English/Chinese Explanations of Electrical Safety Terminology

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Explanations of Terms Related to Electrical Safety 1 Basic Concepts 1.1 Fail-safe A feature designed to prevent dangerous malfunctions of the product itself. 　1.2 Normal condition: A state in which all facilities used to prevent hazards are undamaged. 　1.3 Electrical accident: An incident in which current, electromagnetic fields, lightning, static electricity, and certain circuit failures directly or indirectly cause damage to building facilities and electrical equipment, result in injuries or deaths to people and animals, and lead to fires and explosions. 　1.4 Electric Shock: The pathological and physiological effects caused by electric current passing through the human body or that of an animal. 　1.5 Injury due to electromagnetic field: Damage to the human body resulting from the absorption of energy under the influence of electromagnetic fields. 　1.6 Disruptive discharge and dielectric breakdown: The phenomenon in which solid, liquid, gas dielectrics, or combinations of such materials lose their strength under the influence of high voltages. During destructive discharge, the voltage between the electrodes drops rapidly to zero or near zero. 　1.7 Short circuit: A connection that is made, either accidentally or intentionally, between two or more points in a circuit that under normal conditions are at different voltages, through a relatively low resistance or impedance. 　1.8 Insulation fault: An abnormal decrease in insulation resistance. 　1.9 Earth fault: A fault that occurs when a conductor is connected to the ground or when the insulation resistance to the ground becomes less than the specified value. 　1.10 Overcurrent: A current that exceeds the rated current. 　1.11 Overvoltage: A voltage that exceeds the rated voltage. 　1.12 Overload: A load that exceeds the rated load. 　1.13 Conductive part: A part that can conduct electricity, but not necessarily one that carries operating current. 　1.14 Live part: A conductor or conductive part that is energized during normal operation; it includes the neutral conductor, but conventionally does not include the protective neutral conductor (PEN conductor). Note: This term does not necessarily imply a risk of electric shock. 　1.15 Exposed conductive part: The conductive part of an electrical equipment that can be touched. It is not charged under normal conditions, but it may become charged in the event of a fault. Note: In the event of a fault, the conductive parts of electrical equipment that can become energized only through exposed conductive parts are not considered exposed conductive parts. 　1.16 An extraneous conductive part is a conductive part that is not part of the electrical apparatus and that can introduce a potential (usually ground potential). 　1.17 Simultaneously accessible parts: Conductors or conductive parts that can be touched simultaneously by a person, or in some cases, by animals. Note: The parts that can be touched simultaneously may include: ① Live parts ； ② Exposed conductive parts ； ③ External conductive part ； ④ protective conductor ； ⑤ Ground electrode. 　1.18 Direct contact: Contact between a person or animal and a live part. 　1.19 Indirect contact: Contact between a person or animal and an exposed conductive part that has become charged due to a fault. 　1.20 Touch voltage: The voltage that appears between parts that can be touched simultaneously when the insulation is damaged. Note: ① By convention, this term is used only in aspects related to indirect contact protection. ② In some cases, the value of the contact voltage can be significantly affected by the impedance of the person touching those parts. 　1.21 Step voltage: The voltage applied between a person’s feet when they stand on ground through which an electric current is flowing. 　1.22 Safety Extra-Low Voltage (SELV): An alternating voltage in a circuit isolated from the power supply main by a safety isolation transformer or a converter with separate windings, such that the effective value between conductors or between any conductor and ground does not exceed 50 volts. 　1.23 Voltage to earth: The potential difference between a charged body and the ground (with the ground potential set at zero). 　1.24 Overvoltage to earth: The voltage to earth that is higher than the normal peak voltage to earth (corresponding to the highest system voltage), expressed as a peak voltage. 　1.25 Shock current: A current that passes through a human body or an animal’s body and has the potential to cause pathological or physiological effects. 　1.26 Perception (current) threshold: The minimum current value through the human body that can cause any sensation under given conditions. 　1.27 Let-go current threshold: The maximum current value at which a person holding the electrode can release it under given conditions. 　1.28 Threshold of ventricular fibrillation current: The minimum current value that, under given conditions, induces ventricular fibrillation. 　1.29 Fault current: An accident current that results from insulation damage or short-circuiting of the insulation. 　1.30 Overload current (of a circuit): An excessive current that occurs in a circuit in the absence of any electrical faults. 　1.31 Short-circuit current: In an electrical circuit, it is the excessive current that occurs as a result of a short circuit caused by a fault. 　1.32 The residual current is the algebraic sum of the instantaneous values of the current flowing through all conductive elements in a circuit at a certain point of an electrical apparatus. 　1.33 Total impedance of the human body = the vector sum of the internal impedance of the human body and the skin impedance. 　1.34 Safety impedance: The impedance connected between the live parts and the accessible conductive parts, whose value ensures that the current remains within safe limits both under normal operation of the equipment and in the event of potential faults, while maintaining reliability throughout the equipment’s lifetime. 　1.35 Fault withstandability: The ability of an electrical device to withstand specified electrical fault currents without exceeding the prescribed level of damage. 　1.36 Unsafe temperature: A temperature that may cause combustion and/or may lead operators to perform unconscious dangerous actions. 2 Basic Elements 2.1 Insulation 2.1.1 Insulation (property) – All the properties obtained after a conductor is insulated.