Maximum KVA of the distribution box

Standard LT distribution boxes are available with maximum ratings up to 500 KVA.

Overview of Distribution Box Ratings

Low Tension (LT) distribution boxes are designed to control and protect feeders from distribution transformers. The maximum KVA rating depends on the design, busbar size, and protective devices installed in the box. Commonly available ratings include 63 KVA, 100 KVA, 160 KVA, 200 KVA, 315 KVA, and 500 KVA . The higher the KVA, the larger the busbars, droppers, and MCCBs required to safely handle the load.

Key Specifications for High-Capacity Boxes

• 200 KVA / 500 KVA Boxes: These are typically equipped with Air Circuit Breakers (ACBs) for incoming and outgoing circuits, fabricated from 2 mm MS sheet, and designed for outdoor use with IP-43 protection . They are suitable for three-phase, 4-wire, 433 V, 50 Hz systems with solidly earthed neutral .
• Busbar and Dropper Sizes: For 200 KVA and above, busbars are sized to handle the full transformer load, ensuring minimal voltage drop and safe operation. For example, 200 KVA boxes use 50x6 mm EC grade tin-plated copper strips for isolator connections .
• Protection Devices: High-capacity boxes include triple-pole isolators, HRC fuses, and MCCBs rated for the maximum load, with breaking capacities up to 80 kA for isolators . Porcelain cutouts are used in 160 KVA and 315 KVA boxes to protect outgoing circuits .

Practical Considerations

• Outdoor Installation: Boxes are designed to withstand tropical climates, moderate condensation, and pollution, with robust construction to prevent rust and mechanical damage .
• Maximum Utilization: The 500 KVA distribution box represents the upper limit for standard LT distribution boxes, ensuring full utilization of transformer capacity while providing adequate protection against overload and short circuits .
• Eaton PDUs: For specialized applications like data centers, PDUs are available up to 500 kVA, offering flexible installation, monitoring, and safety features .

In summary, the maximum KVA rating for standard LT distribution boxes is 500 KVA, with appropriate busbar sizing, protective devices, and construction standards to safely handle the load. Lower ratings such as 63, 100, 160, 200, and 315 KVA are also widely used depending on the application and transformer capacity .