IEC TR 62854:2014
(Main)Sharp edge testing apparatus and test procedure for lighting equipment - Tests for sharpness of edge
Sharp edge testing apparatus and test procedure for lighting equipment - Tests for sharpness of edge
IEC TR 62854:2014 details a test procedure and test equipment that may be used to assist the assessment of the risk of hazardous sharp edges that may be exposed to the user or installer of lighting equipment.
Appareil et mode opératoire pour la vérification des bords vifs des appareils d'éclairage - Essais de tranchant des bords
L'IEC TR 62854:2014 indique les détails d'un mode opératoire d'essai et d'un appareillage d'essai pouvant être utilisés pour faciliter l'évaluation du risque constitué par des bords vifs dangereux en présence desquels peut se trouver l'utilisateur ou l'installateur d'un appareil d'éclairage.
Vodilo za električne inštalacije – 413. del: Zaščita pri posrednem dotiku – Samodejni odklop napajanja
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
01-februar-2000
9RGLOR]DHOHNWULþQHLQãWDODFLMH±GHO =DãþLWDSULSRVUHGQHPGRWLNX±
6DPRGHMQLRGNORSQDSDMDQMD
Electrical installation guide - Clause 413: Explanatory notes to measures of protection
against indirect contact by automatic disconnection of supply
Guide pour les installations électriques - Article 413: Notes explicatives sur les mesures
de protection contre les contacts indirects par coupure automatique de l'alimentation
Ta slovenski standard je istoveten z: IEC/TR 61200-413
ICS:
13.260 9DUVWYRSUHGHOHNWULþQLP Protection against electric
XGDURP'HORSRGQDSHWRVWMR shock. Live working
91.140.50 Sistemi za oskrbo z elektriko Electricity supply systems
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
CEI
RAPPORT
IEC
TECHNIQUE - TYPE 3
1200-413
TECHNICAL
Première édition
REPORT - TYPE 3
First edition
1996-03
installations électriques —
Guide pour les
Partie 413:
Protection contre les contacts indirects —
Coupure automatique de l'alimentation
Electrical installation guide —
Part 413:
Protection against indirect contact —
Automatic disconnection of supply
réservés — Copyright — all rights reserved
© CEI 1996 Droits de reproduction
No part of this publication may be reproduced or utilized in
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1200-413 © IEC:1996 - 3 -
CONTENTS
Page
FOREWORD 5
Clause
O Introduction 9
0.1 Principle of the protective measure 9
0.2 Effects of electric current on the human body 9
0.3 Electrical impedance of the human body 15
0.4 Situations 15
0.5 Main equipotential bonding 17
1 Scope 21
2 Reference documents 21
3 Application of types of system earthing 23
413.1.3 TN-system 23
413.1.3.1 Fault loop 23
413.1.3.3 Prospective touch voltage 23
413.1.3.3 Analysis of conditions for protection 25
413.1.3.5 Distribution circuits 27
413.1.3 Practical application of conditions for protection 33
413.1.3.5 Cases where a disconnection time up to 5 s is permitted 41
413.1.3.6, 413.1.3.8 and 413.1.3.9 Protection by residual current protective devices 47
413.1.3.7 Limitation of fault voltage based on voltage balance 45
413.1.4 TT-system 51
413.1.4.1 Fault loop 51
413.1.4.2 Analysis of conditions of protection 51
413.1.4.4 Protective devices 53
413.1.5 IT-system 55
413.1.5.1, 413.1.5.3 No disconnection for the first fault 55
413.1.5.3, 473.3.2.2 Types of IT systems 55
413.1.6 Supplementary equipotential bonding 61
Annexes
A Protection following a second fault (413.1.5.5, 413.1.5.6) 63
B Definition of touch voltage, prospective touch voltage and fault current 75
C Conditions of protection in particular situations 85
D The influence of fault currents on the resistance of conductors 91
1200-413 ©IEC:1996 – 5 -
ELECTRICAL INSTALLATION GUIDE -
Part 413: Protection against indirect contact -
Automatic disconnection of supply
FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization
comprising all national electrotechnical committees (IEC National Committees). The object of the IEC is to
promote international co-operation on all questions concerning standardization in the electrical and electronic
fields. To this end and in addition to other activities, the IEC publishes International Standards. Their
preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt
with may participate in this preparatory work. International, governmental and non-governmental organizations
liaising with the IEC also participate in this preparation. The IEC collaborates closely with the International
Organization for Standardization (ISO) in accordance with conditions determined by agreement between the
two organizations.
2) The formal decisions or agreements of the IEC on technical matters, express as nearly as possible, an
international consensus of opinion on the relevant subjects since each technical committee has representation
from all interested National Committees.
3) The documents produced have the form of recommendations for international use and are published in the
form of standards, technical reports or guides and they are accepted by the National Committees in that
sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the
subject of patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
The main task of IEC technical committees is to prepare International Standards. In exceptional
circumstances, a technical committee may propose the publication of a technical report of one
of the following types:
type 1, when the required support cannot be obtained for the publication of an
•
International Standard, despite repeated efforts;
• type 2, when the subject is still under technical development or where for any other
reason there is the future but not immediate possibility of an agreement on an International
Standard;
• type 3, when a technical committee has collected data of a different kind from that which
is normally published as an International Standard, for example "state of the art".
Technical reports of types 1 and 2 are subject to review within three years of publication to
decide whether they can be transformed into International Standards. Technical reports of
type 3 do not necessarily have to be reviewed until the data they provide are considered to be
no longer valid or useful.
IEC 1200-413 which is a technical report of type 3, has been prepared by IEC technical
committee 64: Electrical installations of buildings.
1200-413 © IEC:1996 – 7 –
This technical report does not form part of IEC 364. It is a supplement to clause 413.1 of
IEC 364-4-41. This report is intended to provide an explanation of the revision of clause 413.1
in the third edition of IEC 364-4-41 (1992) and of clause 481.3 of the first edition of IEC 364-4-
481 (1993).
The text of this technical report is based on the following documents:
Committee draft Report on voting
64(SEC)726 64/799/RVC
Full information on the voting for the approval of this technical report can be found in the report
on voting indicated in the above table.
- 9 -
1200-413 © IEC:1996
0. Introduction
0.1
Principle of the protective measure
The measure of protection by automatic disconnection of supply which is the subject of clause
413.1 of IEC 364-4-41 is intended to prevent a person being subjected to a dangerous touch
voltage for a time sufficient to cause organic damage, in the event of an insulation fault.
In order to meet this requirement, in the event of such a fault the circuit protective device must
interrupt the resulting fault current sufficiently quickly to prevent the touch voltage persisting
long enough to be dangerous.
It follows that this protective measure relies on the combination of two conditions:
the provision of a conducting path, designated "the fault loop", to provide for circulation
a)
of the fault current. The composition of the fault loop depends on the type of system
earthing (TN, TT or IT);
b) the interruption of the fault current within a maximum time by an appropriate protective
device. This maximum time is dependent on parameters such as the magnitude of the
highest touch voltage*, the probability of a fault, and the probability of a person touching
equipment during a fault. Acceptable limits of touch voltage and duration are based on a
knowledge of the effects of electric current on the human body.
Condition a) requires the installation of protective conductors connecting all exposed-
conductive-parts of the electrical equipment supplied by the installation to an earthing system,
thus forming the fault loop as shown for the different types of system earthing in the diagrams
TN, figure 14 - TT and figures 15-17 - IT). The protective conductors must be
(figure 3 - ,
installed in a sound and reliable manner according to the requirements of Chapter 54 which
specifies the cross-sectional areas of such conductors and the conditions to be fulfilled to
ensure the reliability of the connections.
Condition b) requires the installation of protective devices the characteristics of which are
defined according to the type of system earthing - TN, TT or IT.
0.2 Effects of electric current on the human body
The effects of electric current on the human body have been the subject of numerous studies
and experiments, the results of which have been assembled and surveyed in IEC Report 479.
A first edition of that Report was published in 1974 and a second edition, taking account of new
knowledge in this domain, was published in two parts, the first in 1984, the second in 1987.
The first part was published as a third edition in 1994.
In fact, the Report defines two components:
- the effect on the human body of electrical currents of various magnitudes and durations
flowing through the body;
and
the electrical impedance of the human body as a function of touch voltage.
-
These two components permit the establishment of a relationship between the prospective
touch voltage and its duration, which does not usually result in harmful physiological effects on
any person subjected to that touch voltage.
* See annex B for definitions
1200-413 ©
IEC:1996 - 11 -
For alternating current (15 Hz to 100 Hz) the derivation of such a relationship started with the
data provided by figure 14 of IEC Report 479-1, third edition, reproduced here in figure 1. The
relevant portion of that figure was zone AC-3 (between lines b and c 1 ) within which no organic
damage was to be expected. The probability of irreversible disturbances to cardiac impulses,
without ventricular fibrillation, increases with current and duration, but these effects were not
considered to persist generally following the cessation of current.
Above curve c 1 (in zone AC-4) there was the risk of dangerous physiological effects such as
cardiac arrest, breathing arrest and heavy burns, the probability of which increased with
magnitude of current and time up to about 5 % at line c2.
The problem was to define a suitable current-duration relationship within zone AC-3 which
would serve as a basis for a proposal for a voltage-duration curve from which practical limits of
touch voltage and duration could be derived.
Neither of the boundaries to zone AC-3 provided an acceptable solution to the problem.
Bearing in mind the qualifications with regard to accuracy attached to such data, it was clear
that the desired current-duration relationship must incorporate a suitable margin of safety
between itself and the upper boundary. On the other hand, the adoption of the lower boundary
was considered to be over-cautious.
A similar problem arose when the data given in edition 1 of Report 479 was used to derive a
current-duration relationship. At that time a curve was approved by TC 64 which had a certain
margin of safety below the boundary of zone AC-4.
With these points in mind the curve marked "Lc" in figure 1 was adopted because it was
consistent with the former decision on the size of the margin below the boundary with zone
AC-4, and at the same time recognised the revised conclusions in the second edition of IEC
479 on the degree of danger arising from currents of various durations through the human
body.
It was considered that curve "Lc" (a function of disconnection time and current) was a
reasonable basis for the establishment of disconnection times as a function of prospective
touch voltage (see curve L of figure 2), to be used with the method of protection by automatic
disconnection of supply.
1200-413 © IEC:1996 -
13 -
10 000
5 000
ms
2 000
^
1 000
6i
U
ô
C
o
a
mA
0,1 0,2 2 5 10 20 50 100 200 500 1 000 2 000 5 000 10 000 0,5
Body current IB
1EC 269/96
Figure 1 - Time/current zones of effects of alternating current (15 Hz to 100 Hz) on persons
(derived from figure 14, IEC 479-1, third edition)
Zone Zone limits Physiological effects
designation
AC-1 Usually no reaction effects
Below line a
AC-2 Between line a and curve b Usually no harmful physiological effects
AC-3 Between curves b and c 1 Usually no organic damage to be expected. Likelihood of
muscular contractions and difficulty in breathing, reversible
disturbances of formation and conduction of impulses in the heart,
including atrial fibrillation and transient cardiac arrest without
ventricular fibrillation increasing with current magnitude and time.
AC-4 Above curve c 1 In addition to the effects of Zone AC-3, probability of ventricular
fibrillation increasing from about 5 % at curve c 2 up to about 50 %
at curve c 3 and above 50 % beyond curve c 3. Increasing with
current magnitude and time, pathophysiological effects such as
cardiac arrest, breathing arrest and heavy burns may occur.
- 15 -
1200-413 ©IEC:1996
0.3 Electrical impedance of the human body
With regard to the electrical impedance of the human body to be considered for the
determination of touch voltage, two aspects are relevant:
- the most probable path of the fault current in the body of a person;
- the environmental conditions, principally in regard to the presence of water and the
contact of persons with earth.
The electrical impedance paths in different parts of the human body, i.e. hand to hand, hand to
foot, were reported in IEC 479, second edition. The values were dependent on the applied
voltage. The condition of the skin was responsible for a large proportion of the impedance. In
order that touch voltage limits derived from body impedance should be on the safe side, the
lowest impedance values given in IEC 479-1 (table I) which are exceeded by 95 % of the
population, were chosen.
A current path from two hands to both feet was assumed, this being the path which has the
least resistance and involves the heart muscles to the greatest extent.
0.4 Situations
Taking account of conditions encountered in practice, the normal situation was identified
having the following general characteristics:
- dry or moist locations (or places);
- floor presenting significant resistance.
NOTE — For particular situations, see annex C.
Conditions for protection in normal situations were established taking into account the electrical
impedance Z:
Z. 1000 + 0,5 (in ohms) (1)
ZT5%
The value of 1000 S2 was chosen as a contingency to cover both the presence of footwear and
floor resistance and was a compromise. Experience and measurement for dry locations showed
practical values over a very wide range; typical footwear and floor surfaces having values of at
least 1000 SZ. It was considered that the adoption of such a value provided a substantial
additional margin of safety. It was recognised that where environmental conditions are very
unfavourable, such as exposure to wet conditions, a lower value of impedance should be used,
see annex C.
ZT5% is the value of total body impedance stated in IEC Report 479-1, table I that is not
exceeded by 5 % of the population (the lowest figures tabulated).
The value of was based on the assumption that the body resistance is dependent on the
ZT5%
prospective value of the touch voltage (Ut)*. The touch voltage is the potential which could be
applied to the body if there were no shock current flowing. In fact the body is likely to
(Ut) during the current flow, so that such an assumption
experience a rather lower voltage
implied a further margin of safety in the derived value of touch voltage.
See annex B for definitions.
1200-413 ©IEC:1996 – 17 –
The coefficient 0,5 in equation (1) takes account of the double contact two hands to two feet,
as given in figure 2 of IEC Report 479-1, second edition, being given for contact between one
hand and one foot.
Using the IEC data in the manner explained above, the required relationship between
prospective touch voltage and disconnection time for the normal situation was derived as
shown in table A and is illustrated in figure 2.
Specific values given in table A as a function of prospective touch voltage U t are:
the electrical impedance Z determined as previously indicated;
– the current / passing through the human body;
- the disconnection time t
determined from the curve Lc of figure 1.
Table A –The relationship between prospective touch voltage
and maximum disconnection time
Prospective touch voltage Ut Z I t
V
0 mA s
550 1725 29
1625 46
75 0,60
1600 62
100 0,40
1562 80
125 0,33
220 147 0,18
300 1460 205 0,12
400 1425 280 0,07
1400 350 0,04
The value of 50 V is defined as the conventional touch voltage limit (UL).
Chapter 41 (clause 413.1) deals with the general case corresponding to the normal situation for
which the conventional touch voltage limit is AC 50 V or DC 120 V ripple-free. For other
conditions see annex C.
0.5 Main equipotential bonding
In order to avoid the transmission of potentials by metallic wiring systems and by other
services coming from outside the building, sub-clause 413.1.2.1 requires the provision of main
equipotential bonding connecting all extraneous-conductive-parts at their entry into the building
to the main protective conductor.
The main equipotential bonding reduces the prospective touch voltage in case of a fault in the
corresponding electrical installation, whatever the type of system earthing.
– 19 –
1200-413 ©IEC:1996
10 000
ms
Duration
L
10 100 V
Prospective touch voltage, L4
IEC 270/96
Figure 2 - Maximum duration of prospective touch voltage Ut, for normal situations
1200-413 © IEC:1996 - 21 -
ELECTRICAL INSTALLATION GUIDE -
Part 413: Protection against indirect contact -
Automatic disconnection of supply
1 Scope
IEC 1200-413 is a technical report applicable to electrical installations. It contains a compilation
of comments, explanations, examples and electrical systems in order to facilitate the use of
IEC 364-4-41.
2 Reference documents
IEC 38: 1983, IEC standard voltages
IEC 50(826): 1982, International Electrotechnical Vocabulary (1EV) - Chapter 826: Electrical
installations of buildings
IEC 364-4-473: 1977, Electrical installations of buildings - Part 4: Protection for safety -
Chapter 47: Application of protective measures for safety - Section 473: Measures of
protection against overcurrent
IEC 364-4-481: 1993, Electrical installations of buildings - Pa rt 4: Protection for safety -
Chapter 48: Choice of protective measures as a function of external influences - Section 481:
Selection of measures for protection against electric shock in relation to external influences
IEC 364-7-701: 1984, Electrical installations of buildings - Part 7: Requirements for special
installations or locations - Section 701: Locations containing a bath tub or shower basin
IEC 364-7-702: 1983, Electrical installations of buildings - Pa rt 7: Requirements for special
installations or locations - Section 702: Swimming pools
Electrical installations of buildings - Part 7: Requirements for special
IEC 364-7-704: 1989,
installations or locations - Section 704: Construction and demolition site installations
IEC 364-7-705: 1984, Electrical installations of buildings - Part 7: Requirements for special
installations or locations - Section 705: Electrical installations of agricultural and horticultural
premises
IEC 479-1: 1984, Effects of current passing through the human body - Part 1: General aspects
- Second edition
IEC 479-1: 1994, Effects of current on human beings and livestock - Part 1: General aspects -
Third edition
IEC 479-2: 1987, Effects of current passing through the human body - Part 2: Special aspects
- Chapter 4: Effects of alternating current with frequencies above 100 Hz - Chapter 5: Effects
of special waveforms of current - Chapter 6: Effects of unidirectional single impulse currents of
short duration
IEC 755: 1983, General requirements for residual current operated protective devices
1200-413 © IEC:1996 - 23 -
IEC 898: 1987, Circuit-breakers for overcurrent protection for household and similar
installations
Low-voltage switchgear and controlgear - Part 2: Circuit-breakers
IEC 947-2: 1989,
IEC 1008, Residual current operated circuit-breakers without integral overcurrent protection for
household and similar uses (RCCBs)
IEC 1009, Residual current operated circuit-breakers with integral overcurrent protection for
household and similar uses (RCBOs)
3 Application of types of system earthing
The following subclauses contain explanations and comments on clauses or subclauses of
IEC 364-4-41. These have been numbered according to the relevant clauses or subclauses of
IEC 364-4-41 and IEC 364-4-473.
413.1.3 TN System
413.1.3.1
Fault loop
In a TN system, the fault loop comprises the circuit which includes, as shown in figure 3, the
live conductor on which the fault occurs and the protective conductor directly connected to the
neutral of the source (PE or PEN conductor according to whether it is a TN-S or TN-C system).
la
•
L1
L2
L3
O
la
PE N
M JVW.
t\
J
IEC 271/96
Figure 3 - Simplified diagram of a TN-C-S system showing the principle of protection
In case of fault between a phase and an exposed-conductive-part M, a fault current /a
circulates in the fault loop.*
413.1.3.3 Prospective touch voltage
The prospective touch voltage Ut is that which appears between the exposed-conductive-part
M and the point O. It is:
ZP
(2)
Ut = /a E
* See annex B, figure 8.3 and the definitions of the various voltages.
1200-413 © IEC:1996 - 25 -
where
ZPE is the sum of the impedance of the protective conductors between the exposed-
conductive-part M and the point O;
la is the fault current flowing in the protective conductors between M and O.
For installations supplied directly from a public distribution system, the value of the impedance
of that part of the fault loop which is external to the installation is obtained from the supplier.
For installations supplied from a source other than a public distribution system, the fault loop
impedance value will include the transformer or alternator characteristics (e.g. zero sequence
of a transformer or sub-transient for an alternator) and might differ greatly from that of a public
supply.
413.1.3.3 Analysis of conditions for protection
In principle, the prospective touch voltage is:
IIR(DE2 + XpE2
Ut (3)
—Vo
2 )2
.^(Ro + R^ +RPE )+(Xo + XL
+ XPE
where
U0 is the voltage between phase and neutral;
R0, X0 is the internal resistance and the internal reactance respectively of the source;
RL, XL is the resistance and the reactance respectively of the phase conductor from
the source to the exposed-conductive-parts considered;*
is the resistance and the reactances respectively of the protective conductor
R'PE, X'PE
from the main equipotential bonding to the exposed-conductive-part
considered;*
is the resistance and the reactance respectively of the protective conductor from
RPE, XPE
the exposed-conductive-part to the source.
Xi_ and Xp E have been separated here in order to demonstrate the division of voltage
around the fault loop. In practice they cannot be separately measured.
In practice, particularly for cross-sectional area less than 35 mm 2, the prospective touch
voltage is deduced from the simplified formula:
IZS
Ut Vo RPE (4)
=
where
U0 is the voltage between phase and neutral of the installation;
is the resistance of the protective conductor between the exposed-conductive-part
APE
considered and the reference point B (see figure 4);
ZS is the impedance of the fault loop comprising the source, the live conductor on which
the fault occurs, and the protective conductor between the exposed-conductive-part of
the faulty equipment and the source (Zs = Z0 + Zu +
ZPE).
IEC 909.
NOTE — A more detailed treatment is given in
* See annex D.
1200-413 © IEC:1996 - 27 -
ti
PE
•M
C
MEB
lEC 272N6
Reference point is at the MEB
B Reference point
MEB Main equipotential bonding
C Extraneous-conductive-part
PE Protective conductor
M Exposed-conductive-part
Figure 4 - Installation without a distribution circuit
413.1.3.5
Distribution circuits
Additional precautions need to be taken at distribution boards when there are both final circuits
requiring disconnection in say 0,4 s and some within 5 s.
In figure 4 the prospective touch voltage is equal to the voltage drop along the protective
conductor, between points M and B, due to the fault current /a. It is assumed that the potential
of any extraneous-conductive-part which might be touched simultaneously with the exposed-
conductive-part are substantially the same as that of the reference point B.
1200-413 © IEC:1996 - 29 -
PE
'- LEB
•M
. B
MPE
C MPE
: • MEB
t
/EC 273/96
B Reference point
C Extraneous-conductive-part
LEB Local equipotential bonding
MEB Main equipotential bonding
M Exposed-conductive-part
MPE Main protective conductor
PE Protective conductor
Figure 5 - Installation with a distribution circuit where the bonding provides
a local reference point B, for example to a block of flats
In practice the prospective touch voltage is equal to the voltage drop in the conductor between
M and B due to the fault current /a.
In the event that the voltage drop along the protective conductor is too high, the prospective
touch voltage may be reduced by installing local equipotential bonding between a point on the
extraneous-conductive-part which is closer to the exposed-conductive-part M than the main
equipotential bonding and a convenient point (such as a distribution board) on the protective
conductor of the circuit supplying the exposed-conductive-part, see figure 5.
Such equipotential bonding is made under conditions similar to those specified for the main
equipotential bonding (see 413.1.2.1).
The local equipotential bonding is not necessary if the resistance of the protective conductor
between the exposed-conductive-part and the main equipotential bonding does not exceed
ZS
U0
This condition is frequently met in normal situations, so local equipotential bonding is rarely
necessary.
1200-413 © IEC:1996 - 31 -
The protective device is selected so that the fault current
(5)
ensures its operation in a time t not greater than that in table 41A of sub-clause 413.1.3.3.
This necessitates the calculation of the fault loop impedance which is possible only if all
elements of the loop, including the source are known.
ZS may be calculated if live and protective conductors are in immediate proximity without the
intervention of ferromagnetic parts, or may be determined by measurement.
Reactance may generally be ignored for conductors of cross-sectional area of 35 mm 2 or less
where the conductors and the protective conductor are in immediate proximity. Under these
a may be calculated by
conditions the current l
Uo
la (6)
RL +
RPE
where
RI is the resistance of the live conductor from the reference point B to the exposed-
conductive-part;
R'PE is the resistance of the protective conductor from the reference point B to exposed-
conductive-part.
The prospective touch voltage Ut is taken as:
m
=cUo
U PE la
t =R
1+m (7)
where
m is the ratio of the resistance of the protective conductor and of the phase conductor in the
circuit considered. If the conductors are of the same material, it is taken as equivalent to
the ratio of the reciprocal cross-sectional areas:
RDE SL
m= -
RL SPE
c is a conventional factor taking account of the impedance of the part of the loop on the
supply side of the main or local bonding as appropriate. In the absence of precise
information, the factor c may be taken as 0,8.
If the protective conductor and the phase conductor have the same cross-sectional area,
c Uo
(see equation 7)
Ut- 2
From this formula the prospective touch voltage and disconnection times may be determined as
a function of the nominal voltage of the installation, taking into account the parameters
c
and m.
1200-413 © IEC:1996 – 33 –
413.1.3 Practical application of conditions for protection
Experience has shown that it was often difficult to estimate the prospective touch voltages
correctly.
The use of the fault voltage as a reference was found to be too onerous in the utilisation of
overcurrent protective devices and for this reason it was necessary to make various
hypotheses in estimating the prospective touch voltage. This estimate was based in particular
on the value of the coefficient c, the exact value of which depends on the configuration of the
supply network.
Further, it was not possible to be certain that the rise in the potential of the exposed-
conductive-parts of final circuits would not exceed values of the curve L in the case of a fault in
other final circuits or in distribution circuits (see figure 2).
Thus, in order to establish conditions for the application of the rules for protection, maximum
disconnection times have been determined not as a function of prospective touch voltage but of
the nominal voltage of the installation, taking account of the preceding relationship (6) between
the two voltages.
Therefore a study has been made of the influence of variations in the different parameters on
the value of the prospective touch voltage and the corresponding disconnection time.
These parameters are as follows:
which, depending on the situation of the circuit considered, may vary
– the factor c
between 0,6 (e.g. a circuit very far from the source) and 1 (e.g. a circuit supplied directly
from the source);
which will vary according to the ratio of the may vary cross-sectional areas
– the ratio m
of the protective conductor and of the phase conductor in the circuit considered. For cables
may vary between 1 and 3;
or insulated conductors the ratio m
– the supply voltage U0 which in conformity with the recommendations of IEC 38 may
vary ±10 %.
Calculations show that, for a given value of the voltage U0, the prospective touch voltage Ut
varies in relation to the values of the two parameters c and m, between 0,3 U0 and 0,75 Uo.
For example, for a nominal voltage of 230 V, the prospective touch voltage varies between
69 V and 172 V and the resulting current through the human body varies between 42 mA and
119 mA. According to the curves Lc of figure 1 and L of figure 2, the disconnection time shall
be between 0,25 s and 0,8 s.
Table 41A of IEC 364-4-41 specifies a single time of 0,4 s. This time corresponds to a mean
value of the factor c of 0,8 and a ratio m of 1, values which exist in general in final circuits. This
time is confirmed by long experience in many countries as providing satisfactory protection
against electric shock.
The prospective touch voltage using formula (7) is:
Ut = 0,8 2 = 92 V (8)
approximating to a time of 0,4 s according to the curve L of figure 2.
1200-413 © IEC:1996 - 35 -
The current/time relationship given by the line AB on figure 6, depends upon the actual values
0 = 230 V.
of the factor c and the ratio m, at the rated voltage U
U0:
Furthermore as a function of the actual value of the voltage
- the line A'B' corresponds to the minimum value of voltage, or 0,9 U0;
- the line A"B" corresponds to the maximum voltage, or 1,1 U0.
The point corresponding to the disconnection time as a function of touch voltage is situated
within the hatched zone. It is apparent that the conditions of disconnection are found in every
ci.
case in Zone AC-3 and below the curve
However for the purpose of the standard, a specific value of the disconnection time was
chosen for each nominal voltage, independent of the values of factor c and of ratio m.
- 37 -
1200-413 © IEC:1996
10 000
.
^+i^i Ai =su"■^^^
b
ms
■
■r■rir^^^ ii^^■i will^^^
ral
Duration
^
iiC ^i
^.iVI .c i
^
^
d 1 ■
^Î^
1000 _
• *JIL_ mil
C
ll\>•m^^ellll■■e■m lllm ■
ing:::.%^^ e ^
^.i^.ii._7 ^ ,
"^i_:_:_I_.►^^
^ ^
AC-4-
AC-2 I:ifi AC-3 ^'- ` \ \\
.
^
,,
-►_^
I^ , . ^
^
•
^.
Pi
.
^.^- ^
^
.
^
. .
.
I i
1 10 100 1000 mA
Body current I
IEC 274/96
Figure 6 - Effects of variations in parameters c, m, and Uo on body currents
and body current duration, when the overcurrent device is a fuse
NOTE
1 The central hatched area corresponds to the operational area of fuses for a nominal supply voltage U 0 of
230 V and parameter variations as follows:
U0=230V+10%to230V-10%
c – RRE_ + RPE
range 0,6 to 1
Ro + R^ + RPE
m – RPE
range 1 to 3
RL
2 Point B' situated in Zone AC-4 corresponds to c = 1 and Uo = 230 V – 10 %, and m = 3 a low value of
supply impedance and a low value of voltage are an unusual combination.
3 In the case of a circuit-breaker the locus is a horizontal line at its instantaneous operating time (e.g.
0,1 s for circuit-breakers according to IEC 898). Circuits must be designed to ensure the instantaneous
current is exceeded for all likely variations in supply voltage and supply impedance.
1200-413 © IEC:1996 – 39 –
Following these considerations the disconnection times given in table 41A have been
determined for conventional application.
In practice, these disconnection times are taken into consideration only if the disconnecting
will cause the operation of
device is a fuse. It is necessary to ensure that the fault current l a
the fuse in the time t defined by table 41A, confirming that the corresponding point of the fuse
operating diagram 1(t) is above the upper limit of the time current characteristic of the fuse
(figure 7).
When the protective device is a circuit-breaker it is sufficient to ensure that the fault current /a
is at least equal to the smallest current ensuring instantaneous operation of the circuit-
breaker. The operating times of circuit-breakers are generally less than the times defined by
table 41A provided that they are not intentionally delayed (figure 8).
Time
Fuse
Circuit-breaker
Time
to
-- A
A
to
t1
B
B
t1
>
lm la /a Current Current
/EC 276/96
/EC 275/96
Figure 7 – Protection by fuses Figure 8 – Protection by circuit -breaker
The point A corresponding to the time to If the fault current /a is greater than the
defined by table 41A for the fault current /a is smallest current ensuring instantaneous
above the upper limit of the time current operation of the circuit-breaker /m, the
characteristic of the fuse (FF). operating time t 1 of the circuit-breaker is
clearly less than the time to defined table
41A.
t1 is the actual disconnecting time of the fuse,
as the result of fault current /a.
In other respects, when the touch voltage is less than the conventional touch voltage limit U^,
disconnection of the supply is not necessary from the viewpoint of protection against indirect
contact. However, the disconnection may be necessary for other reasons such as risk of fire.
1200-413 © IEC:1996 — 41 —
This is particularly relevant when the ratio of the impedances of the protective conductor and of
the fault loop is sufficiently small (for example, in the use as a protective conductor of several
conductors of a multicore cable in parallel, or of cable armour in parallel with a bare additional
external conductor in close proximity).
The preceding provisions must be applied to circuits which supply portable equipment and to
circuits which supply hand-held equipment.
413.1.3.5 Cases where a disconnection time up to 5 s is permitted
A disconnection time exceeding the value given in table 41A, but not exceeding 5 s, is
permitted for circuits not directly supplying portable or hand-held equipment for the following
reasons:
— faults in such circuits are less likely;
— there is less likelihood of persons being in contact with equipment supplied by such
circuits during a fault;
—
equipment supplied by these circuits is usually not gripped and can therefore be
released easily if a fault occurs;
— touch voltage is reduced due to the main equipotential bonding.
The limitation to 5 s is conventional. This time covers most cases in which disconnecting times
longer than those given in table 41A are needed, e.g. for distribution circuits and for motor
circuits. This time is also compatible with the thermal withstand of equipment constituting the
fault loop.
Attention is drawn to the fact that disconnecting times exceeding the values in table 41A may
be transferred to associated final circuits supplying po
rtable or hand-held equipment.
Where equipotential bonding is provided between all simultaneously accessible conductive
parts, the appearance of a dangerous touch voltage is unlikely in practice and it is then
permissible to dispense with the determination of conditions for protection against indirect
contact for circuits situated up-stream of the equipotential bonding. This is particularly relevant
for main circuits and distribution circuits.
These conditions are illustrated by figure 9.
1200-413 © IEC:1996 - 43 -
1 2 3 4
000 000 000
LEB
'--40
T3
T2
T4 B
D D D
Main or sub-main
C
distribution board
D
MEB
Supply IEC 277/96
Disconnecting times have to observe the values of table 41A.
Disconnecting times may be longer than the values of table 41A, up to 5 s.
T2,T3,T4 Final distribution boards.
LEB Local equipotential bonding.
C Extraneous-conductive-part.
M Fixed equipment (such as a motor).
X Fixed luminaires.
S Socket-outlet.
D Distribution circuits (circuits situated on the supply side of the final circuits).
B Reference point (see figure 5).
Figure 9 - Conditions of protection of various circuits of an installation
The bonding LEB is not necessary if the touch voltage which could appear in case of a fault, on
the board T4 is not greater than UL.
This condition is fulfilled if the ratio between the resistance of the protective conductor between
the board T4 and the point where the protective conductor is connected to the main earth, and
the impedance of the fault loop is not greater than the ratio between the conventional voltage
limit UL and the nominal voltage between phase and neutral U0.
ROC < UL
(9)
ZS Uo
where
Rp E is the resistance of the protective conductor;
ZS
is the loop impedance.
U0 is the nominal voltage between phases;
UL is the conventional touch voltage limit (50 V).
- 45 -
1200-413 © IEC:1996
This time limit of 5 s does not imply intentional delayed operation of protective devices. It takes
into account the characteristics of the protective devices already used for protection against
overcurrent and permits the devices to be used for indirect shock protection.
However, some delayed operation of protective devices may be necessary for the supply of
apparatus with heavy starting currents or to provide for inrush current at the time of their being
switched on, in order to avoid nuisance tripping. This may be applicable for the supply of high
power motors.
413.1.3.7 Limitation of fault voltage based on voltage balance
Figure 10 shows the formula of sub-clause 413.1.3.7 which is based on voltage balance in
UL (50 V).
such manner that the touch voltage does not exceed the conventional voltage limit
RB 50
<
RE Uo — 50
L1
L3
IEC 278/96
Figure 10 - Voltage balance in a TN system
RB
Ut Uo — UL ) RE
= (
If Ut
is to be less than UL
RB < UL
then
(U0 -
RE UL )
1200-413 © IEC:1996 – 47 –
where
is the total earthing resistance of all earth electrodes in parallel;
RB
is the minimum contact resistance with earth of extraneous-conductive-parts not
RE
connected to a protective conductor, through which a fault to earth may occur.
Figure 11 shows an example of a direct fault to earth and in which the conditions above should
be fulfilled.
L2
PEN
MEB
RB
/EC 279/96
L2 Healthy overhead line bare conductor
L1 Broken bare overhead line conductor
F Metal fence
MEB Main equipotential bonding of the building
RE Resistance of fence to general mass of earth
RB Resistance of earth electrodes within the customers installation
and within the supply system.
Figure 11 – Direct fault to earth
413.1.3.6, 413.1.3.8 and 413.1.3.9 Protection by residual protective devices
Where the conditions for protection by overcurrent protective devices cannot be fulfilled, the
protection may be provided by residual current protective devices (RCD): such conditions may
exist in circuits supplying socket-outlets the length of which is unknown, in circuits of great
length and of small cross-sectional areas the impedance of which is excessive.
In this case, the protective conductor of such circuits shall be connected either:
to the protective conductor of the installation – PEN conductor in TN-C system – on the
a)
12;
source side of the RCD, see figure
b) to a separate earth electrode which shall comply with the conditions of protection of TT
systems, see figure 13.
- 49 -
1200-413 © IEC:1996
In the case a), a short circuit occurring on the load side of the RCD will cause a rise in potential
of the protective conductor due to the voltage drop caused by the short-circuit current in this
conductor. Such a rise of potential could appear during the operating time of the overcurrent
protective device.
The main equipotential bonding reduces the risk which could arise in such circumstances and
so there is no need to consider this risk in Chapter 41.
Further, this risk does not exist if one of the conditions a) or b) of 413.1.3.5 is fulfilled.
RCD
SCPD /a
0000 I I
N I
PEN
O
Rpen
Extraneous---
PE
conductive-
part
IEC 280/96
SCPD Protective device against overcurrent
RCD Residual current protective device
Figure 12 - Connection of the protective conductor of a circuit to the PEN -conductor
A short circuit occurring at C between a phase conductor and the neutral will cause a voltage
drop in the PEN conductor between O and N equal to the product of the short-circuit current /a
and the resistance of the PEN conductor, resulting in the touch voltage /a
Ut = Rpen
RCD
60C
...
IEC TR 62854 ®
Edition 1.0 2014-02
TECHNICAL
REPORT
RAPPORT
TECHNIQUE
Sharp edge testing apparatus and test procedure for lighting equipment – Tests
for sharpness of edge
Appareil et mode opératoire pour la vérification des bords vifs des appareils
d'éclairage – Essais de tranchant des bords
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IEC TR 62854 ®
Edition 1.0 2014-02
TECHNICAL
REPORT
RAPPORT
TECHNIQUE
Sharp edge testing apparatus and test procedure for lighting equipment – Tests
for sharpness of edge
Appareil et mode opératoire pour la vérification des bords vifs des appareils
d'éclairage – Essais de tranchant des bords
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX L
ICS 29.140.40 ISBN 978-2-8322-1418-3
– 2 – TR 62854 © IEC:2014
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Test equipment . 5
3 Calibration . 5
4 The preparation of the test head . 6
5 The test procedure . 6
6 Criteria . 6
Figure 1 – Sharp edge tester . 8
Figure 2 – Sharp edge tester with tape cap (alternate construction) . 9
Figure 3 – Typical calibration procedure . 9
Figure 4 – Test Head Preparation . 10
Figure 5 – Test Procedure . 10
Figure 6 – Edges Tested . 10
Table 1 – Average values of tape dimensions and properties . 7
TR 62854 © IEC:2014 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SHARP EDGE TESTING APPARATUS AND
TEST PROCEDURE FOR LIGHTING EQUIPMENT –
TESTS FOR SHARPNESS OF EDGE
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
The main task of IEC technical committees is to prepare International Standards. However, a
technical committee may propose the publication of a technical report when it has collected
data of a different kind from that which is normally published as an International Standard, for
example "state of the art".
IEC/TR 62854, which is a technical report, has been prepared by subcommittee 34D:
Luminaires, of IEC technical committee 34: Lamps and related equipment.
The text of this technical report is based on the following documents:
Enquiry draft Report on voting
34D/1088/DTR 34D/1101A/RVC
Full information on the voting for the approval of this technical report can be found in the
report on voting indicated in the above table.
– 4 – TR 62854 © IEC:2014
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
TR 62854 © IEC:2014 – 5 –
SHARP EDGE TESTING APPARATUS AND
TEST PROCEDURE FOR LIGHTING EQUIPMENT –
TESTS FOR SHARPNESS OF EDGE
1 Scope
This technical report details a test procedure and test equipment that may be used to assist
the assessment of the risk of hazardous sharp edges that may be exposed to the user or
installer of lighting equipment.
2 Test equipment
Sharp-edge tester – The instrument consists essentially of a handle with a pivoted arm
attached. A constant-tension spring secured to the handle is used to apply a steady force to
the arm. The arm head is a piece of cylindrical steel, with an outside diameter of 12,7 mm and
a length of 19 mm, located at the end of the adjustable arm. The arm head is to be wrapped
with three layers of tape, the two outer layers act as sensing tapes; the inner layer acts as an
indicating tape. Alternatively, the tapes are to be applied to a maximum 15,9 mm diameter
removable sleeve (cap) that is placed onto the 12,7 mm steel head. See Figure 1 or 2.
Indicating tape (inner layer) – 19,1 mm wide, adhesive backed, single-adhesive coated, vinyl
foam tape, black in colour, having the tape properties given in Table 1.
Sensing tape no. 2 (middle layer) – 19,1 mm wide, double-adhesive coated, vinyl foam tape,
white in colour, having the tape properties given in Table 1.
Sensing tape no. 1 (outer layer) – 19,1 mm wide, single-adhesive coated skived tetra-
fluorethylene tape – natural colour, having the tape properties given in Table 1. The skived
tetrafluorethylene backing (film) is shaved in a thin layer from a cylindrical block of material.
Calibration equipment – A weight (mass) that can exert 6,672 ± 0,133 N and a length of
string.
3 Calibration
The sharp edge tester shall be calibrated so that 6,7 ± 0,133 N force is present at the centre
of the head when the arm is between stops. The length of the arm is to be adjustable for
calibration purposes. For special evaluations, the force may be adjusted to a different value.
See Figure 3 for a typical calibration procedure were, the length of the arm is to be adjustable
for calibration purposes:
The adjustment set screws that hold the pivoted arm in place in the main drum are to be
loosened.
With the handle securely held in a horizontal position, the calibration weight is to be attached
to the centre of the head.
The length of the arm within the main drum is to be adjusted so that the weighted arm
remains in a horizontal position with the calibration weight attached.
– 6 – TR 62854 © IEC:2014
The adjustment setscrew(s) are to be tightened to securely lock the pivot arm in place within
the main drum.
The calibration is to be rechecked and the weight removed.
4 The preparation of the test head
The curved face of the tester head shall be covered with three layers of tape in the following
order:
a) First layer (inner layer) – Indicating type, black vinyl foam tape as described in Table 1.
b) Second layer (middle layer) – Sensing tape no. 2, white vinyl foam tape as described in
Table 1.
c) Third layer (outer layer) – Sensing tape no. 1, tetrafluorethylene tape as described in
Table 1.
Each tape is to be applied over approximately 180° of the circumference of the test head to
prevent stretching of the tape. The tapes are not to be stretched when positioned on the head.
See Figure 4.
5 The test procedure
The centre of the tape-covered head of the sharp-edge tester shall be positioned on the edge
to be tested in the manner illustrated in Figures 5 and 6. The arm of the tester shall be
between stops so that the tape-covered head exerts a 6,7 N force on the edge. The tester
shall be immediately moved along the edge a distance of 50 mm and then back to its starting
position without removal of the tester from the edge. It shall then be withdrawn from the edge.
The total distance of engagement between the edge and the tape-covered head is not to
exceed 100 mm. The time of travel is not to take longer than 5 s nor less than 2 s. For an
edge less than 50 mm long shall be tested for a distance of twice its length. (Example: For an
edge 40 mm long, the tester is to be moved along its length and back to the starting position
so that the total distance of engagement between the edge and tester is 80 mm.)
6 Criteria
The application of the sharp-edge tester to an accessible edge as described above shall not
result in the cutting through of the two outer layers of the sensing tapes.
The tape-covered head shall be examined to determine whether or not penetration has
occurred through the two sensing layers. If penetration has occurred through the two sensing
layers, the black indicating tape will be visible through the resulting cut.
TR 62854 © IEC:2014 – 7 –
Table 1 – Average values of tape dimensions and properties
a b c
Indicating tape Sensing tape no. 2 Sensing tape no. 1
(1,14 mm to 2,03 mm) (0,64 mm to total with adhesive backing:
Thickness
1,02 mm) 0,114 mm
backing: 0,064 mm to 0,089 mm
Density 256 kg/cubic meter 224 kg/cubic meter –
2 2 2
Tensile 758 kN/m 379 kN/m 110 kN/m
Elongation, percent 370 – 275
7,9 kV/mm to
Dielectric strength – 9 000 V
9,8 kV/mm
Temperature resistance
80 °C 65 °C 180 °C
(continuous)
Compression deflection
90 kN/m – –
at 25 %
Compression modules 8,5 psi (59 kN/m )
– –
at 25 %
Compression set
percent loss of original 3 % 3,0 %
height
a
3M Company Type 4516 or any other tape having the properties meets the requirements.
b
3M Company Type 4432 or any other tape having the properties meets the requirements.
c
Saint Gobain Company #2045-3 or any other tape having the properties meets the requirements.
—————————
3M Company Type 4516 is the trademark of a product supplied by 3M Company. This information is given for the
convenience of users of this document and does not constitute an endorsement by IEC of the product named.
Equivalent products may be used if they can be shown to lead to the same results.
3M Company Type 4432 is the trademark of a product supplied by 3M Company. This information is given for the
convenience of users of this document and does not constitute an endorsement by IEC of the product named.
Equivalent products may be used if they can be shown to lead to the same results.
Saint Gobain Company #2045-3 is the trademark of a product supplied by Saint Gobain Company. This
information is given for the convenience of users of this document and does not constitute an endorsement by IEC
of the product named
...
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