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AL/XLPE/CWS/AL/HDPE-345KV
Grand Cable
Applicable Standard
IEC 60228
IEC 62067
AEIC CS9-15
Rated Voltage
345(362) kV
Cable Construction
CONDUCTOR
The conductor construction shall be compact class 2 segmental type (Milliken) with circular cross-section made of plain aluminum.
The nominal conductor cross section shall be 2000 mm2, with maximum electrical resistance at 20 °C according to IEC 60228.
The conductor design shall guarantee a maximum skin effect factor of 0.25 and maximum proximity effect factor of 0.15 as per the document “Large cross-sections and composite screens design” issued by CIGRÈ Working Group B1.03, 2005.
The conductor shall be blocked against longitudinal water penetration and shall be approved in the test of annex E of IEC 62067, with exception of the pressure that shall be 35 kPa instead of 10 kPa.
The supplier shall demonstrate the compatibility of the water blocking compound with conductor semiconducting screen materials (swelling powder, tapes, and extruded layer) by means of suitable tests of stability of electrical properties.
CONDUCTOR SEMICONDUCTING SCREEN
conductor shall be free of defects and shall not affect the uniformity of the extruded layer over it.
The minimum average thickness of extruded layer shall be 1.20 mm while the lowest thickness shall be at least 90 % of the average thickness.
The semiconducting tapes shall not impair the longitudinal water penetration test performance.
The extruded layer of the conductor semiconducting screen shall be thermoset and be in contact with semiconducting tapes and fully bonded to the inner surface of insulation under all foreseen operating conditions.
The interface between the extruded layer of the conductor semiconducting screen and inner surface of the insulation shall be uniform, continuous, without micro voids, concentric and smooth. As a reference for optical examinations, no protrusions, or irregularities higher than 30 μm are acceptable.
The semiconducting extruded material shall be super smooth and have sulfur and ash content lower than 0.005 % and 0.01 %, respectively.
The maximum electrical resistivity shall be 1000 Ωm, measured according the test of IEC 62067, annex D.
INSULATION
The cable insulation shall be extruded simultaneously to the conductor semiconducting screen and insulation semiconducting screen using a true triple extrusion process.The insulation system shall be dry cured under pressure. The degree of crosslinking of the extruded insulation shall be 100 %, with no traces of remaining peroxide.
The insulation shall be free of micro voids and contaminants.
The degassing process after extrusion shall effectively remove crosslinking by-products and not cause deformations in the insulated core.
The nominal thickness of the insulation shall be designed for 40 years life to withstand the stresses due to:
a) Electrical alternating voltage operation, including periods at maximum operating voltage
b) Electrical lightning impulse voltage of 1175 kV
c) Electrical switching impulse voltage of 950 kV
d) Thermal aging at normal operating temperature
e) Thermal aging at emergency operating temperature
f) Thermal effects of short circuit temperature
In addition, the electrical stresses at outer insulation surface shall be compatible with commercial accessories with good testing and field performance.
The manufacturer shall supply test data and calculations supporting these design and reliability requirements as required in clause 9 of this specification.
The lowest measured thickness shall not fall below 90 % of the nominal thickness.
The insulation shall overcome the following tests of IEC 62067 and IEC 60811
a) Tensile strength and elongation at break without aging
b) Tensile strength and elongation after aging in air oven
c) Tensile strength and elongation after aging of the complete cable for checking compatibility
d) Hot set test
e) Shrink back according to IEC 60811
INSULATION SEMICONDUCTOR SCREE
The extruded layer of the insulation semiconducting screen shall be thermoset, and fully bonded to the outer surface of the insulation under all foreseen operating conditions.
The interface between the extruded layer of the insulation semiconducting screen and the outer surface of the insulation shall be uniform, continuous, without micro voids, concentric and smooth. As a reference for optical examinations, no protrusions, or irregularities higher than 50 μm are acceptable.
The minimum average thickness of extruded layer shall be 1.20 mm while the lowest thickness shall be at least 90 % of the average thickness.
The maximum electrical resistivity shall be 500 Ωm, measured according the test of IEC 62067, annex D.
One or more semiconducting tapes shall be applied over the extruded layer as a bedding to prevent deformation or indentation of the outer part of the insulation underneath.
METALLIC SCREEN AND FOIL
The complete metallic screen shall be composed by copper screen wires and an aluminum foil coated with copolymer.
The screen wires shall be made of annealed copper with minimum conductivity 100 % IACS (International Annealed Copper Standard).
The minimum total cross section of the screen wires shall be 260 mm2, compatible with an allowable short circuit of 50 kA during 0.5 s, calculated with non-adiabatic method described in the IEC 60949 standard.
The number and diameter of copper screen wires shall be chosen to allow sufficient space for inclusion of the monitoring elements described hereafter.
The number and diameter of the wires can be chosen by the manufacture at its convenience, provided a minimum diameter 1.40 mm is respected and compatibility with dimensions of the sensing elements.
The lay length of the screen wires shall not difficult the cable bending or cause damages to the wires due elongation greater than their elastic limit. On the other hand, the increase of electrical resistance due to the lay length shall be limited to 7.5 %.
The aluminum interface of the foil shall be continuously separated to the copper wires by one or more semiconducting tapes to prevent electrolytic corrosion.
The minimum average thickness of the aluminum part of the foil shall be 0.12 mm.
The aluminum foil shall provide radial water tightness and be applied longitudinally with overlap simultaneously with extrusion of the oversheath to ensure a firmly bonding and bending performance without creases or wrinkles.
The metallic screen composed by wires and foil shall overcome longitudinal and radial water penetration tests.
The composite metallic screen shall overcome the tests of IEC 62067:
a) Electrical resistance
b) Water penetration test
c) Radial water penetration test
SENSING ELEMENTS
The sensing elements are distributed thermal sensors and shall consist of low thermal constant optical fiber cables according to IEC 60794, helically applied between two copper wires of the screen.
Two optical cables spaced apart by approximately 120 degrees in the circumference shall be foreseen.
Each optical cable shall have two multimode 50/125 μm optical fibers according to IEC 60793 inside a loose tube and protected by a gel filled stainless steel AISI 316 tube.
The electrical resistance at 20 °C shall be at least 100 times greater than an individual screen copper wire.
The optical fibers shall have the following properties:
a) Phosphor free
b) Low concentration of hydroxyl groups
c) Attenuation at 850 nm lower than 2.4 dB/km
d) Attenuation at 1300 nm lower than 0.5 dB/km
e) Bandwidth greater than 440 MHz.km at 850 nm
f) Bandwidth greater than 500 MHz.km at 1300 nm
Individual optical fibers shall be identified by colors.
The gel filler shall be hydrophobic, have high thermal stability and very low generation of hydrogen.
Alternative constructions shall be subjected to previous approval and technically justified.
The temperatures, minimum bending radius, maximum side wall bearing pressure, and tensile strength which the optical cable is subjected inside the screen shall be compatible with complete power cable requirements.
The lifetime of the optical sensors shall be compatible with thermal and mechanical stresses of the power cable for 40 years.
The optical cable shall be subjected to the following tests according to IEC 60794:
a) Attenuation at 850 nm
b) Attenuation at 1300 nm
c) Impact test
d) Torsion test
e) Crush test
f) Repeated bending
g) Tensile performance
h) Longitudinal water penetration test
Other sensing elements (e.g. humidity penetration sensor) may be included as alternative.
OVERSHEATH
The cable oversheath (or jacket) shall be compatible with ST7 requirements of IEC 62067, and made of black high-density polyethylene.
The minimum average thickness shall be compatible with following requirements:
a) Minimum of 3.30 mm
b) Eccentricity of extrusion process
c) 10 kV withstanding direct voltage test for 1 min (IEC 60229)
d) 62.5 kV lightning transient overvoltages
e) Good abrasion and tearing resistance during pulling operations
f) Sidewall bearing pressures during installations
The oversheath shall contain a minimum carbon black content of 2.0 % to resist to UV radiation due sunlight exposure.
In addition, the oversheath compound shall be suitable to resist to termite attack.
The anti-termite additive shall be safe for people and the environment, and approved for a recognized authority. The material safety data sheet of the additive master batch compound shall be supplied for previous approval.
The oversheath shall overcome the tests of IEC 62067:
a) Tensile strength and elongation at break without aging
b) Tensile strength and elongation after aging in air oven
c) Tensile strength and elongation after aging of the complete cable for checking compatibility
d) Pressure test at high temperature
e) Carbon black content
f) Direct voltage test (IEC 60229)
In order to provide an external electrode for withstanding direct voltage tests during manufacturing, installation, and for periodic maintenance after commissioning, a continuous graphite coating shall be applied on external surface of the oversheath.
Alternatively, a thin coextruded semiconducting layer with average thickness of 0.5 mm, firmly bonded to the high-density polyethylene oversheath is acceptable.
CABLE MARKING
The oversheath of each cable length shall be marked at every meter with the following information:
a) Cable cross section (2000 mm2)
b) Materials (Al/XLPE/Cu/Al/HDPE)
c) Nominal voltage 345 kV
d) Name of the customer
e) Date of manufacturing in format day/month/year
f) Sequential length in meters
g) Traceability information code
The traceability code shall be agreed between supplier and purchaser and contain at least the sequence of insulating core extrusion runs.
The characters height and color shall be clearly visible at naked eye. The characters shall resist to abrasion and sunlight during installation.
PULLING EYES AND SEALING
The outer end of the cable shall be fitted with a pulling eye connected to the conductor suitable for a minimum force of 10.000 daN.
Both cable ends shall be sealed with heat shrink caps for protection against humidity during transportation.
Applicable Standard
IEC 60228
IEC 62067
AEIC CS9-15
Rated Voltage
345(362) kV
Cable Construction
CONDUCTOR
The conductor construction shall be compact class 2 segmental type (Milliken) with circular cross-section made of plain aluminum.
The nominal conductor cross section shall be 2000 mm2, with maximum electrical resistance at 20 °C according to IEC 60228.
The conductor design shall guarantee a maximum skin effect factor of 0.25 and maximum proximity effect factor of 0.15 as per the document “Large cross-sections and composite screens design” issued by CIGRÈ Working Group B1.03, 2005.
The conductor shall be blocked against longitudinal water penetration and shall be approved in the test of annex E of IEC 62067, with exception of the pressure that shall be 35 kPa instead of 10 kPa.
The supplier shall demonstrate the compatibility of the water blocking compound with conductor semiconducting screen materials (swelling powder, tapes, and extruded layer) by means of suitable tests of stability of electrical properties.
CONDUCTOR SEMICONDUCTING SCREEN
conductor shall be free of defects and shall not affect the uniformity of the extruded layer over it.
The minimum average thickness of extruded layer shall be 1.20 mm while the lowest thickness shall be at least 90 % of the average thickness.
The semiconducting tapes shall not impair the longitudinal water penetration test performance.
The extruded layer of the conductor semiconducting screen shall be thermoset and be in contact with semiconducting tapes and fully bonded to the inner surface of insulation under all foreseen operating conditions.
The interface between the extruded layer of the conductor semiconducting screen and inner surface of the insulation shall be uniform, continuous, without micro voids, concentric and smooth. As a reference for optical examinations, no protrusions, or irregularities higher than 30 μm are acceptable.
The semiconducting extruded material shall be super smooth and have sulfur and ash content lower than 0.005 % and 0.01 %, respectively.
The maximum electrical resistivity shall be 1000 Ωm, measured according the test of IEC 62067, annex D.
INSULATION
The cable insulation shall be extruded simultaneously to the conductor semiconducting screen and insulation semiconducting screen using a true triple extrusion process.The insulation system shall be dry cured under pressure. The degree of crosslinking of the extruded insulation shall be 100 %, with no traces of remaining peroxide.
The insulation shall be free of micro voids and contaminants.
The degassing process after extrusion shall effectively remove crosslinking by-products and not cause deformations in the insulated core.
The nominal thickness of the insulation shall be designed for 40 years life to withstand the stresses due to:
a) Electrical alternating voltage operation, including periods at maximum operating voltage
b) Electrical lightning impulse voltage of 1175 kV
c) Electrical switching impulse voltage of 950 kV
d) Thermal aging at normal operating temperature
e) Thermal aging at emergency operating temperature
f) Thermal effects of short circuit temperature
In addition, the electrical stresses at outer insulation surface shall be compatible with commercial accessories with good testing and field performance.
The manufacturer shall supply test data and calculations supporting these design and reliability requirements as required in clause 9 of this specification.
The lowest measured thickness shall not fall below 90 % of the nominal thickness.
The insulation shall overcome the following tests of IEC 62067 and IEC 60811
a) Tensile strength and elongation at break without aging
b) Tensile strength and elongation after aging in air oven
c) Tensile strength and elongation after aging of the complete cable for checking compatibility
d) Hot set test
e) Shrink back according to IEC 60811
INSULATION SEMICONDUCTOR SCREE
The extruded layer of the insulation semiconducting screen shall be thermoset, and fully bonded to the outer surface of the insulation under all foreseen operating conditions.
The interface between the extruded layer of the insulation semiconducting screen and the outer surface of the insulation shall be uniform, continuous, without micro voids, concentric and smooth. As a reference for optical examinations, no protrusions, or irregularities higher than 50 μm are acceptable.
The minimum average thickness of extruded layer shall be 1.20 mm while the lowest thickness shall be at least 90 % of the average thickness.
The maximum electrical resistivity shall be 500 Ωm, measured according the test of IEC 62067, annex D.
One or more semiconducting tapes shall be applied over the extruded layer as a bedding to prevent deformation or indentation of the outer part of the insulation underneath.
METALLIC SCREEN AND FOIL
The complete metallic screen shall be composed by copper screen wires and an aluminum foil coated with copolymer.
The screen wires shall be made of annealed copper with minimum conductivity 100 % IACS (International Annealed Copper Standard).
The minimum total cross section of the screen wires shall be 260 mm2, compatible with an allowable short circuit of 50 kA during 0.5 s, calculated with non-adiabatic method described in the IEC 60949 standard.
The number and diameter of copper screen wires shall be chosen to allow sufficient space for inclusion of the monitoring elements described hereafter.
The number and diameter of the wires can be chosen by the manufacture at its convenience, provided a minimum diameter 1.40 mm is respected and compatibility with dimensions of the sensing elements.
The lay length of the screen wires shall not difficult the cable bending or cause damages to the wires due elongation greater than their elastic limit. On the other hand, the increase of electrical resistance due to the lay length shall be limited to 7.5 %.
The aluminum interface of the foil shall be continuously separated to the copper wires by one or more semiconducting tapes to prevent electrolytic corrosion.
The minimum average thickness of the aluminum part of the foil shall be 0.12 mm.
The aluminum foil shall provide radial water tightness and be applied longitudinally with overlap simultaneously with extrusion of the oversheath to ensure a firmly bonding and bending performance without creases or wrinkles.
The metallic screen composed by wires and foil shall overcome longitudinal and radial water penetration tests.
The composite metallic screen shall overcome the tests of IEC 62067:
a) Electrical resistance
b) Water penetration test
c) Radial water penetration test
SENSING ELEMENTS
The sensing elements are distributed thermal sensors and shall consist of low thermal constant optical fiber cables according to IEC 60794, helically applied between two copper wires of the screen.
Two optical cables spaced apart by approximately 120 degrees in the circumference shall be foreseen.
Each optical cable shall have two multimode 50/125 μm optical fibers according to IEC 60793 inside a loose tube and protected by a gel filled stainless steel AISI 316 tube.
The electrical resistance at 20 °C shall be at least 100 times greater than an individual screen copper wire.
The optical fibers shall have the following properties:
a) Phosphor free
b) Low concentration of hydroxyl groups
c) Attenuation at 850 nm lower than 2.4 dB/km
d) Attenuation at 1300 nm lower than 0.5 dB/km
e) Bandwidth greater than 440 MHz.km at 850 nm
f) Bandwidth greater than 500 MHz.km at 1300 nm
Individual optical fibers shall be identified by colors.
The gel filler shall be hydrophobic, have high thermal stability and very low generation of hydrogen.
Alternative constructions shall be subjected to previous approval and technically justified.
The temperatures, minimum bending radius, maximum side wall bearing pressure, and tensile strength which the optical cable is subjected inside the screen shall be compatible with complete power cable requirements.
The lifetime of the optical sensors shall be compatible with thermal and mechanical stresses of the power cable for 40 years.
The optical cable shall be subjected to the following tests according to IEC 60794:
a) Attenuation at 850 nm
b) Attenuation at 1300 nm
c) Impact test
d) Torsion test
e) Crush test
f) Repeated bending
g) Tensile performance
h) Longitudinal water penetration test
Other sensing elements (e.g. humidity penetration sensor) may be included as alternative.
OVERSHEATH
The cable oversheath (or jacket) shall be compatible with ST7 requirements of IEC 62067, and made of black high-density polyethylene.
The minimum average thickness shall be compatible with following requirements:
a) Minimum of 3.30 mm
b) Eccentricity of extrusion process
c) 10 kV withstanding direct voltage test for 1 min (IEC 60229)
d) 62.5 kV lightning transient overvoltages
e) Good abrasion and tearing resistance during pulling operations
f) Sidewall bearing pressures during installations
The oversheath shall contain a minimum carbon black content of 2.0 % to resist to UV radiation due sunlight exposure.
In addition, the oversheath compound shall be suitable to resist to termite attack.
The anti-termite additive shall be safe for people and the environment, and approved for a recognized authority. The material safety data sheet of the additive master batch compound shall be supplied for previous approval.
The oversheath shall overcome the tests of IEC 62067:
a) Tensile strength and elongation at break without aging
b) Tensile strength and elongation after aging in air oven
c) Tensile strength and elongation after aging of the complete cable for checking compatibility
d) Pressure test at high temperature
e) Carbon black content
f) Direct voltage test (IEC 60229)
In order to provide an external electrode for withstanding direct voltage tests during manufacturing, installation, and for periodic maintenance after commissioning, a continuous graphite coating shall be applied on external surface of the oversheath.
Alternatively, a thin coextruded semiconducting layer with average thickness of 0.5 mm, firmly bonded to the high-density polyethylene oversheath is acceptable.
CABLE MARKING
The oversheath of each cable length shall be marked at every meter with the following information:
a) Cable cross section (2000 mm2)
b) Materials (Al/XLPE/Cu/Al/HDPE)
c) Nominal voltage 345 kV
d) Name of the customer
e) Date of manufacturing in format day/month/year
f) Sequential length in meters
g) Traceability information code
The traceability code shall be agreed between supplier and purchaser and contain at least the sequence of insulating core extrusion runs.
The characters height and color shall be clearly visible at naked eye. The characters shall resist to abrasion and sunlight during installation.
PULLING EYES AND SEALING
The outer end of the cable shall be fitted with a pulling eye connected to the conductor suitable for a minimum force of 10.000 daN.
Both cable ends shall be sealed with heat shrink caps for protection against humidity during transportation.
