Specifications of incoming and outgoing lines for distribution boxes

Incoming and outgoing lines in distribution boxes are designed with specific busbar sizes, isolators, and cable glands to ensure safe and reliable power distribution according to KVA rating and IS standards.

Incoming Lines

• Incomer Dropper Size: For 63/100 KVA boxes, the incomer dropper is 50 x 8 mm; for 160/315 KVA boxes, it is 50 x 15 mm (EC grade aluminum) .
• Connection: Incoming cables are connected via triple pole isolators with detachable handles for safety. The isolator terminals project 80 mm minimum on the cable side and 60 mm minimum on the HRC fuse side .
• Protection Devices: Incoming lines may include MCCBs or switch disconnectors conforming to IS:13411 and IS:13947 standards, with breaking capacity up to 80 kA .
• Mounting and Insulation: Busbars and droppers are mounted on CRCA MS strips with PVC insulating sleeves, maintaining proper phase sequence (RYB) and clearances .

Outgoing Lines

• Feeder Dropper Size: For 63/100 KVA boxes, feeder droppers are 50 x 8 mm; for 160/315 KVA boxes, 50 x 15 mm (EC grade aluminum) .
• Protection: Outgoing circuits are protected by porcelain cutouts or MCCBs, depending on the box rating, ensuring arc extinction and fault protection .
• Cable Entry: Bottom plates with rubber glands are provided for outgoing cables. Glands have a minimum 1 mm thick rubber film to secure cables and prevent dust or moisture ingress .
• Phase Busbars: Busbar strips are sized according to KVA rating: 72 x 50 x 8 mm for 63/100 KVA and 120 x 50 x 15 mm for 160/315 KVA boxes .

General Features

• Material: Busbars, incomer, and feeder droppers are made of EC grade aluminum; enclosures are glass reinforced polyester (SMC) or GI sheet .
• Standards Compliance: IS:13410, IS:13411, IS:8623, IS:2086, and IS:13703 standards are followed for isolators, enclosures, and fuse bases .
• Safety and Operation: Isolators are robust, easy to operate, and include arc-chutes with minimum 12 strips for immediate arc extinction. Handles are detachable for security during maintenance .
• Mounting: Components are mounted on 2 mm thick MS strips with high tensile nuts, bolts, and washers, ensuring mechanical stability . These specifications ensure that both incoming and outgoing lines are properly sized, insulated, and protected, providing reliable operation for low-tension distribution systems in residential, commercial, and rural areas.