Page 8 - Electrical Safety of Low Voltage Systems
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Dr. Massimo A. G. Mitolo
2.2.3 Protection by Obstacles 14
2.2.4 Additional Protection by Residual Current Devices 15
2.3 Protection Against Indirect Contact 18
2.3.1 Protection by Automatic Disconnection of Supply 19
2.3.2 Protection Without Automatic Disconnection of Supply 20
FAQs 26
Endnotes 26
3 Mathematical Principles of Electrical Safety 29
3.1 Introduction 29
3.2 Mathematical Definition of Safety 29
3.3 Risk of Indirect and Direct Contact 32
3.4 The Acceptable Residual Risk 33
3.5 Safety and Risk of Basic Insulation 36
3.6 Safety and Risk of Class 0 Equipment 37
3.7 Safety and Risk of Class I Equipment 38
3.8 Safety and Risk of Class II Equipment 39
3.9 Safety and Risk of Electrical Separation 41
3.10 A Qualitative Comparison Between Safety and Risk of Protective Measures 42
FAQs 43
Endnotes 44
4The Earth 45
4.1 Introduction 45
4.2 The Earth Resistance 45
4.3 The Earth Potential 49
4.4 Independent and Interacting Earth Electrodes 51
4.5 Spherical Electrodes 55
4.6 Voltage Exposure Upon Ground Faults 59
4.6.1 Touch Voltage 59
4.6.2 Extraneous-Conductive-Part (EXCP) 63
4.7 Voltage or Current? 65
FAQs 67
Endnotes 68
5 Effects of Electric Currents Passing Through the Human Body, and Safety 71
Requirements
5.1 Introduction 71
