ADSS fiber optic cable is known as all dielectric self-supporting optical cable, it uses special insulation materials, has good insulation and high temperature performance, high tensile strength, can be set up in the power line on the original towers, has become the first choice of special optical cable power system network.
Power system communication network construction in recent years, mainly ADSS cable-based, so the design and construction of ADSS cable is a comprehensive system engineering. For ADSS cable structural characteristics, service life, the choice of suspension points, loading drum, arc pendant tension table and other aspects of the discussion, to enhance the use of ADSS cable in a particular environment to give a more in-depth understanding.
Structural Characteristics of ADSS Fiber Optic Cable
Currently produced ADSS fiber optic cable from the structure can be divided into two types of stranded and center tube type, in which stranded ADSS fiber optic cable within the FRP reinforcing core, the weight is slightly heavier than the center tube type. At the same time and because of its operation in a high-voltage environment, according to the electric field strength can be divided into AT sheath corrosion-resistant type and PE sheath standard type. ADSS fiber optic cable features are as follows:
- Specially designed for electric power system, it is a self-supporting overhead fiber optic cable with full insulating medium, which does not contain any metal material in its structure.
- Fully insulated structure and high voltage resistance index, which is conducive to the erection and construction of overhead power lines running with electricity without affecting the operation of the lines.
- The use of high tensile strength of the anti-spandex material that can withstand strong tension, to meet the requirements of the large span of overhead power lines, but also to prevent bird pecking and man-made gunshot.
- ADSS fiber optic cable thermal expansion coefficient is small, in the temperature change is very large, the arc of the fiber optic cable line changes are very small , and its weight is light, it’s tracking ice and wind load is also small.
Another guide for introduction of ADSS Fiber Optic Cable.
ADSS Fiber Optic Cable Service Life
ADSS fiber optic cable is erected on high-voltage transmission lines, its general life expectancy is more than 25 years, and there are many factors that affect its life expectancy, the main factors are:
- High-voltage induced electric field gradient near the pole tower varies greatly, and the high-voltage induced electric field has strong galvanic corrosion on the fiber optic cable. Generally, PE type is used for overhead power lines of 35KV and below, and AT type is used for lines of 110KV and above.
- For the double-circuit tower, due to the line of a circuit outage or line reconstruction, in the choice of hanging point to be considered.
- When the line passes through the working zone with salt mist and acid gas, the chemical substances will corrode the outer skin of the fiber optic cable, and its power-resistant protective jacket will be damaged and susceptible to damage by electric arc.
- Improper construction caused by the outer skin injury or wear and tear, etc., in the long-term high-voltage electric field operation, its surface is easy to corrode, and the outer sheath of the smooth smooth fiber optic cable can effectively reduce galvanic corrosion and prolong the life of the cable.
ADSS Fiber Optic Cable Suspension Point Selection Principle
- The ADSS fiber optic cable should be suspended in the position with less electric field strength, i.e. AT sheathed ADSS fiber optic cable ≤ 25KV/m, generally used in 110 KV and above overhead power lines, PE sheathed ADSS fiber optic cable ≤ 12KV/m, generally used in 35KV and below overhead power lines.
- The projection of ADSS fiber optic cable in horizontal and vertical direction should not cross with conductor and ground line, so as not to produce whiplash in wind deflection and swinging.
- ADSS Fiber optic cables should not cause friction and collision with towers.
- ADSS fiber optic cables must be kept at a safe distance from residential areas, railroads, highways, communication lines and other power lines.
- Suspension of optical cable fittings must be installed in the tower can withstand lateral tension on the tower material, so that the tower force is minimized.
Among them, the size of the high-voltage induced electric field generally have ADSS fiber optic cable manufacturers according to the preliminary design of the power design institute for accounting, give the size of the electric field intensity of different tower models and distribution map, and then combined with the construction of the specific degree of difficulty, and ultimately determine the location of the cable’s hanging point.
In the specialized application software, as long as the established coordinate system to provide the phase coordinates of the tower, phase line diameter, ground type, line voltage level, etc., you can get a map of the induced electric field distribution, therefore, in the preliminary design of the preparatory stage, the line information is exhaustive and reliable is a guarantee of the quality of the entire project.
Selection Of Typical Suspension Points For ADSS Fiber Optic Cables
According to the calculation results of the electric field strength of various towers, to meet the requirements of the electric field strength of the hanging point can be divided into high, medium and low hanging point of three kinds of ways.
The high hanging point is generally difficult to construct and inconvenient to operate and manage. The low hanging point in the safety distance to the ground there are some problems, and prone to theft. Generally used in the information network project in the hanging point way.
110KV line tensile pole, door type pole, double circuit tower, steel pipe single pole, cement single pole, etc., ADSS fiber optic cable can be hung in the first layer of cross-arms under the position between 300 to 500mm.
ADSS Fiber Optic Cable Loading Drum Length
Fiber optic cable loading is an important consideration in the construction of fiber optic cabling. When the line used and the condition is clear, it is necessary to consider the length of the optical fiber cable distribution drum, and the factors affecting the distribution drum are:
- As ADSS cable is not like ordinary cable can be arbitrarily connected (because the fiber core can not be stressed), must be carried out in the line on the tension-resistant towers, but also due to the poor conditions of the field connection point, so the loading length of each drum of cable as far as possible to control in the 3 to 5Km. Drum loading length is too long for the construction of the inconvenience. Too short is the number of times to splice, the path of attenuation of the large, affecting the quality of transmission of fiber optic cables.
- In addition to the length of the transmission line is the main basis for the length of the fiber optic cable drum, should also take into account the natural conditions between the towers, such as whether the traction machine is easy to travel, whether the tension machine can be placed, etc.
- Due to the error of line design, the fiber optic cable tray can use the following empirical formula. Fiber optic cable tray length = transmission line length × coefficient + construction consideration length + fusion splicing length + line error. Usually “coefficient” including line sag, tower length, etc., the length of construction considerations for the construction of the length of the traction used.
- ADSS cable hanging point from the ground is generally not less than the lowest 7m, in determining the length of the installed disk, to simplify the gap difference, in order to reduce the type of cable, that is, to reduce the number of spare parts (such as the configuration of a variety of hanging hardware, etc.), but also to facilitate construction.
ADSS Fiber Optic Cable Construction Of The Basic Requirements
- The construction of ADSS fiber optic cable is usually carried out on the electrified line tower, the construction must use insulated induction ropes, insulated safety belts, insulated tools, the wind should not be greater than 5 degrees, must maintain a safe distance from the different voltage levels of the line, i.e., 35KV is greater than 10m, 110KV is greater than 15m, and 220KV is greater than 30m of safety distance.
- Due to the fiber core is very easy to break, construction tension and side pressure can not be too large.
- The fiber optic cable can not be friction and collision with the ground, houses, towers, cable tray edge and other objects during construction.
- The bending of the cable is limited, the general operation of the bending radius ≥ D, D is the diameter of the cable, construction bending radius ≥ 30D.
- The cable will be damaged by twisting, longitudinal twisting is strictly prohibited.
- The fiber core of the cable is easily broken by moisture and water, the cable end must be sealed with waterproof tape during construction.
- The outer diameter of the cable is matched with the representative gear spacing, the construction shall not be arbitrarily adjusted to the drum, and at the same time, the fittings corresponding to the outer diameter of the cable, is also strictly prohibited from indiscriminate use.
- After the completion of the construction of each drum of fiber optic cable, usually reserved a sufficient length of spare cable, in order to hang and fusion splicing at the pole tower, the installation of fiber optic distribution frames in the substation.
ADSS Fiber Optic Cable Arc Sag Tension
Arc sag tension is an important data reflecting the aerodynamic performance of ADSS fiber optic cable, complete understanding and correct use of these data is necessary to improve the quality of the project.
Usually, manufacturers can provide 3 kinds of constant conditions under the arc sag tension table, that is, the installation arc sag constant (installation arc sag for a fixed percentage of the stall distance), the installation of constant tension and load tension constant.
These three types of tension table from different sides of the ADSS cable arc sag tension performance for a specific description, it is only used to illustrate the ADSS cable products in the given conditions of use of the arc sag tension characteristics of the actual engineering applications are different, must be paid attention to.
Secondly, need to pay attention to the arc of the sag tension in the pitch is the actual pitch, accurately the actual pitch of the isolated gear, that is, resistant to tension section only a section of the pitch.
In the actual project, should first find out the tension section of the representative stall distance, and then from the arc sag tension table to find out and the representative stall distance value is the same or similar to that stall corresponding to the arc sag and tension data. Remember that this time the arc is generally composite arc, through the wind deflection angle, find out the horizontal arc and vertical arc, in this representative of the arc, representative of the tension, representative of the theoretical value of the pitch, calculated on the basis of the actual data.
In the control conditions, wind load control and ADSS cable mechanical properties have a relationship.
Usually occurs in more than 600m of large gear distance, more than 30m/s wind, ADSS cable weight is lighter than the wire, its wind deflection angle is greater than the wind deflection angle of the wire, it is easier to elongate. This may cause in the wind ADSS cable and wire touch.
Although the design calculation is more complex, but in the case of small pitch, such as the representative pitch is less than 100m, usually take the frame line arc sag for 0.5m. The representative pitch between 100m and 120m, the frame line arc sag for 0.7m, the lowest point of the arc sag of the ADSS fiber optic cable should not be lower than the lowest point of the arc sag of the wire.
In actual construction, often in the continuous span of the tension pole, choose the middle span or near the middle span of the larger span distance, hanging point height difference is smaller as the observation span. If the number of stalls in 7 to 15 stalls, should be selected at both ends of the 2 observation stalls, common observation methods are equal and different length method to observe the arc prolapse, can also be used to observe the arc prolapse of the tension measurement method.
Summarize
ADSS fiber optic cable engineering design and construction is a complex systematic project, involving mechanical, electrical, meteorological conditions, the quality of construction personnel, and many other aspects, both scientific attitude, but also effective working methods.
With the continuous progress of the power information network project, will accumulate more and more experience in construction and routine maintenance, so that the application of ADSS fiber optic cable to get more development.