three-phase test.
AA.5.1.3 Feeding arrangements
Feeding direction shall be as follows:
62271-200 IEC:2011 – 71 –
– for a connection compartment: supply from the busbar, through the main switching device;
– for a busbar compartment: the supply connections shall not introduce any opening in the
compartment under test. Supply shall be made through one barrier or through a suitable
feeder unit, from the opposite end of the switchgear and controlgear;
NOTE In case of non-symmetrical designs of busbar compartment, the most onerous internal arc initiation
should be considered, with respect to arc energy and burn through.
– for the main switching device compartment: supply from the busbar, with the device in
closed position;
– for a compartment with several main circuit components inside: supply through one
available set of incoming bushings, with all switching devices in closed position, except for
earthing switches, if any, which shall be in open position.
AA.5.2 Arc initiation
AA.5.2.1 General
The arc shall be initiated between all the phases under test by means of a metal wire of about
0,5 mm in diameter or, in the case of a single phase-to earth arc fault current, between one
phase and earth.
The point of initiation shall be located at the furthest point, downstream in the current path
from the supply, within the compartment under test. If the main circuit of the compartment
under test includes current limiting devices (e.g. fuses), the point of initiation shall be chosen
upstream from the limiting device.
The number of phases to be tested, the connection arrangements, and the action to be taken
if other phases are affected, shall be in accordance with Table AA.1, according to the
construction of the compartment under test.
If a value of I Ae is assigned to the switchgear and controlgear at least one compartment shall
be tested single phase to earth. If this value is greater than 87 % of I A any two phase tests
shall use the value of I Ae for the test current.
In the case of single phase-to-earth ignition, the arc shall be initiated between the middle
phase and closest earth.
AA.5.2.2 Compartments with solid insulation
In compartments where the live parts are covered by solid insulating material, the arc shall be
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initiated at the following locations:
a) at gaps or joining surfaces between the insulation of insulation-embedded parts;
b) by perforation at insulated joints made on site when prefabricated insulating parts are not
used;
c) when a) and b) are not applicable, by perforation or partial removal of solid insulation from
the conductors.
AA.5.2.3 Connection compartments
AA.5.2.3.1 Compartments with plug-in solid insulation connections
For outer-cone plug-in connections, the phase(s) to be ignited shall be fitted with lugs without
insulation.
For inner cone connections, the initiation shall be made by perforating or partly removing their
insulation directly below the cable plug(s) of the phase(s) to be ignited.
– 72 – 62271-200 IEC:2011
The other phase(s) shall be provided with a plug-in connector as can be used in service, able
to be energized.
NOTE Experience shows that the fault generally does not evolve towards a three-phase fault; therefore, the
choice of the fitting for the other phase(s) is not critical.
AA.5.2.3.2 Compartments with site-made solid insulation connections
For connection compartments in which connections are made with site-made solid insulation
connections, the phase(s) to be ignited shall be fitted with lugs without insulation.
AA.5.2.3.3 Compartments without plug in or site-made solid insulation connections
Cable connections without plug-in or site-made insulation connections shall be tested without
cables. The ignition shall be made three-phase.
Cable lugs shall be fitted in their service configuration.
AA.5.2.4 Single phase compartments without any earthed metallic parts
For single phase compartments without any earthed metallic parts, a path shall be created
through the insulation to the closest earthed metallic part.
Table AA.1 – Parameters for internal fault test according to compartment construction
Test Number of Action if other phase
current phases/earth for arc affected
initiation
with bare conductors IA Three N/A
Three phase
compartments, conductors with site-made
IA Three N/A
other than solid insulation
connection 87 % I A Two
compartments: conductors with non site-made
Repeat as 3 phase test
solid insulation I Ae One phase and earth
Single phase
I Ae One phase and earth Repeat as 3 phase test
compartments:
connections uninsulated or
fitted with site-made solid IA Three N/A
insulation
Connection connections using outer cone 87 % I A Two
compartments: plugs (screened or Repeat as 3 phase test
unscreened) I Ae One phase and earth
connections using inner cone 87 % I A Two
Repeat as 3 phase test
plugs I Ae One phase and earth
62271-200 IEC:2011 – 73 –
Dimensions in millimetres
Figure AA.1 – Mounting frame for vertical indicators
Figure AA.2 – Horizontal indicator
– 74 – 62271-200 IEC:2011
Accessibility – Type A Accessibility – Type B
h ≥ 1,9 m h < 1,9 m h ≥ 1,9 m h < 1,9 m
ih ih ih
300 100 ih
300
2 000
2 000
2 000
100
S S S S
iv iv iv iv
IEC 2388/11
Dimensions in millimetres
Key
S switchgear and controlgear
h height of switchgear and controlgear
ih horizontal indicators
iv vertical indicators
Figure AA.3 – Position of the indicators
62271-200 © IEC:2011 – 75 –
Simulated ceiling Simulated ceiling
800 500
dC
Horizontal indicators
(1) (2) (3)
300
Front
800 indicators
Functional Functional Functional Functional
unit 1 unit 2 unit 3 unit
if required
2 000
A 100 A 300 300
Simulated floor
Supply cables
Front elevation End elevation
Simulated walls
(2)
800
300
100
(1) indicators for classified lateral side
(2) indicators for classified rear side
Functional Functional Functional (1)
unit 1 unit 2 unit 3 (3) open pressure relief flap
if required 300
dc distance to ceiling
300
Dimensions in millimetres
Front indicators
Simulated ceiling
Section A-A
IEC 2389/11
Figure AA.4 – Room simulation and indicator positioning for accessibility A,
classified rear side, functional unit of any height
– 76 – 62271-200 © IEC:2011
Simulated ceiling Simulated ceiling
800 800
dC
Horizontal indicators
(1) (2) (3) Front
100 indicators
800
Functional Functional Functional Functional
unit 1 unit 2 unit 3 unit
2 000
if required
100 100
A 100 A
Simulated floor
Supply cables
Front elevation End elevation
Simulated walls
100
(2)
800
100 (1) indicators for classified lateral side
(2) indicators for classified rear side
(1)
100 (3) open pressure relief flap
Functional Functional Functional
unit 1 unit 2 unit 3 dc distance to ceiling
if required
Dimensions in millimetres
100
Front indicators
Simulated ceiling
Section A-A IEC 2390/11
Figure AA.5 – Room simulation and indicator positioning for accessibility B,
classified rear side, functional unit greater than or equal to 1 900 mm high
62271-200 © IEC:2011 – 77 –
Simulated ceiling Simulated ceiling
Horizontal indicators
100
100 (1) 800
800
Front
Functional Functional Functional
(2) Functional
indicators
A unit 1 unit 2 unit 3 A 100 unit 100
if required
100
Simulated floor
Supply cables
Front elevation End elevation
Simulated walls
100
800
100 (2)
100 (1) indicators for classified lateral side
Functional Functional Functional (1)
unit 1 unit 2 unit 3 (2) indicators for classified rear side
if required
Dimensions in millimetres
100
Front indicators
Simulated ceiling
Section A-A
IEC 2391/11
Figure AA.6 – Room simulation and indicator positioning for accessibility B,
classified rear side, functional unit less than 1 900 mm high
– 78 – 62271-200 IEC:2011
Test specimen
Minimum approach
distance
Indicators
3 000 3 000
Height for
convenience
of testing
Control box at typical
distance below test
specimen
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Front view Side view
IEC 2392/11
Dimensions in millimetres
NOTE Refer to c) in AA2.2 for convenience of testing
Figure AA.7 – Test arrangement for overhead connected pole-mounted
switchgear and controlgear
62271-200 IEC:2011 – 79 –
Ceiling
Ceiling height
Wall
HV
switch
gear
a) Switchgear assembly
placed on floor
Floor IEC 2393/11
Ceiling
Front Rear
Ceiling height
HV
Wall
switch
Guard rail
Guard rail
gear
False b) Switchgear assembly
floor placed on false floor
Floor IEC 2394/11
Ceiling
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Front Rear
Ceiling height
Wall
HV
switch
Guard rail
gear
c) Switchgear assembly
placed on false floor,
False floor levels different at
floor front and rear side
Floor IEC 2395/11
Figure AA.8 – Ceiling height stated from the floor or false floor level where the
switchgear is actually placed
