ADSS optical cables operate overhead with dual-point support over long spans (typically hundreds of meters or even over 1km), which is completely different from traditional overhead concepts (the standard overhead line hook scheme for postal and telecommunications uses an average of one cable support point every 0.4 meters). Therefore, the main parameters of ADSS optical cables meet the regulations for overhead power lines.

1. Maximum Allowable Tension (MAT/MOTS)

This refers to the tension that the optical cable can withstand under theoretically calculated total load under design meteorological conditions. At this tension, the optical fiber strain should be ≤0.05% (twisted) and ≤0.1% (central tube), with no additional attenuation. In layman's terms, at this control value, the remaining length of the optical fiber is just consumed. Based on this parameter, meteorological conditions, and the controlled sag, the allowable span of the optical cable under these conditions can be calculated. Therefore, MAT is an important basis for calculating the sag-tension-span ratio and is also a key factor in characterizing the stress-strain characteristics of ADSS optical cables.

2. Rated Tensile Strength (UTS/RTS)

Also known as Ultimate Tensile Strength or Breaking Strength, it refers to the calculated value of the total strength of the load-bearing section of the cable (primarily measured by spun fiber). The actual breaking force should be greater than or equal to 95% of the calculated value (a break in any component of the cable is considered a cable break). This parameter is mandatory. Many control values are related to it (such as tower strength, tensile hardware, and vibration isolation measures). For optical cable professionals, if the RTSMAT ratio (equivalent to the safety factor K for overhead lines) is not appropriate, even if a large number of stranded fibers are used and the applicable strain range of the fibers is very narrow, the economic and technical performance ratio will be poor. Therefore, I recommend that industry insiders pay attention to this parameter. Generally, MAT is approximately equivalent to 40% of RTS.

3. Annual Mean Stress (EDS)

Sometimes also called daily mean stress, this refers to the theoretically calculated tension of the optical cable under load under windless, ice-free conditions, and at average annual temperatures. LFT can be considered the average tension (strain) of the ADSS optical cable during long-term operation. EDS is generally (15-25)% of RTS. Under this tension, the optical fiber should experience no strain and no additional attenuation, indicating it is extremely stable. EDS is also a fatigue parameter for optical cables, and its vibration resistance design is determined based on this parameter.

4. Ultimate Operating Tension (UES)

The ultimate operating tension, also known as the special use tension, is the maximum tension at which the cable may exceed its design load during its useful service life. It indicates that the cable can be overloaded for a short period of time, with the optical fiber experiencing strain within a limited allowable range. Typically, the UES should be greater than 60% of the RTS. Under this tension, if the strain on the optical fiber is less than 0.5% (for the central tube) and less than 0.35% (for stranding), additional attenuation will occur, but the fiber should return to normal after the tension is released. This parameter ensures reliable operation of the ADSS optical cable throughout its service life.

5. Voltage Rating

The voltage rating adaptability of the ADSS optical cable is related to the sheath material and is specified in accordance with the IEEE 1222 and IEC 60794-1 technical standards. Specifically, it can be divided into the following three categories:

‌(1) Lines ≤110kV:

Polyethylene (PE) sheath is used, which is suitable for medium and low voltage power lines such as 10kV and 35kV.

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PE sheath has excellent insulation and weather resistance, and is suitable for environments with low electric field strength.

‌(2) Lines ≥110kV

Anti-tracking (AT) sheath must be used, which is suitable for high voltage transmission lines such as 110kV and 220kV. Otherwise, it may cause tracking corrosion and damage the optical cable.

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‌The location of the optical cable hanging point needs to be determined through electric field strength calculation to ensure the stability of operation in a strong electric field environment.

‌(3) Special application scenarios

‌In specific engineering designs, ADSS optical cables can be extended to 500kV voltage level transmission line towers by optimizing the structure and material selection, but the following conditions must be met:

a. Use AT sheath with stronger anti-corrosion performance.

b. Strictly control the safe distance between the optical cable and the live conductor. c. Accurately calculate the impact of meteorological conditions such as icing and wind load on the mechanical properties of optical cables.

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