Bundled conductor
EHV transmission line
These lines are spaced at a certain distance and arranged in a symmetrical polygon. The number of split conductors in EHV transmission lines is generally 3-4.
Split conductors are generally composed of 2-4 conductors with smaller cross-sections in each phase, and the spacing between sub-conductors is 0.3-0.5m, which can increase the diameter of conductors. Compared with the large conductor with the same total cross section, it is not easy to produce corona and has higher transmission capacity. Split conductor is mainly used for lines with voltage of 330 kV and above. China's 330 kV line adopts double split conductor, and the 500 kV line to be erected soon will adopt split conductor.
China began to develop it in the early 1990s, and it was successfully developed in 1992, and obtained the national patent. Now it has been mass-produced and applied in some areas. Low-voltage insulated split conductor (hereinafter referred to as split conductor) is different from conventional conductor. It is a split conductor made of three or four single-core conductors through a certain process, or called conductor bundle. This kind of split conductor is not only different from the conventional conductor in form, but also can change the magnetic field distribution around the conductor, thus equivalently increasing the radius of the conductor and reducing the reactance of the conductor. At the same time, the electric field distribution around the conductor is changed, and the susceptance of the conductor is also increased accordingly. Compared with conventional wires, split wires have obvious advantages. The application of split conductor in low-voltage distribution network can reduce the voltage drop and effectively improve the natural power factor of the line, thus improving the power quality of medium and low-voltage power grid.
What is the horizontal span of this tower? What is the vertical span of the tower?
Answer: The average span on both sides of the tower body is called the horizontal span of the foundation tower.
The horizontal distance between the lowest sag points of the wires in the span on both sides of the tower is called the vertical span of the base tower.
OPGW cable, optical fiber composite overhead ground wire (also called optical fiber composite overhead ground wire).
Optical fiber is placed in the ground wire of overhead high voltage transmission line, and an optical fiber communication network is formed on the transmission line. This structure has the dual functions of ground wire and communication, and is generally called OPGW optical cable.
Because optical fiber has the characteristics of anti-electromagnetic interference and light weight, it can be installed on the top of transmission line tower, without considering the optimal suspension position and electromagnetic corrosion. Therefore, OPGW has the remarkable characteristics of high reliability, superior mechanical properties and low cost. This technology is especially applicable and economical when laying or replacing existing ground wires.
Optical fiber uses the difference of refractive index between core and cladding materials to transmit light energy in optical fiber, which has become a major revolution in the history of communication. Power system uses optical cable to transmit dispatching telephone, telecontrol signal, relay protection, TV image and other information, which is light in weight and small in size. In order to improve the stability and reliability of optical cable, the optical cable structure combining phase conductor of transmission line, overhead ground wire and power cable has been developed abroad. OPGW cable is wrapped with metal wire, which makes it more reliable, stable and firm. Compared with other optical cables, OPGW can not only shorten the construction period, but also save the construction cost. In addition, if OPGW twisted with aluminum-clad steel wire or aluminum alloy wire is adopted, it is equivalent to erecting a good conductor overhead ground wire, which can receive many benefits such as reducing the potential power supply current of transmission lines, reducing power frequency overvoltage, and improving the interference and dangerous influence of power lines on communication lines.
Ordinary OPGW structure
There are three main categories: aluminum tube type, aluminum skeleton type and (stainless steel) steel tube type.
Application of OPGW optical cable
OPGW optical cable is mainly used for 500KV, 220KV, 1 10KV voltage grade lines, but it is mostly used for new lines due to power failure, safety and other factors.
The applicable characteristics of OPGW are:
(1) lines with high voltage exceeding 1 10kv have a large span (generally above 250M);
(2) easy to maintain, easy to solve the problem of crossing lines, and its mechanical characteristics can meet the needs of crossing lines;
(3) (3) The outer layer of OPGW is armored with metal, which has no influence on the corrosion and degradation of high-voltage galvanic couples;
(4) OPGW must be cut off during construction, which will cause great losses, so OPGW should be adopted for new high-voltage lines above 1 100 kV;
(5) In the performance index of 5)OPGW, the greater the short-circuit current, the more it needs to be armored with good conductors, which correspondingly reduces the tensile strength. However, the only way to improve the short-circuit current capacity is to increase the cross-sectional area of metal, which leads to the increase of cable diameter and cable weight, thus bringing security problems to the strength of line towers.
Painting-STW