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Using overhead distribution lines carry fibre optic cables
"Every village and small community in the UK is connected to the electricity distribution network, and in most cases this connection is carried on wooden poles stretching out across fields to the nearest electricity substation. Usually these poles carry two or three electricity conductors and would potentially make an unobtrusive and convenient way to install fibre-optic cables to carry broadband connectivity – providing power and Internet over the same poles.
Electricity is best carried over long distances at high voltages, and then the voltage is reduced in steps as the power is brought closer to houses and businesses. The National Grid operates at 400,000V with conductors carried on massive steel pylons from power stations to primary substations where it is converted to 132,000V for regional distribution. The next set of sub-stations converts the power to 66,000 or 33,000V. Voltages of 66kV and above are usually carried on steel lattice towers and voltages of 33kV and below are normally carried on lines supported by wooden poles. As the voltages come down, the sizes of the support structures get smaller, the number of conductors gets less and the height above ground level decreases.
The next step is to convert the electricity into 11,000V to make the connection to villages and then finally there is a step down to mains voltage for connection to individual properties. Often, all of these final links in the electricity distribution chain are carried on poles above ground with connections to houses at roof-top height. Properties built in the last 25 years will have all of their services connected underground because this has been planning policy since the 1970s, but even so few properties are more than 100m from an overhead electricity distribution line.
Power utility companies are big users of communications to operate and control their networks, and many of the bigger transmission lines already carry fibre-optic communications cables to provide connections between major sub-stations and control centres. Distribution lines radiating outwards from substations towards towns, villages and consumers have, for the most part, not been equipped to carry communications cables because there has been no requirement for the power companies to do so in these parts of their networks.
The same technologies that have been used since the 1980s to add fibre-optic cables to large transmission lines can also be used on medium voltage and low voltage distribution lines, and this has attracted the attention of organisations that are planning to build broadband networks. These lines reach right into the target communities, providing both the means of connecting to the broadband service providers’ infrastructure and also the means of distributing connectivity to individual consumers within the community.
The key advantages of using overhead electricity distribution lines to carry cables providing broadband connectivity can be summarised in three distinct areas: speed, security and cost
Speed: It is always much, much quicker to install fibre-optic cable by attaching it to poles than it is to dig trenches to bury it underground. Directional drilling or ploughing are alternative ways of installing underground cable, but these are also slow and expensive compared to installation on overhead lines. Circumstances will vary according to the time of year with factors including weather conditions, whether or not crops or animals are in the fields and what the ground conditions are like underfoot; however it is generally possible to install at least 1km of fibre optic cable a day on overhead power lines and up to 5km per day is possible in favourable circumstances.
Security: is a key concern in any fibre-optic cable installation. Cables have been installed on overhead power lines since the very early 1980s and have developed an excellent reputation for security and reliability over that time. Power utilities use these cables to carry critical communications for control of the electricity network. Fibre-optic cables installed above ground are not subject to ‘dig-ups’ which is the biggest cause of cable damage in the UK. Cables that are installed as part of the electricity infrastructure are protected by the proximity of power conductors, which provide protection against theft and vandalism.
Cost: The higher unit cost of aerial cables compared to underground cables is more than offset by the much lower cost of installation and therefore aerial cables have the lowest total cost. Aerial cables have much higher installation rates and so networks are built much more quickly, begin to provide services earlier and so have quicker returns on investment. Put another way, with reduced initial costs and earlier in-service dates, aerial cables have shorter pay back times than underground networks.
Several technologies are available to add fibre-optic cables to overhead power lines: ADSS, OPPC and AccessWrap. The choice of which to use will depend upon the type of overhead line.
Using overhead distribution lines carry fibre optic cables
"Every village and small community in the UK is connected to the electricity distribution network, and in most cases this connection is carried on wooden poles stretching out across fields to the nearest electricity substation. Usually these poles carry two or three electricity conductors and would potentially make an unobtrusive and convenient way to install fibre-optic cables to carry broadband connectivity – providing power and Internet over the same poles.
Electricity is best carried over long distances at high voltages, and then the voltage is reduced in steps as the power is brought closer to houses and businesses. The National Grid operates at 400,000V with conductors carried on massive steel pylons from power stations to primary substations where it is converted to 132,000V for regional distribution. The next set of sub-stations converts the power to 66,000 or 33,000V. Voltages of 66kV and above are usually carried on steel lattice towers and voltages of 33kV and below are normally carried on lines supported by wooden poles. As the voltages come down, the sizes of the support structures get smaller, the number of conductors gets less and the height above ground level decreases.
The next step is to convert the electricity into 11,000V to make the connection to villages and then finally there is a step down to mains voltage for connection to individual properties. Often, all of these final links in the electricity distribution chain are carried on poles above ground with connections to houses at roof-top height. Properties built in the last 25 years will have all of their services connected underground because this has been planning policy since the 1970s, but even so few properties are more than 100m from an overhead electricity distribution line.
Power utility companies are big users of communications to operate and control their networks, and many of the bigger transmission lines already carry fibre-optic communications cables to provide connections between major sub-stations and control centres. Distribution lines radiating outwards from substations towards towns, villages and consumers have, for the most part, not been equipped to carry communications cables because there has been no requirement for the power companies to do so in these parts of their networks.
The same technologies that have been used since the 1980s to add fibre-optic cables to large transmission lines can also be used on medium voltage and low voltage distribution lines, and this has attracted the attention of organisations that are planning to build broadband networks. These lines reach right into the target communities, providing both the means of connecting to the broadband service providers’ infrastructure and also the means of distributing connectivity to individual consumers within the community.
The key advantages of using overhead electricity distribution lines to carry cables providing broadband connectivity can be summarised in three distinct areas: speed, security and cost
Speed: It is always much, much quicker to install fibre-optic cable by attaching it to poles than it is to dig trenches to bury it underground. Directional drilling or ploughing are alternative ways of installing underground cable, but these are also slow and expensive compared to installation on overhead lines. Circumstances will vary according to the time of year with factors including weather conditions, whether or not crops or animals are in the fields and what the ground conditions are like underfoot; however it is generally possible to install at least 1km of fibre optic cable a day on overhead power lines and up to 5km per day is possible in favourable circumstances.
Security: is a key concern in any fibre-optic cable installation. Cables have been installed on overhead power lines since the very early 1980s and have developed an excellent reputation for security and reliability over that time. Power utilities use these cables to carry critical communications for control of the electricity network. Fibre-optic cables installed above ground are not subject to ‘dig-ups’ which is the biggest cause of cable damage in the UK. Cables that are installed as part of the electricity infrastructure are protected by the proximity of power conductors, which provide protection against theft and vandalism.
Cost: The higher unit cost of aerial cables compared to underground cables is more than offset by the much lower cost of installation and therefore aerial cables have the lowest total cost. Aerial cables have much higher installation rates and so networks are built much more quickly, begin to provide services earlier and so have quicker returns on investment. Put another way, with reduced initial costs and earlier in-service dates, aerial cables have shorter pay back times than underground networks.
Several technologies are available to add fibre-optic cables to overhead power lines: ADSS, OPPC and AccessWrap. The choice of which to use will depend upon the type of overhead line.