1. E4014 Construction Surveying
Transmission Line Surveys

2. Objectives
provide an understanding of the principles involved and methods used for surveying transmission lines
describe factors that affect the location of transmission lines
describe the basic principles of the survey and design of transmission lines

3. Objectives (cont)
understand the survey & design required for a rural extension line
display a knowledge of the surveys required for high voltage lines

4. Introduction Three main types of transmission lines
(a) rural extension of the distribution network
( low & high voltage )
(b) extra high voltage lines carried on towers
similar design principles apply to types (a) and (b)
factors are more critical and methods more accurate for type (b)

5. Introduction Third type of transmission line
( c ) urban distribution network

6. Power Supply System
Generation
Transmission
Distribution

7. Power Supply System Generation
electrical energy is generated at the power stations using 3-phase a.c. generators
voltage and frequency are controled producing a moderate voltage of, say, 13.8 kV

8. Power Supply System Transmission
high voltage transmission lines are used to transfer electrical energy from the power stations to the load centres
usually 3-phase overhead conductors suspended from insulators attached to towers, and called PRIMARY TRANSMISSION lines
275kV used in Qld, 330kV in NSW and 500kV in Vic

9. Power Supply System Transmission (cont)
power transformers are used at generating stations to step up or step down the voltages
choice of transmission voltage depends on the power to be transmitted and the distance involved

10. Single Wire Earth Return System ( SWER )
Low cost, low maintenance method of supplying power to isolated (country) areas
An isolating transformer separates the main high voltage system ( 11kV or 33kV ) from the SWER line ( 12.7kV to 19.1kV )
separates the different earthing systems
a single conductor overhead line feeds a distribution transformer, which steps-down the voltage to 2 circuits of 250V, or 1 circuit of 500V

11. Single Wire Earth Return System ( SWER )
The SWER system uses a unique method of passing the return current through the earth
the resistivity of the earth must be within a certain range for the system to work effectively

12. Basic Principles of Transmission Line Design
Ideal route between the point of power production and the point of consumption is a straight line
Design Parameters and regional constraints affect the location of power lines

13. Design Parameters Height of Poles or Towers Span Length Foundations
Angles

14. Design Parameters Height of Poles or Towers
minimum height of transmission lines above the ground, for road crossings etc is laid down by an Act of Parliament
most economic design attains this ground clearance and no more
more height increases span length, but
increases cost of pole or tower
increases depth of pole, or
increases foundation costs of tower

15. Design Parameters Span Length
aim is to have as few poles or towers per kilometre
poles should be placed to maximise span length, whilst maintaining the minimum clearance

16. Design Parameters Foundations
location of poles or towers may affect the type of foundations required
cost of towers in 1978
normal foundations - 4 legs, 5m deep, 0.5m deep $2500
special foundation - unstable soil $5000
rock anchor - rocky ground $5000
piled - mangroves, coastal flats $10000

17. Design Parameters Angles
the pole or tower must be able to withstand the tension of an indirect pull
poles will need to guyed on the half angle
angle towers can be up to $20000 more expensive than an ordinary support tower
essential to keep bends to a minimum

18. Design Parameters Summary of Design Parameters
Height of Poles or Towers
Span Length
Foundations
Angles

19. Constraints Built up areas topography recreational areas
mountains, forests, rivers, swamps, flood zones
recreational areas
national parks, development areas

20. Constraints (cont) mining areas cultivation areas future uses
highways, railways, airstrips
environment
aesthetics, erosion

21. Rural Extension Surveys
Extend the power transmission network to small settlements and farm dwellings
may carry high or low voltage
low voltage < 650 volts
high voltage > 650 volts
normal extension is 11kV or 22kV high tension line

22. Rural Extension Surveys
Proposed extension is designed by an electrical engineer and plotted on existing topographical and cadastral maps
shows location of all properties to be served
shows proposed location of transformers etc
actual route location and design functions are carried out in the field by the SURVEYOR

23. Rural Extension Surveys
Aim for
minimum number of poles per kilometre
minimum number of bends
minimum ground clearance (6m at 49°C)
minimum clearance over
road cuttings
railways
telephone wires

24. Rural Extension Surveys
minimum cut angle between telephone and power lines is 45° and parallel lines must be a minimum of 30m apart to avoid interference and power loss
before undergrounding of power and telephone lines power lines were often placed m away from the phone line which was often in the road reserve
advantages - easy connections to sheds and houses set back from road
disadvantages - cultivation, access

25. Rural Extension Surveys Survey & Design
Basic survey problem is to obtain a profile of the land over which the transmission line is to traverse and to negotiate obstacles unforeseen in the proposed design - trees, hedges, buildings etc.
clinometer and chain
total station
GPS

26. Rural Extension Surveys Survey & Design
traverse along proposed centreline from the last pole position
note chainage and RL of grade changes and features
continue past the next pole position
plot profile
horizontal and vertical scales are different
governed by sag templates provided by Electricity Authority

27. Rural Extension Surveys Survey & Design

28. Rural Extension Surveys Survey & Design
by using the sag template the position of the next pole is determined
place a peg at the pole position
only after the chainage and RL of the point have been compared to the plot
surveyor should do a reconnaissance survey of the route before hand so that the topography is known to some extent

29. Rural Extension Surveys Survey & Design
angles are read
where a bend occurs
where a spur or branch line occurs
place a peg at the bend and at the half angle
poles will have to be guyed

30. Rural Extension Surveys Survey & Design
if line is traversing private property and easements are required, then occupation is also located
running chainage to fence, angle along fence and distance along fence to cadastral corner

31. Rural Extension Surveys Survey & Design
surveyor has measured
the profile of the line
the running chainages and RLs
the angles at bends
an accurate plot of the final design is made for construction, easement and record purposes

32. High Voltage Lines on Towers
Basic design factors are the same
the following are critical
cost factor
foundations
length of route
aesthetics and environment

33. High Voltage Lines on Towers Initial Design
most suitable route is chosen based on
voltage, conductor, tower specification
topographical maps
cadastral maps
town planning schemes
aerial photos
local Authorities advice
other Government Department’s advice
ground reconnaissance

34. High Voltage Lines on Towers Initial Design
report on the route is prepared
costing
scheduling
approval
environmental impact assessment
comments of interested Public Authorities

35. High Voltage Lines on Towers Initial Design
route maps are prepared
1:10 000
latest cadastral information
number of lines proposed
easement widths
current land use

36. High Voltage Lines on Towers Initial Design
contact is made with the owners and occupiers
negotiate easements and access tracks
property owners ( and other interested parties ) may object
property owners may state their intended future use of the land
if objections justify an amendment then the centre line may be re-routed

37. High Voltage Lines on Towers Survey of the Route
high accuracy required
control survey for whole of the route
centre lines are cleared, surveyed and marked
further public reaction may be forthcoming and the route may be deviated again
keep lines to a minimum height for aesthetic reasons

38. High Voltage Lines on Towers Survey of the Route
surveyor locates towers and access tracks
appreciate land usage and erosion
report all relevant circumstances particularly those affecting overall location
field data must show enough data for the towers to be located and their positions to be checked in the office

39. Urban Distribution Network
Transmission lines are entirely located in the road or street reserve
span length is not as important
poles are place to service as many consumers as possible
design and survey is usually carried out by electrical engineers and their staff
underground transmission conduits
at least 5 times more expensive