Yuleba name and the locations of Roma, Surat, Miles and Chinchilla

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Yuleba name and the locations of Roma, Surat,
Miles and Chinchilla
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• Thermal sand is widely used throught the power
  industry to improve underground electrical cable
  performance.

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• An electrical cable primarily made up of two
  elements the conductor and the insulator, the
  limiting factor on a power cable capacity is the
  temperature that the insulation can withstand and
  the more power or current that is flowing through
  the conductor the more heat is generated by the
  cable.

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• Different insulation materials are available PVC
  is rated to 60 deg C and XLPE a cross linked poly
  ethylene is rated at 90 deg C meaning that for
  the same size conductor the current carry
  capacity of the cable can be increased by as much
  as

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• Other insulating materials based on ceramic
  materials are used in special applications but
  these types of insulations are very expensive and
  reach the point where there cost is the same as
  the conductor meaning it easier and cheaper to
  increase the size of the conductor.

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• Its widely recognised that a cable will preform
  differently depending on where and how the cable
  is installed. Burying the cable in the ground
  increases the cable capacity, the ground act as a
  heat sink taking heat away from the insulation
  and reducing the cable temperature. Thermal sand
  is a way of increasing this thermal heat
  transfer.

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• Thermal sand is now widely used when installing
  underground cables. The thermal sand is rated or
  tested to provide a known heat transfer
  efficiency. The cable and the thermal sand are
  installed so that the thermal sand is in direct
  contact with the cable.

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• The thermal sands high heat transfer efficiency
  ensures the heat generated by the cable is
  transfered from the cable through the thermal
  sand to the surounding earth.

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• Thermal sand is specified to a thermal
  resisitivity which is measured in deg K m/W or
  C-cm/W and typically the thermal sand may need
  to meet a required standard for example thermal
  resistivity shall be less than or equal to 0.9 K
  m/W

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• The thermal sand becomes the connection between
  the cable and the general mass of the earth.All
  the heat generated by an underground power cable
  must be dissipated through the soil. This is
  quantified by the soil thermal resistivity (or
  thermal rho, C-cm/W), which can vary from 30 to
  500C-cm/W.

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• Electrical engineers understand the performance
  of the cable quite well, but to most, the soil
  behavior is a mystery, usually handled by using a
  thermal backfill with a supposedly safe thermal
  rho.The ability of the surrounding soil to
  transfer the heat determines whether an operating
  cable remains cool or overheats.

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• Improving the external thermal environment and
  accurately defining the soil and backfill thermal
  rho commonly results in a 10 to 15 increase in
  cable ampacity, with 30 improvements noted in
  some cases.Compacted granular backfills can have
  good thermal properties.

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• Since most of the heat conduction is through the
  soil mineral particles and their contacts, one
  must ensure a high-density soil mixture to
  maximize these contacts. A well-graded sand to
  fine gravel can be a good thermal backfill when
  compacted to its maximum density as determined by
  a laboratory standard Proctor test (ASTM D698).

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• The total cost of a compacted backfill must
  include material and transportation costs, as
  well as installation labor and quality-assurance
  costs. Yuleba Minerals makes a thermal sand which
  has been used for projects in and around Roma,
  Chinchilla and the Surat basin.

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• The one often-neglected factor about compacted
  backfills is the need for quality assurance
  during installation. If the gradation of the
  backfill is not correct (sieve analysis ASTM
  D422), or it is not at the optimum moisture
  content (ASTM D698), or not enough compaction
  effort is applied, or the backfill lifts are too
  thick, then the maximum density will not be
  achieved and the thermal capability degraded.

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• Gas Power projects in the Surat basin have been
  the catalyst for Yuleba Minerals developing and
  testing a thermal sand for use in underground
  cable installation.

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• For further information please visit

http//www.yulebaminerals.com.au/