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AECOM Puketoi Wind Farm Technical Report 16Figure 4 Magnetic flux density of the 220kV and 33kV lines.7.0 Preliminary Constructability Review7.1 Planning and MaterialsThe planning of a new transmission line requires the co-ordination of the following main activities,a) Bulk purchase of materials;b) Access preparation;c) Foundation installation;d) Tower construction; ande) Stringing of the conductors.Each activity is dependent on the other to maintain progress in an orderly manner. Therefore foundationinstallation cannot begin until the access has been prepared, the structures cannot be installed until sufficientfoundations (maybe 30%) are complete and the stringing cannot begin until complete strain sections are built.The construction would be organised so that materials are fabricated and delivered to site on time so that damageto property is kept to a minimum and that landowners are kept well informed of any changes.7.2 Vegetation ManagementThe lines are generally located to avoid most large trees, and conductors are generally suspended high abovevalleys with native scrub. However, it will be necessary to fell willow (or other fast growing vegetation) trees atriver and road crossings.7.3 AccessGenerally, access across flat paddocks in pasture is acceptable, unless working during the winter months, when aformed track with compacted chips or river metal may be necessary. The use of existing farm tracks in the hillswill be such as to allow a 20 or 30 tonne tracked digger to get to the sites. Access will be upgraded as the diggerscomplete one site and move to the next. Generally a digger can travel from one ridge system to another,depending upon landowner co-operation and their expectations. An access track which travels along or near tothe line is an advantage for maintenance inspections.
AECOMPuketoi Wind Farm Technical Report177.4 ConstructionThe use of helicopters overcomes difficult access areas where slips and erosion are a hazard. Helicopters can beused for all activities on hill sites, including the daily carriage of construction crews to site, the lifting of reinforcingsteel and concrete for foundations, the cartage of structure steel and its assembly, and the initial phases ofstringing. Track access can be achieved to all or most tower sites so helicopters will be used only where relevant.The structures are fabricated in sections suitable for the crane or helicopter’s lifting capacity, each structuresection being fitted together progressively, using standard procedures based on safe work methods. The latticetowers will be bolted together using plates and cleats and the poles use a compressive jointing system.It is anticipated that steel pole structures will be slip jointed (sometimes bolted plate connections are also used)allowing small lighter sections to be lifted into place with a helicopter or crane.Safety of line construction crews on the job is paramount and all construction activities will follow an approvedprocedure.The stringing of the conductors is completed using the tension stringing method, where all conductors are kept upoff the ground and pulled by a large winch at one end with tensioning equipment at the other end. Helicopters areoften used to pull through a pull rope. This then allows the conductor to be attached to the pull rope and pulledalong the line under a desired tension. A typical stringing length for high voltage heavy conductor is 5-6km.The large drums of conductor are usually set up every 5-6kms along the line, and in an area which is relatively flatand accessible for a rough terrain type crane. The cables and conductors are suspended above the ground asthe drums unwind, and pulled up to final tension once correctly sagged. Each section of conductor is pulled outthrough running blocks on each of the structures, jointed to the end of the previous section, before being clampedto the insulators. The process is then repeated; leap frogging from one area to the next.The construction of the 33/220kV substation will require additional large plant for installing substation equipmentwhich is often very heavy. Helicopters are generally not utilised for such works and therefore the area around thesubstation will be frequently accessed by large cranes, concrete trucks etc.Access tracks to the substation site will be required to be of a condition to with stand the large amount of heavyplant traffic expected.7.4.1 Road or Rail ProtectionAll public roads are generally protected with hurdling (usually made from a timber H structure either side of theroad) providing protection for vehicles using the road during the stringing phase of construction. The sameprotection is installed for the crossing of low voltage (LV) distribution lines and temporary undergrounding of theLV asset can also be used.7.4.2 ReinstatementThe final activity is reinstatement which includes a general tidy up of all structure sites including any outstandingfencing or roading issues to the satisfaction of each landowner.7.4.3 Line MaintenanceThe rate of regular inspections of a transmission line increases as the age of the line increases. Most steelstructures have a minimum design life of 50 years, and are expected to be relatively free of maintenanceproblems for the first 20 years.Generally, an inspection would involve a lineman climbing the structure to check for loose steel or damage. Thelineman would gain access by motorbike or 4X4 vehicle.Typical maintenance duties resulting from adverse weather and vandalism include replacement of damagedinsulators or the installation of repair sleaves for conductors. A landowner would not expect to be visited morethan twice in 3-5 years, unless adverse weather has been prevalent.27 July 2011
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P - Transmission

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