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  • 18.

    CABLE BOX:

    • a)

      HV cable box should be suitable for termination of 1 no. 3 C, 240sq. mm XLPE, armoured,

stranded copper conductor cable with heat shrink type cable termination. Bottom plate should be detachable. Cable Box as per IP-54. Suitable non hygroscopic bushings are required for supporting the cable connection. Looking from the front, HV cable box should be on the right hand side of the transformer.

b) LV cable box should have brought out electro-tinned copper busbars of suitable rating & size for termination of 6 nos. of 3 ½ C x 225 sq. mm PVCA Aluminium cable. The busbar should have suitable holes (two nos. for each cable lug as lug with double hole will be used for termination) and provided with hardwares for termination of cables. The cable box should have detachable cable gland plate fitted with suitable heavy duty single compression cable glands for the cables mentioned above. Support for busbar in LV cable box should be made from FRP/SMC non hygroscopic material. Cable Box as per IP-54. Supports should be able to withstand the short circuit stresses.Looking from the front, LV cable box should be on the left hand side of the transformer.

c) Terminals should be marked as per IS: 2026 #1977.

  • 19.

    TRANSFORMER CORE:

    • a)

      Material: High grade cold rolled grain oriented silicon steel for very low iron loss.

    • b)

      Structure: Grounded and sharp corners avoided.

    • c)

      Lamination: Treated and coated with suitable insulations. The core limbs & yokes are

banded by means of resiglass tape to reduce vibration & noice.

20. TRANSFORMER WINDING:

The winding material should should be Cast Resin type,

be high Class-F.

conductivity electrolytic grade copper. The insulation Conductor should have thermally upgraded paper

(Nomex) insulation reinforced with under vacuum with epoxy resin

fibreglass. The for achieving

coil assembly is to non-hygroscopic,

be impregnated & cast acid & alkali resistant

insulation. The complete winding should have smooth cylindrical ensure high mechanical strength. The thickness of resin should should be self- extinguishing type.

finish after impregnation to be uniform. The insulation

Joints in the winding should be as under.

a) Permanent joints

: Welded/ brazed.

b)

Bolted connection

: Provided with locking devices.

21. ENCLOSURE:

The core & winding assembly should be housed inside a sheet steel enclosure with removable inspection & tap changer covers. The enclosure should offer IP-23 protection as

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