On the "V403/803" construction site in section 1, the existing single 400 kV line was removed and replaced by a double 400 kV line between the Prosenice Distribution Centre (hereinafter referred to as TR) and the Nošovice TR.
The doubled 400 kV line runs through the territory of the Olomouc, Zlín, and Moravia-Silesia regions and runs almost its entire length through undeveloped areas. Fellow surveyors: Ing. Pavel Hladík, Martin Moucha, Bc. Vojtěch Henzl, Jan Prošek, and Ing. Martin Daněk worked on this section, which has 82 masts with a total length of 28 km. And what does removing the single line and replacing it with a double line mean in practice? The conductors and insulators are taken down, all the poles are dismantled, including the removal of the footings to a depth of at least 1 meter. In their places, or elsewhere in the line axis according to the needs of the designer, foundations are built for the installation of new steel structures of the Dunaj and Soudek type. These should already be capable of carrying a double 400 kV line. Build Synergy s.r.o. and EGEM s.r.o. participated in the construction.
What were the next steps for the colleagues?
Based on a detailed geological survey, it was decided that some of the masts would be based on simple foundations and some on micropiles. For our surveying work on site, this meant several different types of work:
It should be added that before the execution of all the construction work, topsoil was removed and deposited in the immediate vicinity of the footing, which will be spread again around the new footing after completion.
After the footing was completed and the required concrete strength was achieved, we proceeded with the work of setting the steel mast structure. This is made up of simple steel angles, the mounting joints are bolted. The mast has the shape of a regular quadrilateral in cross-section with linear variability.
The structure was built in two ways. Either the construction company built the lower part of the steel structure of the mast directly or a "jig" was used and only the lowest part, about 2 meters above the footings, was built. In the latter method, the jig was removed after the structure had settled, the struts were added and then the mast construction continued above. This second method was chosen because of the need to carry out the work of setting the structures in several places at once and the need for technological breaks to keep to and meet the construction schedule and the progress of the follow-up work.
In both cases, we had to settle the structure with the help of two total stations placed in suitable positions "in a cross" with the help of the workers of the implementing company, who "moved" the structure according to our instructions. The structure was settled with millimetre precision. The settlement in the axis of the conductors, the settlement in the axis of the conductor layout and the dimensions and shapes of the lower structure (i.e. the diagonals between the stands) were solved. The whole structure, after settling into the correct position, was then levelled in height to ensure that the mast frame was horizontal and the verticality of the mast structure was ensured. This was sometimes a problem because the footings of the structure were not concreted to exactly the same height - as per the design (probably caused by the concrete vibrating in the foundations). Sometimes the height difference of the footings was as much as five centimetres. This value has a significant effect on the vertical deflection of the mast. The height adjustment was made with steel spacers placed at the junction of the concrete footing and the mast structure.
The total stations we used to settle the masts were TS Trimble S5 and S3 and a reflective minihranol. We used a Trimble R12i GNSS apparatus to determine the S-JTSK coordinate system. The smaller masts were settled within a few units of hours, the larger ones took over 4 hours. The executing company deployed a group of 6 to 12 installers to move the structure.
After the overall height and position settlement of the structure, all the values were still checked and the surveyor handed over the erected transmission line mast. All data was then recalculated checked in the office and uploaded to the underlying 3D drawing. From the surveyor's point of view, there will still be follow-up work to measure the deflections of the wires and to implement the documentation of the actual construction so that the deadline for the approval of the works at the end of 2024 is duly met.
Author: Ing. Pavel Hladík
