Distribution boxes are classified by voltage, application, and function, and are organized into primary, secondary, and tertiary levels to manage power safely from the main supply to end users.

Classification by Voltage and Function

Low-Voltage Distribution Boxes (LVDBs) operate typically at 400V/690V and are used in residential, commercial, and industrial buildings. They house circuit breakers, fuses, and protective devices to control and distribute power safely indoors or outdoors . Medium-Voltage Distribution Boxes, often called Ring Main Units (RMUs), operate at 10kV–12kV and are used in cable-based power distribution networks for cities, utilities, and industrial parks. They are usually sealed, maintenance-free, and resistant to dust, moisture, and corrosion, allowing power to be fed from two directions . By Function, distribution boxes can be further categorized as:

• Single-Phase DB Boxes: Suitable for residential or small commercial loads .
• Three-Phase DB Boxes: Used in industrial or large commercial facilities requiring higher power capacity .
• Lighting Distribution Boxes: Dedicated to lighting circuits .
• Power Distribution Boxes: Support sockets, equipment, and heavy machinery .
• Control Distribution Boxes: Integrate relays, contactors, and timers for automation .

Classification by Installation

• Surface Mounted: Installed directly on walls, ideal for retrofits and industrial environments .
• Flush Mounted: Embedded into walls for a clean appearance, common in residential and commercial buildings .
• Pole Mounted: Designed for outdoor use, such as street lighting and utility applications .

Levels of Distribution Boxes

Distribution boxes are also organized hierarchically into three levels to manage power from the transformer to end users :

1. Primary Distribution Box (First Level): Receives low-voltage output (0.4kV) from the transformer. It generally contains isolation switches, circuit breakers, and leakage protectors. This level does not directly supply electrical equipment.
2. Secondary Distribution Box (Second Level): Distributes power to buildings or large equipment. It typically contains large three-phase circuit breakers and manages higher loads.
3. Tertiary Distribution Box (Third Level): Supplies mains electricity (220V single-phase) to individual units or households. It usually contains single-phase circuit breakers and ensures safe delivery to end users. This hierarchical system ensures safety, load management, and efficient power distribution from the main supply to individual circuits, forming a complete three-level protection system suitable for residential, commercial, and construction applications .

Key Components

All distribution boxes generally include:

• Circuit Breakers or Fuses: Protect circuits from overloads and short circuits .
• Busbars: Copper or aluminum bars for power distribution.
• Enclosures: Metal or plastic housings providing protection from physical damage and environmental factors .
• Control Devices: Relays, contactors, and timers in control distribution boxes . Understanding these classifications and levels helps in selecting the right distribution box for specific applications, ensuring safety, compliance, and long-term reliability.