TABLE 1
RATING FACTORS K FOR VARIATION IN GROUND TEMPERATURE
GROUND TEMERATURE °c
20
25
30
35
40
45
50
55

PVC cables rated 70°C

PVC cables rated 85°C

XLPE cables rated 90 °c

1.00
1.00
1.00
0.95
0.96
0.96
0.90
0.92
0.92
0.84
0.87
0.88
0.78
0.83
0.84
0.71
0.78
0.79
0.63
0.73
0.75
0.54
0.67
0.70
TABLE 2
RATING FACTORS K FOR VARIATION IN AIR TEMPERATURE
AIR TEMERATURE °c
25
30
35
40
45
50
55

PVC cables rated 70°C

PVC cables rated 85°C

XLPE cables rated 90°'c

1.07
1.04
1.04
1.00
1.00
1.00
0.93
0.95
0.96
0.87
0.90
0.91
0.79
0.85
0.87
0.70
0.80
0.82
0.61
0.74
0.76
TABLE 3
RATING FACTORS K FOR VARIATION IN GROUND DEPTH
Depht of laying (m)
0.6
0.7
0.8
0.9
1.0
1.1
1.2
k
1.05
1.03
1.02
1.01
1.0
0.99
0.98
TABLE 4
RATING FACTORS K FOR VARIATION IN SOIL RESISTIVITY
Soil Resistivity ( °C.cm/W)
80
90
100
120
150
200
250
k
1.17
1.12
1.07
1.0
0.91
0.80
0.73
TABLE 5
RATING FACTORS K FOR VARIATION OF MAX. OPERATING
TEMPERATURES FOR PVC INSULATING CABLES
PVC RATED TEMPERATURE
70
85
105

RATING FACTOR

0.84
1.00
1.18
TABLE 6
TREFOIL OR FLAT FORMATION DERATING FACTORS FOR
THREE SINGLE CORE CABLES LAID DIRECT IN GROUND.
NUMBER OF CIRCUITS
TREFOIL FORMATION
FLAT FORMATION
TOUCHING
SPACING = 0.15 M
SPACING = 0.30 M
NR
TREFOIL
FLAT
TREFOIL
FLAT
TREFOIL
FLAT
2
3
4
5
6
0.77
0.66
0.60
0.56
0.53
0.80
0.69
0.63
0.59
0.57
0.82
0.73
0.63
0.64
0.61
0.85
0.76
0.71
0.67
0.64
0.88
0.80
0.74
0.72
0.70
0.91
0.83
0.77
0.75
0.73
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