BS IEC 60479-1:2018:2019 Edition
$215.11
Effects of current on human beings and livestock – General aspects
| Published By | Publication Date | Number of Pages |
| BSI | 2019 | 76 |
This part of IEC 60479 provides basic guidance on the effects of shock current on human beings and livestock.
For a given current path through the human body, the danger to persons depends mainly on the magnitude and duration of the current flow. However, the time/current zones specified in the following clauses are, in many cases, not directly applicable in practice for designing measures of protection against electrical shock. The necessary criterion is the admissible limit of touch voltage (i.e. the product of the current through the body called touch current and the body impedance) as a function of time. The relationship between current and voltage is not linear because the impedance of the human body varies with the touch voltage, and data on this relationship is therefore required. The different parts of the human body (such as the skin, blood, muscles, other tissues and joints) present to the electric current a certain impedance composed of resistive and capacitive components.
The values of body impedance depend on a number of factors and, in particular, on current path, on touch voltage, duration of current flow, frequency, degree of moisture of the skin, surface area of contact, pressure exerted and temperature.
The impedance values indicated in this document result from a close examination of the experimental results available from measurements carried out principally on corpses and on some living persons.
Knowledge of the effects of alternating current is primarily based on the findings related to the effects of current at frequencies of 50 Hz or 60 Hz which are the most common in electrical installations. The values given are, however, deemed applicable over the frequency range from 15 Hz to 100 Hz, threshold values at the limits of this range being higher than those at 50 Hz or 60 Hz. Principally the risk of ventricular fibrillation is considered to be the main mechanism of death of fatal electrical accidents.
Accidents with direct current are much less frequent than would be expected from the number of DC applications, and fatal electrical accidents occur only under very unfavourable conditions, for example, in mines. This is partly due to the fact that with direct current, the let-go of parts gripped is less difficult and that for shock durations longer than the period of the cardiac cycle, the threshold of ventricular fibrillation is considerably higher than for alternating current.
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.
PDF Catalog
| PDF Pages | PDF Title |
|---|---|
| 2 | undefined |
| 4 | CONTENTS |
| 8 | FOREWORD |
| 10 | INTRODUCTION |
| 11 | 1 Scope |
| 12 | 2 Normative references 3 Terms and definitions 3.1 General definitions |
| 13 | 3.2 Effects of sinusoidal alternating current in the range 15 Hz to 100 Hz |
| 14 | 3.3 Effects of direct current |
| 15 | 4 Electrical impedance of the human body and livestock 4.1 General 4.2 Internal impedance of the human body (Zi) 4.3 Impedance of the skin (Zs) 4.4 Total impedance of the human body (ZT) |
| 16 | 4.5 Factors affecting initial resistance of the human body (R0) 4.6 Values of the total impedance of the human body (ZT) 4.6.1 Total body impedance dependence for large, medium and small surface areas of contact 4.6.2 Sinusoidal alternating current 50/60 Hz for large surface areas of contact |
| 17 | Tables Table 1 – Total body impedances ZT for a current path hand to hand AC 50/60 Hz, for large surface areas of contact in dry conditions |
| 18 | Table 2 – Total body impedances ZT for a current path hand to hand AC 50/60 Hz, for large surface areas of contact in water-wet conditions |
| 19 | 4.6.3 Sinusoidal alternating current 50/60 Hz for medium and small surface areas of contact Table 3 – Total body impedances ZT for a current path hand to hand AC 50/60 Hz, for large surface areas of contact in saltwater-wet conditions |
| 20 | Table 4 –Total body impedances ZT for a current path hand to hand for medium surface areas of contact in dry conditions at touch voltages UT = 25 V to 200 V AC 50/60 Hz (values rounded to 25 Ω) |
| 21 | Table 5 – Total body impedances ZT for a current path hand to hand for medium surface areas of contact in water-wet conditions at touch voltages UT = 25 V to 200 V AC 50/60 Hz (values rounded to 25 Ω) Table 6 – Total body impedances ZT for a current path hand to hand for medium surface areas of contact in saltwater-wet conditions at touch voltages UT = 25 V to 200 V AC 50/60 Hz (values rounded to 5 Ω) Table 7 – Total body impedances ZT for a current path hand to hand for small surface areas of contact in dry conditions at touch voltages UT = 25 V to 200 V AC 50/60 Hz (values rounded to 25 Ω) |
| 22 | 4.6.4 Sinusoidal alternating current with frequencies up to 20 kHz and above Table 8 – Total body impedances ZT for a current path hand to hand for small surface areas of contact in water-wet conditions at touch voltages UT = 25 V to 200 V AC 50/60 Hz (values rounded to 25 Ω) Table 9 – Total body impedances ZT for a current path hand to hand for small surface areas of contact in saltwater-wet conditions at touch voltages UT = 25 V to 200 V AC 50/60 Hz (values rounded to 5 Ω) |
| 23 | 4.6.5 Direct current Table 10 – Total body resistances RT for a current path hand to hand, direct current, for large surface areas of contact in dry conditions |
| 24 | 4.7 Value of the initial resistance of the human body (R0) 4.8 Characteristics of the impedance of the body of livestock 5 Effects of sinusoidal alternating current in the range of 15 Hz to 150 Hz 5.1 General 5.2 Threshold of perception 5.3 Threshold of reaction 5.4 Immobilization |
| 25 | 5.5 Threshold of let-go 5.6 Threshold of ventricular fibrillation 5.7 Other effects related to electric shocks |
| 26 | 5.8 Effects of current on the skin 5.9 Description of time/current zones (see Figure 20) |
| 27 | 5.10 Application of heart-current factor (F) Table 11 – Time/current zones for AC 15 Hz to 100 Hz for hand to feet pathway – Summary of zones of Figure 20 |
| 28 | 6 Effects of direct current 6.1 General 6.2 Threshold of perception and threshold of reaction 6.3 Threshold of immobilization and threshold of let-go 6.4 Threshold of ventricular fibrillation Table 12 – Heart-current factor F for different current paths |
| 29 | 6.5 Other effects of current 6.6 Description of time/current zones (see Figure 22) |
| 30 | 6.7 Heart factor Figures Figure 1 – Impedances of the human body Table 13 – Time/current zones for direct current for hand to feet pathway –Summary of zones of Figure 22 |
| 31 | Figure 2 – Internal partial impedances Zip of the human body |
| 32 | Figure 3 – Simplified schematic diagram for the internal impedances of the human body |
| 33 | Figure 4 – Total body impedance ZT (50 %) for a current path hand to hand, for large surface areas of contact in dry, water-wet and saltwater-wet conditions for a percentile rank of 50 % of the population for touch voltages UT = 25 V to 700 V, AC 50/60 Hz |
| 34 | Figure 5 – Dependence of the total impedance ZT of one living person on the surface area of contact in dry conditions and at touch voltage (50 Hz) |
| 35 | Figure 6 – Dependence of the total body impedance ZT on the touch voltage UT for a current path from the tips of the right to the left forefinger compared with large surface areas of contact from the right to the left hand in dry conditions measured on one living person, touch voltage range UT = 25 V to 200 V, AC 50 Hz, duration of current flow max. 25 ms |
| 36 | Figure 7 – Dependence of the total body impedance ZT for the 50th percentile rank of a population of living human beings for large, medium and small surface areas of contact (order of magnitude 10 000 mm2, 1 000 mm2 and 100 mm2 respectively) in dry conditions at touch voltages UT = 25 V to 200 V AC 50/60 Hz |
| 37 | Figure 8 – Dependence of the total body impedance ZT for the 50th percentile rank of a population of living human beings for large, medium and small surface areas of contact (order of magnitude 10 000 mm2, 1 000 mm2 and 100 mm2 respectively) in water-wet conditions at touch voltages UT = 25 V to 200 V, AC 50/60 Hz |
| 38 | Figure 9 – Dependence of the total body impedance ZT for the 50th percentile rank of a population of living human beings for large, medium and small surface areas of contact (order of magnitude 10 000 mm2, 1 000 mm2 and 100 mm2 respectively) in saltwater-wet conditions at touch voltages UT = 25 V to 200 V, AC 50/60 Hz |
| 39 | Figure 10 – Values for the total body impedance ZT measured on 10 living human beings with a current path hand to hand and large surface areas of contact in dry conditions at a touch voltage of 10 V and frequencies from 25 Hz to 20 kHz Figure 11 – Values for the total body impedance ZT measured on one living human being with a current path hand to hand and large surface areas of contact in dry conditions at a touch voltage of 25 V and frequencies from 25 Hz to 2 kHz |
| 40 | Figure 12 – Frequency dependence of the total body impedance ZT of a population for a percentile rank of 50 % for touch voltages from 10 V to 1 000 V and a frequency range from 50 Hz to 150 kHz for a current path hand to hand or hand to foot, large surface areas of contact in dry conditions Figure 13 – Statistical value of total body impedances ZT and body resistances RT for a percentile rank of 50 % of a population of living human beings for the current path hand to hand, large surface areas of contact, dry conditions, for touch voltages up to 700 V, for AC 50/60 Hz and DC |
| 41 | Figure 14 – Dependence of the alteration of human skin condition on current density iT and duration of current flow |
| 42 | Figure 15 – Electrodes used for the measurement of the dependence of the impedance of the human body ZT on the surface area of contact |
| 43 | Figure 16 – Oscillograms of touch voltages UT and touch currents IT for AC, current path hand to hand, large surface areas of contact in dry conditions taken from measurements |
| 44 | Figure 17 – Occurrence of the vulnerable period of ventricles during the cardiac cycle Figure 18 – Triggering of ventricular fibrillation in the vulnerable period – Effects on electro-cardiogram (ECG) and blood pressure |
| 45 | Figure 19 – Fibrillation data for dogs, pigs and sheep from experiments and for persons calculated from statistics of electrical accidents with transversal direction of current flow hand to hand and touch voltages UT = 220 V and 380 V AC with body impedances ZT (5 %) |
| 46 | Figure 20 – Conventional time/current zones of effects of AC currents (15 Hz to 100 Hz) on persons for a current path corresponding to left hand to feet (see Table 11) Figure 21 – Oscillogram of touch voltages UT and touch current IT for DC, current path hand to hand, large surface areas of contact in dry conditions |
| 47 | 6.8 Effects of anodic versus cathodic DC currents Figure 22 – Conventional time/current zones of effects of DC currents on persons for a longitudinal upward current path (see Table 13) Figure 23 – Let-go currents for 60 Hz sinusoidal current |
| 48 | Figure 24 – Effects of anodic versus cathodic DC currents |
| 49 | Figure 25 – Pulsed DC stimulation of single heart cells |
| 50 | Annex A (normative)Measurements of the total body impedances ZT made on living human beings and on corpses and statistical analysis of the results Table A.1 – Total body impedances ZT, electrodes type A for dry conditions and deviation factors FD (5 % and 95 %) Table A.2 – Total body impedances ZT, electrodes type B for dry, water-wet and saltwater-wet conditions and deviation factors FD (5 % and 95 %) Table A.3 – Total body impedances ZT for dry, water-wet and saltwater-wet conditions and deviation factors FD (5 % and 95 %) |
| 52 | Table A.4 – Deviation factors FD (5 %) and FD (95 %) for dry and water-wet conditionsin the touch voltage range UT = 25 V up to 400 V for large, medium and small surface areas of contact |
| 53 | Annex B (normative)Influence of frequency on the total body impedance (ZT) |
| 54 | Annex C (normative)Total body resistance (RT) for direct current |
| 55 | Annex D (informative)Examples of calculations of ZT |
| 56 | Table D.1 – 50th percentile values for the total body impedance for a current path hands-feet, medium surface area of contact for hands, large for feet, reduction factor 0,8, dry conditions, touch currents IT and electrophysiological effects |
| 58 | Annex E (informative)Theories of ventricular fibrillation |
| 59 | Annex F (informative)Quantities of upper limit of vulnerability (ULV)and lower limit of vulnerability (LLV) |
| 60 | Annex G (informative)Circuit simulation methods in electric shock evaluation |
| 61 | Figure G.1 – Electric shock in electrical model by Hart [33]including startle reaction effect Table G.1 – Body impedance examples (uncompensated) |
| 63 | Annex H (normative)Effects of currents passing through the body of livestock H.1 General H.2 Principal consideration of the risk of ventricular fibrillation for livestock |
| 64 | H.3 Characteristics of the impedance of the body of livestock H.4 Internal impedance of animals (Zi) Figure H.1 – Current flow and impedances of the relevant parts of the body of a cow for current path from the nose to the legs Figure H.2 – Diagrams for an animal, for a current path from the nose to the four legs (path A) and from the forelegs to the hind legs (path B) |
| 65 | H.5 Impedance of the hide and skin (ZP) H.6 Impedance (resistance) of the hoof (Zh, Rh) H.7 Total body impedance (ZT) Table H.1 – Impedance (resistance) of the hooves of cattle (Zh, Rh) for ACvoltages up to 230 V, 50/60 Hz |
| 66 | H.8 Initial body resistance (R0) H.9 Values of the total body impedance (ZT) Table H.2 – Total body impedances ZT for AC 50/60 Hz forcattle for touch voltages up to 230 V |
| 67 | H.10 Values of the initial resistance of the body (R0) H.11 Effects on livestock of sinusoidal alternating current in the range from 15 Hz to 100 Hz H.11.1 General Figure H.3 – Diagram for the total body impedance for cattle for a percentage of 5 % of the population Table H.3 – Initial body resistance R0 for cattle |
| 68 | H.11.2 Threshold of reaction H.11.3 Threshold of ventricular fibrillation Figure H.4 – Ventricular fibrillation for sheep |
| 69 | Figure H.5 – Minimum fibrillating currents of sheep as a function of weight for a shock duration of 3 s [55] Table H.4 – Threshold of ventricular fibrillation for AC 50/60 Hz [53] [54] for different species of livestock, for a shock duration of 3 s |
| 70 | Figure H.6 – Minimum fibrillating currents (averages) of various species of livestockas a function of weight for a shock duration of 3 s [53] |
| 71 | Bibliography |
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