NATIONAL ALUMINIUM COMPANY LIMITED - Rites

Construction details
Degree of protection for enclosure IP 52 or better for indoor installation.
Enclosure material: : The minimum thickness shall be 2.5 mm. Tender shall include enclosure
with the thickness required red for the shape and mechanical/ electrical strength point of view.
Aluminium enclosure shall be provided for rating equal or more than 3000A. MS enclosure
may be provided for LT bus ducts of rating less than 3000A. Provision shall also be provided
for draining moisture.
Maximum temperature of enclosure under rated operating conditions limited to 70 70˚C. Rubber
bellows shall be provided at transformer end to take care of vibration.
GI supporting structures, wherever required, shall be provided with necessary hardwares. In
horizontal run of more than 10 mtr of bus ducts expansion joint with copper flexibles shall be
provided at every 10 mtr interval.
Maximum temperature of enclosure under rated operating conditions limited to 70 70˚C.
Bolted covers with gaskets sshall
hall be provided for easy inspection and access to insulators and
bus bar joints.
Gasketted (Neoprene) connections shall be provided between adjacent sections of metallic
enclosure.
Tinned copper flexible shall be considered for connection of bus ducts at transformer end as
well as PCC end.
Rubber bellows at transformer end shall be provided to take care of vibration.
Seal off bushing and frames complete with bolts.
Provision shall be provided for draining the moisture.
Provision shall be provided for mounting the bus ducts on brackets.
The bus duct shall include straight run, 90 degree bend, Phase crossover chamber,
transformer end chamber, tinned copper flexible, wall frame assembly, rubber bellows and
other accessories as per the requirements.]
Busbars rs and connections.
Bus bar material shall be EC grade aluminium alloy equivalent to E91E WP conforming to IS
5082-1981.
Final operating temperature of both bus bars and joints under continuous operation in
enclosure limited to 85˚C ˚C by thermometer method. While designing the bus duct, site
condition and solar radiation shall be taken care of.
Bus bar arrangement shall be as per IS 5578 5578-1991. 1991. Phase identification shall be by colour at
ends and at regular intervals. Busbar joints shall be of bolted type, cad cadmium mium plated with zinc
bichromated high tensile steel bolts, nuts and spring washers and coated with oxide inhibiting
grease prior to jointing.
Copper flexible busbars shall be tinned. Copper flexible connections shall be provided for
termination on equipment as well as on expansion joints.
Bimetallic joints /strips shall be provided for jointing between dissimilar metals (if required).
Bus bar support insulators of non non-hygroscopic hygroscopic material having impact and di di-electrical
strength with an anti-trackin tracking contour.
Bus duct of 3000 A and above rating shall be interleaved type.
Bus conductor shall be given a coat of black mat point.
Protective earthing
Double earthing shall be provided for enclosure of bus ducts.
Technical Specification:Sec-6, Electrical
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