The Steel Lattice Tower

The Steel Lattice Tower is used for power transmission. A transmission tower, also known as an electric power pylon, tower of power, power pylon, electricity pylon, overhead power cable pylon, traction current pylon, grid power line tower, hydro tower and so on. The pylon is a tall structure, usually a steel lattice tower, used to support an overhead power line. In electrical grids, they are generally used to carry high-voltage transmission lines that transport bulk electric power from generating stations to electrical substations; utility poles are used to support lower-voltage subtransmission and distribution lines that transport power from substations to electric customers. They come in a wide variety of shapes and sizes.

A lattice tower is a framework construction made of steel or aluminium sections. Lattice towers are used for power lines of all voltages, and are the most common type for high-voltage transmission lines. Lattice towers are usually made of galvanized steel. Aluminium is used for reduced weight, such as in mountainous areas where structures are placed by helicopter. Aluminium is also used in environments that would be corrosive to steel. The extra material cost of aluminium towers will be offset by lower installation cost. Design of aluminium lattice towers is similar to that for steel, but must take into account aluminium's lower Young's modulus, deformation is easy to occur under uncontrollable natural conditions, so hot-dip galvanized steel structure is the first choice if the budget allows.The steel lattice towers also can be used as communication towers, usually is square or triangular tower, also used for radio mast towers and TV & aerial masts. And the giant gantries.

Transmission tower is a tall structure, which is very sensitive to inclined deformation and requires high uneven settlement of foundation. The common structural forms of transmission tower foundation include independent foundation, expanded foundation and pile foundation, and the transmission tower structure mainly applicates steel structure. It is difficult for conventional transmission tower and foundation structure to adapt to the surface movement and deformation of goaf in coal mine, which may cause the transmission tower to skew and even overturn. Our technical team studied the design of tower foundation in coal mining affected area of UHV transmission line, and found the most appropriate requirements of material and technical parameters by analyzing bending moments of large slab foundation with different plate thicknesses.

The type of electric power pylon

It is classified by construction material, structure type and using function

1. According to the structural materials can be divided into wood structure, steel structure, aluminum alloy structure and reinforced concrete structure tower several. Due to low strength, short life, inconvenient maintenance and limited timber resources, timber structure tower has been eliminated in China.

Steel structure is divided into truss and steel pipe, lattice truss pole tower is the most used, is the main structure of ultra-high pressure lines. For the trussed tower applications,different applications have different designs and standards. This difference lies in weight load capacity and environmental factors.

Aluminum alloy tower structure take high cost, usually only used for transport particularly difficult mountainous areas.

Prestressed reinforced concrete poles are cast by centrifuge and steam curing. Its production cycle is short, service life is long, maintenance is simple, and can save a lot of steel. The disadvantage is that, simple force, the transverse shear capacity is weak, the mass is large, the transportation cost is high. It is limited range of use.

2. According to the structure form can be divided into two categories: self supporting tower and cable tower. A freestanding pylon is a tower that is stabilized by its own foundation. A cable tower is a symmetrical cable installed on the tower head or body to firmly support the tower, and the tower itself only bears vertical pressure.

3. According to the function can be divided into load-bearing tower, linear tower / suspension tower, distribution tower / shunting tower, tension tower, angle tower, terminal tower / dead-end tower, transposition tower and large span tower / special tower. According to the number of circuits of the transmission line set up by the same tower, it can also be divided into single, double and multi-loop tower. Load-bearing tower is the most important structural link in the transmission line.

4. Classification according to the structure, shape and appearance characteristics of the tower, “F” type pylon, wishbone type pylon, cat head type pylon, wine cup type pylon, harpoon type pylon, “V” type pylon.

5. Classification according to corrosion protection conditions

1) Galvanized anti-corrosion steel tower (hot dip galvanized).

2) Oil brush anti-corrosion tower: because of the high maintenance cost of the tower, it has been basically stopped.

6 By current flow direction of transmission lines

1) three-phase AC line tower: use AC power transmission.

2) Two-phase DC line tower: use DC power transmission.

7 Power transmission line voltage level

1) AC transmission voltage levels: 35KV, 66KV, 110KV, 220KV, 330KV, 500KV, 750KV, 1000KV

2) DC power transmission voltage level: ±800KV (DC)

8 Type the cables according to the number of circuits

1) Single loop tower: AC is three-phase wire, DC is two-phase wire.

2) Double circuit tower: AC 2×3 = 6 phase wire, DC 2×2 = 4 phase wire.

3) Multi-loop tower: AC n×3 = 3n phase wire, DC n×2 = 2n phase wire.

9 Type by ground circuitry frame

1) No ground circuitry frame tower: the tower head has neither ground circuitry frame nor lightning wire.

2) Single ground wire frame tower: the tower head is only placed with a single ground wire frame and a lightning conductor, this kind of tower can only be used for small and medium-sized power transmission lines with 66KV and below voltage.

3) Double ground wire frame steel tower: the top of the tower is provided with two ground wire brackets and two lightning wires. This kind of steel tower is generally suitable for 110KV and above voltage level of power transmission lines.

4) Low ground wire frame tower: the height of ground wire frame depends on the protection Angle of ground wire to wire, as long as the protection Angle can meet the requirements of the regulations, ground wire frame as far as possible not too high.

5) High ground wire frame tower: because of the lightning in some areas, the geological conductivity is poor, it is necessary to improve the grounding device outside the appropriate height of the ground wire frame, in order to meet the requirements of lightning protection.

10 Iron towers are classified according to the number of single-phase wires split

1) Single line system of iron tower: each phase of the wire only one.

2) Double split wire tower: each phase of wire is composed of two parallel.

3) Three split wire tower: each phase of the wire is composed of three permutations.

4) Four split wire tower: each phase of the wire is composed of four permutations.

5) n split wire tower: each phase of wire is composed of n permutations.