Direct Laid Underground

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Last Updated on Monday, 17 October 2011 10:07

RATING FACTOR :

The Following correction factors are used for calculation on the basis of the values stated in the brochure for cables with cross-linked polyethylene (XLPE), polyvinyl chloride (PVC) or ethylene propylene rubber (EPR) insulation.

A. CABLES LAID DIRECT IN GROUND

A1. Rating factor for variation of ground temperature

Ground temperature

 10 15 20 25 30 35 40 45

50
Rating factor XLPE / EPR cables 1.15 1.12 1.08 1.03 1.00 0.96 0.91 0.86 0.82
PVC Cables 1.22 1.17 1.12 1.06 1.00 0.94 0.87 0.79 0.71

A2. Rating factor for thermal resistivity of soil

Thermal resistivity of soil (°Km/watt)

 0.7 1.0 1.5 2.5
Rating factor XLPE / EPR Cables 1.12 1.00 0.88 0.79
PVC Cables 1.14 1.00 0.85 0.72

A3. Rating factor for variation of depth of laying in ground

Depth of laying (m)

 0.5 0.7 1.0 1.2 1.6
Rating factor XLPE / EPR Cables 1.02 1.00 0.98 0.98 0.95
PVC Cables 1.01 1.00 0.99 0.98 0.97

 

A4. Rating factor for grouping of three-single core cables in three-phase systems

Formation

Number of group 1 2 3 4 5 6 8 10
Rating factor XLPE / EPR Cables 1.00 0.87 0.77 0.73 0.70 0.68 0.65 0.63
PVC Cables 1.00 0.87 0.78 0.74 0.70 0.68 0.65 0.63

 

Formation

Number of group 1 2 3 4 5 6 8 10
Rating factor XLPE / EPR Cables 1.00 0.85 0.75 0.70 0.66 0.63 0.59 0.56
PVC Cables 1.00 0.85 0.75 0.70 0.66 0.63 0.59 0.56

 

Formation

Number of group 1 2 3 4 5 6 8 10
Rating factor XLPE / EPR Cables 1.00 0.89 0.82 0.78 0.75 0.73 0.70 0.68
PVC Cables 1.00 0.90 0.82 0.79 0.76 0.74 0.71 0.69

A5. Rating factor for grouping multi core cables in three-phase systems

Formation

Number of group 1 2 3 4 5 6 8 10
Rating factor XLPE / EPR Cables 1.00 0.85 0.75 0.70 0.66 0.63 0.59 0.56
PVC Cables 1.00 0.86 0.76 0.71 0.67 0.64 0.60 0.57