Main Functions and Roles
Cable Splitting and Connection: Divides the power supply of a main cable into several branch cables, supplying power in different directions or areas.
Line Transfer: Serves as an intermediate joint point on long-distance cable lines, facilitating line segmentation and extension.
Ring Network Power Supply: In a ring network distribution system, it is a key node for realizing ring-in and ring-out functions and interconnection. It can isolate faulty areas and restore power supply to non-faulty areas through switching operations, improving power supply reliability.
Equipment Protection: Internally configured with circuit breakers and other protective devices to provide overload and short-circuit protection for branch lines.
Convenient Maintenance and Expansion: Provides a centralized, safe, and standardized operating point, facilitating line outage maintenance, fault diagnosis, and future capacity expansion for users.
Energy Metering: Some branch boxes can be equipped with metering devices for boundary point metering.
Main Structure and Types
Basic Structure: Typically consists of a casing, busbars, cable connectors (such as T-joints and elbow joints), insulation components, operating mechanisms (if any), and necessary accessories such as surge arresters and fault indicators.
Classification by Insulation Medium (Most Important Classification):
Air-Insulated Branch Boxes: Commonly seen in the past, simple in structure and low in cost, but large in size and susceptible to environmental factors (humidity, pollution).
Gas-Insulated Branch Boxes: Commonly use SF6 (sulfur hexafluoride) as the insulation and arc-extinguishing medium. Features include compact size, fully sealed design, maintenance-free operation, and strong environmental adaptability; currently the mainstream choice for urban power distribution networks.
Solid-Insulated Branch Boxes: Use epoxy resin and other materials for insulation; environmentally friendly (does not contain SF6), and is also an important current development direction.
Classification by Function:
Ordinary Branch Boxes: Only allow for simple cable branching; contain no switching equipment and cannot be operated while energized.
Branch box with switch (intelligent ring network cabinet): It is equipped with load switch, circuit breaker, etc., and can perform on/off, isolation and switching operations to realize the distribution network automation functions (such as remote control, remote signaling, fault location).
