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Revealed: Do you know the safety secrets of Separate Extra Low Voltage (SELV) systems?
In modern electrical engineering, ultra-low voltage (ELV) occupies a very important position. Not only is this system widely used in domestic and industrial settings, it is also trusted for its low-risk nature. In particular, the separated ultra-low voltage (SELV) system has attracted many people's attention and research due to its unique safety design and application scope.
Ultra-low voltage is defined as a voltage that does not exceed specific limits under normal and single fault conditions, which lays the foundation for safe operation.
Definition and categories of ELV
According to the International Electrotechnical Commission (IEC) and the UK's IET, an extra-low voltage system is one in which, under certain conditions, the potential between two conductors or between an electrical conductor and the ground does not exceed 120 volts (V) DC, or 50 Volts Root Mean Square (VRMS) AC. This system is divided into different categories based on its design and safety attributes, including Separate Extra Low Voltage (SELV), Protected Extra Low Voltage (PELV) and Functional Extra Low Voltage (FELV).
According to the latest standards, the electronic design of separate extra-low voltage (SELV) systems must include electrical protective separation to prevent accidental exposure of electrical current to high voltages.
Characteristics of Separate Extra Low Voltage (SELV) Systems
The SELV system is composed of two parts. First, the voltage it supports cannot exceed ELV under normal circumstances. Second, in the case of a single fault, ground faults in other circuits are not allowed to occur. This design ensures that the risk of electric shock is minimized even in unexpected situations.
Basic requirements for a SELV system include: electrical protective separation and simple separation, which ensures safe isolation from ground or other circuits that may carry higher voltages.
Equipments such as modern cordless power tools and garden decorative lighting fixtures often use this type of system. They are designed so that operation of these devices does not create a shock hazard, even in wet environments, thus protecting the user's safety.
Comparison of Protected Extra Low Voltage (PELV) and Functional Extra Low Voltage (FELV)
The PELV system can be connected to the ground system in the event of a single fault, so its design is slightly different. Although PELV is also required to ensure low-risk contact, it is connected to the grounding system in some cases. This makes PELV systems relatively more flexible in certain industrial applications, whereas FELV systems lack this protection.
In FELV systems, although ultra-low voltage is used, insufficient safety protection may lead to accidents when in contact with other high-voltage equipment, so higher safety regulations are required.
Practical application of LE voltage system
Ultra-low voltage systems are found in many everyday applications. From household appliances to building construction, SELV and PELV electrical systems provide a safe electrical environment. For example, power tools on construction sites often use RLV (Reduced Low Voltage) systems. Although the voltage of these systems is slightly higher than the ultra-low voltage standard, the transformer design used makes the voltage when exposed to a ground fault still lower than the ultra-low voltage. level.
Safety regulations for detached extra-low voltage systems
In the latest safety standards, the electrical connections of SELV systems need to be specially designed to prevent accidental insertion of connectors of ordinary electrical equipment. Adequate isolation must be maintained between high-voltage and low-voltage electrical components, which must be followed during design and construction to ensure the safety of the overall system.
Many electrical accidents are related to improper use of equipment and improper voltage design. Understanding the specifications of these systems can effectively reduce the risk of accidents.
Future electrical safety research and development directions
Researchers and engineers are continuing to explore new ultra-low voltage technologies, with a focus on further improving their safety and adaptability. With the advancement of technology, more and more smart devices are beginning to introduce these security designs. This not only protects users’ lives, but also supports everyone’s demand for low-power devices.
Looking at the current demand for ultra-low voltage and practical applications in the market, it is necessary to think about: behind the advancement of technology, has the user's understanding of electrical safety kept up with the changes of the times?
