Specifications of copper plates used in distribution boxes

Copper busbars in distribution boxes are typically made of high-conductivity copper, with standard thicknesses ranging from 4 mm to 25 mm and widths from 25 mm upwards, designed to meet IEC or IS standards for safe electrical distribution.

Material and Conductivity

Copper busbars are generally made from high-density 99.99% conductivity copper, ensuring minimal electrical losses and high thermal performance. They may be epoxy-coated for insulation, or optionally tin or silver plated to improve corrosion resistance and heat dissipation . The epoxy coating is non-hygroscopic, chemical-resistant, flame-retardant, and impact-resistant, suitable for sandwich construction in distribution boards .

Dimensions and Configuration

• Flat copper busbars in LT distribution boxes are commonly 25 mm wide and 4 mm thick for standard MCCB arrangements .
• Busbars can be configured in single, double, or multiple bar arrangements, including neutral, double neutral, earth, and half-earth configurations .
• The length of busbars is typically modular, with tap-off points every 3 meters, allowing connection of outgoing feeders without welding .
• Tolerances for dimensions are usually ±10%, and the busbars are mounted to provide adequate clearance from the box body to comply with safety regulations .

Safety and Installation Features

• Busbars are often shrouded or insulated to prevent accidental contact and reduce the risk of hot spots .
• Joint pack construction with double-headed shear nuts allows quick installation and secure connections .
• Tap-off points include mechanical/electrical interlocks with an “earth first, break last” safety feature .
• Distribution boxes may include metallic or heat-resistant insulating barriers between MCCBs to prevent heat transfer and maintain safe clearances .

Standards and Compliance

• Copper busbars and distribution boxes are manufactured according to IEC 61439-1 and IEC 61439-6 for low-voltage switchgear .
• LT distribution boxes conform to IS 13947 (Part 2) / 1993 with latest amendments, ensuring compliance with Indian electrical safety standards .
• Type tests for impulse and short-circuit withstand are required, typically certified by CPRI or other government-approved laboratories .

Additional Considerations

• Busbars may be aluminium-cased for lightweight and reduced reactance, while the copper conductor remains the primary current-carrying element .
• Detachable plates and cable glands are provided for easy installation and maintenance of incoming and outgoing cables .
• The design allows for adequate wiring space and flexibility in mounting MCBs or MCCBs without obstruction . In summary, copper plates in distribution boxes are carefully engineered for high conductivity, mechanical strength, safety, and modularity, with standard dimensions like 25x4 mm for LT applications, epoxy insulation, and compliance with IEC or IS standards to ensure reliable and safe electrical distribution .