Use of conventional touch voltage limits - Application guide

Provides guidance on the use of conventional touch voltage limits with reference to thresholds given in IEC 60479-5. Consideration is given to different physiological effects, environmental conditions, contact conditions, etc. This specification only discusses voltages for sinusoidal a.c. at 50/60 Hz and pure d.c. having no significant a.c. component. This specification does not consider immersion of body parts or medical applications. Touch voltage limits are for use by technical committees as guidance for the determination of their own specific limits. This basic safety publication is primarily intended for use by technical committees in the preparation of standards in accordance with the principles laid down in IEC Guide 104 and ISO/IEC Guide 51. It is not intended for use by manufacturers or certification bodies One of the responsibilities of a technical committee is, wherever applicable, to make use of basic safety publications in the preparation of its publications. The requirements, test methods or test conditions of this basic safety publication will not apply unless specifically referred to or included in the relevant publications. This second edition cancels and replaces the first edition which was issued as a technical report in 1992. It constitutes a technical revision and now has the status of a technical specification. The main changes with respect to the previous edition are listed below: - proposal of maximum contact areas for various conventional touch voltage limit; - introduction of different current pathways through the human body for the selection of conventional touch voltage limit; - introduction of conventional touch voltage limit corresponding to the startle reaction current threshold, the inability of let-go current threshold and the ventricular fibrillation current threshold; - possibility of interpolation on contact area for other conventional touch voltage limits. It has the status of a basic safety publication in accordance with IEC Guide 104 and ISO/IEC Guide 51.

Utilisation des tensions limites conventionnelles de contact - Guide d'application

Fournit des lignes directrices pour l'utilisation des tensions limites conventionnelles de contact en se référant aux seuils fournis par la CEI 60479-5. Des considérations sont données pour différents effets physiologiques, conditions d'environnement, conditions de contact, etc. Cette spécification examine seulement les tensions alternatives sinusoïdales à 50/60 Hz ainsi que les tensions continues pures sans composantes alternatives significatives. Cette spécification ne considère pas l'immersion de parties du corps ainsi que les applications médicales. Les limites de tension de contact sont à l'usage des comités techniques afin qu'ils puissent déterminer leur propres limites spécifiques. Cette publication fondamentale de sécurité est d'abord prévue pour être utilisée par les comités techniques dans la préparation des normes en conformité avec les principes du Guide 104 et du Guide ISO/CEI 51. Il n'est pas prévu qu'elle soit utilisée par les constructeurs ou par les organismes de certification. L'une des responsabilités d'un comité d'études consiste, le cas échéant, à utiliser les publications fondamentales de sécurité dans le cadre de l'élaboration de ses publications. Les exigences, les méthodes ou les conditions d'essai de la présente publication fondamentale de sécurité s'appliqueront seulement si elles servent spécifiquement de référence ou sont intégrées dans les publications correspondantes. Cette deuxième édition annule et remplace la première édition parue comme rapport technique en 1992. Elle constitue une révision technique qui conduit au statut de spécification technique. Les modifications principales par rapport à l'édition précédente sont les suivantes : - propositions de surfaces de contact maximales pour différentes tensions limites conventionnelles de contact; - introduction de différents cheminements de courant au travers du corps humain pour le choix de la tension limite conventionnelle de contact; - introduction de la tension limite conventionnelle de contact correspondant au seuil de tressaillement en courant, au seuil de fortes réactions musculaires en courant et au seuil de fibrillation ventriculaire en courant; - possibilité d'interpolation sur la surface de contact pour d'autres tensions limites conventionnelles de contact. Elle a le statut de publication fondamentale de sécurité, conformément au Guide CEI 104 et au guide ISO/CEI 51.

General Information

Status
Published
Publication Date
29-Aug-2007
Current Stage
PPUB - Publication issued
Start Date
30-Aug-2007
Completion Date
30-Aug-2007
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IEC/TS 61201
Edition 2.0 2007-08
TECHNICAL
SPECIFICATION
SPÉCIFICATION
TECHNIQUE
BASIC SAFETY PUBLICATION
PUBLICATION FONDAMENTALE DE SÉCURITÉ
Use of conventional touch voltage limits – Application guide
Utilisation des tensions limites conventionnelles de contact – Guide
d’application
IEC/TS 61201:2007
---------------------- Page: 1 ----------------------
THIS PUBLICATION IS COPYRIGHT PROTECTED
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---------------------- Page: 2 ----------------------
IEC/TS 61201
Edition 2.0 2007-08
TECHNICAL
SPECIFICATION
SPÉCIFICATION
TECHNIQUE
BASIC SAFETY PUBLICATION
PUBLICATION FONDAMENTALE DE SÉCURITÉ
Use of conventional touch voltage limits – Application guide
Utilisation des tensions limites conventionnelles de contact – Guide
d’application
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX
ICS 13.260; 29.020; 91.140.50 ISBN 2-8318-9291-0
---------------------- Page: 3 ----------------------
– 2 – TS 61201 © IEC:2007
CONTENTS

FOREWORD...........................................................................................................................3

INTRODUCTION.....................................................................................................................5

1 Scope...............................................................................................................................6

2 Normative references .......................................................................................................6

3 Use of this technical specification.....................................................................................7

4 Conditions and values of thresholds .................................................................................7

4.1 Physiological effects of body current .......................................................................7

4.2 Body impedance......................................................................................................7

5 Voltage thresholds and limits............................................................................................8

5.1 Voltage threshold as a function of contact area .......................................................8

5.2 Conventional voltage limits....................................................................................11

6 Limits of applicability ......................................................................................................14

6.1 Higher frequency alternating voltages and currents ...............................................14

6.2 Immersion .............................................................................................................14

6.3 Medical applications ..............................................................................................14

Annex A (informative) Voltage thresholds - charged capacitors............................................15

Bibliography..........................................................................................................................17

Figure 1 – Minimum touch voltage threshold corresponding to a.c. and dry conditions

for current startle reaction (a), muscular reaction (b) and ventricular fibrillation (c )................8

Figure 2 – Minimum touch voltage threshold corresponding to a.c. and water-wet

conditions for current startle reaction (a), muscular reaction (b) and ventricular

fibrillation (c ) .........................................................................................................................9

Figure 3 – Minimum touch voltage threshold corresponding to a.c. and saltwater-wet

conditions for current startle reaction (a), muscular reaction (b) and ventricular

fibrillation (c ) .........................................................................................................................9

Figure 4 – Minimum touch voltage threshold corresponding to d.c. and dry conditions

for current startle reaction (a), muscular reaction (b) and ventricular fibrillation (c )..............10

Figure 5 – Minimum touch voltage threshold corresponding to d.c. and water-wet

conditions for current startle reaction (a), muscular reaction (b) and ventricular

fibrillation (c ) .......................................................................................................................10

Figure 6 – Minimum touch voltage threshold corresponding to d.c. and saltwater-wet

condition for current startle reaction (a), muscular reaction (b) and ventricular

fibrillation (c ) .......................................................................................................................11

Figure A.1 – Values of charged capacitances .......................................................................16

Table 1 – Examples of maximum contact areas corresponding to given a.c. touch

voltages .........................................................................................................................12

Table 2 – Examples of maximum contact areas corresponding to given d.c. touch

voltages................................................................................................................................13

Table A.1 – Limits for steady state voltage............................................................................15

Table A.2 – Limit values of accessible capacitances (threshold of pain)................................16

---------------------- Page: 4 ----------------------
TS 61201 © IEC:2007 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
USE OF CONVENTIONAL TOUCH VOLTAGE LIMITS –
APPLICATION GUIDE
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 provides no marking procedure to indicate its approval and cannot be rendered responsible for any

equipment declared to be in conformity with an IEC Publication.

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

Publications.

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. In

exceptional circumstances, a technical committee may propose the publication of a technical

specification when

• the required support cannot be obtained for the publication of an International Standard,

despite repeated efforts, or

• the subject is still under technical development or where, for any other reason, there is the

future but no immediate possibility of an agreement on an International Standard.

Technical specifications are subject to review within three years of publication to decide

whether they can be transformed into International Standards.

IEC/TS 61201, which is a technical specification, has been prepared by IEC technical

committee 64: Electrical installations and protection against electrical shock.

This second edition cancels and replaces the first edition which was issued as a technical

report in 1992. It constitutes a technical revision and now has the status of a technical

specification.
---------------------- Page: 5 ----------------------
– 4 – TS 61201 © IEC:2007
The main changes with respect to the previous edition are listed below:

– proposal of maximum contact areas for various conventional touch voltage limit;

– introduction of different current pathways through the human body for the selection of

conventional touch voltage limit;

– introduction of conventional touch voltage limit corresponding to the startle reaction current

threshold, the inability of let-go current threshold and the ventricular fibrillation current threshold;

– possibility of interpolation on contact area for other conventional touch voltage limits.

It has the status of a basic safety publication in accordance with IEC Guide 104 and ISO/IEC

Guide 51.
The text of this technical specification is based on the following documents:
Enquiry draft Report on voting
64/1584/DTS 64/1605/RVC

Full information on the voting for the approval of this technical specification can be found in

the report on voting indicated in the above table.

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 maintenance result 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

• transformed into an International standard,
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
---------------------- Page: 6 ----------------------
TS 61201 © IEC:2007 – 5 –
INTRODUCTION

This technical specification replaces the first edition of IEC/TR 61201 and provides voltage

limits which are intended to be used by IEC technical committees as conventional touch

voltage limits with regard to protection against electric shock. Its purpose is to facilitate

harmonization and consistency among different IEC publications.

The values proposed in this specification are derived from IEC/TS 60479-5. IEC 60479-5

gives the methodology used for the determination of touch voltage from the application of the

Ohm’s law between different current thresholds corresponding to different physiological

effects and body impedances corresponding to various current paths through the human body,

contact areas, skin moisture at this contact area and on the type of current. Current

thresholds and body impedances are provided by IEC/TS 60479-1.

This specification discusses 50/60 Hz sinusoidal alternating voltage and pure direct voltage

having no significant alternating component. Higher frequency alternating voltage is not

included in this type of analysis as this would require a more complex body impedance model

and would require the use of frequency factors for the current thresholds for the unwanted

physiological effects. As this technical specification does not cover frequencies higher than

50/60 Hz, technical committees are requested to inform IEC/TC 64 about experience gained

on this subject. Suggestions for modifications and additions to the technical specification

should be submitted to IEC/TC 64.
---------------------- Page: 7 ----------------------
– 6 – TS 61201 © IEC:2007
USE OF CONVENTIONAL TOUCH VOLTAGE LIMITS –
APPLICATION GUIDE
1 Scope

IEC/TS 61201, which is a technical specification, provides guidance on the use of

conventional touch voltage limits with reference to thresholds given in IEC 60479-5.

Consideration is given to different physiological effects, environmental conditions, contact

conditions, etc.

This specification only discusses voltages for sinusoidal a.c. at 50/60 Hz and pure d.c. having

no significant a.c. component.

This specification does not consider immersion of body parts or medical applications.

Touch voltage limits are for use by technical committees as guidance for the determination of

their own specific limits.

This basic safety publication is primarily intended for use by technical committees in the

preparation of standards in accordance with the principles laid down in IEC Guide 104 and

ISO/IEC Guide 51. It is not intended for use by manufacturers or certification bodies.

One of the responsibilities of a technical committee is, wherever applicable, to make use of

basic safety publications in the preparation of its publications. The requirements, test

methods or test conditions of this basic safety publication will not apply unless specifically

referred to or included in the relevant publications.
2 Normative references

The following referenced documents are indispensable for the application of this document.

For dated references, only the edition cited applies. For undated references, the latest edition

of the referenced document (including any amendments) applies.

IEC/TS 60479-1:2005, Effects of current on human beings and livestock – Part 1: General

aspects

IEC/TS 60479-2:2007, Effects of current on human beings and livestock – Part 2: Special

aspects

IEC/TR 60479-5, Effects of current on human beings and livestock – Part 5: Touch voltage

threshold values for physiological effects

IEC Guide 104:1997, The preparation of safety publications and the use of basic safety

publications and group safety publications

ISO/IEC Guide 51:1999, Safety aspects – Guidelines for their inclusion in standards

---------------------- Page: 8 ----------------------
TS 61201 © IEC:2007 – 7 –
3 Use of this technical specification

As voltage thresholds of IEC/TR 60479-5 are fully derived from current thresholds of IEC/TS

60479-1, differences between normal conditions and fault conditions are not considered in

this specification.

Technical committees may use these voltage values in conjunction with appropriate risk

factors to set their own voltage limits in their product standards. Such risk factors will consider

other aspects such as probability of faults, probability of contact with live or faulty parts, ratio

between touch voltage and fault voltage, etc.

Product committees should carry out risk assessment for their products based on the

information in this specification. For example, product committees may specify the maximum

touch area. Where touch areas are unknown, conservative figures need to be used.
4 Conditions and values of thresholds
4.1 Physiological effects of body current

Thresholds for the physiological effects associated with electric current through a human body

are reported in IEC/TS 60479-1.
This specification addresses the following physiological effects:
– startle reaction from current;

– strong involuntary muscular reaction (such as inability to let-go from an electrode for a.c.);

– ventricular fibrillation.

Other effects, such as perception, might be important for some applications but are not

addressed in this specification.

For the purposes of this specification, the values corresponding to physiological effects of

greatest interest are curves a, b and c as described in IEC/TS 60479-1.
4.2 Body impedance

Touch voltage limit is a function of the body impedances as described in IEC/TS 60479-1. The

appropriate value of body impedance to use is a function of many factors. The selection of the

proper value should include consideration of the following:
− the type of power source (a.c. or d.c.); and
− the magnitude of the touch voltage; and

− the pathway of the current through the body (hand-to-hand, or both-hands-to-both feet or

one-hand-to-seat);

NOTE These different pathways have been selected for their characteristics. The reason comes from the

body impedance model described in Annex A of IEC/TR 60479-5. The voltage thresholds determined for the

current path both-hands-to-feet may be generally considered conservative compared to the current path one-

hand-to-both-feet.
and
− the area of contact with the skin; and
− the condition of the skin contact area (saltwater-wet, water-wet, dry).
---------------------- Page: 9 ----------------------
– 8 – TS 61201 © IEC:2007
5 Voltage thresholds and limits
5.1 Voltage threshold as a function of contact area

The following figures (Figures 1 to 6) show threshold touch voltage versus contact area. It is

assumed that since the plotted points are close to being in line when plotted on a log-log

scale, the best fit curve to represent points between those actually calculated will be on a line

joining the calculated points on the log-log scale.

These threshold figures are intended to document the effect of contact area which might be

used in products as a key design parameter for limiting the effect of touch voltage. It should

be noted that contact area may be affected by contact with other conductive parts such as

tools or interconnected equipment.

NOTE 1 Tables 1 and 2 illustrate examples of maximum contact areas for traditional accessible voltages.

1 000
Hand-to-hand Both-hands-to-feet Hand-to-seat
100
b 1
1 10 100
Contact area (cm )
IEC 1660/07

Figure 1 – Minimum touch voltage threshold corresponding to a.c. and dry conditions

for current startle reaction (a), muscular reaction (b) and ventricular fibrillation (c )

Touch voltage (V)
---------------------- Page: 10 ----------------------
TS 61201 © IEC:2007 – 9 –
1 000
Hand-to-hand Both-hands-to-feet Hand-to-seat
100 c
10 a b
0,1
1 10 100
Contact area (cm )
IEC 1661/07
Figure 2 – Minimum touch voltage threshold corresponding to a.c. and water-wet
conditions for current startle reaction (a), muscular reaction (b)
and ventricular fibrillation (c )
1 000
Hand-to-hand Both-hands-to-feet Hand-to-seat
100
a b
0,1
1 10 100
Contact area (cm )
IEC 1662/07

Figure 3 – Minimum touch voltage threshold corresponding to a.c. and saltwater-wet

conditions for current startle reaction (a), muscular reaction (b)
and ventricular fibrillation (c )
Touch voltage (V)
Touch voltage (V)
---------------------- Page: 11 ----------------------
– 10 – TS 61201 © IEC:2007
1 000
Hand-to-hand Both-hands-to-feet Hand-to-seat
100 c
0,1
1 10 100
Contact area (cm )
IEC 1663/07

Figure 4 – Minimum touch voltage threshold corresponding to d.c. and dry conditions

for current startle reaction (a), muscular reaction (b) and ventricular fibrillation (c )

1 000
Hand-to-hand Both-hands-to-feet Hand-to-seat
100
b 1
0,1
1 10 100
Contact area (cm )
IEC 1664/07
Figure 5 – Minimum touch voltage threshold corresponding to d.c. and water-wet
conditions for current startle reaction (a), muscular reaction (b)
and ventricular fibrillation (c )
Touch voltage (V)
Touch voltage (V)
---------------------- Page: 12 ----------------------
TS 61201 © IEC:2007 – 11 –
1 000
Hand-to-hand Both-hands-to-feet Hand-to-seat
100
0,1
1 10 100
Contact area (cm )
IEC 1665/07

Figure 6 – Minimum touch voltage threshold corresponding to d.c. and saltwater-wet

condition for current startle reaction (a), muscular reaction (b)
and ventricular fibrillation (c )

NOTE 2 Complete description of curves "a", "b" and "c " is provided in Table 11 of IEC/TS 60479-1 for a.c. and

in Table 13 of IEC 60479-1 for d.c.
5.2 Conventional voltage limits

Some conventional voltage limits have been identified from common practice and from various

standards such as IEC 61140.

Conventional voltage limits based on these voltage thresholds are generally acceptable in

practice because external factors have reduced the risk such as:
– small contact area (finger rather than full hand contact),
– additional resistance in series (any clothing),
– non-conductive accessible surfaces.

Tables 1 and 2 illustrate maximum contact areas corresponding to given touch voltages that,

in turn, relate to commonly used voltage limits. These values directly result from Figures 1 to

6. For example, in water-wet condition, for a hands-to-feet current path, a voltage limit for

muscular reaction of 25 V a.c. corresponds to 12 cm² (see Figure 2 and Table 1). In order to

prevent ventricular fibrillation, the contact area must never be greater than 80 cm².

Safety factors should be applied in the selection of limits by users of this specification leading

to smaller maximum allowable contact areas.
Touch voltage (V)
---------------------- Page: 13 ----------------------
– 12 – TS 61201 © IEC:2007
Table 1 – Examples of maximum contact areas corresponding
to given a.c. touch voltages
Max contact Max contact Max contact
Touch
area for touch area for touch area for touch
voltage
voltage voltage voltage
Moisture Pathway of body
threshold * for threshold * for threshold * for
condition current
startle reaction muscular ventricular
current ** reaction ** fibrillation **
a.c. r.m.s.
2 2 2
cm cm cm
Hand-to-hand 1 26 >100
15 Water-wet Both-hands-to-feet <1 26 >100
Hand-to-seat <1 9 >100
Hand-to-hand <1 3 >100
Saltwater-
15 Both-hands-to-feet <1 3 >100
wet
Hand-to-seat <1 <1 >100
Hand-to-hand <2 25 >100
16 Water-wet Both-hands-to-feet <1 25 >100
Hand-to-seat <1 8 >100
Hand-to-hand <1 12 >100
25 Water-wet Both-hands-to-feet <1 12 80
Hand-to-seat <1 3 >100
Hand-to-hand <1 1 >100
Saltwater-
25 Both-hands-to-feet <1 1 40
wet
Hand-to-seat <1 <1 100
Hand-to-hand 1 20 >100
30 Dry Both-hands-to-feet <1 20 90
Hand-to-seat <1 4 >100
Hand-to-hand <1 7 >100
33 Water-wet Both-hands-to-feet <1 7 45
Hand-to-seat <1 <2 60
Hand-to-hand <2 16 >100
33 Dry Both-hands-to-feet 1 16 80
Hand-to-seat <1 <4 85
Hand-to-hand <1 8 >100
50 V Dry Both-hands-to-feet <1 8 35
Hand-to-seat <1 1 30
Hand-to-hand <1 6 >100
55 V Dry Both-hands-to-feet <1
6 30
Hand-to-seat <1 <1 25

* The maximum tolerable contact area is for each single contact with conductive surfaces. For hand-to-hand,

the area is per hand. For both-hands-to-feet, the area is per hand and per foot. For hand-to-seat, the area is

the hand contact alone. The seat contact is assumed to be very large, independent of the hand contact.

** In Tables 1 and 2 reference is made to:

– startle reaction current which corresponds to the “a” curve of Figures 20 and 22 of IEC/TS 60479-1;

– muscular reaction current corresponds to the “b” curve of Figures 20 and 22 of IEC/TS 60479-1;

– ventricular fibrillation current which corresponds to the “c ” curve of Figures 20 and 22 of IECT/S 60479-1.

---------------------- Page: 14 ----------------------
TS 61201 © IEC:2007 – 13 –
Table 2 – Examples of maximum contact areas corresponding
to given d.c. touch voltages
Max contact Max contact Max contact
Touch
area for touch area for touch area for touch
voltage
voltage voltage voltage
Moisture Pathway of body
threshold * for threshold * for threshold * for
condition current
startle reaction muscular ventricular
current * reaction * fibrillation **
d.c.
2 2 2
cm cm cm
>100
Hand-to-hand 3 80
30 Water-wet Both-hands-to-feet 1 30 >100
Hand-to-seat 1 22 >100
Hand-to-hand <1 40 >100
30 Saltwater-wet Both-hands-to-feet <1 6 >100
Hand-to-seat <1 5 >100
Hand-to-hand <2 60 >100
35 Water-wet Both-hands-to-feet <1 25 >100
Hand-to-seat <1 18 >100
Hand-to-hand 1 25 >100
60 Water-wet Both-hands-to-feet <1 9 >100
Hand-to-seat <1 3 >100
Hand-to-hand <1 5 >100
60 Saltwater-wet Both-hands-to
...

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