Width of maximum right of way permitted as per forest conservation act ‘1980 and its subsequent amendment dated 25thOctober, 1992, are as per Table 1. Researches are being carried out for further optimizing the Right of Way.
Guidelines of forest environmental rules shall be followed to avoid excessive tree cutting i.e. all the trees should be cut from root level in the 3 m corridor below each line conductor / earth wires. In the balance corridor, trees branches are only to be lopped to attain the specified clearance as per Table 1.
Table 1 – Guidelines for Right of Way as per forest conservations act 1980 and subsequent amendment dated 25thOctober, 1992
Line voltage (kV)
66
110
132
220
400
500 HVDC
765
Row width (Meter)
18
22
27
35
52
52
85
Electrical clearance: Electrical clearance while power lines crossing each other.
In case of power line crossings, minimum clearance between lowest conductor of line and ground wire / top conductor of the other line shall be as per Table 2.
Table 2 – Minimum clearance in mmbetween lines when crossing each other.
Sr. No.
Line voltage (kV)
66
132
220
400
500 HVDC
765
1
66
2440
3050
4580
5490
6790
7940
2
132
3050
3050
4580
5490
6790
7940
3
220
4580
4580
4580
5490
6790
7940
4
400
5490
5490
5490
5490
6790
7940
5
500 HVDC
6790
6790
6790
6790
6790
7940
6
765
7940
7940
7940
7940
7940
7940
Jumpers in the tension tower are properly bolted with the tension clamp and form a parabolic shape in order to achieve adequate clearance from the structure.
Ground clearance:
Normally, at the time of construction, adequate clearance is provided between lowest conductor and ground, but due to delay in charging / commissioning there are chances of dumping / heaping soil, earth and concrete etc. or stacking bricks etc., that may cause reduction in ground clearance. In such cases the stored materials shall be removed.
Temporary or permanent structures which do not fulfill the requirement of rule no. 80 of IE rules should be removed prior to charging of transmission line.
The various clearances are given in Table 3 are mandatory. However all the clearance indicated as per approved drawings by Engineering / Design department of the utility, are to be referred.
Ground clearance of lowest conductors at critical points shall be checked at prevalent temperature in the field by any of the prevalent method and the values of ground clearance at these critical points shall be recorded in the prescribed format.
In case of hilly terrain and for building clearance, the side clearance from conductors and jumpers at critical points shall also be checked and recorded for all phases of conductor/ earth wire towards hill/ building side.
Table 3 – Permissible minimum ground clearance for difference voltage level.
Line voltage (kV)
66
110
132
220
400
500 HVDC
765
Minimum ground clearance (mm)
5500
6100
6100
7000
8840
12500
15500
Clearance for telephone line crossings
The minimum clearances between the conductors of the power line and tale-communication lines are specified in Table 4
Table 4 – Minimum clearance between conductor of power line and telecommunication line.
Line voltage (kV)
66
110
132
220
400
500 HVDC
765
Clearance (mm)
2440
2750
2750
3050
4480
6860
7900
As per regulations for power lie crossings of railway tracks- 1987 and its subsequent amendment dated 26th August, 1988, the minimum clearance between railway track and the bottom most conductor or power line crossing the railway track shall be as per Table 5
Table 5 – Clearance between conductor and ground wire at mid span
Line voltage / clearance (kV)
66
132
220
400
500 HVDC
765
Clearance Above track (mm)
14100
14600
15400
17900
19300
23400
Over Crane (mm)
2000
2500
3500
6000
7250
11500
Clearance between conductor and ground wire at mid span
The vertical clearance between conductors and earth wire shall be checked randomly say in anyone span of all sections and 10% sections of hilly areas from single line diagram of the towers. These clearance are specified in Table 6
Table 6 Clearance between conductor and ground wire “at mid span” as per clause no. 4.10.2 of CBIP Transmission Line Manual.
Line voltage (kV)
66
132
220
400
500 HVDC
765
Minimum mid span Clearance (mm)
3000
6100
8500
9000
8500
12400
Minimum clearance above rivers/ lacks
In case of accessible frozen rivers/ lacks, the minimum clearance above frozen rivers/ lacks should be equal to he minimum ground clearance given in Table 3. The minimum clearance of power conductor over the highest flood level in case of rivers shall be as given in Table 7
Table 7 – Minimum clearance between lowest conductor and highest flood level of river
Line voltage / clearance (kV)
66
132
220
400
765
500 HVDC
Minimum Clearance above river or lack or water stretches Non navigable river (from HFL) in mm
3650
4300
5100
6400
13200
10650
Minimum clearance above navigable river (from HFL) in mm