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hat is Extra Low Voltage (ELV)? Why is it so critical in safety design
Extra-Low Voltage (ELV) is a power supply voltage that is generally considered to avoid dangerous electric shocks in low-risk situations. The definition of extra-low voltage is developed by multiple standards, including the International Electrotechnical Commission (IEC) and the British IET (BS 7671:2008). According to these standards, the voltage between two conductors or between a conductor and ground cannot exceed 120 volts (V) direct current or 50 volts alternating current (VRMS). These standards not only define extra-low voltage systems, but also include different types of ultra-low voltage systems such as separated extra-low voltage (SELV), protective extra-low voltage (PELV) and functional extra-low voltage (FELV).
Safety is always one of the most important considerations when choosing a suitable voltage system.
Different types of ultra-low voltage systems
Separated Extra Low Voltage (SELV)
According to the IEC definition, SELV is a system whose voltage does not exceed the ELV under normal conditions and under single fault conditions, including ground faults on other circuits. This system generally requires electrical protection separation, that is, double or reinforced insulation from other circuits such as non-SELV and PELV.
Protected Extra Low Voltage (PELV)
According to the definition of IEC 61140, the voltage of a PELV system will not exceed ELV under normal conditions, but there may be connections to other PELV systems and to ground. This is a major difference from SELV systems, which can be grounded to handle unexpected currents.
Functional Extra Low Voltage (FELV)
FELV refers to any other extra-low voltage circuit that does not meet SELV or PELV requirements. Although the FEV system uses ultra-low voltage, there is insufficient protection for other parts of the circuit that are exposed to higher voltages, which requires a series of protection measures to be considered for the high voltage of the entire circuit.
How ultra-low voltage systems promote safe design
One of the primary functions of ultra-low voltage systems is to reduce the risk of electric shock. Whether SELV, PELV or FELV, these systems allow safe operation under certain environmental conditions. Especially in humid or conductive environments, using voltages below 25 VRMS or 60 V (DC) not only meets safety design requirements, but also further reduces hazards.
In the correct application, ultra-low voltage systems can significantly improve safety and reduce the potential risk of electric shock in industrial and domestic environments.
Compliance and Regulation
In different regions, the specific definitions and requirements of ultra-low voltage vary. For example, the European Union standard (DIN EN 61140) and its related regulations clarify the scope of ultra-low voltage, while in Australia and New Zealand, ultra-low voltage is defined according to "AS/NZS 3000 Wiring Rules". In addition, Brazilian law also proposes similar definitions and norms.
Future development direction
With the advancement of technology, ultra-low voltage systems are becoming more and more widely used. Whether it is on construction sites or in home installations, the use of power tools at hand is moving in the direction of low voltage. In the future, it is likely that more innovative solutions will emerge to further promote safe ultra-low voltage applications.
This forces us to think about what changes and challenges may arise in the field of safety design in the future as we gain a deeper understanding of ultra-low voltage technology?
