The significant technological advancements in the airborne remote systems with possible application in transmission lines allow a new vision for the gathering of data for the design of TL’s and other engineering services.
Most of the necessary data for a design or project can be obtained with LASER scanning systems, considering that the swiftness in the acquisition allows the work of dozens of kilometers in a single day, with a precision in the geodetic referencing of around 10 to 20 cm due to the usage of the airborne GPS.
The main applications of the LASER technology for Transmission Lines are the following:
Identification of Cables
The main characteristic of a LASER scanning system when applied in TL’s surveys is the identification of the electric energy transmission cables, which does not easily occur with the conventional methods as Photogrammetry or Topography.
The LASER technology allows the spatial determination of reduced diameter cables and with relative altimetric definition, compatible with engineering calculations purposed to the determination of the catenary and consequently, efforts about the towers structure.
The data proceeding from the survey are depurated in order to remove non-relevant points for the reconstruction of the line model. The alignment of the remaining points allows the definition of the position of the cable making use of specific software.
Invasion in Right-of-Way
Because of the condition of multiple return that the LASER system provides, the use in right-of-ways or TL’s passageways, allows the identification of approaching points or contact of elements harmful to the structure of the TL.
Making use of longitudinal or transversal profiles it is possible to quickly evaluate the strip regions where the maintenance has priority.
In a likely way, the inspection of invasion in the passageway or in the Right-of-Way by unauthorized buildings is another application relevant to the process.
DTM
The Digital Terrain Model (DTM) originated from the LASER scanning allows the preliminary study of routes for future implantation of linear infrastructure projects (telecommunication using microwaves, optic fiber cabling, transmission lines, etc.). Creation of Digital Terrain Models (DTM) in 3D for GIS.
Other products, such as Elevation Models, include the determination of the following faces or characteristics:
Characteristics
ESTEIO S.A. was hired to carry out the LASER scanning over the TL 345 kV – denominated Interlagos – São Roque with around 60 m in length.
In this TL, the diameter of the aluminum cable is of 26mm and these cables are 25 m above the ground in average.
The flight altitude for the LASER scanning was 700 m with a respective LASER sweeping width of 200 m. This survey was planned in order to allow a spacing of 0,85 m between the LASER beams shot to the ground.
With a divergence of the LASER beam of about 1,4 mrad, the diameter of the LASER point in the ground was 0,98 m. With the spacing and the divergence above, there was an overlapping of around 10 cm between the LASER beams shot to the ground. In this way, it is possible to guarantee the lack of blanks in the LASER coverage at least on the transversal direction.
With the information of the processed data (E,N,h coordinates) of the points obtained and making use of the ERMAPPER software and of its tool GRIDING WIZARD, hypsometric images were formed; images in which the elevation difference is presented as a tonality difference.
These images are characterized by the representation of the topography and of the vegetal coverage in a graphic way, which facilitates the visual interpretation.
The TerraScan software was used for the visualization of cables and for the catenary determination. The catenary models between the towers are created from the manipulation of LASER data and any interference can be identified and the potential risk for the TL can be determined.
Another product derived from this survey is the Digital Mosaic developed based on the digital video, making a georeferenced photographic composition in low resolution of the strip surveyed.
Products
The results of the LASER scanning allowed the making of the following cartographic products: