Protection against Electric Shock

Abstract:
IEC Technical Committee (TC) 108 is developing an entirely new safety standard, applicable to Consumer Electronics, Information Technology Equipment and Telecommunications Equipment. The standard will be performance based and technology independent. The standard is being developed using sound engineering principles and will clearly identify the hazards addressed. This is a "Hazard Based Safety Engineering" concept (HBSE-Concept). (IEC = International Electrotechnical Commission) This new standard is radically different from previous standards. It is a "Hazard Based Standard" (HBS) addressing all hazards, which could be present in equipment falling under the scope of the new IEC 62368. In this presentation an overview of the new standard will be given. On the example of the protection against electric shock details of the hazard-based concept will be discussed. An electric shock depends on various parameters and causes different reflexes of the human body. This presentation will discuss the parameters of the electrical power energy source and the parameters of the human body. It shows that an injury of a person could only happen, if energy is transferred to the body of the person. This is shown in model of injury (energy source => energy transfer => injury of the human body). As consequence, there is no injury if there is no energy transfer. To avoid an injury, the transfer of energy has to be blocked by a safeguard or by limiting the energy of the source to safe levels. It is shown in a model for safety (energy source => safeguard => safe human body). Limits for three classes of electrical energy sources are presented depending on the different parameters of the power source, such as voltages and currents for dc, low and high frequencies, as well as for single pulses. Depending on the classification of the electrical energy source different kinds of safeguards are specified (principle safeguards, supplemental safeguards, reinforced safeguards). Safeguards for protection against electric shock could be insulation (Basic; supplemental, reinforced), components (e.g. transformers, capacitors, resistors) and conductors (PE-conductor). Detailed requirements for the parameters of the safeguards will be given in the standard. This presentation shows the concept, only. The classification of the electrical energy source are based on pilot publication such as IEC 60479 and IEC 61201 taking into account the latest proposals for the modification of theses publications. The requirements for the parameters of the safeguards are detailed in the new standard. This presentation gives a short overview, only.