IEC TS 62996:2017

Industrial electroheating and electromagnetic processing equipment - Requirements on touch currents, voltages and electric fields from 1 kHz to 6 MHz

IEC TS 62996:2017(E) addresses the safety assessments in the frequency range between 1 kHz and 6 MHz and provides limits for touch and touch currents for industrial installations or equipment for electroheating (EH) and electromagnetic processing of materials (EPM). Indirect contact by capacitive currents to parts of an earthed human body in an open space are also included, since the current is then distributed analogously in the part of the body and differs from cases of induced electric shock.

General Information

• Status: Published
• Publication Date: 14-Sep-2017
• ICS: 01 - GENERALITIES. TERMINOLOGY. STANDARDIZATION. DOCUMENTATION
• ICS: 17.140.20 - Noise emitted by machines and equipment
• ICS: 23.120 - Ventilators. Fans. Air-conditioners
• ICS: 25.180.10 - Electric furnaces
• Technical Committee: TC 27 - Industrial electroheating and electromagnetic processing
• Drafting Committee: MT 33 - TC 27/MT 33
• Current Stage: PPUB - Publication issued
• Start Date: 05-Oct-2017
• Completion Date: 15-Sep-2017

Standards Content (Sample)

IEC TS 62996 ®
Edition 1.0 2017-09
TECHNICAL
SPECIFICATION
colour
inside
Industrial electroheating and electromagnetic processing equipment –
Requirements on touch currents, voltages and electric fields from 1 kHz
to 6 MHz
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IEC TS 62996 ®
Edition 1.0 2017-09
TECHNICAL
SPECIFICATION
colour
inside
Industrial electroheating and electromagnetic processing equipment –

Requirements on touch currents, voltages and electric fields from 1 kHz

to 6 MHz
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 25.180.10 ISBN 978-2-8322-4798-3

– 2 – IEC TS 62996:2017 © IEC 2017
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 9
2 Normative references . 9
3 Terms and definitions . 9
4 Organization and use of this document . 11
5 Prospective source voltage limits . 12
6 Assessment of the source impedance . 12
7 Touching and access considerations . 13
7.1 General . 13
7.2 Primary contact areas . 13
7.3 Special protective gloves, footwear and clothing . 13
7.4 External metallic objects and tools . 14
7.5 Considerations for the secondary contact area assessment . 14
8 Impedances of parts of the body, and touch current densities . 14
8.1 General . 14
8.2 The equivalent circuit of skin and parts of the body . 15
8.3 Touch current density consideration for large contact areas . 16
9 Capacitively coupled currents in the body due to an external electric field or
insulated live part . 16
9.1 General and measurement frequency . 16
9.2 Determination of the capacitance . 16
9.3 Assessment of the electric field and use of reference level data . 17
9.4 Measurement methods and limiting values . 17
9.4.1 Simplified measurement of the prospective current in the parts of the
body . 17
9.4.2 More accurate method for determination of currents in the parts of the
body . 17
9.4.3 Limiting touch current values . 17
10 Electric shock – immediate nerve and muscle reactions. 17
10.1 General . 17
10.2 Touch current limits – immediate nerve and muscle reactions . 17
11 Electric shock – local overheating and burns of parts of the body . 18
11.1 General and initial thermal conditions . 18
11.2 Awareness, perception and withdrawal . 19
11.2.2 Heat sensing nerves exist only in the skin region, and thus not in the
interior of for example fingers. Conditions where such interior heating
occurs while the skin sensing is insufficient for perception are dealt with
in 11.3. . 19
11.2.3 The perception conditions for hazard calculations are skin temperature
rises of at least 3 K over 5 s to 10 s and 5 K over 20 s or less. These
times then include the time for withdrawal. The high alternative value 10
s applies if the touching part of the body is large and less easy to
withdraw (i.e. the upper arm, leg or torso) than a hand or finger for
which 5 s applies. . 19
11.3 Long-term tissue overheating . 19
12 Requirements and risk group classification . 20
12.1 General . 20

12.2 Conditions for the touch current limits up to 100 kHz . 20
12.3 Requirements related to skin temperature rises and times of awareness,
perception and withdrawal . 21
12.3.1 Skin heat capacity considerations . 21
12.3.2 Skin temperature considerations . 21
12.4 Risk level categorisation as function of the prospective contact voltage . 22
12.5 Additional protection: residual current protective devices (RCDs) . 22
13 Non-sinusoidal touch currents . 22
14 Warning marking and risk group classifications . 23
Annex A (informative) Examples of calculations . 24
A.1 General . 24
A.2 Skin heating . 24
A.3 Examples of tissue heating conditions . 29
A.3.1 With 1 500 mm fingerskin area, i.e. gripping . 29
A.3.2 With the maximal fingerskin area 230 mm . 29
Annex B (informative) Rationales, references and volunteer studies in the non-thermal
case . 31
B.1 Background and observations . 31
B.2 Discussion of Figure B.1 . 31
B.3 A volunteer study at 11 kHz sinusoidal conditions . 33
B.3.1 Experimental setup and data . 33
B.3.2 Discussion and analysis of the experimental data . 33
B.4 Contact/touch current data from standards and other published documents . 34
B.5 Reference levels for the external electric field . 35
B.6 Prospective touch voltage limits . 35
B.7 Perception and pain in relation to risk levels . 35
B.8 Remarks on the slope of the curves for frequencies higher than 10 kHz . 36
B.9 Remarks on the touch current levels above 100 kHz in ICNIRP and IEEE
specifications . 36
Annex C (informative) Additional information and rationales – skin data and
impedances of parts of the body . 37
C.1 Skin anatomy . 37
C.2 Comparative calculation procedure for wet skin impedances . 38
C.3 Some data for dry skin . 38
C.4 Frequency dependence of the body tissue electrical conductivities . 39
C.5 Calculations for Table 1 . 39
Bibliography . 41

Figure 1 – Complex impedances of various parts of the body, 1 kHz to 6 MHz . 15
Figure 2 – Maximum allowed touch and touch currents, 1 kHz to 100 kHz, immediate
nerve and muscle electric shock . 18
Figure 3 – Warning markings . 23
Figure B.1 – Maximum allowed touch and touch currents in various standards, 1 kHz to
100 kHz, immediate nerve and muscle electric shock . 32
Figure B.2 – Setup for touch current and voltage measurements with index and middle
fingers on 50 mm flat conductors . 33
Figure B.3 – Current measuring circuit for unweighed touch current, from
IEC 60990:2016 . 35
Figure C.1 – Human skin anatomy (from Wikipedia) . 37

– 4 – IEC TS 62996:2017 © IEC 2017
Figure C.2 – Average electrical conductivities for homogeneous body modelling from
10 Hz to 10 MHz (from EN 50444:2008) . 39

Table 1 – Maximally allowed skin power density per surface area, under various
conditions of withdrawal . 22
Table A.1 – Comparison of impedances of parts of the body,
...