Precautions for purchasing steel core aluminum stranded wire

The overhead of the transmission line facilitates our lives, and the steel core aluminum stranded wire is a necessary product. From the name, we can see the structure of this aluminum stranded wire. The first thing we need is the aluminum wire as the basic part. Secondly, steel wire is needed. The two are combined by twisting technology. It has a high sales volume in the society. Many departments will use it. Generally, companies that produce cables will produce this product. Quality is an issue that cannot be ignored. When choosing, we should pay attention to the following points.
Everyone knows that if there is a problem with power transmission, it will have a huge impact on us. Therefore, the choice of steel core aluminum stranded wire is very important. Only high-quality stranded wire can ensure the stability of power transmission from the source. However, ASTM 477 MCM ACSR Cable manufacturer on the market There are many. Everyone needs to be screened when buying. The relevant departments of each city will select excellent companies every year. Therefore, we can conduct inspections based on the evaluation of the government. In order to support some companies, the government will also give With a certain amount of assistance and support, this type of enterprise is generally more reliable.
At the same time, we should also understand the material composition of the strands, such as the characteristics of steel and aluminum, so that we can compare them through cross-sections.


Generally, when determining the price, it needs to be considered together with the quality issue. If only a single consideration is taken, it is very imperfect. If you choose a stranded wire of unqualified quality, the later maintenance work will also cost a lot of money. At present, the branding of the stranded wire is still developing nationwide, and we need to understand the knowledge of the stranded wire and then add it. Screened. Be sure to investigate more from the market.
How to choose power cables and steel-cored aluminum stranded wires used in substations? Transmission lines or power lines, due to year-round operation, require comprehensive consideration of investment and operating economy, so you need to choose cables or bare wires based on economic current density The specifications and models.
From the user’s distribution transformer to the user’s electrical equipment, the wires used are generally not in continuous operation for a long time, and the number is small, so you can choose according to the maximum current.
Regarding economic current density: Because the size of the wire cross section affects the line investment and the power loss in operation, on the one hand, in order to save investment, the wire cross section is required to be smaller; on the other hand, in order to reduce the power loss, the wire cross section is required to be larger. Comprehensive consideration, determine a more reasonable wire cross-section, called the economic cross-sectional area, and its corresponding current density is called the economic current density.
It can be understood in this way that economic current density means that the power loss, maintenance cost, and construction investment are the most economical in the operation of the transmission line. According to different annual maximum load utilization hours, different materials and safe current values ​​per square millimeter are selected.

The role of shielded cables

Shielded cable refers to a overhead cable with electromagnetic induction shielding characteristics that is manually braided by iron wire or covered by steel tape. It is suitable for transformers and similar machinery and equipment that must be shielded from electromagnetic induction signals. Cable shielding means that the braided wire of the net-like structure on the surface of the cable has been grounded at a single end, which can make the external electromagnetic wave radiation and electromagnetic field radiation source immediately enter the ground without affecting the inner cable.
Generally used for routes with high frequency and low data signal pulse signals, such as cable digital TV, the wires from the inverter to the motor, analog input wires, and some influential transmission routes, such as electronic computer shielded cables Wait. As long as the cables with shielding layer are called shielded cables, power engineering cables and control cables can all be shielded. Computers and dashboard cables are generally shielded to avoid the influence of external electromagnetic signals.


Shielded cables are suitable for motor connection cables, especially for variable frequency speed regulators and servo motor drives. They are based on all polyurethane material sheaths and copper core cable insulation applications. They are suitable for cable drag chains, especially when applicable. It is used in extremely harsh software environment and places with corrosive coolant and grease.
In the case of single-ended grounding of the shielding layer, there is an induced voltage between the non-grounded metal shielding layer and the ground. The induced voltage is positively related to the length of the cable, but the shielding layer has no electric potential difference electric field basis. Single-ended grounding is to use the potential difference to suppress the potential difference to eliminate the interference signal. ? This kind of grounding method is suitable for short and long routes, and the induced voltage corresponding to the length of the cable cannot be higher than the working voltage. The existence of electrostatic induction induced voltage

The main role of PVC in overhead cable

In the late 1990s, the demand for high-performance fire-retardant cable for sale rubber was increasing, especially the development of the overhead cable industry and auto parts manufacturing industry, which drove the consumer demand for rubber-based CPE. Rubber CPE is a special synthetic rubber with excellent comprehensive performance, heat-resistant oxygen ozone aging, and good flame retardancy. Mainly used in: wire and cable (cables for coal mines, wires specified in UL and VDE standards), hydraulic hoses, automotive hoses, tapes, rubber sheets, PVC profile pipe modification, magnetic materials, ABS modification, etc.
Among them, the application mainly has the following functions:
1) Reinforcing filling system
CPE is a kind of non-self-reinforcing rubber, and it needs a reinforcing system to achieve better strength. Its reinforcing filling system is similar to general rubber. The reinforcing agent is mainly carbon black and white carbon black. White carbon black can improve the tear resistance of CPE, and it can form a meta-white system to improve the adhesion between CPE and the skeleton. . CPE has high filling properties, and the filling system mainly includes calcium carbonate, talcum powder, clay and so on.


2) Plasticizing system
Ester plasticizers are the most commonly used plasticizers for CPE, such as dioctyl phthalate (DOP) and dioctyl adipate (DOA). Their solubility parameters are close to CM and their compatibility is good. DOA and DOS are used in rubber compounds to give them excellent cold resistance.
3) Stable protection system
When CPE is heated or vulcanized (non-peroxide vulcanization system), hydrogen chloride will be released. Therefore, stabilizers with acid absorption should be used in the formulation, such as calcium stearate, barium stearate, tribasic lead sulfate or Magnesium oxide.
4) CPE curing system (important)
CPE is a saturated rubber, and the general common sulfur vulcanization system cannot effectively vulcanize it. The thiourea system is the earliest application of CPE curing system. The most effective one is Na-22, but Na-22 has a slow curing speed, poor aging performance, and high compression set. Moreover, Na-22 is a serious carcinogen. Produces an unpleasant smell, and its use abroad has been restricted.

A small solution for repairing damaged insulated and sheathed cables

1. Scope of application
When the PVC insulation layer and sheath layer of the overhead cable have local defects, they are allowed to be repaired, such as broken glue, collapsed pits, disconnections, wrinkles, bumps, ears, edges, breakdowns, joints, etc.
2. Use the same plastic strips, skins, blocks and tubes for materials and equipment raw materials. The raw materials should be smooth, clean, and free of other defects. The instruments used are fine wooden files, knives, scissors, pliers, screwdrivers, copper sheets or flat and smooth cable paper. The power of hot-air plastic welding torch, electric soldering iron and welding torch for plastic welding is above 300W.
3. The repair method of local defects
Repair methods such as breakdown points, holes, and collapse pits. Repair defects with a knife and cut into plastic blocks of the same size with a slope of 45°, place them on the repair area, fix them with pliers or a screwdriver, and then use a hot air speed welding gun to continuously weld them, and use copper sheets to compact and compact them. ,To flatten. When welding plastic, pay attention to the hot air temperature of the welding torch not to be too high to avoid scorching of the plastic in the repaired area. The repaired defect is tested by a spark machine, and it is qualified if it does not break down. Use a knife to cut the defect of the plastic layer into a slope of 45°, remove the plastic block or strip with the same shape, color and thickness, and fix it with pliers or a screwdriver. After completion, connect it with a hot-air speed welding gun, then use a copper sheet to compact, compact, flatten, and finally pass the spark machine test, and it is qualified if it does not break down. Scrape the plastic defect flat with a knife, fill in the recessed part with the same plastic strip under the action of a hot-air plastic welding gun, and then flatten, compress and compact the defect repair place with a copper sheet. After the spark machine test, no breakdown Is qualified.


4. The repair method of large joints
1) Repair of general large joints: use a knife to cut the plastic layer on both sides of the broken plastic layer into a slope of 45° along the circumference, and take it clean, the color and thickness are the same, and the length and outer diameter are the same as the broken glue. The plastic pipe is cut on one side of the pipe to form openings with an angle of 45° to each other. Put it at the glue break, tie it at equal distances with a thin copper wire, and then use the same plastic strip to be welded by a hot-air plastic welding torch. After welding, use copper sheet to compact, compact and flatten. It is qualified if it does not break down after the spark machine test.
2) Repair of large joints in the production process: During the production process, due to other reasons, the temporary stop, the sheath is disconnected, and the joint can be continuously connected. The method is to cut the plastic sheath into a circular slope with a 45° angle, retreat to the machine head, extend it into the mold core mouth for 30mm, and then run the glue. After the glue is run, the crew will cooperate with each other and drive the car. Connect the plastic layers by hand, and then reshape and repair.
3) Quality defects appear in the longer length of the cable sheath from one end, and most of the sheath of the other broken end is good, and the cable length is fixed, and the large joint repair method in the production process can also be used. Only after removing the defective end of the sheath, select a larger mold on the extruder, according to the process, first extrude the end of the sheath, and gradually increase the traction speed to the large joint so that the sheath at the interface gradually It is thinned and wrapped on the original sheath that is cut into a slope shape, and it will be reshaped and repaired after the machine is off.

YC cable and BV cable

YC rubber-sheathed cable stands for heavy-duty general-purpose rubber-sheathed flexible cable, which is a kind of rubber-sheathed cable. YC cable is suitable for household appliances, power tools and various mobile electrical equipment or light mobile electrical equipment with AC rated voltage below 450/750V, or for temporary construction on construction sites, and can withstand large mechanical external forces. The long-term allowable working temperature of the core should not exceed 60°C.
Y stands for rubber insulation and C stands for heavy-duty cables. The sheath inside is also rubber insulated, and the conductor is copper wire. Rubber cables are divided into heavy cables (yc cables), medium cables (yz cables) and light cables (YQ cables). The insulating layer of a good YC cable is made of pure natural rubber, and the conductor is made of oxygen-free copper rods with good conductivity. However, most of the products in the current market are more or less unable to achieve this quality.


BV wire and cable knowledge
BV cable: Copper core PVC insulated wire and cable, referred to as plastic copper wire, is the most commonly used wire in wire and cable, and it is also the wire that we touch most in daily life.
Conductor material: oxygen-free copper
Insulation material: PVC
Color: black, yellow, blue, red, brown, white, etc.
Working temperature: 60 degrees, 70 degrees, 95 degrees
Rated voltage: 450/750V
When laying the cable (line), the ambient temperature shall not be lower than minus 15 degrees.
Cable allowable bending radius:
Cable outer diameter (D) less than 25mm is not less than 4D;
Cable outer diameter (D) of 25mm and above should not be less than 6D.
The finished overhead cable (wire) and cable core must pass the power frequency spark withstand voltage test.
The mark of the cable (line) must be implemented in accordance with the GB6995 standard, and the mark should be clear and scratch-resistant.
National standard bv wires and cables are used for electrical installations, meters, decorations, telecommunications equipment, power lighting and lines with AC rated voltages of 450/750V and below or DC voltages of 1000V and below, and can be covered or covered in dark.
Product standard: GB5023.3-1997 JB8734-98 conforms to the IEC CCC standard, the national standard bv cable production certificate must be printed with the 3C certification mark.

What kind of wire and cable is safer?

Electricity is closely related to our lives, and it brings us all kinds of conveniences in life. Therefore, wires and cables are indispensable to people’s lives, because they are not only related to people’s electricity use, but also related to the safety of electricity use. So what kind of wire and cable manufacturers produce safer wires? Will they be favored by many people?
1. High-quality Overhead cables are safer and can withstand high temperatures. It is also resistant to cold, so it can be used well in summer or winter. This will not affect people’s normal electricity consumption and ensure that people can better use electricity under any circumstances.


2. It has a longer service life. Generally speaking, the wires produced by good wire and cable manufacturers can continue to be used for up to ten years or even longer. Therefore, it is very convenient and reliable, and does not require frequent replacement. This saves a lot of trouble and, of course, also saves a lot of human and material resources. The more secure wire and cable manufacturers, the products produced will be more popular with people.
3. There are many wire and cable manufacturers, but the good and the bad are still mixed. In order to save production costs, some small

manufacturers often use poorer materials. However, the quality of the products is relatively guaranteed for large manufacturers with a relatively long history and a relatively well-known brand. Each manufacturer produces many types of MV abc cables, some are for commercial use, and some are for household use, and there are corresponding models for products at each price. Buyers need to choose according to their own requirements. Before purchasing a product, you must carefully look at the production certificate, inspection certificate, etc. of the wire and cable manufacturer and the product. This is the easiest and most intuitive way to check whether the product is qualified.
After seeing the above, the wire and cable manufacturers remind everyone to use wire and cable safely, from choosing wire and cable manufacturers, installation, to daily living habits, daily maintenance, etc., all aspects should be done. In place.

How to find broken overhead cables

The core of the cable is an important part of overhead cable. We transmit information through the core of the cable. If the core of the cable is broken, it will bring a lot of troubles and dangers. If the core of the cable is broken, how should we check? Someone may I would say to take a multimeter, but if it’s a big project, can’t I also use a multimeter?
One, the method of energizing the capacitor
Some cable factories usually use the capacitance comparison method to find the approximate location of the disconnection. Using continuous power-on method to accurately determine the disconnection point of the cable, the efficiency of this method is very low. Generally, it takes about one and a half hours to find a disconnection point. With this method, it is almost impossible to find a broken core for flame-retardant cables whose shielding, armoring, and sheathing processes have been completed. If it is not done properly, the flame-retardant cable will be scrapped. This method is basically no longer needed.


2. Combination of capacitance method and induction method
This method is used for the broken core of the cable core, which requires that LV ABC  cable core is not covered with a metal layer and there is no extruded sheath. When searching, first use the capacitor to find the approximate location of the cable disconnection, and then use the induced voltage method to accurately find the disconnection point. This method is very simple and quick, and it is also the most used method at present. The induction voltage method is to connect one end of the broken core of the cable with an AC voltage of 650V, and the other end and other cores are grounded, and then test with a sensor pen that can emit light signals. When the sensor pen slides over the broken core during the test, The signal will change, so that the cable break point can be accurately found.


3. Combination of constant current source and bridge method
This method is used for finished cables or cable cores that have been coated with a metal layer. Use is to find the method is to burn the insulation at the broken core of the flame-retardant cable with a constant current source and breakdown, and then use the bridge method fault locator to accurately locate the fault point, which is also a frequently used method.

What are the types of coaxial cables

Coaxial cables can be divided into two basic types, baseband coaxial cables and broadband coaxial cables.
Baseband coaxial cable
The shielding layer of the baseband coaxial cable is usually a mesh structure made of copper, and its characteristic impedance is 50Ω. This cable is used to transmit digital signals, and the commonly used models are generally RG-8 (thick cable) and RG-58 (thin cable). The most intuitive difference between a thick cable and a thin cable is the cable diameter. Thick cable is suitable for relatively large local networks. It has a long standard distance and high reliability; however, the thick cable network must be equipped with transceivers and transceiver cables, which is difficult to install, and therefore the overall cost is high. On the contrary, the thin cable is relatively simple and the cost is lower; but because the cable has to be cut during the installation process, it is easy to cause the hidden danger of poor contact when there are many connectors.

 


Whether it is a network connected by a thick cable or a thin cable, the point of failure often affects all machines on the entire cable, and it is troublesome to diagnose and repair the fault. Therefore, baseband coaxial cables have been gradually replaced by unshielded twisted pairs or optical cables.
Broadband coaxial cable
The shielding layer of broadband coaxial cable is usually stamped from aluminum, and its characteristic impedance is 75Ω. This kind of cable is usually used to transmit analog signals. The commonly used model is RG-59. It is a standard transmission cable used in cable television networks. It can transmit multiple channels of TV signals in one cable at the same time. Broadband coaxial cable can also be used as the transmission medium of some computer networks.

Causes of wire and cable oxidation

opper is a transition metal with an atomic number of 29, a density of 8.92g/cm3, and a melting point of 1083.4. It has good thermal and electrical conductivity, so it is widely used as ACSR  conductor. However, in humid air, the surface of copper chemically reacts with oxygen to form Cu2(OH)2CO3, which is patina. Usually, the copper oxidation of the cable factory manifests as the surface blackening, which is the surface oxidation phenomenon of copper conductors that plagues many cable companies and users. However, in addition to the production process, there are various factors that cause the wire and cable to turn black during use.

   1. Improper handling of cable joints
The cable connector is not sealed properly, which causes the air to invade the copper conductor and turn black. Most of the masters who pack the cable head will use insulating tape to seal it directly. In fact, the insulating tape is not waterproof and there is a layer of glue on it. Make the cable black.
  2. Moisture insulation
   This kind of situation is also very common, and it usually occurs at the cable joints in direct burial or piping. If the cable connector is not made qualified and the connector is made in a humid climate, water or steam will enter the connector, and the cable will turn black over time. This phenomenon is more common in the hot summer, because the humidity in the air in summer is relatively high, and the temperature will accelerate the oxidation reaction of the copper conductor.
  3. Construction and installation
  Some users do not standardize construction when laying and installing cables, which is easy to cause mechanical damage; civil construction on directly buried cables is also very easy to damage the cables in operation. If the copper conductor of the cable is locally damaged, it will be oxidized and blackened if it is exposed to moisture or exposed surface underground for a long time.
In addition to the reasons for the blackening and discoloration of the cable ports, copper is prone to blackening but also shows a more important problem, that is, the poor quality of copper, which accounts for most of the cable cost. If the quality of the copper is not good, there are other problems. After taking protective measures, the copper is still oxidized and blackened, and such cables should be replaced in time.

Causes of power cable failure

1.The insulation has deteriorated due to aging. The insulation of power cables is subject to thermal, chemical and mechanical actions that are accompanied by electrical action, so that physical and chemical changes occur in the insulating medium, and the insulation level of the medium is reduced. The insulation is damp. Intermediate joints or terminal heads are damp due to the top and bottom sealing of the structure or poor installation quality; defects such as blisters or cracks are left when the abc cable is covered with lead, which will also make the cable damp.


2.The cable is overheated. There are many reasons for the overheating of the cable. The internal cause is that the internal air gap of the cable insulation causes local heating, which causes the insulation to be carbonized. The external cause is the cables installed in densely-cable areas, cable tunnels, etc. The aac cables passing through the drying pipes and the cables close to the pipes will cause accelerated insulation damage due to cable overload or poor heat dissipation.
3.mechanical injury. Mainly refers to cable damage caused by external force. This is mainly due to mechanical action such as vehicle vibration, which deforms the cable. Deformation of the cable leads to excessive bending, damaging the internal insulation or causing an air gap inside the insulation.


4.Corrosion of the protective layer. The lead bag of the cable corrodes due to electrolysis or chemical action. Due to the different nature and degree of corrosion, the lead bag has red, yellow, orange and light yellow compounds or fine pores like sponge.
5.Overvoltage causes breakdown. Atmospheric overvoltage and internal overvoltage cause the stress on the cable insulation to exceed the allowable value and cause breakdown.
6.Moreover, analysis of actual failures shows that many outdoor terminal head failures are caused by atmospheric overvoltages.
7.Problems in the design and manufacturing process of the intermediate joint and terminal head. When the semiconductor is peeled off, the internal insulation is damaged or there are particles, dust and other impurities on the insulation surface; poor sealing of the cable head causes moisture inside the insulation, resulting in damp insulation; non-standard cable joint technology and non-standard sealing, resulting in grounding; high humidity in the production environment , Causing the insulation integrity of the production part (cable head) to be damp; the cable grounding error occurs, causing the grounding wire to form a circulating current or break.