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Walkover Survey

An EHV Transmission line generally links a Generating station and a sub-

station or two sub-stations or two Generating stations as may be necessary.

The basic requirement of a transmission line is to carry the desired bulk power 

at maximum efficiency and to achieve this, the line should be of shortest

length feasible, and since the line losses are proportional to the length of the

line. Therefore the aim of the preliminary survey is to explore in the field the

most economical and feasible route of constructing a particular transmission

line. Hence, while selecting the route one should be fully aware of the

requirements of transmission lines, statutory provisions, information required

to be collected, prevailing cost of various elements of transmission lines etc.

Bee-line

Bee-line is the shortest distance between the two points of origin of the

transmission line proposed. It is straight line drawn connecting the two points.

Routing the transmission line along this line may not always be possible due

to site conditions. However, survey should be carried out as closed to the bee-

line as possible keeping in mind of the other required statutory conditions.

Plotting of route on topo map

The latest available topographical maps covering the area between the two

end points of the transmission line drawn to the scale of 1:50000 (1 cm =

0.5km) should be procured from Survey of India. A master mosaic has to beprepared by fixing all the topographical maps in their respective position and

obtaining a belt width of minimum 10 km (20 cms) on either side of centre line

between the two terminal points. In the master mosaic, the Bee-line which is

the straight line joining the two terminal points should be neatly marked with

pencil. The Bee-line joining the two end points will have the shortest length. It

may not be feasible to construct the power line along the Bee-line due to

various technical as well as site conditions.

Walk over Survey

The Objective of the study is to examine all the possible altern ate routes and

suggest the best, most economical & constrained free route for the

Transmission Line. The following criteria have been considered while doing

the Walkover Survey:

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i. The alignment of the Transmission Line should be most

economical from construction and maintenance point of view.

ii. The number of angle points to be kept to a minimum.

iii. The distance between the terminal points specified to be kept

shortest possible and consistent with the terrain that it

encounters.

iv. Marshy and low lying areas, river beds and earth slip zones to beavoided to minimize the risk to the foundations.

v. It would be preferable to utilize level ground for the alignment.

vi. Crossing of power lines should be kept to minimum. Alignment

should be kept at a minimum distance of 300 meters from power 

lines to avoid induction problems on the lower voltage lines.

vii. Crossings of communication lines should be minimum and should

be preferably at right angles. Proximity and parallelism with

telecommunication lines should be eliminated to avoid dan ger of 

induction between them.

viii. Areas subject to flooding such as nalah should be avoided.

ix. Restricted areas such as civil and military airfields should be

avoided including aircraft landing approaches.

x. All alignments should be easily approachable in dry and rainy

seasons to enable maintenance throughout the year.

xi. Areas that will present the problems of ³Right of Way´ and ³Way

Leave´ during construction and maintenance should be avoided.

xii. Routing of transmission lines through protected/reserved forest

area should be avoided/restricted as far as possible.

xiii. Effort should be made to keep the route at a distance from miningarea.