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1. OPGW optical cable Optical Fiber Composite Overhead Ground Wire (also called optical fiber composite overhead ground wire). The optical fiber is placed in the ground wire of the overhead high-voltage transmission line to form an optical fiber communication network on the transmission line. This structure has the dual functions of ground wire and communication, and is generally called OPGW optical cable. 2. OPPC optical cable (Opticalphase Conductor, OPPC for short) is a new type of special optical cable for power communication systems. It is an optical cable that combines optical fiber units in wires in a traditional phase line structure. It makes full use of the power system's own line resources. Especially the power distribution network system avoids conflicts with the outside world in terms of frequency resources, routing coordination, electromagnetic compatibility, etc., so that it has the dual functions of power transmission and communication. 3. ADSS is the abbreviation of AllDielectricSelf-Supporting (all dielectric self-supporting). All-dielectric, that is, the optical cable uses all-dielectric materials. Self-supporting refers to the strength of the optical cable itself that can bear its own weight and external load. This name clarifies the use environment of this optical cable and its key technologies: because it is self-supporting, its mechanical strength is important; the use of all-dielectric materials is because the optical cable is in a high-voltage and strong-electric environment and must be able to withstand strong electricity Impact: Because it is used overhead on power poles, there must be matching pendants to fix the optical cables on the poles. That is, ADSS optical cable has three key technologies: optical cable mechanical design, determination of suspension points, and selection and installation of supporting hardware. 4. OPLC optical fiber composite low voltage cable or power optical fiber. Combining optical fibers in the structural layer of power cables to enable both power transmission and optical fiber communication functions are called optical fiber composite power cables. Like the optical fiber composite overhead ground wire (OPGW), the optical fiber composite power cable integrates two functions, thus reducing the total cost of construction investment and operation and maintenance, and has obvious technical and economic significance.
1 Ground wire wound optical cable GWWOP and bundled optical cable ADL
(1) Ground Wire Wind Optical Cable GWWOP (Ground Wire Wind Optical Cable)-is an optical cable directly wound on an overhead ground wire, which is spirally wound on the ground wire along the transmission line with the ground wire as the central axis, forming An optical transmission medium attached to the support of a power line.
(2) Bundled optical cable ADL (All Dielectric Lashed Cable)-is a kind of bundled on the ground wire or phase wire by one or two weatherproof tapes, coated aramid wires or metal wires. Compared with the GWWOP optical cable, it reduces the attenuation or stress increase caused by the bending and winding of the optical cable.
These two types of optical cables are collectively referred to as Attached Optical Cables—OPAC (Optical Attached Cable), which are generally used in lines below 35kV. They were developed and used by the power sector as early as the early 1980s. They are used to build optical fiber communications in power systems. The network is both economical and fast. They are not self-supporting optical cables, but are attached to the original ground wire or phase wire, as shown in Figure 1. Therefore, the cable has the advantages of light weight, softness, and small outer diameter. Generally, it adopts an all-dielectric central tube optical cable structure, such as As shown in Figure 2, the non-metallic reinforcing layer usually uses flexible materials such as aramid fiber yarn, glass fiber yarn, and glass fiber tape.
The installation of these two types of cables requires special equipment. After installation, the optical cable directly contacts the power line, so both need to withstand the high temperature generated by the phase line or the ground line when the line is short-circuited, and both have the problem of aging of the outer sheath material. And the application is earlier than the ADSS optical cable, but there is no large-scale application in China. When designing the circuit, the strength of the power line and the tower must be verified by ice coating and wind load.
2 All-dielectric self-supporting optical cable ADSS and metal self-supporting optical cable-MASS
(1) All dielectric self-supporting optical fiber cable ADSS (All dielectric self-supporting optical fiber cable) is a special optical fiber cable that uses existing high-voltage power transmission towers and is erected on the same pole as power lines. It has low engineering cost, convenient construction, The advantages of high safety and easy maintenance.
ADSS optical cable is self-supporting overhead laying and should have a large tensile strength to ensure that it can carry the external environment during normal operation. The main bearing element of ADSS optical cable is aramid yarn. According to the structure, it can be divided into central tube type and stranded type. The stranded type structure is divided into single-sheath and double-sheath structures, as shown in Figure 3.
In the mechanical design of ADSS optical cable, in addition to having a certain tensile strength, it is also necessary to consider the safe distance to the ground when the ADSS optical cable is installed at a certain pitch and the safe distance to the ground under a full load environment to prevent the normal operation of the road from being affected. On the other hand, because there is a certain high-voltage electric field environment around the high-voltage power line, it is easy to corrode and damage the ADSS optical cable. Therefore, when laying the ADSS optical cable, not only should the appropriate suspension point be selected, but the outer sheath must also have a certain resistance to electrical corrosion. According to the standard requirements of DL/T 788-2001 "All dielectric self-supporting optical cable", the outer sheath can be divided into Class A (potential less than 12kV) and Class B (potential greater than 12kV), of which Class B sheath (usually called resistant Tracking sheath material) According to actual applications, it is generally recommended that the operating potential of the suspension point does not exceed 25kV.
(2) Metal aerial self-supporting optical fiber cable-MASS (Metal Aerial Self-Supporting optical fiber cable)-stainless steel tube optical fiber unit structure, considering that MASS optical cable and ADSS optical cable are erected on the same pole as the existing pole tower, in order to reduce the extra The load requires the MASS cable to be small in structure and light in weight. Therefore, the MASS optical cable structure adopts the central tube type, that is, a layer of galvanized steel wire or aluminum-clad steel wire is stranded outside the stainless steel optical fiber unit. Usually, from the cost consideration, the galvanized steel wire is mainly used, as shown in Figure 3.
The mechanical design of the MASS optical cable is similar to the ADSS optical cable, and the span-pull-sag check is also required. However, when installing and laying, you should choose a suitable suspension point. On the one hand, keep a certain safe distance from the power line; on the other hand, because the MASS cable is a metal structure, it can be easily solved by good grounding treatment and selection of weak electric field installation points. Electric corrosion problem. Because the MASS optical cable is an all-metal structure, it can also be used as an effective anti-rodent optical cable for aerial applications in some areas where rodent infestation is rampant.
3 Optical fiber composite overhead ground wire OPGW and optical fiber composite overhead phase wire OPPC
(1) OPGW (Optical fibre composite overhead ground wires)-it has the function of traditional ground wire lightning protection, and provides shielding protection for the transmission wire against lightning, and at the same time, it uses the optical fiber composite in the ground wire to protect transmit information. There are three main types of common OPGW structures, namely aluminum tube type, aluminum frame type and stainless steel tube type, as shown in Figure 4.
One of OPGW’s key technologies is the temperature rise caused by the short-circuit current and the OPGW’s maximum operating temperature. When the short-circuit current impacts the OPGW of the first two structures in Figure 4, the aluminum tube and aluminum skeleton will generate relatively high temperatures and move to the inside. Diffusion, which in turn affects fiber transmission and even fiber breakage, has significantly improved the shape of stainless steel tubes. If the structure contains aluminum, after the temperature exceeds 200°C, the aluminum will produce irreversible plastic deformation. While the structure is destroyed, the increased sag of the OPGW will not only be able to maintain a safe distance from the wire, it may also collide with the wire. The all-steel structure can work at 300°C for a short time.
OPGW has a higher cost performance in the application of new lines. In the design, the greater the short-circuit current of the OPGW, the more aluminum cross-sectional area is needed, and the tensile strength is correspondingly reduced; and when the tensile strength is constant In order to increase the short-circuit current capacity, the only way to increase the metal cross-sectional area is to increase the cable diameter and cable weight, which raises safety issues for the strength of the line tower. However, when OPGW is designed, its electrical properties (such as DC resistance) and mechanical properties (such as span-tension-sag characteristics) should be close to another ground wire.
(2) OPPC (Optical Fiber Composition Phase Conductor)-is a combination of optical fiber units in the phase line, with the dual functions of phase line and communication, to make up for the new power grid line without overhead ground wire but need to communicate There are mainly two types: central tube type and stranded type, as shown in Figure 5.
Although the structure of OPPC is similar to OPGW, there are big differences in design. First of all, OPPC has the function of phase line, long-term carrying power transmission, because of the long-term operating temperature's influence on fiber transmission performance and fiber life; second, the mechanical and electrical properties of OPPC should be consistent with adjacent wires, such as DC resistance or The impedance is similar to that of adjacent wires to ensure that the remote voltage changes maintain three-phase balance; again, OPPC is installed in a high-voltage system, and its installed fittings and accessories (such as strain clamps, suspension clamps and terminal joint boxes) need to be insulated , The wire clamp can be used with the corresponding insulated tensile string or insulated suspension string. Photoelectric insulation/separation and connection require special technology, and the requirements for construction are relatively high.
4 Optical hybrid cable GD for access network
Optical and electrical hybrid cables for access network GD (Optical and electrical hybrid cables for access network)-commonly known as integrated optical cables, which integrate optical fibers, metal wire pairs and feeders, and can transmit optical signals, electrical signals and electrical energy at the same time. The structure is shown in Figure 6.
With the rapid development of access network technology and the market, optical fiber communications have entered a new round of rapid growth. Mobile communications, digital television (intermediate conversion), broadband access, FTTx, rural village-to-village projects, etc. will integrate communications optical cables and equipment Continuously extending to users, remote base stations, communication rooms, user access points and other equipment began to be widely used, but the power supply of the equipment has become a very difficult problem for communication operators. In order to solve this problem, the China Communications Standards Association issued YD/ T 2159－2010 "Photoelectric Hybrid Cable for Access Networks" provides a theoretical basis for the design and application of this product.
Although we can supply power and transmit information to remote devices through GD optical cables, there is line loss in the feeder, which increases with the lengthening of the transmission distance, and there is also a voltage drop problem. Therefore, high-voltage DC remote power supply is undoubtedly the best solution for long-distance communication. The principle of the high-voltage DC remote power supply system is to isolate and boost the 48 V DC power of the switching power supply in the computer room to about 200-400 V DC high voltage through the remote power supply local equipment, and transmit the DC high voltage power to the remote through the feeder in the GD optical cable. At the end device, the power supply is suspended to the ground during transmission, and the remote device performs voltage inversion and transforms it to the voltage required by the remote device (such as DC48 V or AC220V), and finally realizes the normal communication of the remote device, as shown in Figure 7. .
In the process of structural design of GD optical cable, it is mainly the selection of the cross-sectional area of the feeder. The cross-sectional area of the feeder is related to the transmission distance, the power of the electrical equipment, the transmission voltage level, and the receiving voltage range of the remote power supply