IEC TS 60479-2:2007

TECHNICAL IEC
SPECIFICATION
CEI
TS 60479-2
SPÉCIFICATION
Third edition
TECHNIQUE
Troisième édition
2007-05
Effects of current on human beings and livestock –
Part 2:
Special aspects
Effets du courant sur l’homme et
les animaux domestiques –
Partie 2:
Aspects particuliers
Reference number
Numéro de référence
IEC/CEI/TS 60479-2:2007
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TECHNICAL IEC
SPECIFICATION
CEI
TS 60479-2
SPÉCIFICATION
Third edition
TECHNIQUE
Troisième édition
2007-05
Effects of current on human beings and livestock –
Part 2:
Special aspects
Effets du courant sur l’homme et
les animaux domestiques –
Partie 2:
Aspects particuliers
PRICE CODE
CODE PRIX W
Commission Electrotechnique Internationale
International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
For price, see current catalogue
Pour prix, voir catalogue en vigueur

– 2 – TS 60479-2 © IEC:2007
CONTENTS
FOREWORD.5

1 Scope.7
2 Normative references .7
3 Terms and definitions .7
4 Effects of alternating currents with frequencies above 100 Hz .10
4.1 General .10
4.2 Effects of alternating current in the frequency range above 100 Hz up to and
including 1 000 Hz.10
4.2.1 Threshold of perception .10
4.2.2 Threshold of let-go .11
4.2.3 Threshold of ventricular fibrillation.11
4.3 Effects of alternating current in the frequency range above 1 000 Hz up to
and including 10 000 Hz .12
4.3.1 Threshold of perception .12
4.3.2 Threshold of let-go .12
4.3.3 Threshold of ventricular fibrillation.12
4.4 Effects of alternating current in the frequency range above 10 000 Hz.13
4.4.1 Threshold of perception .13
4.4.2 Threshold of let-go .13
4.4.3 Threshold of ventricular fibrillation.13
4.4.4 Other effects.13
5 Effects of special waveforms of current .13
5.1 General .13
5.2 Equivalent magnitude, frequency and threshold.13
5.3 Effects of alternating current with d.c. components.14
5.3.1 Waveforms and frequencies and current thresholds.14
5.3.2 Threshold of startle reaction .15
5.3.3 Threshold of let-go .15
5.3.4 Threshold of ventricular fibrillation.16
6 Effects of alternating current with phase control .20
6.1 Waveforms and frequencies and current thresholds .20
6.2 Threshold of startle reaction and threshold of let-go .21
6.3 Threshold of ventricular fibrillation.22
6.3.1 Symmetrical control .22
6.3.2 Asymmetrical control .22
7 Effects of alternating current with multicyle control .22
7.1 Waveforms and frequencies .22
7.2 Threshold of startle reaction and threshold of let-go .23
7.3 Threshold of ventricular fibrillation.23
7.3.1 General .23
7.3.2 Shock durations exceeding 1,5 times the period of cardiac cycle .24
7.3.3 Shock durations less than 0,75 times the period of cardiac cycle.24
8 Estimation of the equivalent current threshold for mixed frequencies .24
8.1 Threshold of perception and let-go .24
8.2 Threshold of ventricular fibrillation.24

TS 60479-2 © IEC:2007 – 3 –
9 The effect of repeated pulses (bursts) of current on the threshold of ventricular
fibrillation .25
9.1 Ventricular fibrillation threshold of multiple bursts of current separated by 1 s
or more .25
9.2 Ventricular fibrillation threshold of multiple bursts of current separated by
less than 1 s.25
9.2.1 General .25
9.2.2 Example 1 .26
9.2.3 Example 2 .28
10 Effects of electric current through the immersed human body .28
10.1 General .28
10.2 Resistivity of water solutions and of the human body.28
10.3 Conducted current through immersed body .30
10.4 Physiological effects of current through the immersed body.30
10.5 Threshold values of current .31
10.6 Intrinsically safe voltage values .32
11 Effects of unidirectional single impulse currents of short durations .32
11.1 General .32
11.2 Effects of unidirectional impulse currents of short duration .32
11.2.1 Waveforms .32
11.2.2 Determination of specific fibrillating energy F .33
e
11.3 Threshold of perception and threshold of pain for capacitor discharge.34
11.4 Threshold of ventricular fibrillation.35
11.4.1 General .35
11.4.2 Examples .36

Bibliography.39

Figure 1 – Variation of the threshold of perception within the frequency range
50/60 Hz to 1 000 Hz .10
Figure 2 – Variation of the threshold of let-go within the frequency range 50/60 Hz to
1 000 Hz .11
Figure 3 – Variation of the threshold of ventricular fibrillation within the frequency
range 50/60 Hz to 1 000 Hz, shock durations longer than one heart period and
longitudinal current paths through the trunk of the body.11
Figure 4 – Variation of the threshold of perception within the frequency range
1 000 Hz to 10 000 Hz .12
Figure 5 – Variation of the threshold of let-go within the frequency range 1 000 Hz to
10 000 Hz .12
Figure 6 – Waveforms of currents .14
Figure 7 – Let-go thresholds for men, women and children .15
Figure 8 – 99,5 percentile Let-Go threshold for combinations of 50/60-Hz sinusoidal
alternating current and direct current .16
Figure 9 – Composite alternating and direct current with equivalent likelihood of
ventricular fibrillation .18
Figure 10a − Half wave rectification .19
Figure 10b − Full wave rectification.19
Figure 10 – Waveforms of rectified alternating currents .19
Figure 11a − Symmetrical control.21

– 4 – TS 60479-2 © IEC:2007
Figure 11b − Asymmetrical control .21
Figure 11 – Waveforms of alternating currents with phase control.21
Figure 12 – Waveforms of alternating currents with multicycle control.23
Figure 13 – Threshold of ventricular fibrillation (average value) for alternating current
with multicycle control for various degrees of controls (results of experiments with
young pigs).24
Figure 14 – Series of 4 rectangular pulses of unidirectional current. .26
Figure 15 – Series of 4 rectangular pulses of unidirectional current .27
Figure 16 – Series of 4 rectangular pulses of unidirectional current .27
Figure 17 – Forms of current for rectangular impulses, sinusoidal impulses and for
capacitor discharges.33
Figure 18 – Rectangular impulse, sinusoidal impulse and capacitor discharge having

the same specific fibrillating energy and the same shock-duration .34
Figure 19 – Threshold of perception and threshold of pain for the current resulting
from the discharge of a capacitor (dry hands, large contact area) .35
Figure 20 – Threshold of ventricular fibrillation .36

Table 1 – Example of estimate for ventricular fibrillation threshold after each burst of
current in a series.26
Table 2 – Resistivity of water solutions .29
Table 3 – Resistivity of human body tissues.29
Table 4 – Relative interaction between resistivity of water solution and the impedance

characteristic of the electrical source .30

TS 60479-2 © IEC:2007 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
EFFECTS OF CURRENT ON HUMAN BEINGS AND LIVESTOCK –

Part 2: Special aspects
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 60479-2, which is a technical specification, has been prepared by IEC technical
committee 64: Electrical installations and protection against electric shock.
This third edition cancels and replaces the second edition, published in 1987, and constitutes
a technical revision.
– 6 – TS 60479-2 © IEC:2007
The major changes with regard to the previous edition are as follows:
– The report has been completed with additional information on effects of current
passing through the human body for alternating sinusoidal current with d.c.
components, alternating sinusoidal current with phase control, alternating sinusoidal
current with multicycle control in the frequency range from 15 Hz up to 100 Hz.
– An estimation of the equivalent current threshold for mixed frequencies.
– The effect of repeated pulses (bursts) of current on the threshold of ventricular
fibrillation.
– Effects of electric current through the immersed human body.
The text of this technical specification is based on the following documents:
Enquiry draft Report on voting
64/1544/DTS 64/1579/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.
A list of all the parts in the IEC 60479 series, under the general title Effects of current on
human beings and livestock, can be found on the IEC website.
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.
TS 60479-2 © IEC:2007 – 7 –
EFFECTS OF CURRENT ON HUMAN BEINGS AND LIVESTOCK –

Part 2: Special aspects
1 Scope
IEC 60479-2, which is a technical specification, describes the effects on the human body
when a sinusoidal alternating current in the frequency range above 100 Hz passes through it.
The effects of current passing through the human body for
– alternating sinusoidal current with d.c. components,
– alternating sinusoidal current with phase control,
– alternating sinusoidal current with multicycle control,
are given but are only deemed applicable for alternating current frequencies from 15 Hz up to
100 Hz.
NOTE 1 Other waveforms are under consideration.
This standard furthermore describes the effects of current passing through the human body in
the form of single unidirectional rectangular impulses, sinusoidal impulses and impulses
resulting from capacitor discharges.
NOTE 2 The effects of sequences of impulses are under consideration.
The values specified are deemed to be applicable for impulse durations from 0,1 ms up to and
including 10 ms. For impulse durations greater than 10 ms, the values given in Figure 20 of
IEC 60479-1 apply.
This standard only considers conducted current resulting from the direct application of a
source of current to the body, as does IEC 60479-1 and IEC 60479-3. It does not consider
current induced within the body caused by its exposure to an external electromagnetic field.
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 60479-1:2005, Effects of current on human beings and livestock – Part 1: General
aspects
IEC 60479-3, Effects of current on human beings and livestock – Part 3: Effects of currents
passing through the body of livestock
IEC 60990, Methods of measurement of touch current and protective conductor current
3 Terms and definitions
For the purposes of this document, the following definitions, in addition to those given in
IEC 60479-1, apply.
– 8 – TS 60479-2 © IEC:2007
1)
NOTE Certain definitions are taken from the IEV. Such references are listed in the bibliography [27], [28] .
3.1
frequency factor
F
f
ratio of the threshold current for the relevant physiological effects at the frequency f to the
threshold current at 50/60 Hz
NOTE The frequency factor differs for perception, let-go and ventricular fibrillation.
3.2
phase control
process of varying the instant within the cycle at which current conduction in an electronic
valve device or a valve arm begins
(IEV 551-16-23)
3.3
phase control angle (current delay angle)
time expressed in angular measure by which the starting instant of current conduction is
delayed by phase control
(IEV 551-16-32)
3.4
multicycle control
process of varying the ratio of the number of cycles which include current conduction to the
number of cycles in which no current conduction occurs
(IEV 551-16-31)
3.5
multicycle control factor
p
ratio between the number of conducting cycles and the sum of conducting and non-conducting
cycles in the case of multicycle control
(IEV 551-16-37) (and see Figure 12 in this standard)
3.6
specific fibrillating energy
F (Ws/Ω or A s)
e
2⋅
minimum I t value of a unidirectional impulse of short duration which under given conditions
(current-path, heart-phase) causes ventricular fibrillation with a certain probability
NOTE F is determined by the form of the impulse as the integral
e
t
i
i²dt
∫
where t is defined in Figures 17 and 18. F multiplied by the body resistance gives the energy dissipated in the
i e
human body during the impulse.
3.7
specific fibrillating charge
F (C or As)
q
minimum I⋅t value of unidirectional impulse of short duration which under given conditions
(current-path, heart-phase) causes ventricular fibrillation with a certain probability
___________
1)
References in square brackets refer to the bibliography.

TS 60479-2 © IEC:2007 – 9 –
NOTE F is determined by the form of the impulse as the integral
q
t
i
idt
∫
Where t is defined in Figures 17 and 18.
i
3.8
time constant
time required for the amplitude of an exponentially decaying quantity to decrease to
= 0,3679
e
times an initial amplitude
(IEV 801-21-45, modified)
3.9
shock duration of a capacitor discharge
t
i
time interval from the beginning of the discharge to the time when the discharge current has
fallen to 5% of its peak value (see Figures 17 and 18)
NOTE When the time constant of the capacitor discharge is given by T, the shock duration of the capacitor
discharge is equal to 3T. During the shock duration practically all the energy of the impulse is dissipated.
3.10
shock duration for complex asymptotic waveform
t
i
shortest duration of that part of the impulse that contains 95 % of the energy over the total
impulse
3.11
threshold of perception
minimum value for the charge of electricity which under given conditions causes any
sensation to the person through whom it is flowing
3.12
threshold of pain
2⋅
minimum value for the charge (I·t) or specific energy (I t) that can be applied as an impulse
to a person holding a large electrode in the hand without causing pain
3.13
pain
unpleasant experience such that it is not readily accepted a second time by the subject
submitted to it
NOTE Example are an electric shock above the threshold of pain described in 11.3, the sting of a bee or burn of a
cigarette.
– 10 – TS 60479-2 © IEC:2007
4 Effects of alternating currents with frequencies above 100 Hz
NOTE Values for 50/60 Hz are given in IEC 60479-1.
4.1 General
Electric energy in the form of alternating current at frequencies higher than 50/60 Hz is
increasingly used in modern electrical equipment, for example aircraft (400 Hz), power tools
and electric welding (mostly up to 450 Hz), electrotherapy (using mostly 4 000 Hz to
5 000 Hz) and switching mode power supplies (20 kHz to 1 MHz).
Little experimental data is available for this clause, so that the information given herein should
be considered as provisional only but may be used for the evaluation of risks in the frequency
ranges concerned (see bibliography). Attention is also drawn to the fact that the impedance of
human skin decreases approximately inversely proportional to the frequency for touch
voltages in the order of some tens of volts, so that the skin impedance at 500 Hz is only about
one-tenth of the skin impedance at 50 Hz and may be neglected in many cases. This
impedance of the human body at such frequencies is therefore reduced to its internal
impedance Z (see IEC 60479-1).
i
NOTE The use of peak measurements. At current levels that produce physiological responses of perception,
startle reaction and inability of let-go, the physiological response from non sinusoidal and mixed frequency periodic
current is best indicated by the peak value of an output signal from measuring circuits containing a frequency-
weighting network such as those described in IEC 60990.
These frequency weighting networks attenuate the signal according to the frequency factors of Clause 4 of
IEC 60479-1 so that the output signal corresponds to a constant level of physiological response. Attenuation is
provided for narrow impulses of current that would produce less physiological response because of the short
duration of their peak value. The network output allows a fixed value to be read independent of waveshape or mix
of frequencies to be provided for ease of determination of the leakage current and evaluation of the level of hazard
present.
Comparable physiological effects are produced by non sinusoidal and sinusoidal current producing the same peak
value by this measurement method.
Representative network can be found in IEC 60990 and in bibliographic reference [16].
4.2 Effects of alternating current in the frequency range above 100 Hz up to and
including 1 000 Hz
4.2.1 Threshold of perception
For the threshold of perception the frequency factor is given in Figure 1.

2,0
1,8
1,6
1,4
1,2
1,0
50/60 100 200 300 500 1 000
Frequency  f (Hz)
IEC  801/07
Figure 1 – Variation of the threshold of perception
within the frequency range 50/60 Hz to 1 000 Hz

Frequency factor  F
f
TS 60479-2 © IEC:2007 – 11 –
4.2.2 Threshold of let-go
For the threshold of let-go the frequency factor is given in Figure 2.

2,0
1,8
1,6
1,4
1,2
1,0
50/60 100 200 300 500 1 000
Frequency  f (Hz)
IEC  802/07
Figure 2 – Variation of the threshold of let-go within the frequency range 50/60 Hz to
1 000 Hz
4.2.3 Threshold of ventricular fibrillation
For shock durations longer than the cardiac cycle, the frequency factor for the threshold of
fibrillation for longitudinal current paths through the trunk of the body is given in Figure 3.
For shock durations shorter than the cardiac cycle no experimental data is available.

50/60 100 300 1 000
Frequency  f (Hz)
IEC  803/07
Figure 3 – Variation of the threshold of ventricular fibrillation within the frequency
range 50/60 Hz to 1 000 Hz, shock durations longer than one heart period and
longitudinal current paths through the trunk of the body
Frequency factor  F
f
Frequency factor  F
f
– 12 – TS 60479-2 © IEC:2007
4.3 Effects of alternating current in the frequency range above 1 000 Hz up to and
including 10 000 Hz
4.3.1 Threshold of perception
For the threshold of perception the frequency factor is given in Figure 4.
1 2 3 5 10
Frequency  f (kHz)
IEC  804/07
Figure 4 – Variation of the threshold of perception
within the frequency range 1 000 Hz to 10 000 Hz
4.3.2 Threshold of let-go
For the threshold of let-go the frequency factor is given in Figure 5.

1 2 3 5 10
Frequency  f (kHz)
IEC  805/07
Figure 5 – Variation of the threshold of let-go
within the frequency range 1 000 Hz to 10 000 Hz
4.3.3 Threshold of ventricular fibrillation
Under consideration.
Frequency factor  F
f
Frequency factor  F
f
TS 60479-2 © IEC:2007 – 13 –
4.4 Effects of alternating current in the frequency range above 10 000 Hz
4.4.1 Threshold of perception
For frequencies between 10 kHz and 100 kHz, the threshold rises approximately from 10 mA
to 100 mA (r.m.s. values).
For frequencies above 100 kHz the tingling sensation characteristic for the perception at
lower frequencies changes into a sensation of warmth for current intensities in the order of
some hundred milliamperes.
4.4.2 Threshold of let-go
For frequencies above 100 kHz, there is neither experimental data nor reported incidents
concerning the threshold of let-go.
4.4.3 Threshold of ventricular fibrillation
For frequencies above 100 kHz, there is neither experimental data nor reported incidents
concerning the threshold of ventricular fibrillation.
4.4.4 Other effects
Burns may occur at frequencies above 100 kHz and current in the order magnitudes of
amperes depending on the duration of the current flow.
5 Effects of special waveforms of current
5.1 General
As is to be expected, the effects of such currents on the human body are between those
caused by direct and by alternating current; therefore equivalent current magnitudes with
regard to ventricular fibrillation can be established.
This clause describes the effects of current passing through the human body for
– alternating sinusoidal current with d.c. components,
– alternating sinusoidal current with phase control,
– alternating sinusoidal current with multicycle control.
NOTE Other waveforms are under consideration.
The information given is deemed applicable for alternating current frequencies from 15 Hz up
to 100 Hz.
5.2 Equivalent magnitude, frequency and threshold
In this clause, hazard may be taken as being approximately the same effect as with an
equivalent pure alternating sinusoidal current I having the following characteristics:
ev
– Magnitude equivalence
The following current magnitudes have to be distinguished:
I = r.m.s. value of the current of the proposed waveform;
rms
I = peak value of the current of the proposed waveform;
p
I = peak-to-peak value of the current of the proposed waveform;
pp
I = r.m.s. value of a sinusoidal current presenting the same effect as the waveform
ev
concerned.
– 14 – TS 60479-2 © IEC:2007
NOTE The current I is used instead of the current I in Figures 20 and 22 of IEC 60479-1 to estimate the
B
ev
risk of ventricular fibrillation.
Most physiological effects are related to the filtered peak current (in magnitude and in
duration) with the natural body filter defined by the frequency factor F. The peak value of
the current should be used in all cases except where there is a known relationship
between the r.m.s. value and the peak value, i.e. for a pure sinusoidal current.
– Frequency equivalence
The waveform under study has a time period equal to the period of the equivalent
sinusoidal waveform.
– Threshold equivalence
The different current thresholds (perception, inability of let-go and ventricular fibrillation)
for waveforms consisting of specific ratio of alternating to direct current is equivalent as
for a pure sinusoidal alternating current with a current having the characteristic equal to
I . This I value is different for each of these thresholds.
ev ev
5.3 Effects of alternating current with d.c. components
5.3.1 Waveforms and frequencies and current thresholds
Figure 6 shows typical waveforms which are dealt with in this clause. Pure d.c. and pure a.c.
are represented as well as combined waveforms of various ratios a.c. to d.c.

I = I /2√2*
ev pp
I = I
p pp
Ip
I = I /√2
ev p
I /2
p
I = I /√2**
ev p
I
pp
I
p
T T
*  for shock duration >1,5 cardiac cycle
** for shock duration <0,75 cardiac cycle
IEC  806/07
Iev = Ipp/2√2*
I = I /2√2*
ev pp
I = I
p pp
I = I /2√2*
I = I ev pp
p pp
I
pp
I /2
p
I /2 I
p p
I = I /√2**
ev p
I = I /√2**
ev p
I = I /√2**
ev p
T T T
*  for shock duration >1,5 cardiac cycle
** for shock duration <0,75 cardiac cycle
IEC  807/07
Figure 6 – Waveforms of currents

TS 60479-2 © IEC:2007 – 15 –
5.3.2 Threshold of startle reaction
The threshold of startle reaction depends on several parameters such as the area of the body
in contact with an electrode (contact area), the conditions of contact (dry, wet, pressure,
temperature) and also on physiological characteristics of the individual.
These effects are related to the peak value of the current [13] and the currents have to be
combined frequency by frequency to estimate the total effect. A measurement circuit is
described in IEC 60990.
5.3.3 Threshold of let-go
The threshold of let-go depends on several parameters, such as the contact area, the shape
and the size of the electrodes and also on the physiological characteristics of the individual.
From the standpoint of let-go (hand contacts with energized circuitry that can last a few
seconds), this standard uses Figure 5 [17] to determine the let-go current threshold for
combinations of alternating current and direct current. The frequency of the alternating current
in this case was 60 Hz with 7,07 mA peak a.c. (5 mA r.m.s. for a sinusoidal current) and
30 mA d.c. were used as the touch current thresholds for pure a.c.and d.c. respectively.
These thresholds are considered to be adequate to represent the entire population (including
children) from inability to let go.
The equation, I = 7,176*exp(−0,143 4*DC) −0,1061, represents this combined a.c. and
acpk
d.c. case and may be used to calculate the result of any combination of a.c. and d.c. in the
range specified.
The following Figure 7 illustrates the Dalziel [17] information.

50 percentile for men
99,5 percentile for men
99,5 percentile for women
99,5 percentile estimated for children
0 10 20 30 40 50 60 70 80
DC component  (mA)
IEC  808/07
Figure 7 – Let-go thresholds for men, women and children
The above curves can be described by an equation fitted to the data.
The equation, I = 12,890 5*exp(−0,069 39*DC)-0,190 5, represents the 99,5 percentile
acpk
curve for men.
The equation, I = 8,523*exp (−0,104 9*DC) −0,126 0, represents the 99,5 percentile curve
acpk
for women.
Peak of the a.c. component measured
in the direction of the maximum peak of
the composite (a.c. + d.c.) wave (mA) peak

– 16 – TS 60479-2 © IEC:2007
The equation, I = 6,394 5*exp(−0,138 8*DC) −0,094 5, represents the 99,5 percentile
acpk
estimated curve for children.
For practical considerations, some standards allow for some ripple (e.g. up to 10 %) on a d.c.
supply as an exception.
Figure 8 shows the let-go threshold expressed in peak mA for combinations of 50/60 Hz
sinusoidal alternating current and direct current. The peak of the composite a.c. + d.c. wave
in mA at the let-go threshold estimated for the population of humans including children, is
shown as a function of the direct current component in mA.
Figure 8 is represented by the following equation for the composite d.c. current:
I + I = 7,176*exp (−0,143 4*DC) −0,106 1 + DC
acpk dc
Let-Go threshold for (a.c. + d.c.) combinations
0 5 10 15 20 25 30
DC component  (mA)
IEC  809/07
Figure 8 – 99,5 percentile let-go threshold for combinations
of 50/60 Hz sinusoidal alternating current and direct current

These effects are related to the peak value of the current [6] and the currents shall be
combined frequency by frequency to estimate the total effect. A measurement circuit is
described in IEC 60990.
5.3.4 Threshold of ventricular fibrillation
5.3.4.1 Waveforms consisting of specific ratios of alternating to direct current
The fibrillation hazard may be taken as being approximately the same as with an equivalent
alternating sinusoidal current I having the following characteristics:
ev
a) For shock durations longer than approximately 1,5 times the period of the cardiac cycle,
I is the r.m.s. value of the sinusoidal alternating current having the same peak-to-peak
ev
value I as the current of the waveform concerned:
pp
I
pp
I =
ev
2 2
b) For shock durations shorter than approximately 0,75 times the period of the cardiac cycle,
I is the r.m.s. value of the sinusoidal alternating current having the same peak value I
ev p
as the current of the waveform concerned:

Peak of the composite wave  (mA)

TS 60479-2 © IEC:2007 – 17 –
I
p
I =
ev
NOTE 1 This correlation is less applicable the smaller the ratio a.c. to d.c. becomes. For pure d.c. shocks of
a duration less than 0,1 s the threshold is equal to the corresponding r.m.s. value of the alternating current
(see Figure 20 and Figure 22 in IEC 60479-1, respectively).
c) In the duration range from 0,75 to 1,5 times the period of the cardiac cycle, the amplitude
parameter changes from peak value to peak-to-peak value.
NOTE 2 The details of the nature of the transition that takes place are subject to further studies.

According to Knickerbocker’s [5] findings, the likelihood of ventricular fibrillation for a
combination of 50/60 Hz sinusoidal alternating and direct current lasting a few seconds or
more, is the same for a purely sinusoidal current of the same duration provided the pure
50/60 Hz sinusoidal alternating current has the same peak-to-peak value as the peak-to-peak
value of the combination current waveform. This would be on condition that the direct current
component were not large enough to preclude reversal of the instantaneous current (to
prevent zero crossing) during each cycle. For example, the combination of a 40 mA r.m.s.
50/60 Hz sinusoidal current combined with direct current up to 40 × 2 mA has approximately
the same likelihood of causing ventricular fibrillation as a 40 mA r.m.s. 50/60 Hz sinusoidal
current alone.
Where the exposure is a few seconds or more, and the direct current component is large
enough so that the instantaneous current does not reverse during each cycle, then the
composite of alternating plus direct current has the same likelihood of ventricular fibrillation
when the peak value of the composite current is the same as the peak-to-peak value of the
50/60 Hz purely sinusoidal alternating current. For example, the combination of a 50/60 Hz
sinusoidal current and direct current with a
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