www.tratos.eu

Tratos Open Day: 27 March 2014

Cables for a moving world

TRATOS OHC-HVThe new solution for overhead lines

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TRATOS OHC-HV

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TRATOS OHC-HV

Case Study October 2011Mountain Pass of the Alps

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TRATOS OHC-HV

A completely new, more efficient, hybrid, high load carrying conductor for overhead lines based upon a high load carrying carbon fibre core with two compact, space saving, segmental thermal resistant aluminum alloy (AT1) wire layers, helically applied around in accordance with IEC 62004.

Reduce and ease the cost of installation, increase the power transmitted.

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New innovative load bearing core

Prototyped using a hybrid high strength composite material core based on a special carbon fibre and extruded aluminum sheath.

a novel use of a non metallic material as a constituent part of a conductor operating at high temperatures

• central core of pure carbon fibers

• impreganation using a special, non-migrating, high temperature resistant compound

• an outer layer of high modulus glass yarn

• aluminium sheath extruded over the nucleus as a plastic material (high pressure, low temperature

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Characteristics of this hybrid high strength composite core

Characteristic TRATOS hybrid core

Galvanised steel

Invar

Breaking load daN/mm2 200-220 216 120

Elongation at break

% 1.6-1.8 1.5 1.5

Coefficient of linear expansion

x10-6 per oC

1.04 11.5 2.4

Density (S.G.) Kg/dm3 1.78 7.8 8.13

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A perfect elastic materialA study to evaluate the elastic behavior of this hybrid core this proved that they are absolutely free of any hysteresis areas, behaving as a perfect elastic material.

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New conductor materials

One new material is an alloy of Aluminium Zirconium (Al-Zr), this alloy is:

• a high conductivity material • has a maximum tensile strength comparable to pure aluminium • the maximum strength remains unchanged at high temperatures

Using this alloy it is possible to build a conductor with high thermal limits, working at temperatures not attainable with traditional conductors.

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Types of Aluminium Zirconium (Al-Zr) alloy

Four kinds of Al-Zr alloys have been developed, with the percentage of zirconium determining the thermal resistance. Of these four alloys the two most widely used are

• AT1, called TAL (Thermal resistant Aluminium alloy) and • AT3, ZTAL (Zirconium ultra Thermal resistant Aluminium alloy)

These new alloys have a life of over 40 years when operating continuously at 150 oC (TAL) and 210 oC (ZTAL)

These are included in BS EN 62004 Thermal-resistant aluminium alloy wire for overhead line conductor

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New conductor design

Tratos design their new conductors using using a spatial distribution optimization technique.

Spatial optimization consists of making maximum use of the conductive section of the conductor, by removing the free space between the wires in the conductor.

Tratos achieve this by using sector shaped wires.

These conductors are characterised by an electric resistance lower than that of a conventional compacted conductor of the same overall diameter.

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Benefits against traditional conductors

1. Current carrying capacity increased by up to twice that of the equivalent size of traditional designs.

2. Existing pylons and installation techniques can be used due to reduced weight and strain.

3. Greater tensile strength to withstand snow, ice and wind loadings. 4. Reduced sag and increased ground clearance at maximum

current rating.

5. Fully compatible with existing ACSR and AAAC networks.

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First prototype conductor

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First prototype conductor

Design and construction and of a high load-carrying conductor, 7x3.00mm carbon fibre centre with a concentric layers of 12 sector shaped and 24-alloy TAL wires (d = 2.55 mm), having an external diameter of 22.70 mm

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Technical characteristics

This conductor was subjected to numerous tests in the laboratories of TRATOS and the Institute of RSE laboratories followed by a trial installation and evaluation by TERNA.

Overall diameter mm 22.70

Mass kg/m 0.88567

Load at break daN 10500

Electrical resistance Ω/km 0.0998

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Second prototype low sag conductor

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Second prototype low sag conductor

Design, testing and installation of a conductor with a hybrid high load-carrying 7x3,30mm carbon fibre centre, with two alloy-TAL sector shaped concentric layers (12 +16), having an external diameter of 22.70 mm.

This second prototype conductor has also been tested in the TRATOS Cavi and the Institute of RSE (formerly CESI) Laboratories using the same test protocols as the previous conductor, with positive results and fully in line with expectations.

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Technical characteristics

Overall diameter mm 22.70

Mass kg/m 0.9964

Load at break daN 10500

Electrical resistance Ω/km 0.095

TERNA installed this conductor in the San Pellegrino Pass in the Alps, on the 132 KV Moena-Cencenighe overhead line the installation being comparable with those of a traditional conductor of a similar size.

A report, prepared by the engineer Pirovano dell'Erse, clearly states:"The installation of the line at high altitude (2000 meters above sea level) is a severe test for the conductor: in fact, at low temperatures the mechanical load is transferred from the carbon core to aluminum alloy coats, determining a state of high stress for the latter. "

This conductor has operated successfully to date without problems.

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Advantages gained

This second prototype low sag conductor gave the following advantages; • an extra safety margin to the breaking load (the carbon fibre

hybrid load-carrying section was increased from 49.48 to 59.87mm²); • an additional lowering of the electrical resistance, which reduced

from 0.0998 Ω / km at 20 ° C to 0.095 Ω / km;

• a more uniform and smooth outer surface of the rope;

• an increase of the electrical and mechanical sections in comparison to the previous design;

• a reduction in the permanent elongation after loading cycles from 0.001 mm down to 0.0007 mm.

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Third Development Conductor

Design, production and testing of an experimental conductor with a single hybrid high load-carrying core of 7x4,50mm carbon fibre centre, with two alloy-TAL sector shaped concentric layers (12 +16), having an external diameter of 30.00 mm

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Technical characteristics

This development conductor has already been tested successfully in the laboratories of TRATOS and Gorla Morsetterie. In September 2012 it was sent to the Institute Erse for official tests in their System Research Department.

When tested the actual breaking load was equal to 24,000 daN.

This variation has advantages compared to the conductor with load-carrying in ACI. The most important advantages are the lower ohmic resistance, the higher breaking load and the improved tension transfer point.

Overall diameter mm 30.00

Mass kg/m 1.74484

Load at break daN 22000

Electrical resistance Ω/km 0.054364

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Comparison old and new

A comparison between the characteristics of a high thermal limit, reduced deformation at high loads hybrid load-carrying conductor and an ACI 20 SA aluminium load-carrying traditional conductor revealed:

at a temperature of 130 ° C the high load-bearing hybrid conductor of 7x4.70 mm, with a diameter of 31.50 mm, has a current capacity 17% higher than the conductor with a 20 SA ACI load-carrying conductor in both summer and winter.

At the same temperature the conductor with the hybrid centre of 7x4.50 mm, with a diameter of 30.00 mm, compared to the same ACI 20 SA rope has a current current capacity which is 11% higher in both summer and winter.

The current capacities of the hybrid load-carrying conductors at 130 ° C are even higher than those with load-carrying ropes in ACI 20 SA at 150 ° C.

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A further design of conductor

Single supporting hybrid load-carrying composite core of 7x4.70 mm, aluminium sheath and 2 concentric layers of (13+17) round wires of 3.75 mm, having an external diameter of 32.20 mm

This conductor has been ordered by one of the major companies in the overhead cable sector and will be installed over a section of 4.66 km in a 380 kV line, with three conductors in each phase, the total quantity ordered is 42 km.

This type of conductor, using round wires, has been selected from several proposed designs having outer diameters of 30.0 mm and 31.50 mm respectively, for the following reasons:

• Smaller mass• Reduced corona effect• Reduced sag but with the same tension applied to the pylons

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Description of the conductor

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Comparison of current ratings

Calculated using Shurig & Frick formula including solar irradiation

Conductor Diameter mm

30.00 32.20 31.25 31.50

Core type Composite core 7x4,50mm

Composite core 7x4,70 mm

ACI 20SA core Steel core(ACSR type)

Conductor type 2 layers of sector shaped TAL wires (12+16)

2 layers of circular TAL wires (17+23) x 2.75mm

19x3,25 mm 19x2,10 mm

Electrical Resistance Ω/Km

R=0,054364 R=0,05712 R=0,06857 R=0,05564

Temperature of conductor°C

Current (A) Current (A) Current (A) Current (A)

Winter Summer10°C 30 °C

Winter Summer10 °C 30 °C

Winter Summer10 °C 30 °C

Winter Summer10 °C 30 °C

35 614 610 363 554 616 368

90 1257 1075 1248 1061 1132 968 1260 1076

130 1521 1391 1504 1376 1371 1255

150 1630 1516 1612 1500 1470 1368

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The comparison is made between the following conductors:

• Hybrid core 7x4,50mm , 2 layers of trapezoidal TAL wires (12+16) , overall diameter 30,00 mm.

• Hybrid core 7x4,70mm , 2 layers of 40 circular TAL wire (17+23) x 3,75 mm overall diameter 32,20 mm

• ACI core 20 SA, 19x3,25 mm, overall diameter 31.00 mm• Steel core, 19x2,10mm, 3 layers of circular wires 54x3,50mm,

overall diameter 31,50

Calculated using the following parameters

- Solar radiation 1000W/m2- Coefficient of emission 0,5- Wind velocity 2 Km/h- Atmospheric pressure 1 Atm - Coefficient of absorption 0,5

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Comparison of the sags in conductors

Conductor Diam. mm 30.00 32.20 31.25 31.50

Core type Composite hybrid core 7x4,50mm

Composite hybrid core 7x4,70 mm

ACI 20SA core Steel core(ACSR type)

Conductor type 2 layers of sector shaped TAL wires (12+16)

2 layers of circular TAL wires(17+23)x2.75mm

19x3,25 mm 19x2,10 mm

Diameter, mm 30.00 32.20 31.25 31.50

Pulling load, daN 3539 3539 3539 3539

Pulling load/load at break 0,197 0,192 0.1361 0.2100

Mass, kg/m 1,74484 1,676762 2,240 1,953

Pulling load/mass, m 2030 2110 1586 1812

Span, m 400 400 400 400

Temperature of conductor °C

Sag ( m ) Sag ( m ) Sag ( m ) Sag ( m )

15 9,67 9,30

75 10,24 9,99 14,10 13,31

95 10,43 10,16 14,51 14,07

105 10,52 10,24 14,44 14,44

115 10,62 10,33 14,81 14,81

125 10,71 10,41 15,17 15,17

135 10,81 10,50 15,52 15,52

155 11,03 10,67

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The comparison is made between the following conductors:

• Hybrid core 7x4,50mm , 2 layers of sector shaped TAL wires (12+16) , overall diameter 30,00 mm

• Hybrid core 7x4,70mm , 2 layers of 40 circular TAL wire (17+23) x 3,75 mm overall diameter 32,20 mm

• ACI core 20 SA, 19x3,25 mm, overall diameter 31.00 mm

• Steel core, 19x2,10mm, 3 layers of circular wires 54x3,50mm, overall diameter 31,50

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The Future

The technology employed by Tratos can be applied to various designs

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The Future

Tratos GroupCables for a moving world

www.tratos.eu