6-I.1. Selection of Route

download 6-I.1. Selection of Route

of 2

Transcript of 6-I.1. Selection of Route

  • 8/9/2019 6-I.1. Selection of Route

    1/2

    CHAPTER 1

    SELECTION OF ROUTE

    1.0 CRITERIA FOR ROUTE SELECTION:

    1.1 The route of a transmission line is decided from the following main considerations.

    a) Shortest length, hence least capital cost.

    b) Ease during construction and ease in maintenance of the line (route near roads for

    easy approach & accessibility).

    c) Requirement of future loads (sub stations) near the proposed route so that the line can

    be easily connected.

    d) Required separation distance from parallel communication lines (P&T, Railways,

    etc.) for meeting the conditions of induced voltage for obtaining PTCC approval.

    e) Avoiding of forest areas as well as wild life sanctuaries.

    f) Cost of securing and clearing right of way (ROW).

    g) Maintaining statutory distances from Airports / Helipads.

    1.2 The following areas are to be avoided as far as possible while selecting the route of the line.

    a) Tough inaccessible areas where approach is difficult.

    b) Towns and villages, leaving sufficient margin for their growth.

    c) Areas subject to floods, gushing nalas during rainy seasons, tanks, ponds, lakes, etc.

    and natural hazards.

    d) Wooded areas with high trees or fruit bearing trees involving payment of heavy

    compensations for cutting of the trees.

    e) Swamps and shallow lands subject to flood, marshy areas, low lying lands, river beds,

    and earth slip zones, etc. involving risk to stability to foundations.

    f) High hillocks / hilly areas / sand dunes and areas involving abrupt changes in levels

    and requiring too many long spans.g) Series of irrigation wells.

    h) Rifle shooting areas and other protected areas such as army / defence installations and

    ammunition depots.

    i) Areas which involve risk to human life, damage to public & private properties,

    religious places, cremation grounds, quarry sites and underground mines, gardens,

    orchards and plantations.

    j) Areas which will create problems of right of way and way leaves.

    k) Buildings / Storage areas for explosives or inflammable materials, bulk oil storage

    tanks, oil or gas pipelines, etc.

    1.3 The route of the transmission line shall, as far as possible, be the shortest length between the

    pre determined sub stations.

    1.4 The route of the transmission line is to be so located that, as far as possible, it is protected

    from high winds and falling trees & branches. In hilly tracks, the line is to be routed, as far as

    possible, along the side of the hills or through valleys rather than over high points. However,

    a route of the line very close to steep slopes of hills be avoided as far as possible as there may

    be difficulty in obtaining lateral (side) clearance to ground for conductors. Also, there may be

    overhanging / loose boulders which may roll down and damage the line.

    1.5 It is desirable to take the line as near the paths and roads as practicable without unduly

    increasing the length of the line so as to facilitate transportation of material during

    construction and the patrolling / maintenance of the line. Where the line cannot be routed near

    paths / roads economically, care shall be taken to see that easy access is possible at every 5 to8 km. It shall be ensured that all angle / tension points, particularly in the case of 400 kV

  • 8/9/2019 6-I.1. Selection of Route

    2/2

    6 Construction Manual for Transmission Lines

    lines, are approachable to facilitate easy transportation of stringing equipment during

    construction and for maintenance / breakdowns.

    1.6 In hilly / mountainous type of terrain or in thickly populated areas, it is generally not

    advisable to attempt a direct route or try to locate towers in long spans. Small angles of a few

    degrees cost a little more and add little to the length of the line. Suspension towers (A type)

    can be provided for line angles of upto 2 degrees and small angle towers (B type) can be

    provided for angles upto 15 degrees.

    1.7 In general, large angles in the line are to be avoided wherever possible. The magnitude of the

    angle be small as far as possible and should never be more than 60 degrees.

    1.8 The line shall be aligned suitably so that it can be diverted / looped in looped out (LILO) to

    cater for possible future loads / sub stations along the route.

    2.0 APPROVAL OF THE POWER & TELECOMMUNICATION CO ORDINATION

    COMMITTEE (PTCC):

    2.1 The line route shall be so selected that the voltage induced in parallel running telegraph /telephone / communication / signaling lines / circuits of the P&T Department/ Railways does

    not exceed the prescribed permissible values under fault conditions. The PTCC approval

    should be obtained before energizing the line.

    3.0 APPROVAL OF THE AVIATION AUTHORITIES:

    3.1 The line route shall be at a sufficient distance from the aerodromes / airports so that clearance

    from the aerodrome / airport authorities is not required or, otherwise, can be obtained easily.

    4.0 CROSSING OF RAILWAY TRACKS:

    4.1 The crossing of Railway tracks shall normally be outside the railway station limits.

    5.0 CROSSING OF RIVERS / NALAS / ROADS:5.1 Crossing of rivers / nalas is preferably done at points where the bed is of the smallest width

    and the banks on both sides of the rivers / nalas are high. The crossing is done at points of the

    river path where it is unlikely to cut the banks when it is flowing.

    5.2 The route is selected such that multiple crossings of the same road are avoided.

    5.3 Crossing of roads at very small angles is to be avoided.

    6.0 CROSSING OF POWER LINES:

    6.1 When crossing existing higher voltage power lines, the new line shall normally be below such

    existing lines except in extremely limiting circumstances.

    6.2 When crossing existing lower voltage power lines, the new line shall normally be above such

    existing lines except in circumstances where it is not possible.

    6.3 When crossing existing power lines of the same voltage, the new line may be above or below

    such existing lines as per site conditions.

    7.0 APPROVAL OF FOREST DEPARTMENT:7.1 Forest area is to be avoided as far as possible.

    7.2 If forest area cannot be avoided, or if the line route is uneconomical in case forest area is

    avoided, then the approval of the Forest Department is required.