Joints - Sterlite

RATING FACTORS
Table 20
RATING FACTORS FOR DEPTH OF LAYING
(For cables laid directly in ground)
Depth of laying
(mm)
500- 750
750- 900
900- 1050
1050- 1200
1200- 1500
1500- 1800
1.1 KV
Cables
1.00
0.98
0.96
0.94
0.92
0.90
3.3, 6.6,11 KV
Cables
-
1.00
0.99
0.98
0.96
0.95
22 & 33 KV
Cables
-
-
1.00
0.99
0.98
0.96
Table 21
GROUP RATING FACTORS FOR MULTI CORE CABLES OR GROUPS OF SINGLE CORE CABLES IN HORIZONTAL FORMATION
(For cables laid directly in ground)
Number of cables or group of single core
cables in same trench
Spacing between cables or groups touching
70 mm
250 mm
2 3
4 5
6
0.79
0.85
0.87
0.69
0.75
0.79
Table 22
GROUP RATING FACTORS FOR MULTI CORE CABLES OR GROUPS OF SINGLE CORE CABLES IN AIR ON LADDER SUPPORTS, METAL TRAYS , WALLS
etc WITH MAINTAINED SPACING BETWEEN CABLES OR GROUPS
Number of cables or group of single core cables
Vertically
1
2
3
0.93
0.83
0.76
0.63
0.68
0.75
0.58
0.64
0.72
0.55
0.60
0.69
1 2
Horizontally
3 4
5
1.00
0.89
0.80
0.87
0.79
0.72
0.84
0.76
0.70
0.83
0.75
0.69
4 0.77 0.72 0.68 0.67 0.66
Table 23
RATING FACTORS FOR VARIATION IN GROUND TEMPERATURE
(For cables laid directly in ground)
GROUND TEMPERATURE ° C
RATING FACTOR
15
1.12
20
1.08
Table 24
RATING FACTORS FOR VARIATION IN AMBIENT AIR TEMPERATURE
AIR TEMPERATURE ° C
RATING FACTOR
20
1.18
25
1.14
Table 25
RATING FACTORS FOR VARIATION IN THERMAL RESISTIVITY OF SOIL
Voltage rating of cables
1.1 & 3.3 KV
6.6, 11 & 22 KV
33 KV
25
1.04
30
1.10
30
1.0
35
1.05
35
0.96
40
1.0
40
0.91
45
0.95
45
0.87
50
0.89
Thermal resistivity of soil (° C cm/W)
100
1.18
120
1.08
150
1.0
200
0.88
250
0.81
0.16 1.08 1.0
0.90 0.83
0.12 1.07 1.0
0.90 0.83
50
0.82
55
0.84
300
0.74
0.76
0.78
6
0.82
0.74
0.68
0.65
Issued: June 2012
15