Main Types of Overhead Cable & Wire

Overhead power lines mainly refer to overhead electrical wires, erected on the ground, and are transmission lines that use insulators to fix transmission wires on poles standing upright on the ground to transmit electrical energy.

What type of wire is used for overhead?
The wires used in low-voltage overhead lines are divided into bare wires and insulated wires. According to the structure of the conductor, it can be divided into single-strand conductor, multi-strand conductor and hollow conductor; its common types are AAC/AAAC/ACSR/ACAR.
The bare wire is the main body of the overhead line and is responsible for transmitting electrical energy. Since the wires are erected on the poles, they must often bear the effects of self-weight, wind, rain, ice, snow, harmful gas erosion, and air temperature changes. Therefore, the wire is required not only to have good electrical conductivity, but also to have sufficient mechanical strength and good corrosion resistance.

(1). All Aluminum Conductor (AAC): This bare concentric-lay stranded conductor is constructed with a straight round central wire surrounded by one or more layers of helically layed wires. These wires are of aluminum 1350 and can be provided in different classes of stranding and tempers.

(2). All Aluminum Alloy Conductor (AAAC): This bare concentric-lay-stranded conductor, made from round aluminum alloy 6201 -T81 wires, is constructed with a central core surrounded by one or more layers of helically laid wires.
It was designed to attend the needs of an economic conductor for the applications on aerial circuit that require a larger mechanical resistance than the one of an All Aluminum Conductor (AAC), and a better corrosion resistance than the one produced by the aluminum conductor steel reinforced(ACSR). The conductors of Aluminum Alloy 6201-T81 are harder and have a better resistance to the abrasion than the conductors of aluminum 1350.

(3).Aluminum Conductor Steel Reinforced Conductor (ACSR) : This bare concentric-lay-stranded conductor is made from round aluminum 1350-H19 (extra hard) wires and round zinc-coated or aluminum-coated steel core wire(s) to be used as overhead electrical conductors.Used as bare overhead transmission cable and as primary and secondary distribution cable. ACSR offers optimal strength for line design. Variable steel core stranding enables desired strengthto be achieved without sacrificing ampacity.

(4).Aluminum Conductor Alloy Reinforced Conductor (ACAR)This bare concentric-lay-stranded conductor is made from round aluminum 1350-H19 (extra hard) wires and round aluminum alloy 6201-T81 core wires for use as overhead electrical conductors.It presents a higher mechanical resistance.

Overhead insulated cable is an overhead wire equipped with an insulating layer and a protective sheath. It is a special cable manufactured by a production process similar to that of a cross-linked cable. It is a new transmission method between overhead wires and underground cables.

Aerial bundled cables (also aerial bundled conductors or simply ABC) are overhead power lines using several insulated phase conductors bundled tightly together, usually with a bare neutral conductor. The conductor can be all aluminum, aluminum alloy or aluminum with a steel core, used for overhead power distribution as an alternative to bare conductor.

 

Construction:
ABC cable used for low voltage overhead line transfer, structured by stranded aluminum conductor or aluminum conductor with steel core , both single core and multi-cores ,insulated by UV resistant XLPE.

Overhead ABC Cable Advantage:
ABC cable provide better level of safety and reliability ,lower power losses, easier to install ,less maintenance and operative cost.

  1. High reliability of power supply
    The use of overhead cables can greatly reduce various short-circuit faults (especially the common flashover faults of overhead bare wires). Compared with overhead bare wires, the failure rate is 4-6 times lower.
  2. Good power supply safety
    The use of overhead cables greatly reduces personal injury and death accidents due to electric shock.
  3. Convenient installation and maintenance
    Overhead cables can be erected on any kind of poles and towers, or along walls. Under special circumstances, they can also run through the bushes and be directly fixed on tree poles with hardware. It can be erected on a single circuit or multiple circuits on the same pole without requiring a wide “electrical corridor”.
  4. Reasonable economy
    Although the use of overhead cables is more expensive than the use of overhead bare wires, it is cheaper than ordinary underground cables. Therefore, although the one-time investment is slightly higher for the use of overhead cables, the operating cost will be significantly lower than that of overhead bare conductors based on other factors.

Laying method of overhead ABC cable 
A single conventional laying method. This erection method is to use the current conventional cement poles, iron accessories and ceramic insulator accessories with bare conductors, and erect according to the bare conductor erection method, which is more suitable for the area where the old line is reconstructed and the corridor is sufficient.
A special insulating bracket is used to suspend the wires for single laying. This method can increase the number of circuits erected, save the line corridors, and reduce the cost of the line unit.

How to Ensure Outdoor Cable Performance ?

Many users and installations are faced with the problem of cheap and efficient data transmission between buildings in the park environment. The choice of routing, transmission distance and application environment will all affect the choice of cable medium. Incorrect or inappropriate choice will result in a shortened period of wiring investment, and reinstallation will also cause the network system to stop running.
If it is an outdoor application, the fiber optic system is usually the choice for campus network connection. The real cost of optical fiber lies in the termination of optical fiber cabling system and optoelectronic equipment. When users only need to transmit 10Mbps or 100Mbps within a distance of 50 meters between buildings, optical fibers are generally not used.

Buying conventional Category 5 copper cables underground or laying overhead may cause transmission failure of a certain network along the wiring line. Therefore, choosing the existing outdoor direct-buried enhanced type cable will bring a cheap link. Before deciding to choose these outdoor LAN cables, you should fully understand their design.

Anti-moisture protection nets have been used in communication cables for many years. These aluminum polymer materials have overlapping seals as protection to reduce the penetration path of water vapor to prevent water from entering. However, an unprotected dry cable will need to suffer as long as six months to a year of liquefaction due to infiltration, and a dry cable with a moisture-proof protective net will be completely protected. The cable designed in this way is approximately similar to a foil-screened LAN cable, and it is easy to connect and use.

Therefore, the wiring system designer must consider the application environment, which includes the following environment and parameters that affect the cable:
1. Whether the cable is placed under the eaves; as long as the cable is not directly exposed to sunlight or ultra-high temperature, the standard LAN cable can be used. It is recommended to use pipes:
2. External walls; avoid direct sunlight on the walls and man-made damage;
3. In the pipe (plastic or metal); if in the pipe, pay attention to the damage of the plastic pipe and the heat conduction of the metal pipe;
4. For suspended applications/overhead cables, the sag and pressure of the cable should be considered. Which bundling method you intend to use. Whether the cable is directly irradiated by sunlight; laying directly in the underground cable trench, this environment is the smallest control range. The installation of the cable trench should be checked regularly for dryness or humidity;
5. Underground pipeline. In order to facilitate future upgrades, cable replacement, and isolation from surface pressure and the surrounding environment, laying pipes is a better method. But don’t expect that the pipe will always remain dry, which will affect the choice of cable types.

Factors affecting cable performance include:
1. Ultraviolet (UV)-Do not use cables without UV protection in direct sunlight. You should choose cables with black polyethylene or PVC sheaths, such as Brand-Rex’s 4 pairs of reinforced type 5 MegaOutdoor outdoor cable, with metal mesh moisture-proof protective layer and black polyethylene sheath, is suitable for most inter-building connections, whether it is overhead laying, ground installation or pipeline construction, it can be used:

2. Heat-the temperature of the cable in the metal pipe or trunking is very high. Many polymer materials will reduce the service life at this temperature. Black polyethylene or PVC sheathed power cable should be selected;

3. Water-Water is the real killer of LAN cables. The moisture in the twisted-pair cable of the local area network will increase the capacitance of the cable, thereby reducing the impedance and causing near-end crosstalk problems. If it is extremely effective to prevent moisture and water vapor, a protective layer of metal shielding net is required;

4. Mechanical damage (repair costs)-the repair of optical cables is very expensive, and at least two terminations are required at each discontinuity;

 

Grounding-if the shielding layer of the cable needs to be grounded, the corresponding standards must be followed;

The total length of the route (not only between the buildings)-Use outdoor-grade LAN twisted-pair cables between the buildings, and the total length should be limited to 90 meters.
For a network of 100Mbps or 1000Mbps, the laying distance cannot exceed this limit. If the laying distance is between 100 meters and 300 meters, optical cable should be selected.
The following simple experiments can be used to self-test whether the wiring investment is safe: use a 20-meter enhanced category 5 UTP cable to terminate at both ends; carefully remove the cable sheath at the midpoint of the cable to expose a small section of copper cable (1 cm ); Test the cable according to AN/NZSD standard; soak the cut part of the cable in water for 1-2 minutes, and then retest.