The power line fiitings of high-voltage transmission lines and tranformation lines are the crucial parts of overhead transmisson line and transmission lines. They are also closely related to the safe operation of the entire line. The materials of these fittings are malleable cast iron-based freeomagnetic. The design focus on mechanical stress and the application of casting and forging. Thus, the structure is bulky and heavy, and the construction is inconvenient. The research of fittings’ quality have been developed in recent year. Yet, they are focus on the mechanics and reliability of the application of wire fittings. By contrast, the electrical energy loss of fittings does not reach more attention.
Reason for Above Problem
The conventional power fittings intall on the wire. The materials are iron and steel, malleable cast iron-based ferromaganetic materials. This kind of fittings are for the transmission and transformation line. The power fittngs are in the alternating electromagnetic field as a whole. This will generate the hysteresis loss and eddy current loss. Meanwhile, there will be a tempreture increase in the hardware. This is because the tempreture of the wire may transfer to the hardware. Thus, it may affact the porperties of metals. If the current increase at the same time, the hysteresis loss will increase. It will increase to 1.6-2.0 power of the magnetic flux density. The eddy current loss will increase with the square of the meganic flux density as well. According to the srvey, the loss caused by ordinary fittings accounts for about 0.01% to 0.03% of the transmission capacity. The aluminum made helical fittings can elimate the hysteresis loss. They also can reduce eddy current loss at large. Moreover, the helical fittings can change the strucure from bolt-based to helical structure. The easy installation procedure improve the working effeciency and reduce the buget.
The adveantages
Anti-fatigue performance
In the overline teansmission and distribution lines, the conductor is the vital component for various lode. It is suspectible to damage in case of fatige. Moreover, the fatigue damage of the wire occurs in the area where the wires are in contact with the hardware in the span. That is, the place where has a high dynamic bending stress and a high static pressure.
The pre-twisted metal fittings have no bolts acting on the wire. This reduces the static compressive stress of the wire. At the same time, the pre-pattern fittings have relatively long pre-formed spiral lines. Some pre-pattern fixtures such as overhangs and split lead spacers also have rubber pads. The static compressive stress of the wire can be further limited or uniformly distributed to a larger area. Besides, This feature enhance the bending stiffness of the contact area between the wire and the metal tool. The dynamic bending stress caused by aeolian vibration is weakened in these areas as well. Under the same conditions, they pre-textured metal fittings and traditional bolt-pressed metal fittings. The static and dynamic stresses on the conductor are obviously reduced. It also improved the The harsh stress environment in the contact area between the conductor and the hardware. Thus, the conductor is free from destructive vibration and fatigue. The practic e proved that the pre-twisted metal fittings have superior fatigue resistance. They can prolong the service life of the metal fittings and wires.
Simple and Quick Installation
Free install without installation tools, light weight, easy to carry and transport. These improved the installation speed of metal fittings. It also reduce the labor intensity of workers and improve labor efficiency. Under normal circumstances, skilled workers can install a pre-twisted metal fittings only a few minutes. Since it is installed by hand, the installation quality can be checked . The installation inconsistency caused by the use of tools by the installer is eliminated. These characteristics make it more cheap.
High Efficiency and Energy Saving
Ferromagnetic materials have hysteresis and eddy current loss. The research and energy consumption underdstandings of ferromagnetic material fittings are not enough. Thus, some of the metal fittings used in the past a large number of this material, fittings energy consumption is serious. With the rapid development of Chinese economy, the power transmission capacity greatly increased. Hence, it is urgent to use energy-saving fittings. Many pre-twisted metal tools such as pre-twisted hanging wire clips are made of aluminum alloy materials. They not only meet the mechanical performance requirements of the metal tool line, but they also have low consumptions.
Strong Applicability
Pre – patterned fittings can be applied to the following wire and strand:
galvanized steel wire,
aluminium – clad steel wires,
aluminium strand,
aluminium alloy wire, and
steel conductor steel reinforced aluminium strand. It’s also useful in high-temperature conductors, Paraben conductors, dielectric self-supporting optical whiskers (ASS), ground composite optical group (OGW), and other applications . It can be applied to all overhead lines.
Strong Corrosion Resistance
Pre-grain fittings are generally made of the same material as wires. The materials can reduce the electric corrosion candle. The corrosion is caused by different metals in the electrical environment. They prolong the service life of fittings as well.
Use in the Heavy Icing Area
Pre-twisted metal fit around the wire on the line. This is because the grip length can be distributed evenly, and no bolt directly on the wire. Thus, the utility model has more protective effect on the wire than the bolt-type fittings. It is not easy to cause the wire breakage as well.
The Future
Pre-twisted fittings have been developed for various voltage levels of transmission lines and put into use. Its mechanical properties and life are higher than ordinary cast iron fittings. This can be widely used in transmission, substation line construction and transformation, and has a broad market. The length of distribution line in our country is about 20 million meters. According to the calculation of 10 sets (30 pieces) fittings per kilometer, the market potential is 600 million pieces. The annual energy savings from replacing 10% of ferromagnetic material fittings with pre-twisted fittings can reach 6 billion kwh.
