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Typical Defects In Construction Of Carbon Fiber Conductor And Precautions For Operation
Feb 01, 2018

Carbon fiber conductor is called carbon fiber composite core aluminum strand (ACCC), the wire from the beginning of this century has been used only a short more than 10 years, has a certain degree of application experience. Carbon fiber conductor has the characteristics of high strength, light weight, high elastic modulus, small linear expansion coefficient, small sag, small line loss, large load flow (high allowable temperature), corrosion resistance, long service life and so on. Especially suitable for the coastal, mining area corrosion intensity, high pollution intensity, the use of wire easy to dance environment.


The development background of the wire is that the transmission capacity of the original line can not meet the rapid growth of the load, and it is imperative to replace the wire or new line with larger section and large load flow. The traditional method of dismantling old lines, rebuilding towers and erecting new conductors is costly, the long duration, or the difficulty of land requisition under the original route, lead to the new line will not be able to use the original line channel, to the power grid planning and construction brought great difficulties, to a certain extent, improve the project cost and prolong the construction period; long time power failure during the erection of the line , but also greatly affects the power supply reliability and equipment availability factor. In order to solve the above contradictions, it is the only way to find a kind of engineering construction method which can not only use the original line channel but also can reduce the tower transformation to a great extent and increase the transmission capacity of the transmission line greatly.


Carbon fiber conductors have many of his advantages, but also has his shortcomings, such as most carbon fiber conductor carbon fiber core single core (it is understood that now in the development of carbon fiber core stranded wire), the construction is easy to damage, because in the aluminum inside, it is not appropriate to find, damaged after the operation will be left behind a little security risks. Today's small series on the collection of some of the problems prone to share the case with everyone, mainly in the construction phase, and on the operation of a number of considerations to do a simple explanation.


Defect Type 1: Surface burr


Introduction: A 500kV overhead transmission line capacity increase transformation, the original steel core aluminum stranded wire replacement carbon fiber wire. In the construction, the carbon fiber lead wire arrives, carries on the opening acceptance to discover the wire surface to prick.

Reason Analysis: The factory produces the craft to have the flaw in the processing process, causes the wire surface to appear the burr.

The result: the circuit after the operation will cause corona and cutting-edge discharge phenomenon.

Suggestion: The goods should be inspected by the plate after arrival.


Defect Type 2: broken stock


Introduction: A 500kV overhead transmission line capacity increase transformation, the original steel core aluminum stranded wire replacement carbon fiber wire. In line construction, found that the conductor has broken strands, the broken stock did not find the construction of the force traces.

Reason Analysis: The factory produces the process to have the flaw, causes the factory wire to appear the broken stock.

Consequences: The line after the operation will produce scattered stocks and the phenomenon of throwing shares.

Proposal: Material arrival should be carried out by the plate, the three-span paragraph should focus on acceptance.


Defect Type 3: "Lantern", drum kit


Introduction: A 220kV transmission line increase capacity renovation project, the original 1XLGJ-400/35 steel core aluminum stranded wire replacement for 1xjrlx/t-400-type carbon fiber wire. In the line construction process, the wire "lantern", drum bulge phenomenon.

Reason analysis: Carbon fiber wire is made from inner carbon fiber core and outer aluminum wire, carbon fiber conductor in the exhibition or tightening process, due to the role of tension, carbon fiber wire surface of the aluminum wire will be "Creep elongation" (aluminum line will have a gap between the strands, force to make the wire strands between the tighter, the gap becomes smaller, Although the length of the conductor is variable, but the whole conductor is stretched, the inner carbon fiber mandrel is characterized by high strength and small deformation. The outer aluminum wire and the inner layer of carbon fiber mandrel will occur relative slippage, when the slip is obstructed or one side of the sheet-clamping clamp is completed, will lead to carbon fiber conductor surface aluminum stock appears "lantern" (drum kit).

The result: (1) carbon fiber conductor aluminum wire appears "lantern" (drum kit), for the operation of the line, generally difficult to repair, aluminum wire after loose also lead to long-term exposure of carbon fiber core in the air, if the operating environment is bad, to the carbon fiber core disadvantage; (2) The aluminum line appears "Lantern" (drum kit), due to the changes in the tension during the operation, will make the surface of each layer of aluminum wire is uneven, resulting in aluminum wire broken stock.

Recommendations: (1) The various wire manufacturers in the process of the technical indicators are not the same, will lead to the end of the wiring of finished wire, the degree of tightness is not the same, before the operation should be carried out by the manufacturers technical disclosure, in strict accordance with the operation requirements of manufacturers to show the tightening of the Wire; (2) in the construction process of the tight line hanging line should use special pre-stranded Reduce the use of pull head and card wire, avoid the phenomenon of stress concentration, (3) in the construction of large resistant section, in the tight line painting before printing, in order to meet the length of the section line, should be tight line side of the wire open after the end of the line, so that the "creep elongation" of the aluminum line as far as possible in the open break away.


Defect Type 4: Disconnection


Introduction: A 220kV transmission line capacity increase transformation, the original 2XLGJ-300/25 steel core aluminum stranded wire replacement of 240/30 double split carbon fiber composite core aluminum stranded wire. During the construction of the wire line, all the wires in the air line are broken from the Crimping area (near the pipe mouth) of the cable clamp after hanging.


Causes analysis: After the correlation test, the dissection disconnection line clamp and so on to verify the disconnection reason, from the test conclusion analysis, the main existence carbon fiber conductor's radial withstand pressure test unqualified question. National standard GB/T 29324-2012, National network standard Q/GDW 1851-2012 all require radial pressure-resistant standard for "interception length is not less than 100mm composite mandrel, to 1mm/min to 21mm/min loading speed smoothly loaded to destroy, The composite mandrel shall withstand pressure not less than 30kN, its end should not crack and desquamate "), but the test of carbon fiber wire does not meet the requirements, the model wire suppliers themselves to produce carbon fiber core can not meet the standard requirements, the current GB on carbon rods in the radial pressure test requirements, The vast majority of domestic suppliers only φ7.5 and above the specifications of carbon rods can be met, the Φ6 carbon rod for the radial pressure test is difficult to achieve 100mm test piece is not less than 30kN requirements. Combined with the relevant test conclusions and investigation, the causes of disconnection are mainly concentrated in the process of crimping and other pressing process problems, as well as the quality of wire products.

Result: Disconnection

Recommendation: Carbon fiber wire in the construction process should strictly implement the "carbon fiber composite core overhead conductor construction technology and acceptance guidelines (for trial)" in the relevant provisions.


Defect Type 5: lateral scratch


Defect Description: A 500kV transmission line capacity-increasing transformation, the original LGJ-400/35 steel core aluminum stranded wire replacement for jlrx/f2a-460/40-26 carbon fiber wire, line completion and acceptance of the process found that lead wear, cracks.

Reason analysis: The wire in the transportation, unfolds the process to be sharp material scratches the surface to cause the carbon fiber outer layer soft aluminum scratching, rubs the wound.

Consequences: Affect the appearance of quality, but also produce corona, serious when the wire will burn, and even cause disconnection accident.

Proposal: Material arrival should be carried out after the acceptance, wire exhibition should be a file after acceptance.


Defect Type 6: bulk stock


Defect Description: A 500kV transmission line capacity-increasing transformation, the original LGJ-400/35 steel core aluminum stranded wire replacement for jlrx/f2a-460/40-26 carbon fiber wire, line completion and acceptance of the process found in the conductor running stock.

Cause analysis: During the display of the wire during the spread of the pulley because of the point of view too small or pulley model mismatch caused by the line when the extrusion and pine stock; After the completion of the Wire exhibition, attachment installation when the wire is too tight twist leads to pine stock.

Consequences: Affect the appearance of quality, but also produce corona, serious when the wire will burn, and even cause disconnection accident. It also affects the conductor strength.

Proposal: Material arrival should be carried out after the acceptance, wire exhibition should be a file after acceptance.


Defect Type 7: Wear


Defect Description: A 500kV transmission line capacity-increasing renovation, the original LGJ-400/35 steel core aluminum stranded wire replacement for jlrx/f2a-460/40-26 carbon fiber wire, the line completion of the acceptance process found in the end of the Strand has annular wear marks.

Reason analysis: One is the wire pre-stranded wire binding when the last few stocks are not easy to position, the use of screwdriver and other tools when the scratch, and the second is the pre-stranded wire binding found not to remove the pre-stranded when the construction protection is not in place damage leads.

Consequences: Affect the appearance of quality, but also produce corona, serious when the wire will burn, and even cause disconnection accident. It also affects the conductor strength.

Suggestion: We should focus on strengthening the acceptance of the wire near the pre stranded wire.


Summary


Through the above 3 engineering 7 kinds of defects Summary, found the following two problems:


1. Carbon fiber quality problems, because the manufacturers do not strictly according to the corresponding rules of processing, resulting in partial product parameters unqualified, to the construction process and even the operation brought unpredictable hidden dangers.

2. Poor construction technology, some of the construction units are still used by the traditional wire construction methods, resulting in carbon fiber wire drum bulging, broken strands and even disconnection.

The above two problems to run a certain security risks, in particular, the problem of product quality, according to the current case, the main carbon rod does not meet the requirements of the specification, however, carbon rods are part of the load, unqualified carbon rods will lead to the mechanical performance of the wire drop, even if the construction process is good, run the process of encountering bad conditions, Also very easy to break down accident.


As the operating unit, in the use of carbon fiber need to pay attention to the following aspects:

1. As the carbon fiber conductor although the development of more than 10 years, but in the project application is not much, lack of operational experience, the important leap, large span does not recommend the use of carbon fiber wire, can choose the same load current capacity of aluminum alloy core high conductivity aluminum stranded wire.

2. Strict initial examination, especially capacity-increasing projects, must have a detailed selection of wire comparison options, carefully selected carbon fiber wire. To determine the use of carbon fiber conductor engineering, understand the design unit to provide carbon fiber conductor positioning temperature and the maximum allowable temperature, to understand the corresponding wire sag characteristics, as well as the selection of wire connectors and so on.

3, due to the important leap once the problem, the impact is too large, in order to important across the section can be safely and reliably run, important across the principle must not use carbon fiber wire, can use the same load capacity of aluminum alloy core high conductivity aluminum stranded wire.

4. Strict implementation of the carbon fiber composite core overhead conductor construction technology and acceptance guidelines (for trial), grasp the construction unit of the crimping process, check the quality of the crimping, 500kV line to do the line by file, 220kV line to take the drone along the way, do a good job in the middle and the completion of the link acceptance, the acceptance of the close.

5, the construction unit in the construction process and carbon fiber conductor has hard contact with the place, such as card wire card in the position of the wire, etc., put forward traces of record requirements to avoid problems after the wrangling.

6. For the transport of carbon fiber lines, the maintenance process as far as possible to avoid the use of speed line, to prevent the occurrence of aluminum stock deformation, at the same time properly prepared some suitable for carbon fiber wire broken strands of high temperature pre-twisted repair bar.

7, the exploration can detect the core rod breakage practical method, because the core bar at present is the single core, from the breakage starts to the disconnection, temporarily does not have the effective detection means, therefore, explores the effective detection method, grasps the carbon rod breakage Development The law, is imperative.

8, the promotion of carbon fiber conductor operating life cycle concept, from the beginning of the operation, the overall grasp of the operation, evaluation of the operating conditions, to infer the remaining operating time, is also a key issue, because once the carbon fiber wire into the end of life, the operating unit is equivalent to a time bomb, so, it is recommended from the life cycle perspective , to master the best running time of carbon fiber wire, to provide strong support for subsequent replacement, to avoid major failure after the replacement.

As a new type of wire, carbon fiber conductor has very good effect on the capacity-increasing transformation, it is expected that in the future industry, the old line in the capacity-increasing transformation will be used in large quantities, but because of the current lack of operational experience, for such products, operating units generally conservative attitude, because of disconnection and other failures will bring huge security pressure to the operating unit.


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