Comprehensive analysis of lighting electrical ready board with three-level protection of overcurrent, short circuit, and leakage

In the electrical lighting system, the electrical ready board serves as the core device for power distribution and safety protection, and its performance directly affects the stable operation of the entire lighting system and the safety of personnel and equipment. The three-level protection lighting electrical ready board for overcurrent, short circuit, and leakage, with its multi-level and all-round safety protection design, has become an indispensable key equipment in modern building electrical design. This article will provide a comprehensive and in-depth analysis of the principles of three-level protection, the core components of electrical ready boards, their advantages and characteristics, selection, installation, and maintenance points.

1、 Three level protection principle: layered defense to safeguard electrical safety

The three-level protection of overcurrent, short circuit, and leakage does not operate independently, but forms a coordinated and progressive safety protection system. Starting from different types and stages of fault development, it quickly cuts off the faulty circuit and minimizes the harm of electrical accidents.

（1） Level 1: Overcurrent Protection - Resist the Risk of Current Overload

Overcurrent protection is the first line of defense for lighting electrical ready boards, mainly targeting overload faults in circuits where the current exceeds the rated value. When the current in the lighting system continues to exceed the rated carrying current of the equipment and circuit due to excessive number of lamps, aging of the circuit, increased resistance, or other unexpected situations, the overcurrent protection device will respond quickly.

Its core working principle is based on the thermal or electromagnetic effects of electric current. The common overcurrent protection component is the overcurrent release in circuit breakers. When the current is overloaded, the bimetallic strip in the release will generate too much heat due to the excessive current and bend, or the electromagnetic coil will generate strong enough electromagnetic force to push the release mechanism to open the contacts of the circuit breaker, thereby cutting off the fault circuit and avoiding insulation burning, short circuit or even fire accidents caused by long-term overload and overheating of the line. The action time of overcurrent protection is usually adjusted according to the magnitude of the overload current, following the principle of "inverse time limit", that is, the larger the overload current, the shorter the action time, and can more quickly handle serious overload faults.

（2） Second level: Short circuit protection - quickly blocking extreme fault currents

Short circuit is one of the most dangerous faults in electrical systems. When the live wire and neutral wire or the live wire and ground wire of a circuit are directly connected due to insulation damage or other reasons, a short-circuit circuit will be formed. At this time, the resistance in the circuit is extremely small, and the current will rapidly increase, instantly generating huge heat and electric force, which may cause the circuit to burn out, equipment to be damaged, and even cause explosions and fires. As the second line of defense, the core requirement of short-circuit protection is "fast and reliable".

The key component for implementing short-circuit protection is also integrated into the circuit breaker, namely the short-circuit release. When a short circuit fault occurs, the instantaneous increase in current will cause the electromagnetic coil in the short-circuit release to generate strong electromagnetic attraction, quickly attracting the armature and driving the release mechanism to operate, causing the circuit breaker to disconnect the circuit in a very short time (usually within tens of milliseconds), limiting the duration and damage range of the short-circuit current to the maximum extent. Unlike overcurrent protection, short-circuit protection usually adopts the "instantaneous action" method. As long as the short-circuit current reaches the set action value, the circuit will be immediately cut off without delay.

（3） Level 3: Leakage protection - preventing potential electric shock hazards to individuals

In lighting systems, situations such as damaged insulation of circuits and energized lamp casings may lead to leakage faults. When the human body comes into contact with the casing or leakage circuit of a charged device, the leakage current will flow into the ground through the human body, causing electric shock accidents. Leakage protection, as the third line of defense, is also a key line of defense that directly ensures personal safety. Its core function is to detect the "residual current" (i.e. the difference between the live current and the neutral current) in the circuit, and quickly cut off the circuit when the residual current reaches a dangerous value.

The core component of leakage protection is the residual current device (RCD), which works based on the "zero sequence current transformer" technology. Under normal circumstances, the live current and neutral current in the circuit are equal in magnitude and opposite in direction. The magnetic flux in the iron core of the zero sequence current transformer cancels each other out, and there is no induced electromotive force output from the secondary coil. The leakage protector is in normal working condition. When a leakage fault occurs, some current will flow into the ground through the leakage point, causing the live current to be greater than the neutral current, resulting in a difference between the two (i.e. residual current). At this time, alternating magnetic flux will be generated in the iron core of the zero sequence current transformer, and an electromotive force will be induced in the secondary coil. When the induced electromotive force reaches the set value, the tripping mechanism in the leakage protector will quickly operate to cut off the power supply of the main circuit, thereby cutting off the power supply before or in the early stage of electric shock accidents, protecting personal safety. Usually, the residual operating current of the leakage protector in the lighting electrical ready board is set to 30mA, and the operating time does not exceed 0.1 seconds. This parameter can effectively ensure personal safety and avoid misoperation caused by slight leakage.

2、 Core composition of electrical ready board: integrated design to ensure protection efficiency

The three-level protection lighting electrical ready board for overcurrent, short circuit, and leakage is not simply a stacking of components, but an organic combination of various protection components and distribution components through scientific layout and integrated design, forming a fully functional and reliable power distribution and safety protection unit. Its core components mainly include the following categories:

（1） Protective element: the core execution unit of three-level protection

Protective components are the key to achieving three-level protection against overcurrent, short circuit, and leakage, mainly including circuit breakers and leakage protectors.

Circuit breaker: It simultaneously undertakes overcurrent protection and short-circuit protection functions, and is one of the core protective components in the electrical ready board. According to the power requirements and line specifications of the lighting system, the rated current of the circuit breaker needs to be accurately selected. For example, in residential lighting circuits, miniature circuit breakers with a rated current of 10A-16A are usually selected; For high-power lighting circuits in public areas (such as emergency lighting and landscape lighting), 20A-32A circuit breakers should be selected according to the actual load. At the same time, the breaking capacity of the circuit breaker also needs to match the expected short-circuit current of the system, ensuring reliable breaking of current in the event of a short-circuit fault and avoiding component damage.

Leakage protector: divided into two forms: leakage protection module and leakage protection circuit breaker. In the three-level protection lighting electrical ready board, leakage protection circuit breakers are usually used, which integrate the overcurrent, short-circuit protection and leakage protection functions of the circuit breaker, and can be used as a separate protection component for a lighting circuit, simplifying the wiring and layout of the electrical ready board. For the case where multiple lighting circuits share a set of leakage protection, the leakage protection module will be used in conjunction with the main circuit breaker. When any circuit experiences a leakage fault, the leakage protection module will operate to drive the main circuit breaker to cut off the power supply.

（2） Distribution components: achieving reasonable distribution of electricity

The distribution components are mainly responsible for reasonably distributing the superior power supply to various lighting circuits, ensuring that the electrical equipment in each circuit can obtain stable power supply, mainly including busbars, terminal blocks, wires, etc.

Busbar: also known as busbar, usually made of copper material, with good conductivity and current carrying capacity. Busbars are divided into live wire busbars, neutral wire busbars, and ground wire busbars, which respectively distribute the live wire, neutral wire, and ground wire of the upper power supply to each branch circuit breaker, avoiding wiring confusion caused by multiple wires directly connected, while reducing contact resistance and minimizing the risk of heat generation.

Wiring terminals: used to achieve reliable connections between wires and components, as well as between wires, mainly including terminal blocks and crimping terminals. Terminal blocks are usually installed on one side or bottom of the electrical ready board, used to centrally connect wires of various circuits for easy maintenance and repair; The crimping terminal is used to fix the wire to the wiring terminal of components such as circuit breakers and leakage protectors, ensuring a firm connection and preventing loose wiring caused by vibration or other reasons, which may lead to poor contact or arc faults.

Wire: As a carrier of power transmission, its specifications and materials need to meet the current requirements and safety requirements of the lighting system. The wires inside the electrical ready board usually use copper core insulated wires, and the cross-sectional area of the wires needs to be selected according to the rated current of the circuit. For example, for the 10A-16A lighting circuit, a wire with a cross-sectional area of 1.5mm ² should be selected; The lighting circuit of 20A-32A uses wires with a cross-sectional area of 2.5mm ². At the same time, the insulation layer of the wire needs to have good heat resistance and insulation performance to withstand the high temperature environment that may occur inside the electrical ready board, and avoid leakage or short circuit faults caused by aging and damage of the insulation layer.

（3） Box and accessories: provide safety protection and installation support

The box body and accessories are the outer shell and auxiliary components of the electrical ready board, mainly used to protect internal components, prevent external interference, and facilitate installation and maintenance.

Box body: usually made of PC material, with good mechanical strength and protective performance. The protection level of the box should be selected according to the installation environment. For electrical ready boards installed outdoors or in humid environments, the protection level should reach IP54 or above (to prevent solid foreign objects from entering, with a diameter greater than 1.0mm; to prevent splashing water from all directions from entering).

Attachment: including box door, installation guide rail, nameplate, etc. The box door is connected to the box body through hinges, and an observation window is usually installed on the door to facilitate personnel to observe the working status of internal components without opening the box door; Installation rails are used to fix components such as circuit breakers, residual current devices, and terminal blocks. Standard DIN rails are usually used to facilitate the installation, disassembly, and replacement of components; The nameplate indicates the model, specifications, rated voltage, rated current, manufacturer, and other information of the electrical ready board for easy identification and management;

3、 Conclusion

As the safety core of modern lighting systems, the three-level protection lighting electrical ready board for overcurrent, short circuit, and leakage provides solid guarantees for personnel safety and stable equipment operation through layered protection mechanisms, integrated structural design, and comprehensive functional advantages. In practical applications, only scientific selection, standardized installation, and regular maintenance can fully exert its protective effectiveness and effectively prevent the occurrence of electrical accidents. With the continuous development of electrical technology, the three-level protection lighting electrical ready board will also develop towards a more intelligent, efficient, and safe direction.