TECHNICAL SPECIFICATION FOR 33 KV, XLPE COPPER CABLE

Required Technical Specification for 33 KV, XLPE, ICX800 sq.mm Copper Core Underground Cable


General Requirements


Where a Manufacturer's Standard or a national Standard equal to or better than the appropriate specified standard has been issued and is acceptable to the Purchaser, any material or goods supplied shall be manufactured. Installed and tested in accordance with the latest revision of the relevant standard unless otherwise specified.

Where any Standard referred to in this Specification has been superseded by a new standard prior to date letter or invitation to tender, the reference shall be deemed to be to such superseding standard.

Deviations from this Specification or standards referred to above shall be given in the bid shall be accepted by the Purchaser before contract placement.

The goods shall be designed to ensure continuity of service under all working condition at the site as the first consideration and to facilitate inspection, maintenance and repairs. All electrical components shall be adequately rated for their most onerous duty and the specified ambient temperature.

References           

The recommendations and tests specified in the standards shall be adhered to. It shall be the responsibility of the Contractor to demonstrate to the Purchaser that any proposed Standard is equal to or superior to the equivalent IEC or BS. All costs for providing such equivalence are deemed included in the Contractors Tender Prices.

Climatic Condition


The offered XLPE U/G cables with jointing Kits must be suitable for working in the climate conditions of Bangladesh as described below:

Altitude

Maximum ambient temperature     :           0-300 meters above the sea level
Minimum ambient temperature     :           4500C
Humidity                                            :           50C
Mean annual rainfall                      :          98%
No. of annual rainy days                :           1500-3000 mm
Average isokeraunic level              :           80-120 days
Pollution of ambient air                  :           dust, salt, chemical

General Technical Requirements


Cross Link Polyethylene (XLPE) cable shall be suitable for operation at voltage of 33kV between phases at continuous maximum conductor temperatures of 90 deg. C the cable shall be suitable in all respect for use on 33kV system nominal three phase fault level of 25KA.

The cables and associated fittings, joints and termination shall be so designed to prevent damage to the cable or fittings, except in the immediate vicinity of the fault, in the event of an installation failure at any point which results in a fault current to earth of 25KV for sec.

Single core, Copper Conductor, XLPE Insulated Copper screened 800 sqmm. Power Cable shall comply with IEC 502, except as modified or extended by the requirement of the specification. The length of cable on a drum shall be 500M continuous or as specified by the Purchaser and it shall be shipped on standard non-returnable steel drum, each drum having stenciled on it side; size, type and length of cable, together with its gross weight, net weight and contract number.

Conductors


All conductors shall be stranded, circular and compacted and comply with IEC 228. Copper conductor cables shall be constructed core of size ICX800 mm2

Conductor Screening


The conductor shall be screened with an extruded layer of semi-conducting compound, compatible in all respects with the conductor and insulation materials.

Conductor screen shall be bounded to the insulation such that no voids or discontinuities are present. The bound shall be adequate to withstand the normal electrical and mechanical stresses in service without degradation or separation.

Lapped semi-conducting tape shall not be used for conductor screens.
 

Insulation


The insulation shall consist of cross-linked polyethylene tightly extruded over the conductor screen. The insulation shall generally comply with IEC 502.  

The highest possible purity of insulation material is required. The Renderer shall confirm that adequate precautions are taken to remove contaminants and to eliminate the introduction of particles of contaminants during material handling or extrusion process.

The Cable shall be manufactured through CCV/VCV.

The insulation material shall be cross-linked by a dry process. A cross-linking process steam curing will not be permitted.

Insulation Thickness

The thickness of insulation shall be determined by taking the average of number of measurements and shall be not than the tabulated in IEC Publication 502.

Insulation thickness shall not depart from the specified nominal value by an amount exceeding the tolerances specified in IEC Publication 502.

The thickness at any point, however, is less than the specified value, provided the difference does not exceed 10 percent plus 0.1mm.

The thickness of the semi conducting screens on the conductors and over the insulation shall not be included in the measurement of insulation thickness.

Insulation Screening

The insulation screen shall comprise a non-metallic semi-conducting polyethylene part in combination with a metallic part.

The non-metallic semi-conducting part shall be applied directly upon insulation of the core and shall comprise a layer of extruded semi-conducting polyethylene compound.

The conductor screen, insulation and semi-conducting part of insulation screen layer shall be applied to the conductor in common extrusion process with dry curing system.

The metallic part shall be stranded copper applied over the layer of semi conducting compound.

On single core cable, it shall be comprised of single layer of copper wires adequately spaced apart.

The non-metallic part shall be applied directly upon the insulation and shall be a layer of extruded semi-conducting compound. This screen shall be formed such a way that it can be readily removed for jointing.

The insulation screen shall be capable of withstanding an fault current of 25KA for 1 sec. without damage.

Over sheath


The cable shall be sheathed overall with a MDPE outer sheath. The outer sheath shall be of smooth and uniform composition and free of holes, cracks, and bisectors.

As a protection against termite attack, the outer covering shall contain the termite repellent substance of Pb napthalate.

The outer sheath shall have adequate strength and thickness to withstand the test voltage and mechanical tests and suitable for ambient conditions at site.

The outer sheath material shall be capable of withstanding the highest temperature achieved with the cable at its rated current without damage or deformation at site ambient conditions.

The outer surface of the polyethylene outer sheath shall be as specified in IEC 502.

Armour


The amour shall consist of a single layer of non-magnetic wires in accordance with IEC 502.

The non-magnetic joints are brazed or welded and any wire shall be not less than 1mm from the nearest joints in any amour wire in the complete cable.

Manufacturer Identification


The external surface of the cable shall be marked by the following at an interval of 1000 mm with 10mm high character throughout the length of the cable:

(i)            33KV, XLPE, 1-Core, 800sq.mm Cu''
(ii)           "Manufacturers Name"

Continuous Current Rating

The continuous rating of the cable shall be calculated in accordance with the procedure described in IEC 287 based on the site ambient condition, with the insulation parameters as specified. Cable heating due to other cables or other sources of heat where these can be identified shall be taken into consideration.

The maximum conductor temperature shall not exceed 90 deg. C when carrying the rated current under the most onerous site conditions.

Short Circuit Rating

The cable shall be capable of withstanding the specified maximum short circuit current without damage or permanent distortion for the specified times.

The temperature of the conductor at maximum fault current for the specified time shall not exceed 250 deg. C as specified in IEC 502.

Type Tests


The following type tests shall be made on cables covered in scope of contract by contractor before the dispatch of cable from manufacturer’s works if the cables are already tested it will be at the sole discretion of the purchase whether to waive the type test or ask for repetition of all or some specific tests. Contractor may quote type test charges for individual test in his bid for evaluation purpose.

The following tests shall be included in the type tests Electrical Tests:

a)            Bending test followed be partial discharge test
b)            Ten δ measurement
c)            Heating cycle voltage test followed by partial discharge measurement
d)            Impulse withstand test followed by a power frequency voltage test

Test on cable components

a)            Check of cable construction
b)            Resistively of semi conducting layers
c)            Test for determining the mechanical properties of insulation before and after ageing.
d)            Test for determining the mechanical properties of non-metallic sheath before and after ageing.
e)            Ageing tests on pieces of complete cable to check compatibility of materials



General Requirement of 33KV, XLPE, 1C x 800 mm² Copper Cable


Item No.
Description of Items
Unit
Particulars
1
Nominal System Voltage
KV
33
2
Maximum System Voltage
KV
36
3
Rated Voltage (IEC 183)
KV
18/30(36)
4
Short Circuit Current
KA
25 KA, 3 sec.
5
Cross sectional Area of Conductors
mm2
800
6
Insulation thickness
mm
Average thickness shall not be less than 8.0 mm nominal value as per IEC 502. However, thickness at any point may be less than nominal value provided that the difference does not exceed 0.1mm+10% of nominal value.
7
Manufacturing process

Manufactured through CCV/VCV with dry curing.
8
Conductor Material

Copper
9
Shape of Conductor

Compact Circular
10
Type of Conductor Screen

Semi-conducting XLPE
11
Conductor Temperature at end of short Circuit
0C
250

Indoor Termination Kits for 33KV XLPE, 1C x 800 mm² Copper cable


Item No.
Description of Items
Particulars
i)
Application
For 33KV, XLPE, ICx800 mm² Copper cable
ii)
Insulation
For Indoor switchgear terminations
iii)
System
33KV, effectively earthed system
iv)
Cable conductor
800 mm² Copper Conductors
v)
Kit content
-Heat shrinkable high voltage insulating and non-tracking tubing
-Heat shrinkable stress control tubing
-Stress relieving mastic strip
-Truck resistant sealant tape
-Cable preparation kit
-Solder less earth connection kit
-Compression lugs for 500 mm² Copper Conductors
-Misc. other material
-Installation instructions

Outdoor Termination Kits for 33KV XLPE, 1C x 800mm² Copper cable


Item No.
Description of Items
Particulars
i)
Application
For 33KV, XLPE, ICx800 mm² Copper cable
ii)
Insulation
For Outdoor installation on poles/structures 
iii)
System
33KV, effectively earthed system
iv)
Cable conductor
800 mm² Copper Conductors
v)
Kit content
-Heat shrinkable high voltage insulating and non-tracking tubing
-Heat shrinkable stress control tubing
-Stress relieving mastic strip
-Truck resistant sealant tape
-Heat shrinkable truck resistant rain shirt
-Support insulator
-Cable preparation kit
-Solder less earth connection kit
-Compression lugs for 500 mm² Copper Conductors
-Misc. other material
-Installation instructions

Straight-through joint box for 33KV XLPE, 1C x 800 mm² Copper cable


Item No.
Description of Items
Particulars
1
Application
For 33KV, XLPE, ICx800 mm² Copper cable
Ii
Insulation
For underground horizontal mounting  
Iii
System
33KV, effectively earthed system
Iv
Cable conductor
800 mm² Copper Conductors
V
Construction
The joint shall be proof against ingress of moisture and water 
Vi
Kit content
-Compression ferrules
-Valid filling tape
-Heat shrinkable stress control tubing
-Truck resistant sealant tape
-Heat shrinkable high voltage insulating tape
-Heat shrinkable black/red dual wall
-Elastomeric tube
-Roll spring 
-Heat shrinkable outer jacket tube
-Cable preparation kit
-Solder less earth connection kit 
-Misc. other material
-Installation instructions


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