Ejecutar tareas en los equipos

Supply, installation, storing, laying, fixing, jointing, terminating, testing and

commissioning of High Voltage XLPE insulated Armoured Aluminium Conductor cores laid-up with Polypropylene central filler and tape, extruded PVC inner sheathed, GI wire/strip armoured and PVC outer sheathed overall confirming to IS 7098 part I 1988 with latest amendments and specifications given below, laid in built up trenches, directly buried underground, on cable trays, in pipes, clamped directly to wall or Structures. Cable shall be capable of satisfactory performance when laid on trays, trenches, conduits, ducts and when directly buried in the ground.

Cables shall be capable of operating satisfactorily under a power supply system voltage variation of +10%, frequency variation +5%, and combined voltage and frequency variation of +10%.

Cables shall normally be laid under the following conditions:

21. In air : Ambient temperature of 45 .C

22. In ground : Ground temperature of 35 C

23. Depth of laying in ground : 900mm(11KV)

: 1050mm (22&33KV)

24. In conduits : Space factor of not more than 60%

25. In trays : Single layer, touching each other

26. The maximum conductor temperature for operation under Normal rated current carrying conditions and under short Circuit conditions are as follows:

Technical specification Page 38 of 182 Maximum conductor temperature & Standard Installation Conditions

(τ) Maximum Conductor temperature at continuous load 90 C

(υ) Ambient Air temperature 45 C

(ϖ) Ground Temperature 30 C

(ω) Thermal resistivity of XLPE 350 C cm/W (ξ) Thermal resistivity of PVC 70 C cm/W

(ψ) XLPE cables shall be rated to carry the specified fault current for specific duration.

(ζ) Method of laying - Multi core cables laid singly Single core cables laid in trefoil Touching / in flat formation XLPE Construction

7. Voltage grade :11KV/33 kV

8. Conductor :Well compacted Aluminium

9. Conductor screen : This shall be extruded shield in the same operation as the

insulation. The semiconductor polymer shall be cross

linked.

10. Insulation : Shall be cross-linked polyethylene.

11. Laying up : The core shall be laid up with Polypropylene filling and tape.

12. Inner sheath :Shall be extruded PVC

13. Armour :Single galvanized steel wire/strip armour

14. The cable outer sheath shall be extruded ST-2 type PVC. 15. General: The cable shall withstand all mechanical and 16. Thermal stresses under steady state and transient 17. Operating conditions.

18. Operation and Maintenance Manuals

Conductor

The conductor consists of annealed Copper or Aluminium wires compacted having a smooth circular or the required shape as per IS: 8130-84. (IEC 60228 / BS 6360)

Conductor screen

The conductor screen consists of a layer of smooth black extruded semi-conducting XLPE compound firmly bonded with the insulation. This eliminates electrical discharges at the interface between conductor and insulation.

Insulation

The insulation consists of super clean XLPE compound. The extrusion process is conducted in clinically clean environment. The insulation thickness conforms to IS: 7098./ IS 5831

Insulation screen

The screen consists of smooth black semi conducting XLPE compound firmly bonded with a smooth interface with the insulation. Also the conductor screen, insulation and insulation screen are extruded simultaneously in Dry cure process.

Conductor screen

Conductor screen shall be extruded semi conducting compound as per IS 7098 part -2 Moisture barrier

To make the cable longitudinally watertight a semi conducting tape is applied over the core to prevent water penetration in the cable. The tape is of non-woven material which has non-biodegradable characteristics.

Copper wire screen

Copper wires are applied to carry the necessary earth fault current. A counter open helix copper tape is provided over the copper wires.

Poly – Aluminium foil

Aluminium foil coated with polyethylene used longitudinally as a moisture barrier is designed for making cable lighter in weight.

Inner sheath

After the above process cables are to be provided with inner sheath with high quality PVC which shall act as bedding for steel wire/strip armour. Filler cords are to provided to maintain the circularity of cables

Technical specification Page 40 of 182 Armouring

Mechanical protection to the cable is provided with armouring. Armour shall be of GI wire or strip as specified. For single core cables the armour shall be aluminium ( if specified) or GI. Armouring shall conform to IS 3975 specifiications

Outer sheathing

The jacketing material consists of extruded black PVC or high-density polyethylene (HDPE). A graphite coat is provided over the outer surface of the sheath. In specific cases with ST2 compound as spefiied.

General purpose sheathing compound ST1

Heat resistant Compund ST2

IS specification for sheathing is IS 5831.Cables are to be sequentially marked for length at every meter throughout its length.

The following letter designations shall be used to specify type of cables:

A - Aluminium conductor

Y - PVC insulation or PVC sheath or overall

PVC Jacket (over armour)

F - GI Flat steel (strip) armour

W - Galvanized round steel wire armour

If the conductor is copper then A is not mentioned

Letter designations for cables shall be indicated in the following order: Conductor size

Insulation Sheath Armour Overall jacket

Testing of Cables TESTS

10. Cable Insulation Tests shall be conducted between phases and between phase and earth for each length of cable, before and after jointing. As such all phase cables may be checked before being laid for above tests. On completion of cable laying work, the following tests shall be conducted in the presence of the

Consultant/Employer.

Construction tests

Test for conductor and compaction. Test for aluminium conductor:

7. Tensile test 8. Wrapping test 9. Annealing test

10. Resistance test for both copper and aluminium

• Test for eccentricity of insulation. • Test for thickness of insulation

• Test for laying up along with Polypropylene tape and fillers. • Virgin material test for PVC insulation.

• Test for thickness of inner sheath

• Test for armouring and armour coverage which should be more than 95% Test for thickness of outer sheath

• Insulation Resistance Test (sectional and overall) • Continuity resistance test.

• Sheathing continuity test.

• Cable size, sequential and manufacturers identification marking on the outer sheath.

Technical specification Page 42 of 182 • Earth test.

All tests shall be carried out in accordance with relevant Indian Standard Code of Practice and Local Electricity Rules. The Contractor shall provide necessary instruments, equipment and labour for conducting the above tests and shall bear all expenses in connection with such tests. All tests shall be carried out in the presence of the Consultant/Employer.

CABLING SYSTEM