Outdoor Cable Distribution Box

The Outdoor Cable Distribution Box produced by Cotenele is a medium-voltage complete electrical equipment specially designed for the distribution of electrical energy, implementation of cable line tapping, branching, connection, and conversion circuits in AC 12kV-35KV distribution network cabling projects. This DFWK Outdoor Cable Distribution Box with switch is a fully insulated, sealed and shielded medium-voltage complete electrical equipment, which is mainly composed of 12kV/35KV cable accessories, SF6 load switch, 12kV/35KV electrical components, secondary components and box. It fully and flexibly utilizes the advantages of series and parallel connection of cable connectors, and can be reliably combined according to user needs to achieve full sealing, full protection, full insulation, anti condensation, anti dust, anti-corrosion, and maintenance free characteristics. It can operate outdoors 24/7.

Main Technical Parameters

Product Structures and Main Components 

1. Enclosure Structure

The DFWK Type Outdoor Cable Distribution Box uses a double-layer stainless steel enclosure, compact and aesthetically pleasing, with a protection rating up to IP65 or IP67 and a service life of more than 20 years. The enclosure is typically provided with several hinged doors – some for operating the switchgear, others for installing cable connectors or maintenance access. The base has removable partitions, cable entry/exit openings, and ventilation holes to prevent small animals from entering, creating bottom-to-top convective airflow for good heat insulation, ventilation, and rain protection. The outer surface is finished with electrostatic powder coating in various colours (e.g., army green, State Grid green, ice grey) according to the environment. Internal cable clamps and grounding terminals are provided.

2. Internal Compartments

A switch-equipped Outdoor Cable Distribution Box is generally divided into the following functional areas:

• Switch compartment: Contains the SF6 load switch or circuit breaker in a fully enclosed metal gas‑tight tank filled with SF6 gas for insulation and arc extinction.
• Cable compartment: Contains cable connectors and cable clamps for incoming/outgoing cable connections and fixing.
• Operating mechanism compartment: Contains the switch operating mechanism, interlock mechanism, and mechanical key interlock.
• Busbar compartment (if applicable): Contains busbars connecting switch units.

The medium-voltage switch in the switch compartment is the core control element. It is a three-position load switch (closed, open, earthed) housed in an SF6‑filled metal gas-tight tank. A robust interlock mechanism between the operating mechanism and the switch ensures safe operation.

3. Main Components（see the table below）：

Cable Connectors

The DFWK type Outdoor Cable Distribution Box uses pre‑moulded “touchable” silicone rubber cable connectors, manufactured by fully automatic injection from imported high-quality insulating rubber, with both inner and outer semiconductor shielding layers. The inner layer equalises the internal electric field; the earthed outer shielding layer keeps the connector surface at zero potential. The stress cone, with its lower end in close contact with the cable’s semiconductor layer and the outer semiconductor layer earthed, solves the electric field concentration problem at the cut of the cable’s outer shield and ensures personal safety. The touchable cable front connector is mounted directly on the equipment bushing; it can be connected to a rear cable connector to form multiple outgoing lines, or to a surge arrester for overvoltage protection.

Working Principle

The working principle of the DFWK type switch-equipped Outdoor Cable Distribution Box can be understood from the following aspects:

1. Electrical Working Principle

The incoming main cable is connected via a pre‑moulded silicone rubber cable connector to the internal busbar plate. The busbar plate acts as an electrical busbar – fully insulated and fully sealed. Multiple outgoing circuits are also connected to the busbar plate via cable connectors, achieving “one in, multiple out” branching. An SF6 load switch is placed between the incoming and outgoing lines. By operating the switch, the line can be opened or closed. When the switch is open, the gap separates the cable circuit into an incoming side and an outgoing side, allowing different potentials, thus enabling local power outage maintenance without affecting the main grid.

2. SF6 Load Switch Working Principle

The SF6 load switch operates in an SF6 gas atmosphere. SF6 has excellent insulating and arc‑quenching properties. When the switch opens, the arc is rapidly cooled and extinguished in the SF6 gas, preventing severe contact burning and ensuring reliability and long life. The switch is typically a three‑position design (closed, open, earthed). The earthed position provides a safe ground for the cable side, facilitating subsequent maintenance.

3. Full Insulation and Electric Field Control Principle

The cable connector uses a double-layer semiconductor shielding structure: the inner semiconductor layer equalises the internal electric field to avoid local concentration; the outer semiconductor layer is earthed to maintain zero potential, making the connector surface safe to touch. The stress cone solves the electric field concentration at the cut of the cable’s outer shield, ensuring a uniform and safe electric field throughout the connection system.

4. Interlock Principle

A robust mechanical interlock system is provided between the switchgear and the enclosure doors:

• When the load switch is closed, the disconnector operating hole is blocked.
• The disconnector can only be operated after the load switch is opened.
• When the disconnector is open, the load switch cannot be closed.
• After the earthing switch is closed, the disconnector operating hole is blocked.

This five-prevention interlock prevents misoperation and ensures personnel and equipment safety.

Several typical wiring solutions

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