ADSS Optical Cable Main Technical Parameters

ADSS optical cable is an “additive” to the old line, ADSS optical cable can only try to adapt to the original line conditions, these conditions include (but not limited to) weather load, tower strength and shape, the phase sequence of the original wire and Diameter, sag tension, span and safety distance, etc. Although ADSS optical cables are similar in appearance to ordinary “all-plastic” or “non-metallic” optical cables, they are two completely different products.

1. Representative structure

At present, two kinds of ADSS optical cables are mainly popular at home and abroad.

(1) Central tube structure:

The optical fiber is placed in a PBT (or other suitable material) tube filled with water blocking ointment with a certain excess length, wrapped with suitable spinning yarn according to the required tensile strength, and then extruded into 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.

(2) Layer twist structure:

The fiber optic loose tube is wound on the central reinforcement (usually FRP) at a certain pitch, and then the inner sheath is extruded (it can be omitted in the case of small tension and small span), and then wrapped according to the required tensile strength Suitable spun yarn, then extruded into PE or AT sheath. The cable core can be filled with ointment, but when the ADSS works with a large span and a large sag, the cable core is easy to “slip” due to the small resistance of the ointment, and the loose tube pitch is easy to change . It can be overcome by fixing the loose tube on the central strength member and the dry cable core by a suitable method, but there are certain technological difficulties.

The layer-stranded structure is easy to obtain a safe optical fiber excess length, although the diameter and weight are relatively large, which is more advantageous in medium and large span applications.

2. Main technical parameters

ADSS optical cable works in an overhead state supported by two points with a large span (usually hundreds of meters, or even more than 1 km), which is completely different from the traditional concept of “overhead” (post and telecommunications standard overhead hanging wire hook program, an average of 0.4 meters has no effect on optical cables). 1 pivot). Therefore, the main parameters of ADSS optical cables are in line with the regulations of power overhead lines.

(1) Maximum allowable tension (MAT/MOTS)

Refers to the tension of the optical cable when the total load is theoretically calculated under the design meteorological conditions. Under this tension, the fiber strain should be ≤0.05% (layer twist) and ≤0.1% (center tube) with no additional attenuation. In layman’s terms, that is, the excess length of the optical fiber is just “eaten” at this control value. According to this parameter and meteorological conditions and the controlled sag, the allowable use span of the optical cable under this condition can be calculated. Therefore, MAT is an important basis for the calculation of sag-tension-span, and it is also an important evidence to characterize the stress-strain characteristics of ADSS optical cables.

(2) Rated tensile strength (UTS/RTS)

Also known as ultimate tensile strength or breaking force, it refers to the calculated value of the sum of the strengths of the bearing cross-section (mainly textile fibers). The actual breaking force should be ≥95% of the calculated value (the breakage of any element in the optical cable is judged as cable breakage). This parameter is not optional, and many control values ​​are related to it (such as the strength of the tower, tensile fittings, anti-vibration measures, etc.). For optical cable professionals, if the ratio of RTS/MAT (equivalent to the safety factor K of overhead lines) is not appropriate, even if a lot of fiber is used, and the available optical fiber strain range is very narrow, the economic/technical performance ratio is very poor. Therefore, the author recommends that people in the industry pay attention to this parameter. Typically, MAT is approximately equivalent to 40% RTS.

(3) Annual mean stress (EDS)

Sometimes referred to as the daily average stress, it refers to the tension of the cable under the load of theoretical calculation under the condition of no wind, no ice and annual average temperature, which can be regarded as the average tension (strain) of the ADSS during long-term operation. EDS is generally (16~25)%RTS. Under this tension, the fiber should be strain-free, without additional attenuation, i.e. very stable. EDS is also the fatigue aging parameter of the optical cable, and the anti-vibration design of the optical cable is determined according to this parameter.

(4) Ultimate Operating Tension (UES)

Also known as special use tension, it refers to the maximum tension that the cable is subjected to when the load exceeds the design load during the effective life of the optical cable. It means that the optical cable is allowed to be overloaded for a short time, and the optical fiber can withstand strain within a limited allowable range. Usually, the UES should be > 60% RTS. Under this tension, the fiber strain is less than 0.5% (center tube) and <0.35% (layer twist), the fiber will have additional attenuation, but after the tension is released, the fiber should return to normal. This parameter ensures the reliable operation of the ADSS cable during its lifetime.

3. The cooperation of hardware and optical cable

The so-called hardware refers to the hardware used to install the optical cable.

(1) Tension clamp

Although it is called “clamp”, it is actually better to use spiral pre-twisted wire (except for small tension and small span). It is also called “terminal” or “static end” fittings. The configuration is based on the outer diameter and RTS of the optical cable, and its holding force is generally required to be ≥95% RTS. When necessary, it should be tested with the optical cable.

(2) Suspension clip

It is also better to use the spiral pre-twisted wire type (except for small tension and small span). Sometimes referred to as “mid-range” or “overhanging” fittings. Generally, its holding force is required to be ≥ (10-20)% RTS.

(3) Vibration isolator

ADSS optical cable mostly adopts spiral damper (SVD). If EDS≤16%RTS, anti-vibration can be ignored. When EDS is (16-25)%RTS, anti-vibration measures should be taken. If the optical cable is installed in a vibration-prone area, the anti-vibration method should be determined by testing if necessary.