Factors Affecting Cable Performance and Placement in Wiring

Factors affecting Aerial Bundled Cable (ABC) SANS 1418 Standard and placement in the wiring six factors affecting cable performance:

  • Ultraviolet (UV)– Do not use cables without UV protection in direct sunlight.
  • Heat — The temperature of the cable in the metal tube or groove is very high, and many polymeric materials will degrade their service life at this temperature.
  • Water — moisture in a twisted-pair cable on a LAN can increase the capacitance of the cable, thereby reducing the impedance and causing near-end crosstalk problems.
  • Mechanical damage (repair cost)– Cable repair is very expensive and requires at least two terminations at each break point.
  • Grounding — If the shielding of the cable needs to be grounded, the appropriate standards must be complied with.
  • Total length of routing (not just between buildings)– Outdoor LAN twisted pair cables are used between buildings and the total length is limited to 90 meters. For 100Mbps or 1000Mbps networks, the paved distance cannot exceed this limit. If the laying distance is between 100 meters and 300 meters, optical cable should be chosen.

Is the cable placed in:

1.Under the eaves. 4/0 Aluminum Cable can only be used when they are not directly exposed to sunlight or ultra-high temperatures. Standard LAN cables are recommended.

  1. Exterior wall. Avoid direct sunlight exposure to the wall and man-made damage.
  2. In pipes (plastic or metal).If in pipes, pay attention to the damage of plastic pipes and the heat conduction of metal pipes.
  3. Hanging applications/overhead cables. Consider cable sag and pressure. What kind of binding do you plan to use? Whether the cable is exposed to direct sunlight.

  1. It is directly laid in the underground cable trench, which is the least controlled environment. The installation of cable trench should be checked regularly for dryness or humidity.
  2. Underground pipes. In order to facilitate future upgrades, cable replacement and isolation from surface pressure and surrounding environment, auxiliary pipe isolation, auxiliary pipe is a better method. But don’t expect the pipes to stay dry forever, which will affect the type of cable you choose.

Cable Quality Defects and Their Elimination Methods

The crosslinking degree (thermal elongation) is not acceptable

If the crosslinking degree is not up to the standard, the thermal and mechanical properties of the cable are not qualified and can not meet the requirements of the working temperature of 90℃. The reasons for the unqualified crosslinking degree are as follows: first, the formula is unqualified, and the type and proportion of the complex agent is improper, so the formula should be adjusted to solve the problem; Two is the vulcanization process is not appropriate, such as the pressure is too low, the line speed is fast, the cooling water level is high, The solution is to first find out what the reason is, it may be one or several reasons exist at the same time, and eliminate the reasons.

Disqualified structure and appearance

(1) The thinnest point of insulation layer thickness is lower than the minimum value specified in the standard, or the average thickness is lower than the nominal value. The reasons for the unqualified insulation thickness are high linear speed, small amount of extruder, improper selection of mold, etc.

The solution is to reduce the linear speed or extruder speed, adjust the size of the die.

(2) eccentricity

The reason for the eccentricity is that the mold is not adjusted or the suspension control has changed after being collected and adjusted.

The solution is to keep the drape as stable as possible during driving.

The cable outside the bamboo joint is caused by the electrical, mechanical system causes the traction speed is not stable, the second is the die core is too small, or the conductor outside diameter is not uniform.

The elimination method is to check the mechanical, electrical system, troubleshooting. Properly adjust the size of the core, control the outer diameter of suburban counties as uniform as possible, more than the process requirements of the strand can be used.

Surface scratch

(1) the ACSR conductor encounters the upper or lower wall or foreign body in the vulcanized pipe. Therefore, it is required to adjust the suspension degree, try to make the wire core move in the middle of the crosslinked pipe, and clean it up in time when foreign bodies are found.

(2) there is burnt material on the outer edge of die sleeve. The solution is to adjust the temperature of the mold sleeve when starting the car to prevent overheating. Once burnt, it should be stopped immediately, or it will not get better by itself.

impurities

Most of the impurities in insulating material and semi-insulating material are brought into the process of mixing and extruder feeding. During the operation, strict attention should be paid to the cleaning of the material to prevent external impurities from mixing. Another impurity is coke pimp, its existence affects the performance and service life of the cable, so the temperature is strictly controlled when mixing and extrusion, to prevent the occurrence of coke phenomenon.

Air bubbles

There are two possible causes of air bubbles in insulation. One is caused by extrusion. The solution is to choose the right mold. The shielding layer has bubbles, the main reason is that there is water in the material, before extrusion should be dry, two is not sufficient cooling, then there will be as follows, in the isometric circumference of the line core appears a circle of bubbles.

The elimination method is to strengthen cooling, rise the water level and lower the temperature of cooling water.

(1) Cable performance is not up to standard

Disqualification of free discharge and dielectric loss

Free discharge and dielectric loss unqualified causes are very complex, it has to do with external shielding. Whether the insulation contains bubbles and impurities, and the properties of raw materials are closely related. Elimination method is to keep raw materials clean, strictly according to the process of production.

(2) cable insulation breakdown

Cable insulation breakdown is mainly caused by the insulation material mixed with impurities and external damage. Due to the strict avoidance of external damage, impurities should be avoided as far as possible. Semi-finished products should be strictly managed to prevent tripping and bruising.

(3) cushion breakdown

The main reason for the breakdown of the cushion is that the steel has burr, roll edge and puncture the cushion. The method to eliminate the steel strip is not equal to the unqualified quality requirements. The cushion is made of plastic belt with greater hardness, and the thickness of the cushion should be ensured.

Plastic Extrusion and Traction Speed of Cable Technology

The rate of plastic extrusion

According to the flow rate analysis of the viscous fluid in the material conveying and homogenizing section of the ABC conductor,  the flow rate of the plastic (that is, the extrusion speed) is proportional to the screw speed, and the screw speed is an important operating variable to characterize the extrusion speed in the extrusion process because of the convenience of adjustment. Therefore, in general, increasing the screw speed is an important means to improve the production capacity of modern plastic extruder and realize high-speed extrusion. But the analysis of the plastic melting length shows that the increase of the screw speed, on the one hand, increases the viscous dissipation heat due to the enhanced shear effect; On the other hand, in the absence of head pressure control, the screw speed increases, the flow rate increases, and the material stays in the machine time is shortened. Moreover, the influence of the latter is more than that of the former, and the normal extrusion process will be destroyed due to the extension of the melt length to the homogenizing section. Therefore, it is necessary to increase the screw speed to improve the extrusion speed, but also to increase the heating temperature or use the control of the head pressure to achieve the purpose.

Plastic extrusion speed or the quality of plasticizing is related to the use of plastic material and temperature control, the plasticizing temperature of various plastics is different. If you want to quickly extrude plastic, only the material is good, the temperature is appropriate, to achieve. In addition, the extrusion speed is closely related to the extrusion thickness. In the normal extrusion process, the amount of glue is large and the extrusion speed is slow. On the contrary, the extrusion speed is fast, on the premise of ensuring the quality, the extrusion speed can be appropriately improved.

Traction speed

Extruded products are dragged through the machine head by traction device, in order to ensure the quality of products, the traction speed is required to be uniform and stable, in coordination with the screw speed, to ensure the uniformity of extrusion thickness and outer diameter of products. If the traction speed is not stable, the extrusion layer is easy to form bamboo joints, and the extrusion thickness is large when the traction speed is too slow, and the phenomenon of glue stacking or empty pipe occurs. When the traction speed is too fast, it is easy to cause extruding and thinning, or even the phenomenon of degumming and leakage. Therefore, in the normal extrusion process, we must control the traction speed.

International Advanced Level of Environmental Protection Wire and Cable Indicators

Environmental protection wire refers to the material is environmental protection wire.

The material includes insulating material, conductor material and shielding material. Insulation such as PVC, irradiated cross-linked PVC (XL-PVC), irradiated cross-linked polyethylene (XL-PE), low smoke free (Halogen-free), silicone rubber, Teflon Telflon and so on. The environmental protection of insulation materials is mainly the EU’s RoHS environmental protection directive and the EU’s environmental regulations on children’s toys do not contain 6P (Non-6P), that is, does not contain phthalates. Now the most environmentally friendly is low smoke halogen-free, does not contain halogen elements.

The most common conductor material is copper. Copper has bare copper (brass, red copper), tinned copper, silver-plated copper wire, etc., which are essentially copper, but the surface is plated with other substances. Now there are copper – coated aluminum and copper – coated steel conductors on the market. If the electrical performance requirements are high, copper is the best. The environmental protection of conductors is mainly required to be free of heavy metals (RoHS).

Environmental protection cable means that it does not contain lead, cadmium, hexavalent chromium, mercury and other heavy metals, and does not contain brominated flame retardants. The environmental protection performance of the cable is tested by SGS recognized testing institutions, and it is in line with the European Union Environmental Protection Directive (ROSH) and higher than its index requirements. No harmful halogen gas, no corrosive gas, less fever when burning, no pollution of soil wires and cables.

Main technical indicators:

  1. Rated voltage: 450/750V and below
  2. The maximum permissible operating temperature of the conductor shall not exceed 70 ℃, 90 ℃ and 125℃ respectively.
  3. Cable combustion smoke density in line with GB/T 17651-1998 (equivalent to IEC1043) standard requirements, light transmittance ≥60%.
  4. Cable halogen acid content test conforms to GB/T 17650-1998 (equivalent to IEC 754-2) standard requirements.

(1) PH ≥4.3

(2) Conductivity ≤10μs/mm

  1. The flame retardant performance of the cable conforms to the requirements of GB/T 12666-1990.

6.Toxicity index of cable ≤3.

National Standard Cable

In today’s wire and cable market, product quality levels are uneven, and production companies are mixed. Many Party A simply uses price as the procurement standard, which breeds a market for substandard products. So that when users are faced with different prices of “national standard cables”, they will be at a loss, not knowing how to identify and buy national standard cables. Today’s article mainly introduces the standards and identification of national standard cables. What kind of cables are produced in accordance with national standards? How to distinguish and distinguish cables of different qualities? What kind of quality is “enterprise standard/non-standard”, “market national standard” and “protected resistance national standard”? No matter you are selling cables , Or purchasing, I believe it will be helpful to you.

What is Aerial Bundled Cable (ABC) HD 626 S1 Standard

The national standard cable, literally understood, is the wire and cable produced in strict accordance with the national standard. my country has clear regulations on the appearance, mechanical strength, insulation of the sheath, pressure resistance, wire resistance and other aspects of the cable. Different types of cables have different national standards, mainly as follows:

Irradiation cross-linked power cable (0.6/1KV) executive standard: GB/T12706.1-2008

Medium voltage cross-linked cable (6/6KV-26/35KV) executive standard: GB/T12706.2-2008

High voltage cross-linked cable (64/110KV) executive standard: GB/T 11017-[/B]2002

Control cable (450/750V) executive standard: GB9330-88

Aluminum stranded wire and steel core aluminum stranded wire (0.6/1KV) executive standard: GB/T 1179-1999

How to identify the (ABC) SANS 1418 Standard

  1. It depends on

See if there is a quality system certification; see if the certificate is standardized; see if there is a factory name, site, inspection stamp, and date of production; see if there are trademarks, specifications, voltages, etc. printed on the wires. It also depends on the cross-section of the copper core of the wire. The high-quality copper is bright in color and soft in color, otherwise it is inferior.

  1. Try

It is recommended to bend a wire head repeatedly by hand. Anything with soft hand feeling, good fatigue resistance, elastic plastic or rubber hand feeling and no cracks on the wire insulator is the best product.

  1. Weighing

Good quality wires are generally within the specified weight range. For example, the commonly used plastic insulated single-strand copper core wire with a cross-sectional area of ​​1.5mm² has a weight of 1.8~1.9 kg per 100 meters; a 2.5mm² plastic insulated single-strand copper core wire has a weight of 3~3.1 kg per 100 meters; poor quality The weight of the wire is insufficient, or the length is not enough, or the copper core of the wire is too much impurity

  1. Look at copper

The copper core of the qualified copper core wire should be purple-red, shiny, and soft to the touch.

The fake and inferior copper core wires are purple-black, yellowish or white, with many impurities, poor mechanical strength, poor toughness, and will break with a little force, and there are often broken wires in the wires.

When checking, you only need to peel off the wire 2cm, and rub a piece of white paper on the copper core. If there are black substances on the white paper, it means that there are more impurities in the copper core. In addition, the insulating layer of fake wires seems to be very thick, but in fact, most of them are made of recycled plastics. Over time, the insulating layer will age and cause leakage.

  1. Look at the price.

Due to the low production cost of counterfeit and shoddy wires, vendors often sell them at low prices under the guise of low prices and good quality when selling.

“Non-standard/enterprise standard/market national standard” and “protected resistance national standard”?

When many sales companies are asked whether they are national standard cables, they often hear words like “market national standard” and “resistance protection national standard”. Many people have a little understanding. What do these vague words mean?

National standard for resistance protection: The cable is used to energize, and the resistance value of the conductor directly affects the conductivity. If the conductor resistance is too large, the conductivity will be poor, and a large amount of heat will be generated when a large current passes, which will cause a fire. At the same time, due to the large resistance, heat will be generated and the power will be consumed inaction.

The resistance-protected cable is to ensure that the resistance value of the cable is in compliance with the national standard, but it does not guarantee that the component materials of the cable are produced in full accordance with the national standard, such as the number of conductor squares, insulation, and sheath. To put it bluntly, it means that the manufacturer can achieve safe use of cables under the premise of reducing material costs through various technological innovations (or means).

Note that two words are used here: innovation and means. Innovation refers to reducing costs through technological innovation, such as current aluminum alloy conductors, special-shaped conductors, etc., such cables reduce the price on the premise of ensuring safe use. Some manufacturers use some illegal means to reduce costs, such as using second-generation materials, reducing conductor purity, etc. Even if the resistance value of such a cable is within the standard range, its use is extremely unsafe. The cable must be checked again and again.

Wire and cable common sense questions and answers

1. What are the requirements for cable piping?

Answer: (1) The distance from the top of the pipe to the ground is 0.2m in the workshop, 0.5m under the sidewalk, and 0.7m in general areas;

(2) Pipe pits should be installed at the change direction and branch, and pits should also be added when the length exceeds 30mm;

(3) The pit depth is not less than 0.8m, and the manhole diameter is not less than 0.7mm;

(4) The drain pipe should have a drainage slope of 0.5% to 1% inclined to the pit.

2. What are the requirements for the resistance of the cable conductor connection point?

Answer: The resistance of the connection point is required to be small and stable. The ratio of the resistance of the connection point to the conductor of the same length and the same cross-section should not be greater than 1 for the newly installed terminal head and intermediate head; This ratio should not be greater than 1.2.

3. What requirements should the design of cable joints and intermediate head meet?

Answer: The requirements that should be met are:

(1) High compressive strength and good conductor connection;

(2) High mechanical strength, low medium loss;

(3) Simple structure and strong sealing.

4. What is a cable fault? There are several common types?

Answer: Cable failure refers to the failure of the cable’s insulation breakdown during the preventive test or during the operation, which forces the aerial bundled cable 33-209 standard  to power out due to insulation breakdown, wire burnout, etc. Common faults include ground faults, short-circuit faults, disconnection faults, flashover faults and mixed faults.

5. How to deal with the single-phase ground fault of the cable line?

Answer: Generally speaking, the damage to the cable conductor is only partial. If it is a mechanical damage and the soil near the fault point is relatively dry, local repairs can generally be carried out and a fake connector is added, namely Without sawing the cable core, only the fault point is insulated and sealed.

6. What tests and inspections should be carried out on power cables before laying?

Answer: Before laying, check whether the type, specification and length of the cable meet the requirements and whether there is external force damage. Low-voltage cables use a 1000V megohmmeter to remotely measure the insulation resistance, and the resistance is generally not less than 10MΩ, and high-voltage cables are measured with a 2500V megger. The resistance is generally not less than 400MΩ.

7. What should be paid attention to when laying cables in the main workshop?

Answer: When laying cables in the main factory building, generally pay attention to:

(1) All control cables leading to the centralized control room should be laid overhead;

(2) 6KV cables should be laid in tunnels or pipes, and the high groundwater level can also be laid overhead or pipes;

(3) For 380V cables, tunnels, trenches or pipes should be used when the two ends of the cable are at zero meters. When one end of the equipment is on the top and the other is on the bottom, it can be partially overhead laid. When the local water level is high, it should be overhead.

8. Where are the inner and outer shielding layers of power cables? What material is used? What’s the effect?

Answer: In order to make the insulation layer and the cable conductor have better contact and eliminate the increase in the electric field strength of the conductor surface caused by the unevenness of the conductor surface, the conductor surface is generally covered with an inner shielding layer of metalized paper or semiconductor paper tape. In order to make the insulating layer and the metal sheath have better contact, generally the outer surface of the insulating layer is covered with an outer shielding layer. The material of the outer screen layer is the same as that of the inner screen layer, and sometimes copper tape or braided copper ribbon is tied outside.

9. Briefly describe the composition and performance of epoxy resin compound.

Answer: The epoxy resin compound is composed of epoxy resin added with hardener, filler, toughening agent and diluent. Has the following properties:

(1) Have sufficient mechanical strength;

(2) Excellent electrical performance;

(3) Stable electrical performance;

(4) It has sufficient adhesion to non-ferrous metals;

(5) Good corrosion resistance;

(6) When used outdoors, it is resistant to rain, light, and humidity.

Physical characteristics of aluminum alloy cables

The advantage of aluminum alloy cable over ordinary cables is that under the same volume, the actual weight of aluminum alloy is about one-third of copper. According to this calculation, under the premise of meeting the same electrical conductivity, the length of the aluminum alloy cable with the same weight is twice that of the copper cable. Therefore, the weight of the aluminum alloy cable is about half of the copper cable at the same current carrying capacity. The use of aluminum alloy cables instead of copper cables can reduce the weight of the aerial bundled cable ASTM b231, reduce the installation cost, reduce the wear of the equipment and the cable, and make the installation work easier.

Aluminum alloy power cable is a new type of material power cable created by advanced technologies such as AA-8000 series aluminum alloy material as the conductor, using special pressing technology, annealing treatment, and chain armoring technology.

The difference between aluminum alloy cables and ordinary cables: aluminum alloy cables use AA-8000 series aluminum alloy conductors, while ordinary cables use copper or pure aluminum as cable conductors.

Tensile strength and elongation

Compared with pure aluminum conductors, aluminum alloy conductors have greatly improved tensile strength due to the addition of special ingredients and special processing techniques, and the elongation rate has increased to 30%, making it safer and more reliable to use.

Thermal expansion coefficient

The coefficient of thermal expansion is used to calculate the dimensional change of the material when the temperature changes. The coefficient of thermal expansion of aluminum alloy is equivalent to that of copper. Aluminum connectors have been reliably used for copper and aluminum conductors for many years, and most of the electrical connectors used today are made of aluminum, which is especially suitable for aluminum alloys. So the expansion and contraction of the aluminum alloy conductor and the connector are exactly the same.

Strong weight bearing capacity

Aluminum alloy improves the tensile strength of pure aluminum. Aluminum alloy cables can support a weight of 4000 meters, while copper cables can only support 2750 meters. This advantage is particularly prominent when wiring large-span buildings (such as stadiums).

Armour characteristics

Most commonly used armored aerial bundled cables(abc) b230 standard in China are armored with steel tape, with low security level. When subjected to external destructive forces, their resistance is poor, which is easy to cause breakdown, and the weight is heavy, the installation cost is quite high, and the corrosion resistance is poor. The service life is not long. The metal interlocking armored cable we developed according to American standards uses aluminum alloy tape interlocking armor. The interlocking structure between the layers ensures that the cable can withstand the strong destructive force from the outside, even if the cable is subjected to greater pressure The cable is not easy to be punctured under the impact force, which improves the safety performance. At the same time, the armored structure isolates the cable from the outside world. Even in the event of a fire, the armored layer improves the flame-retardant and fire-resistant level of the cable and reduces the risk of fire. Compared with the steel tape armored structure, the aluminum alloy tape armored structure is lighter in weight and convenient to lay. It can be installed without bridges and can reduce installation costs by 20% to 40%. Different outer sheath layers can be selected according to different places of use, which makes the use of armored cables more extensive.

Talking about the advantages of prefabricated branch cables

With the strong growth of my country’s national economy, the speed of various infrastructure, capital construction, and real estate development has accelerated. It is a historical necessity to use mining aerial bundled cables(abc) as the main supply, distribution, and trunk lines in various buildings and facilities. Therefore, construction units, design units, and construction units are seeking more advanced, more economical, superior performance, less effective space, and shorter construction period power supply construction technology and methods. It is also under such historical environmental conditions that prefabricated branch cables have entered my country’s architectural electrical stage in strides.

1) In the middle and high-rise buildings, prefabricated branch cables can be widely used in various middle and high-rise buildings such as residential buildings, office buildings, office buildings, commercial buildings, teaching buildings, scientific research buildings, etc., as the main and trunk cables for power supply and distribution use;

2) In airports and ports, it is used as the main cable for airport runway lighting, port terminal lighting, and power supply and lighting in building facilities;
3) It can be used as lighting power supply in tunnels; it can be used as lighting and power supply network in mines;
4) In the transformation and construction of urban power grids, as the main, kydl_yyyb trunk line mining cables can be buried or overhead;
5) In the modern standard factory building, it is used as the main and trunk cable for mining;
6) In various buildings, facilities, buildings, halls, halls, venues, and even sports facilities, swimming pools, etc., it can be used as main and trunk mining aerial bundled cables BS 7870.
7) Prefabricated branch cables can be used in various other occasions where mining cables are used, such as main and trunk lines of power systems such as ships and ships.

Pre-branch cables have many advantages:

1) The cost of insulation treatment of branch joints is greatly reduced;
2) On-site construction costs are greatly reduced;
3) On-site construction cycle and time are greatly shortened;
4) Reduced on-site construction personnel and equipment; reduced technical requirements for construction personnel;
5) Not restricted by the space and environmental conditions of the construction site;
6) The insulation performance of the branch connector is consistent with that of the cable body, with superior insulation performance and high reliability;
7) It has higher seismic, waterproof and fire resistance performance;
8) The power supply is safe and reliable, and the one-time effective opening rate can reach 100%;
9) Wide application range, many varieties and specifications;
10) Users can conveniently choose cables of various specifications, models, cross-sections, and lengths as the main and branch cables;
11) It has more intuitive maintenance operability.

Causes of fire accidents on overhead cables

Now the use of Aerial Bundle Cable has become more and more extensive, but with its popularity in the national power supply lines, some of its safety problems have gradually attracted people’s attention, especially in recent years, the  cable fire accidents reminds people to pay more attention to when using this kind of cable. So, what are the causes of fire accidents of overhead cables?

1. The nominal conductor cross section of cable core does not meet the requirements. Generally, the specified nominal interface is larger than the actual cable produced, and the cable whose nominal value deviates from the standard will have larger unit current density. In its working process, the cable is easy to cause fire accident because it can not generate heat normally.

2. (ABC)XLPE  Insulated cable production process is poor. Although not every manufacturer is like this, it is inevitable that some businesses in the market will not operate strictly according to the standards in the process of cable production in order to seek personal interests. Even some businesses will use some low-quality products to make rough, resulting in the final production of the cable because the quality is not up to standard, causing fire in the process of use.

3. The material of the cable is impure or unqualified. The core wire of the cable is generally made of some copper or aluminum conductive materials, and many businesses often use unqualified or insufficient purity materials in the production process, which will lead to the reduction of power due to the presence of more impurities. Therefore, the materials used as core wires must be some high-quality electrolyte materials, mainly copper and aluminum.

4.Improper transportation. Most cables are subject to strict quality inspection before leaving the factory, but in the process of transportation, due to the lack of proper protection measures, it is squeezed and collided, resulting in the damage of insulation layer or the breakage of internal core wire

5. The composition of the insulating material does not meet the requirements or the processing is poor. We know that the outside of the cable is generally wrapped with a kind of insulating material. If the quality of the insulating material is unqualified, it will reduce its own withstand voltage performance in the process of use, and will form unqualified resistance value. In addition, long-term use will also shorten its service life, it is easy to have some short-circuit faults and cause fire.

Basic cable performance test

1. Inspection method
Routine test: It is an experiment conducted by the manufacturer on all finished cables. Its purpose is to check whether the quality of the product meets the requirements of the technical conditions in order to find accidental defects in the manufacturing process. It is a non-destructive experiment, such as the DC resistance of the wire and the insulation resistance time. And withstand voltage test, partial discharge detection, etc.
Type test: It is the manufacturer who regularly conducts comprehensive performance inspection of the product, especially for a new product before it is finalized for mass production, or the structure, material and main process of a product have changed, which may affect the performance of the cable Time. Pass type test: It can be tested whether the product can meet the requirements of operation, and can be compared with the old product. Such as thermal aging performance of insulation and sheath, long-term stability test of power cable, etc.
Acceptance test: It is an acceptance test performed on the cable after the cable is installed and laid in order to check the installation quality and find possible damage during the construction. Such as withstand voltage test after installation.

2. Test items
2.1 Measurement of DC resistance of wires
The conductive core of the wire and cable mainly transmits electric energy or electric signal. The resistance of the wire is the main indicator of its electrical performance. When the AC voltage is applied, the core resistance is larger due to the skin effect and the adjacent effect surface than when the DC voltage is applied, but the difference between the two is very small when the electric eye frequency is 50Hz. The current standard stipulates That can only require the detection of whether the DC resistance or resistivity of the core exceeds the value specified in the standard. Through this inspection, certain defects in the production process can be found: such as wire breakage or partial single wire breakage; Meet the standard; the length of the product is incorrect, etc. For aerial bundled cables 1418 standard, you can also check whether it will affect the allowable current carrying capacity of wire and cable products during operation.
There are single-arm DC resistance method and double-arm DC bridge method to measure the DC resistance of conductors. The accuracy of the latter is higher than that of the former. The test procedure is also more complicated than the former.

2.2 Test of insulation resistance
Insulation resistance is an important indicator reflecting the insulation characteristics of wire and cable products. It is closely related to the product’s electrical strength, dielectric loss, and the gradual deterioration of insulating materials under working conditions. For communication cables, low insulation resistance between wires will also increase loop attenuation, crosstalk between loops, and long-distance power supply leakage on conductive cores. Therefore, insulation resistance should be higher than the specified value.
Defects in the process can be found by measuring the insulation resistance, such as the insulation is dry and impermeable or the sheath is damaged and damp; the insulation is contaminated and conductive impurities are mixed in; the insulation layer is cracked due to various reasons. In the operation of aerial bundled cables(abc) sans1418, the insulation resistance and leakage current are often tested as the main basis for continued safe operation.
At present, in addition to the ohmmeter (shaking meter), the current measurement of the insulation resistance of wires and cables is the galvanometer comparison method and the high resistance meter method (voltage-current method).