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News of Hotlink HAS477A for ACSR 477.0 Kcmil 26/7


Warmly Congratulations to Guangzhou Xinyuan Hengye Power Transmission Device Co., Lt for wins of REB (Bangladesh Rural Electrification Board) bid. (Lot No. UREDS-G-03-002 for Supply of Connector)

As of the only Automatic Tension Splice manufacturer in Asia, Guangzhou Hotlink is the contract supplier to Guangzhou Xinyuan Hengye, and Hotlink product line cover full range of HAS ( Hotlink Automatic Tension Splice) from HAS42 to HAS477A, which cover the conductor range from ASTM #4 to ASTM #477-ACSR-26/7. Especially for HAS477A, The diameter range of HAS477A is from 0.842” to 0.890”, which makes the splice capable to apply on ASTM #477-ACSR-26/7 and ASTM #477-ACSR-24/7. HAS477A has passed the mechanical / electrical tests by the third party lab and it's approved to stand 95% RBS of the conductor. We are confident for its’ better performance to the competitor after comparison test. 

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Construction of Overhead


To achieve good high-speed current collection, it is necessary to keep the contact wire geometry within defined limits. This is usually achieved by supporting the contact wire from above by a second wire known as the messenger wire (US & Canada) or catenary (UK). This wire approximates the natural path of a wire strung between two points, a catenary curve, thus the use of catenary to describe this wire or sometimes the whole system. This wire is attached to the contact wire at regular intervals by vertical wires known as droppers or drop wires. The messenger wire is supported regularly at structures, by a pulley,link, or clamp. The whole system is then subjected to a mechanical tension.

As the contact wire makes contact with the pantograph, the carbon insert on top of the pantograph is worn down. Going around a curve, the"straight" wire between supports will cause the contact wire to cross over the whole surface of the pantograph as the train travels around the curve,causing uniform wear and avoiding any notches. On straight track, the contact wire is zigzagged slightly to the left and right of centre at each successive support so that the pantograph wears evenly. The movement of the contact wire across the head of the pantograph is called the 'sweep'.

The zigzagging of the overhead line is not required for trams using trolley poles or for trolleybuses.

Depot areas tend to have only a single wire and are known as simple equipment. When overhead line systems were first conceived, good current collection was possible only at low speeds, using a single wire. To enable higher speeds, two additional types of equipment were developed:

Stitched equipment uses an additional wire at each support structure, terminated on either side of the messenger wire.

Compound equipment uses a second support wire, known as the auxiliary, between the messenger wire and the contact wire. Droppers support the auxiliary from the messenger wire, and additional droppers support the contact wire from the auxiliary. The auxiliary wire can be constructed of a more conductive but less wear-resistant metal, increasing the efficiency of power transmission.

Dropper wires traditionally only provide physical support of the contact wire, and do not join the catenary and contact wires electrically. Contemporary systems use current-carrying droppers, which eliminate the need for separate wires.

The present transmission system originated about 100 years ago. A simpler system was proposed in the 1970s by the Pirelli Construction Co consisting of a single wire embedded at each support for 2.5 metres (8 ft 2 in) of its length in a clipped extruded aluminum beam with the wire contact face exposed. With a somewhat higher tension than used before clipping the beam yielded a deflected profile for the wire which could be easily handled at 250 miles per hour (400km/h) by a pneumatic servo pantograph with only 3 G accelerations.

For tramways there is often only a contact wire and no messenger wire.

Where there is limited clearance to accommodate wire suspensions systems such as in tunnels, the overhead wire may be replaced by rigid overhead rail. This was done when the overhead line was raised in the Simplon Tunnel to accommodate taller rail vehicles. A rigid overhead rail may also be used in places where tensioning the wires is impractical, for example on moveable bridges.

Tensioning of Overhead 

Catenary wires are kept at a mechanical tension because the pantograph causes mechanical oscillations in the wire and the wave must travel faster than the train to avoid producing standing waves that would cause wire breakage. Tensioning the line makes waves travel faster.

For medium and high speeds, the wires are generally tensioned by means of weights or occasionally by hydraulic tensioners. Either method is known as auto-tensioning (AT), or constant tension and ensures that the tension in the equipment is virtually independent of temperature. Tensions are typically between 9 and 20 kN (2,000 and 4,500 lbf) per wire. Where weights are used, they slide up and down on a rod or tube attached to the mast, to prevent the weights from swaying.

For low speeds and in tunnels where temperatures are constant, fixed termination (FT) equipment may be used, with the wires terminated directly on structures at each end of the overhead line. Here the tension is generally about 10 kN (2,200 lbf). This type of equipment will sag on hot days and taut on cold days.

Where AT is used, there is a limit to the continuous length of overhead line which may be installed. This is due to the change in the position of the weights with temperature as the overhead line expands and contracts. This movement is proportional to the tension length, that is, the distance between anchors. This leads to the concept of maximum tension length. For most 25 kV OHL equipment in the UK, the maximum tension length is 1970 m.

An additional issue with AT equipment is that, if balance weights are attached to both ends, the whole tension length will be free to move along track. To rectify this issue, a midpoint anchor (MPA), close to the centre of the tension length, restricts movement of the messenger wire by anchoring it; the contact wire and its suspension hangers can move only within the constraints of the MPA. MPAs are sometimes fixed to low bridges; otherwise,they are anchored to the typical vertical catenary poles or portal catenary
supports. Therefore, a tension length can be seen as a fixed centre point, with the two half tension lengths expanding and contracting with temperature.

Most overhead systems include a brake to stop the wires from unravelling completely should a wire break or tension be lost for any other reason. German systems usually use a single large tensioning pulley with a toothed rim, mounted on an arm hinged to the mast. Normally the downward pull of the weights, and the reactive upward pull of the tensioned wires, lifts the pulley so its teeth are well clear of a stop on the mast. The pulley can turn freely while the weights move up or down as the wires contract or expand. If a wire breaks or tension is otherwise lost, the pulley falls back toward the mast, and
one of its teeth will jam against the stop. This stops further rotation, limits the damage, and keeps the undamaged part of the wire intact until it can be repaired. Other systems use various other braking mechanisms, usually with multiple smaller pulleys in a block and tackle arrangement.

Electric fence

An electric fence is a barrier that uses electric shocks to deter animals or people from crossing a boundary. The voltage of the shock may have effects ranging from uncomfortable, to painful or even lethal. Most electric fencing is used today for agricultural fencing and other forms of animal control purposes, though it is frequently used to enhance security of sensitive areas, and places exist where lethal voltages are used.

 Design and function

Electric fences are designed to create an electrical circuit when touched by a person or animal. A component called a power energizer converts power into a brief high voltage pulse. One terminal of the power energizer releases an electrical pulse along a connected bare wire about once per second. Another terminal is connected to a metal rod implanted in the earth, called a ground or earth rod. A person or animal touching both the wire and the earth during a pulse will complete an electrical circuit and will conduct the pulse, causing an uncomfortable electric shock. The effects of the shock depend upon the voltage, the energy of the pulse, the degree of contact between the recipient and the fence and ground and the route of the current through the body; it can range from barely noticeable to uncomfortable, painful or for some fences even lethal.

Fence energizers

Early alternating current (AC) fence chargers used a transformer and a mechanically-driven switch to generate the electrical pulses. The pulses were wide and the voltage unpredictable, with no-load peaks in excess of 10,000 volts and a rapid drop in voltage as the fence leakage increased. The switch mechanism was prone to failure. Later systems replaced the switch with a solid-state circuit, with an improvement in longevity but no change in pulse width or voltage control.

"Weed burner" fence chargers were popular for a time and featured a longer-duration output pulse that would destroy weeds touching the fence. These were responsible for many grass fires when used during dry weather. Though still available, they have
declined in popularity.

Modern "low impedance" fence chargers use a different design. A capacitor is charged by a solid-state circuit – upon contact with a grounded animal or person, the charge is then
released using a thyristor or similar solid-state component. Voltage is consistent due to electronic output controls, within the limits of output power. Pulse width is much narrower, often about 10 microseconds. This design works for either battery or mains power sources.

Depending on the area to be fenced and remoteness of its location, fence energizers may be hooked into a permanent electrical circuit, may be run by lead-acid or dry cell batteries, or a smaller battery kept charged by a solar panel. The power consumption of a
fence in good condition is low, and so a lead-acid battery powering several hundred metres of fence may last for several weeks on a single charge. For shorter periods dry cell batteries may be used. Some energizers can be powered by more than one source.

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Although silver is the best conductor, its cost limits its use to special circuits. Silver is used where a substance with high conductivity or low resistivity is needed.
The two most commonly used conductors are copper and aluminum. Each has positive and negative characteristics that affect its use under varying circumstances.
A comparison of some of the characteristics of copper and aluminum is given in below table.
Comparative Characteristics of Copper and Aluminum




Tensile strength (lb/in2).



Tensile strength for same conductivity (lb).



Weight for same conductivity (lb).



Cross section for same conductivity (C.M.).



Specific resistance (W/mil ft).



Copper has a higher conductivity than aluminum. It is more ductile (can be drawn out). Copper has relatively high tensile strength (the greatest stress a substance can bear along its length without tearing apart). It can also be easily soldered. However, copper is more expensive and heavier than aluminum.

Although aluminum has only about 60 percent of the conductivity of copper, its lightness makes long spans possible. Its relatively large diameter for a given conductivity reduces
corona. Corona is the discharge of electricity from the wire when it has a high potential. The discharge is greater when smaller diameter wire is used than when larger diameter wire is used. However, the relatively large size of aluminum for a given conductance does not permit the economical use of an insulation covering.


The resistance of pure metals,such as silver, copper, and aluminum, increases as the temperature increases.
However, the resistance of some alloys, such as constantan and manganin, changes very little as the temperature changes. Measuring instruments use these alloys because the resistance of the circuits must remain constant to get accurate measurements.

In table 1-1, the resistance of a circular-mil-foot of wire (the specific resistance) is given at a specific temperature, 20°C in this case. It is necessary to establish a standard temperature. As we stated earlier, the resistance of pure metals increases with an increase in temperature. Therefore, a true basis of comparison cannot be made unless the resistances of all the substances being compared are measured at the same temperature. The amount of increase in the resistance of a 1-ohm sample of the conductor per degree rise in temperature above 0°C is called the temperature coefficient of resistance. For copper, the value is approximately 0.00427 ohm.
A length of copper wire having a resistance of 50 ohms at an initial temperature of 0°C will have an increase in resistance of 50 X 0.00427, or 0.214 ohms. This applies to the entire length of wire and for each degree of temperature rise above 0°C. A 20°C increase in resistance is approximately 20 X 0.214, or 4.28 ohms. The total resistance at 20°C is 50 + 4.28, or 54.28 ohms.

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6061 Aluminium Alloy


6061 is a precipitation hardening aluminium alloy, containing magnesium and silicon as its major alloying elements. Originally called "Alloy 61S," it was developed in 1935. It has good mechanical properties and exhibits good weldability. It is one of the most common alloys of aluminium for general purpose use.

It is commonly available in pre-tempered grades such as 6061-O (annealed) and tempered grades such as 6061-T6 (solutionized and artificially aged) and 6061-T651 (solutionized, stress-relieved stretched and artificially aged).

T6 temper 6061 has an ultimate tensile strength of at least 42,000 psi (300 MPa) and yield strength of at least 35,000 psi (241 MPa). More typical values are 45,000 psi (310 MPa) and 40,000 psi (275 MPa), respectively. In thicknesses of 0.250 inch (6.35 mm) or less, it has elongation of 8% or more; in thicker sections, it has elongation of 10%. T651 temper has similar mechanical properties. The typical value for thermal conductivity for 6061-T6 at 80°C is around 152 W/m K. A material data sheet defines the fatigue limit under cyclic load as 14,000 psi (100 MPa) for 500,000,000 completely reversed cycles using a standard RR Moore test machine and specimen. Note that aluminum does not exhibit a well defined "knee" on its S-n graph, so there is some debate as to how many cycles equates to "infinite life". Also note the actual value of fatigue limit for an application can be dramatically affected by the conventional de-rating factors of loading, gradient, and surface finish.

6061-T6 is used for:

·        The construction of bicycle frames and components.

·        Many fly fishing reels.

·        The famous Pioneer plaque was made of this particular alloy.

·        The secondary chambers and baffle systems in firearm sound suppressors (primarily pistol suppressors for reduced weight and functionality), while the primary expansion chambers usually require 17-4PH or 303 stainless steel or titanium.

·        The upper and lower receivers of many AR-15 variants.

·        Many aluminum docks and gangways are constructed with 6061-T6 extrusions, and welded into place.

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