ADSS optical cable overview
In the power system, there are two main types of optical fiber cables commonly used on high-voltage overhead transmission lines. One is optical fiber composite phase (earth) cable, and the other is all-dielectric supported optical cable, which is called ADSS optical cable. ADSS is suitable to be installed on the established line, although the number of OPGW optical cable lines has increased dramatically in recent years with the increase of infrastructure projects, there are still a large number of old lines that need to be erected with ADSS optical cables to ensure the optical fiber communication of the power system. In addition, note that the ADSS optical cable is suitable for erecting lines in medium and light ice regions, but not suitable for erecting lines in heavy ice regions.
ADSS optical cable is an "additive" to the old line. ADSS optical cable can only adapt to the original line conditions as much as possible. These conditions include (but are not limited to) meteorological load, the strength and shape of the tower, and the phase sequence arrangement of the original conductors. Diameter, sag tension, span and safety distance, etc. Although the appearance of ADSS optical cable is similar to ordinary "full plastic" or "non-metal" optical cable, it is two completely different products.
The structure and characteristics of ADSS optical cable
Common types of ADSS optical cables
At present, the structure of ADSS optical cables that are widely used in power systems mainly includes three types. Central loose tube type ADSS optical cables, Single sheath layered stranded ADSS optic cabel and Double sheath layered stranded ADSS optical cables.
Central tube structure of ADSS Optical Cable
The optical fiber is placed in a PBT (or other suitable material) tube filled with water-blocking grease with a certain excess length, and suitable spun yarn is wrapped according to the required tensile strength, and then PE (≤12KV electric field strength) or AT (≤20KV electric field strength) sheath. The central tube structure is easy to obtain a small diameter, and the ice wind load is small. The weight is also relatively light, but the excess length of the optical fiber is limited.
Single Sheath and Double Sheath Layered Stranded Structure of ADSS Optical Cable
The loose tube of optical fiber is wound on the central reinforcing member (usually FRP) at a certain pitch, and then the inner sheath is extruded (can be omitted when the tension is small and the span is small). Then, according to the required tensile strength, suitable spun yarn is wrapped, and then PE or AT sheath is extruded. The cable core can be filled with grease. However, when ADSS works with a large span and large sag, the cable core is easy to "slip" and the loose tube pitch is easy to change due to the small resistance of the grease. Fixing the loose tube on the central strengthening member and the dry cable core by a suitable method can be overcome, but there are certain technological difficulties.
The stranded structure is easy to obtain a safe fiber excess length, although the diameter and weight are relatively large, it has advantages in medium and large span applications.
ADSS cable characteristics
A high-strength aramid yarn with high elastic modulus is used as the tensile element. Aramid yarn (Vectran) is a high-strength, high-modulus polyarylate fiber product which is mainly made of polyarylate fiber. Kuraray was launched in the 1990s. The characteristics of the fiber are: excellent low creep, non-hygroscopicity, high mechanical and physical properties at very low temperatures, and moisture and abrasion resistance. The strength of Vectran is about 6 times that of ordinary polyester fiber, which is equivalent to the strength of metal fiber. And the material is light (the strength is about 5-6 times that of steel wire under the same weight), does not absorb moisture, has strong low-temperature characteristics, and will not freeze at ultra-low temperatures. Vectran has high tensile strength, low moisture absorption (no moisture absorption), dimensional stability (elongation less than 2.5%), good heat resistance (heat resistance temperature higher than 400C), abrasion resistance, cutting resistance, acid resistance, impact resistance, and flame resistance The sex is excellent. Vectran fiber has better abrasion resistance, UV resistance and low moisture absorption than Kevlar and Twaron.
The ADSS cable has a small geometric size, and the weight of the cable is only one-third of that of an ordinary optical cable. It can be directly hung on the appropriate position of the power pole, and the additional load on the pole is small. The outer sheath is impregnated with neutral ionization, so that the optical cable has a strong resistance to electrical corrosion. The ADSS optical cable is made of metal-free materials and has good insulation performance, which can avoid lightning strikes. When the power line fails, it will not affect the normal operation of the optical cable. Utilizing the existing power poles and towers, it can be constructed without power failure. And it can be erected on the same pole as the power line, which can reduce the project cost. the operating temperature range is wide:-40~+70°C. Wide span range: 50~1200m.
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