Bare Overhead Conductors

Transcription

1 Bare Overhead Conductors AAC, ACSR, ACSR II A global cable expert

2 Bare Overhead Conductors Nexans is a diversified wire and cable manufacturer. Nexans has been designing, manufacturing and delivering cables to customers in North America since Major utilities, distributors and contractors recognize Nexans as a quality supplier and a technology leader. Substantial investment in research and development of product and process technologies continuously reinforces our commitment to excellence. Nexans offers a combination of sales, design, manufacturing and quality control which ensures that all relevant standards of design and service are met. With our multi-plant manufacturing base, we are able to produce all standard types and sizes of bare overhead conductors, as well as a wide range of non-standard conductors, for virtually every application. Applications The bare overhead conductors described in this brochure are suitable for installation in all practical spans on transmission towers, wood poles and other structures. Installations range from long-distance EHV transmission lines to sub-service spans at distribution or utilization voltages on private premises. The choice of conductor size, type and strength should take into account factors such as electrical load, voltage regulation, corona losses, ice and wind loading, extreme temperatures and vibration. Nexans is prepared to assist in the evaluation of these factors as they relate to the design of a transmission or distribution line. Specifications Nexans bare overhead conductors are designed, manufactured and tested in accordance with the following specifications: ASTM B 231 Standard Specification for Concentric-Lay-Stranded Aluminum 1350 Conductors ASTM B 232 Standard Specification for Concentric-Lay-Stranded Aluminum Conductors, Coated-Steel Reinforced (ACSR) Packaging is provided as per Aluminum Association Packaging Standards for Aluminum Conductor and ACSR, Sixth Edition AAC Bare Overhead Conductor Product Construction Bare all aluminum conductors (AAC) are concentric-lay-stranded consisting of one or more layers of aluminum alloy 1350 wires wrapped helically around a central wire. Each successive layer has six wires more than the underlying one. Increasing the number of wires for any given cross-sectional area provides greater flexibility. The most commonly used strandings consist of 7, 19, 37, 61 and 91 wires. Class AA strandings are used for bare overhead lines. The direction of lay for the outer layer is right-hand and is usually reversed in successive layers. The temper of the wires is full harddrawn (H19). Class A strandings are used primarily for overhead conductors that are to be covered. They have greater flexibility than Class AA. The outermost layer is right-hand lay and the temper is normally H19. Successive layers are reverse lay. Features and Benefits AAC conductors are the most economical since their lighter weight means lower unit length costs, easier handling during installation and the use of simpler fittings. They are inherently corrosion resistant due to their homogeneous construction. Applications Stranded bare AAC conductors may be used in overhead line installations where the design parameters do not require the higher tensile strength or temperature ratings provided by ACSR, ACCR or other types of conductors. ACSR Bare Overhead Conductor Product Construction ACSR is a composite concentric-lay stranded conductor consisting of a central steel core around which are stranded one or more layers of aluminum alloy 1350-H19 wires. The steel core may consist of a single wire, 7, 19, 37 or more concentrically stranded wires. They are normally protected against corrosion by the application of zinc coating. The standard Class A coating is usually adequate for ordinary environments. Heavier Class B or C coatings may be specified for greater protection. A special high-strength steel core with a Class A coating is also available. There are numerous combinations of aluminum and steel wires and layers that are available. The sizes and strandings most frequently used for overhead lines are listed on the following pages. Features and Benefits ACSR conductors have a long service record due to their economy, dependability and favourable strength to weight ratio. Such conductors combine the lightweight and high conductivity of the aluminum wires with the tensile strength and ruggedness of the steel core. For overhead line design, this enables higher tensions to be used with less conductor sag and longer spans than would be possible with most other types of conductors. Applications Aluminum conductors, steel reinforced (ACSR) are widely used for overhead transmission and distribution lines. 1

3 Physical Data for Aluminum 1350 Conductors Diameter (inch) Rated Size No. of Individual Complete Weight Strength Codeword (AWG/kcmil) Wires Wires Conductor (lb/kft) (Ibf) Peachbell Rose Iris Pansy Poppy 1/ Aster 2/ Phlox 3/ xlip 4/ Daisy Laurel Tulip Cosmos Syringa Zinnia Dahlia Orchid Violet Arbutus Magnolia Bluebell Columbine Coreopsis Cowslip Lupine

4 Electrical Data for Aluminum 1350 Conductors Resistance Reactance at 60 Hz** Size DC at 20 C AC at 25 C AC at 50 C AC at 75 C Capacitive Inductive at 25 C Ampacity* Codeword (AWG/kcmil) (ohm/kft) (ohm/kft) (ohm/kft) (ohm/kft) (megohm-kft) (ohm/kft) (A) Peachbell Rose Iris Pansy Poppy 1/ Aster 2/ Phlox 3/ Oxlip 4/ Daisy Laurel Tulip Cosmos Syringa Zinnia Dahlia Orchid Violet Arbutus Magnolia Bluebell Columbine Coreopsis Cowslip Lupine * Ampacity is with sun and wind at 2 ft/s ** Reactance at 1 foot equivalent spacing 3

5 Physical Data for ACSR Conductors Diameter (inch) Weight (lb/kft) Size Stranding Complete Rated Codeword (AWG/kcmil) (AI/Steel) Steel Wire Aluminum Wire Steel Core Conductor Aluminum Steel Total Strength (Ibf) Turkey 6 6/ Swan 4 6/ Swanate 4 7/ Sparrow 2 6/ Sparate 2 7/ Robin 1 6/ Raven 1/0 6/ Quail 2/0 6/ Pigeon 3/0 6/ Penguin 4/0 6/ Waxwing / Partridge / Merlin / Linnet / Oriole / Chickadee / Ibis / Pelican / Flicker / Hawk / Hen / Osprey / Parakeet / Dove / Rook / Grosbeak / Drake / Tern / Rail / Cardinal / Curlew / Bluejay / Bittern / Lapwing / Bluebird /

6 Electrical Data for ACSR Conductors Resistance Reactance at 60 Hz ** Inductive Inductive Inductive Size DC at 20 C AC at 25 C AC at 50 C AC at 75 C Capacitive at 25 C at 50 C at75 C Ampacity* Codeword (AWG/kcmil) (ohm/kft) (ohm/kft) (ohm/kft) (ohm/kft) (megohm-kft) (ohm/kft) (ohm/kft) (ohm/kft) (A) Turkey Swan Swanate Sparrow Sparate Robin Raven 1/ Quail 2/ Pigeon 3/ Penguin 4/ Waxwing Partridge Merlin Linnet Oriole Chickadee Ibis Pelican Flicker Hawk Hen Osprey Parakeet Dove Rook Grosbeak Drake Tern Rail Cardinal Curlew Bluejay Bittern Lapwing Bluebird * Ampacity is with sun and wind at 2 ft/s ** Reactance at 1 foot equivalent spacing 5

7 ACSR-II Overhead Conductors ACSR-II Overhead Conductors are manufactured from two standard ACSR conductors which are twisted together with a very long lay (8-10 feet). This simple cable design is very effective in reducing ice loading and wind-induced conductor motion, and the costly damage that these can cause. AAC (all aluminum conductor) and AAAC (all aluminum alloy conductor) are also available in the twisted configuration, and are identified as AAC-II and AAAC-II respectively. Wind-Induced Conductor Motion Aeolian Vibration Steady, low speed wind loading can impart vertical motion to a standard overhead conductor. At resonant frequencies, the amplitude of this motion (aeolian vibration) is sufficient to cause fatigue damage to the conductor strands, and can reduce the life expectancy of the conductor. ACSR-II conductor reduces aeolian vibration to harmless levels through two mechanisms: 1) Prevention of resonant vibrations 2) Conversion of vertical motion to rotational motion. The twisted configuration of ACSR-II results in a constantly changing profile along its length. Consequently, the wind-force applied to the conductor is different at each point along its length. This variation in wind force effectively prevents resonant vibration and reduces vertical conductor motion. A further reduction is achieved as a result of the ease of rotation of a twisted assembly compared to a single conductor. Since a cabled conductor is much easier to rotate than a single conductor, much of the wind s energy is dissipated through harmless rotation of an ACSR-II conductor rather than imparting damaging aeolian vibration. Conductor Galloping The combination of an eccentric ice coating and high wind-loading can create a situation where a standard overhead conductor is subjected to wind-induced lift. Vertical motion of several feet can result as the ice-coated conductor, behaving like an airfoil, is lifted and then dropped by the wind. Severe damage to the conductor and accessories can result as this cycle repeats itself. However, the twisted configuration of the ACSR-II design changes the angle of wind attack along the cable s length and prevents the formation of an ice airfoil. This effectively eliminates one of the key causes of conductor galloping. Sub-Conductor Oscillation Wind speeds in excess of 20 mph can cause damaging wake-induced motion of bundled conductors in amplitudes of up to 5 feet. However, it is known that if one of the conductors in a bundled system is a different diameter than the other, the likelihood of resonant vibrations being created is greatly reduced. When two ACSR-II conductors are used in a bundled configuration, it is very likely that at any point along the length of the bundle the apparent diameter of one ACSR-II conductor will be different from that of the other. In addition, wind vortices formed in a standard bundled system cause vertical forces and vertical conductor motion. As stated previously, an ACSR-II conductor will convert these vertical forces into rotational motion. Operating Temperatures Compared to a standard ACSR conductor of equivalent cross-sectional area, ACSR-II conductor has a larger surface area. This allows for greater heat dissipation, and means that for a given current, ACSR-II conductor will operate at a lower temperature. Similarly, ACSR-II conductor has a greater ampacity than the equivalent single ACSR conductor. Cost Savings The unique physical properties of ACSR-II conductors can result in real savings in the cost of a T & D system. Fatigue damage to conductor strands is reduced, thus enhancing lifeexpectancy and delaying replacement. Accessories (i.e. vibration dampers, armor rods, and anti-galloping devices) normally used with standard conductors to reduce conductor motion can be eliminated. The higher installation tension permitted with ACSR-II conductor results in reduced structure costs through fewer and smaller structures. Lower operating temperature and resistance is obtained. Higher load capacity is achieved. 6

8 Physical Data for ACSR-II Conductors Size Stranding Steel Wire Aluminum Major Overall Aluminum Steel Total Rated Codeword (AWG/kcmil) (Al/Steel) Diameter Wire Diameter Diameter * Weight Weight Weight Strength (inch) (inch) (inch) (lb/kft) (lb/kft) (lb/kft) (lbf) ACSR-II Turkey 6 2 6/ ACSR-II Swan 4 2 6/ ACSR-II Swanate 4 2 7/ ACSR-II Sparrow 2 2 6/ ACSR-II Robin 1 2 6/ ACSR-II Raven 1/0 2 6/ ACSR-II Quail 2/0 2 6/ ACSR-II Pigeon 3/0 2 6/ ACSR-II Penguin 4/0 2 6/ ACSR-II Waxwing / ACSR-II Partridge / ACSR-II Merlin / ACSR-II Linnet / ACSR-II Oriole / ACSR-II Chickadee / ACSR-II Ibis / ACSR-II Pelican / ACSR-II Flicker / ACSR-II Hawk / ACSR-II Hen / * Minor Overall Diameter is 1/2 of Major Overall Diameter Electrical Data for ACSR-II Conductors* Size Resistance Reactance at 60 Hz ** Codeword (AWG/kcmil) Inductive Inductive Inductive DC at 20 C AC at 25 C AC at 50 C AC at 75 C Capacitive at 25 C at 50 C at 75 C (ohm/kft) (ohm/kft) (ohm/kft) (ohm/kft) (megohm-kft) (ohm/kft) (ohm/kft) (ohm/kft) ACSR-II Turkey ACSR-II Swan ACSR-II Swanate ACSR-II Sparrow ACSR-II Robin ACSR-II Raven 1/ ACSR-II Quail 2/ ACSR-II Pigeon 3/ ACSR-II Penguin 4/ ACSR-II Waxwing ACSR-II Partridge ACSR-II Merlin ACSR-II Linnet ACSR-II Oriole ACSR-II Chickadee ACSR-II Ibis ACSR-II Pelican ACSR-II Flicker ACSR-II Hawk ACSR-II Hen * For single-aluminum-layer ACSR, the AC values are approximate, based on assumed current for 75 C, 75% of assumed current for 50 C, and 10% of assumed current for 25 C. Reactances for multi-layer conductors are not temperature dependent. Data is adapted from conventional ACSR data given in Tables 4-15 and 4-16 of Aluminum Electrical Conductor Handbook, Second Edition, published by the Aluminum Association. ** Reactance at 1 foot equivalent spacing 7

9 US Sales Office Corporate Office 10 North Hill Drive 140 Allstate Parkway Suite 2A Markham, Ontario Warrenton, Virginia Canada L3R 0Z7 Telephone (540) Telephone (905) Facsimile (540) Facsimile (905) Internet Web Site Manufacturing Locations Weyburn, Saskatchewan Quebec City, Quebec Nov. 2003