Oil-filled cable and XLPE cable

XLPE cable is solid insulation, do not need complex oil filling system, do not need to detect oil level, control oil pressure, low operating cost;

XLPE cable without lead sheath, small bending radius, light weight, can produce, lay the length of longer, and in laying installation and transportation are simpler than oil cable;
XLPE submarine cable electrical and mechanical properties are better than oil – filled cable. Because of this, the development of XLPE insulated submarine cables has a broader prospect, but there are also many technical problems to be solved. Under the action of DC voltage, the space charge in the insulation of common crosslinked polyethylene cable will be concentrated in a certain place, which will cause the local field intensity to be too high and be broken down. The use of additives in insulation material can reduce the space charge accumulation in cable insulation and make the CROSSlinked polyethylene cable suitable for DC high voltage power supply. In 2002, the first extruded single-core DC submarine cable (light DC cable, ABB Sweden), with voltage ±150kV, length 40km and capacity of 330MW, was used to connect Long Island, New York with Connecticut, USA. This dc submarine cable is extruded into a unipolar cable by three layers of polymeric material, and extruded by both internal and external shielding layer and insulating layer at the same time. It has the advantages of high strength, environmental protection and easy burial, and is suitable for deep sea and other harsh environments.

Described.properties of dc insulation cable is in the highest voltage is 320 kv ac cable insulation equivalent capacitance increases with the increase of cable length, in the process of energy transfer, the equivalent capacitance and power between discharge but go around the charge, the charging current can achieve maximum and affect the normal active load transmission, so the communication cable has a theoretical limit of transmission distance, multiple sea-crossing engineering show that the range of about 40 km, more than the distance, adopting ac power transmission is not economical. The length of DC cable is not limited by charging current, no reactive power compensation device is needed, it is easy to manufacture and install, medium loss and conductor loss are small, and it has a good market prospect. However, many problems such as space charge accumulation mechanism and its suppression method, insulation aging mechanism under DC voltage, long-term stability of newly developed insulation materials, influence of partial discharge and so on remain to be studied and solved.

Generally, ultra-high voltage AC submarine cables are single-core, but three-core AC submarine cables can save the cost of production and laying, so the three-core XLPE AC submarine cables with large cross sections and high voltage classes are gradually being promoted. In 2008, nexen installed the world’s first three-core XLPE insulated submarine cable with a voltage of 245kV in Canada. Compared with XLPE cable (TG ≤0.0005), the dielectric loss tangent value tg and the dielectric constant are higher, but they are more protective against branch and partial discharge than the POLYETHYLENE cable, which is generally only used for submarine cables of medium voltage. To date, the highest grade of b-C rubber submarine cable is the 150kV submarine cable installed in Venezia Murano-Mestre, Italy, in 2001.

Waterproofing of submarine cables

When mechanical stress or external force causes cable sheath and insulation damage and joint damage, moisture or moisture will be immersed along the longitudinal and radial gap of the cable, reducing the electrical strength of insulation. Therefore, most high voltage submarine cables have longitudinal and radial waterproofing measures to prevent moisture invasion. Radial measures are mainly on the outside of the insulation block and metal shielding layer winding and half resistance water expansion zone, adding metal waterproof layer on the outside of the metal shielding layer metal sheath, medium voltage cable electric field intensity is relatively low, the general use of lu: su composite sheath, there are only with polymer sheath, high voltage cable, the use of the lead, aluminium, stainless steel metal seal. Polymer sheath is waterproof, but has a certain water absorption rate, because its structure is mainly composed of crystalline phase and amorphous phase semi crystalline polymer. The structure of crystalline phase is compact, the arrangement of molecules in amorphous phase is loose, and there are large intermolecular gaps. Under the action of alternating electric field, polar water molecules constantly flip back and forth and can penetrate into the insulating material through the interstitial and grain boundary defects. When using polymer sheath, the sheath should be added with water-absorbing water-blocking agent.

Longitudinal water resistance mainly adopts compression type line center; Add water-repellent substances between the wires and the shielding area of the cable heart to block the diffusion channel of water in the cable heart. Longitudinal water resistance with water resistance powder filling effect is good, its water absorption is dozens of times or even thousands of times its own, water absorption strength is large, high expansion rate, water absorption can rapidly expand into gelatinous material, block water seepage channel, terminate the moisture and moisture further diffusion and extension, so that the length of the damp cable to the minimum.

Wire and cable products five categories

1. Bare wire and bare conductor products
The main features of this class of products are: pure conductor metal, no insulation and sheath layer, such as steel-cored aluminum strand wire, copper-aluminum busbar, electric locomotive wire; The processing technology is mainly pressure processing, such as melting, rolling, drawing, stranded/pressed stranded, etc. Products are mainly used in suburbs, rural areas, user lines, switch cabinets and so on.
2. Power cables
The main features of this class of products are: extruded (wound) outer conductor covering insulation layer, such as overhead insulated cables, or twisted several cores (corresponding to the phase, zero and ground wires of the power system), such as overhead insulated cables with more than two cores, or additional sheath layer, such as plastic/rubber sheathed wires and cables. The main technologies are drawing, stranding, insulation extruding (wrapping), cabling, armor, sheath extruding, etc. The different process combinations of various products are different to some degree.
The products are mainly used in the transmission of strong electric energy in the power lines of generation, distribution, transmission, transformation and power supply, with large current (tens to thousands of amps) and high voltage (220V to 500kV and above).

3. Wires and cables for electrical equipment
Such products, the main characteristics are: various specifications, application range, use voltage in 1 kv and below is more, to derive new products constantly, in the face of special occasions, such as fireproof cables, flame retardant cable, low smoke zero halogen/against termites, low smoke low halogen cable, mouse cable, oil/cold/heat resistance, abrasion resistance cable, medical/farm/mining cable, thin wire, etc.
4. Communication cable and optical fiber (brief introduction)
With the rapid development of the communication industry in the past twenty years, the products have also developed at an amazing speed. From the past simple telephone and telegraph cables to thousands of pairs of voice cables, coaxial cables, optical cables, data cables, and even combined communication cables.
The structure size of this kind of product is usually small and uniform, and the manufacturing precision is high.
5. Electromagnetic wire (winding wire)
Mainly used for all kinds of motors, instruments and meters.
A derivative/new product of wire and cable
The derivative/new products of wires and cables are mainly produced by adopting new materials, special materials, changing product structure, improving process requirements, or combining different kinds of products due to different application occasions, different application requirements, convenience of equipment and reducing equipment cost.
Use different materials such as flame retardant cable, low smoke halogen-free/low smoke halogen-free cable, termite proof, mouse proof cable, oil/cold/temperature resistant cable, etc.
Change product structure such as: fire-resistant cable, etc.
Improve the process requirements such as: medical cable;
Combined products such as OPGW, etc.
Easy to install and reduce equipment cost such as: prefabricated branch cable.

Mineral insulated cable

BTTZ mineral insulated cable
1.BTTZ cable structure
Its structure is: 1. Solid conductor;  2. Magnesium oxide mineral insulation; 3. Copper sheath.
2. Performance characteristics of BTTZ cable
The advantages of BTTZ cable are: it is a non-combustible cable with excellent waterproof performance and radial waterproof and moisture-proof function.
The disadvantage of BTTZ cable is: (1) first of all it is not suitable for moving occasions, copper pipe once damaged insulation performance will rapidly decline, and the insulation performance under high temperature will rapidly decline, so the project should not be used in large quantities; (2) Secondly, this cable due to magnesium oxide insulation is easy to absorb moisture, cable longitudinal moisture-proof requirements and from metal sheath damage is particularly important, end sealant, will seriously affect the service life; (3) In addition to the manufacturing process also limited the cable manufacturing length, resulting in increased joint, joint waterproof treatment is also very difficult, often because of the joint water, resulting in unqualified insulation resistance.

YTTW mineral insulated cable

1.YTTW cable structure
(1)Copper conductor. (2)High temperature (1375℃) will not burn the inorganic (mineral) insulation with insulation. (3)Outer copper sleeve.
2.YTTW cable performance characteristics
Advantages: metallic sheathed inorganic mineral insulated cable. Is a flexible fire cable.

1. Fire resistance
Copper and magnesium oxide, two materials used in mineral insulated cables, are inorganic. This cable does not burn or assist combustion and can continue to operate under conditions close to the flame. The copper sheath melts at 1083 ° C, while the magnesium oxide insulation solidifies at 2800 ° C.
2. High operating temperature
Mineral insulated cables can withstand continuous operating temperatures up to 250℃. However, in an emergency, the cable can continue to operate for a short period of time at temperatures close to the melting point of the copper sheath.
3. Long life
The inorganic materials used in mineral insulated cables can ensure the cables have stability, long service life and fire resistance.

Shortage: YTTW cable, first of all, its sheath USES copper sheath, with copper increased production costs. The cable with a larger section is still hard and not flexible enough, so the larger section (greater than 630mm2) cannot be produced and cannot meet the requirements of large current of the system.

Comparison of YTTW cable and BTTZ cable performance
1. YTTW– Flexible fire cable;
BTTZ– Rigid fireproof cable.
2. YTTW– Unlimited cable manufacturing length;
BTTZ– Cable is limited by manufacturing process, conductor section is small, manufacturing length is short.
3. YTTW– Meet the requirements of design and construction acceptance specifications;
BTTZ– It is mandatory to meet the requirements of “No joints in the middle of cable Lines” in Cable Design Code for Power Engineering, “Avoid intermediate joints” and “Reduce cable joints” in Electrical Design Code for Civil Buildings and “Code for Construction and Acceptance of Cable Lines in Electrical Installation Engineering”.

Cable with copper difference

Cable is often used in reality, we can’t tell the difference from the surface, copper wire inside the cable is different, copper rod is the main raw material of the cable industry, there are two main production methods — continuous casting continuous rolling method and up-leading continuous casting method. The oxygen content and appearance of copper rods are different due to different processes. So let’s take a look at the cable copper difference in what aspects.
I. Process defects:
The cable copper is melted while being added. There is no condition for full reduction of the molten copper water. The entire melting process and the copper water production process cannot be separated by oxygen, so the oxygen content is very high. Molten copper fuel is generally a gas, gas combustion process, will directly affect the copper liquefaction branch, the impact of sulfur and hydrogen. When the casting machine crystallizes the copper liquid into a solid, oxygen isolation cannot be carried out, so a second large amount of oxygen is taken during the casting process. Due to a variety of factors, the temperature is not easy to control, the ingot temperature into the mill, the temperature is required to control at 850℃, the greater the deviation, the greater the impact on the quality of copper rod, and a link slightly some problems, will affect the temperature control.

Ii. Technological Advantages:
(1) High output, the average output of small units can reach 10 ~ 14 tons per hour.
(2) The copper rod unloading wire adopts plum-style, which is easy for the wire drawing machine to lay out.
(3) The drawing line is of large weight, generally up to 4 tons per plate.

Low oxygen copper bar grades and characteristics: There are three grades of low oxygen copper bar, T1, T2 and T3. Low oxygen copper bar is hot rolled, so it is soft bar, code name is R.
(1) T1: Use high purity electrolytic copper as raw material (copper content greater than 99.9975%) to produce low oxygen copper rod.
(2) T2: Use 1# electrolytic copper as raw material (copper content greater than 99.95%) to produce hypoxic copper rod.
(3) T3: Use 2# electrolytic copper as raw material (copper content > 99.90%) to produce hypoxic copper rod. Because high pure electrolytic copper and 2# electrolytic copper market is very few, generally use 1# electrolytic copper as raw materials, so the general low oxygen copper bar brand is: T2R.

Damp damage to cables

Although the summer heat, but the rain is also very much, especially in the rainy season, is wet, there are a lot of products because of the improper storage, all be affected with damp be affected with damp, the late is certainly will affect the use, wire and cable, not to mention was electricity is not able to touch water, if be affected with damp be affected with damp the use will not only influence, will certainly bring us some harm, so let’s to find out what are the dangers of cable to be affected with damp be affected with damp.

1. When the new whole cable leaves the factory, both ends of it are sealed with plastic sealing sleeve. However, after it is used for a period at the construction site according to the actual situation, the rest part is simply wrapped with plastic cloth for the fracture.
2.During cable laying, it is often necessary to cross roads, Bridges and culverts, etc. Due to weather or other reasons, a lot of water is often accumulated in the cable trench. During the laying process, it is inevitable that the cable end will be immersed in water, and water will enter the cable due to the loose wrapping or damage of the plastic cloth; In addition, sometimes the outer sheath and even the steel armor will be scratched during the traction and tube penetration. This phenomenon is particularly prominent when mechanical traction is used.
3. After the completion of cable laying, due to the limitation of on-site construction conditions, the cable ends that have not been sealed are exposed to the air for a long time, or even immersed in water, so that a large amount of water vapor enters into the cable.
4.During the production of cable ends (including terminal ends and intermediate joints), due to the negligence of the construction personnel, the newly treated cable ends sometimes accidentally fall into the water on the site.
5. During the normal operation of the cable, if breakdown occurs for some reason, the water in the cable trench will enter the cable interior along the fault point; In civil construction, especially in the use of large construction machinery construction sites, due to a variety of human factors caused by cable damage or breakdown accident, also common. When such an accident occurs, the insulation of the cable is severely damaged, which can also cause water to the cable.

Common misunderstanding of wire and cable

Wires and cables are used in all walks of life, so before the purchase of wires and cables, we will understand all kinds of parameters and evaluation through the network way, but many of the online evaluation is not very professional, often cause psychological doubts and worries of users, will be blocked in the purchase. The following is a detailed explanation of our common misunderstanding of cable.
One, wire and cable will there be radiation?
Wires and cables do have radiation, but the fact is that all live things have radiation, such as the 220V wire also has radiation, but the radiation is very small, basically can be ignored, and the radiation of the wire is far lower than the radiation of a mobile phone, if you are really afraid of radiation of the wire, so you can throw away the phone first. The geomagnetic field is even more frightening if you are afraid of the magnetic field generated by electric wires and cables and think that the magnetic field will cause any harm to the human body.

Two, wire square is insufficient unqualified?
This may seem like common sense to a lot of people, but it’s not. As the conductor material production technology improvement and the progress of science and technology, advanced production technology of oxygen free copper has been widely used, copper conductor material resistivity is enough to ensure that use less than the nominal diameter copper wire can meet the requirements of corresponding specifications dc resistance, and resistivity of a conductor of wire and cable conductor have strict requirements, for example, rules of 25 mm square copper conductor at 20 ° dc resistance is not greater than 0.727 Ω / km, so as long as no greater than the value of the conductor is qualified.
Three,the thicker the cable insulation, the better?
Is not the case, can increase the difficulty of cable laying cable insulation is too thick, now give priority to with bridge or wear tube cable laying, many companies are now in the cable requirements, small diameter, has space during the installation process, send out heat, guarantee the cable outer sheath is not damaged, otherwise, bring some difficulties in the construction unit and cable laying. Work in the summer, the temperature will rise, the temperature will be through the outer sheath, and sheath thickness increase, the heat is difficult to send out, will affect the service life of the cable, because of polyvinyl chloride (PVC) under the action of heat, has brought a series of physical and chemical changes in the insulating layer, lost the original fine performance, lead to a significant reduction in the insulation performance, can appear even short circuit, so choosing cable, the thickness of the cable must conform to the standard.

Four,flame retardant cables will not burn?
Is not correct! Flame retardant of wire and cable means that in the event of fire accident of wire and cable, it can block and delay the spread of flame along the wire and cable, so as to minimize the expansion of fire scope of wire and cable. This type of cable has the characteristic of self-extinguishing after fire. Fire-resistant wire and cable refers to that in a fire accident of wire and cable, the wire and cable product can stick to the normal operation for a certain period of time while the external flame is still burning, so as to maintain the integrity of the wire and cable line and the normal operation of the line equipment.
Five, water and electricity laying stress on horizontal and horizontal vertical?
Not necessarily! Although horizontal vertical laying of water and electricity lines look very good, but they are really a lot of hidden dangers! First of all, the material cost of the pipe is much higher than the laying of other ways. Secondly, because it is horizontal and vertical 90 degrees, it is easy to get stuck in the later stage when you wear the wire! So as long as it conforms to the specification!

What are the common faults of wire and cable?

Common faults of wire and cable lines cause mechanical damage, insulation damage, insulation dampness, insulation deterioration, over-voltage, cable overheating faults. When the above faults occur in the line, the power supply of the fault cable should be cut off, to find the fault point, to the fault.
The direct cause of the cable failure is the breakdown of insulation. Mainly include:
1.Overload operation: long-term overload operation will increase the temperature of the cable and make the insulation aging, which will lead to the breakdown of insulation and reduce the construction quality.

2. Electrical interview: the construction of the cable head fails to meet the requirements, the cable head seals badly, moisture intruded into the cable interior, the cable insulation performance declined, no protective measures were taken when laying the cable, the protective layer was damaged, and the insulation declined.This problem is particularly obvious in all aluminum cables.
3. Civil engineering aspects: poor drainage in working well pipe trench, cable soaked in water for a long time, damaging insulation strength; The working well is too small, the bending radius of the cable is not enough, and the cable is damaged by extruding force for a long time. Mainly in the municipal construction of mechanical barbaric construction, cut and cut the cable.
4. Corrosion: The protective layer suffers chemical corrosion or cable corrosion for a long time, resulting in the failure of the protective layer and the decline of insulation.
5. The cable itself or the cable head accessories are of poor quality, the cable head seals are poor, the insulation glue dissolves and cracks, and the resonant phenomenon of the station is that the phase-to-phase capacitance of the line and the capacitance to the ground and the excitation inductance of the voltage distributor form a resonant circuit, so as to excite the ferroresonance.

Basic process flow of plastic wire and cable manufacturing

1. Copper and aluminum single wire drawing
Copper and aluminum rods commonly used in electric wires and cables are used to reduce the cross section, increase the length and increase the strength by drawing machine through one or several die holes of drawing dies at room temperature. Wire drawing is the first process of each wire and cable company. The main technological parameter of wire drawing is die matching technology.
2. Monofilament annealing
When heated to a certain temperature, copper and aluminum single wire can be recrystallized to improve the toughness and reduce the strength of single wire, so as to meet the requirements of wire and cable for conducting wire core. The key of annealing process is to prevent oxidation of copper wire.

3. Stranding of conductors
In order to improve the softness of wires and cables and facilitate laying and installation, the conductor core is made of several single strands. The twisted form of conductor core can be divided into regular twisted and irregular twisted. Irregular skewing can be divided into bundle skewing, concentric wringing, special skewing, etc.
In order to reduce the area occupied by the conductor and reduce the geometry size of the cable, the compact form is adopted while the conductor is twisted, so that the ordinary circle is changed into semicircle, sector, tile and compact circle. This conductor is mainly used in power cables.
4. The insulation extrusion
Plastic wire and cable mainly adopts extruded packing solid insulation layer. The main technical requirements of plastic insulation extrusion are as follows:
4.1. Eccentricity: the deviation value of extruded insulation thickness is an important symbol to reflect the level of extrusion technology. Most product structure size and deviation value are clearly stipulated in the standard.
4.2. Smoothness: the surface of the extruded insulation layer shall be smooth, and the surface shall not be rough, scorched, or contaminated
4.3. Density: The cross section of the extruded insulation layer should be compact and strong, and no visible pinholes should be allowed, so as to eliminate the existence of bubbles.

5. Cabling
In order to ensure the shape of multi-core cable and reduce the shape of cable, it is generally necessary to twist the cable into a round shape. The mechanism of stranded is similar to that of conductor stranded. The technical requirements of cable forming are as follows: first, the twisted bending of the cable caused by the turning over of the abnormal insulation core is eliminated; The second is to prevent the insulation layer from being scratched.
Most of the cables are completed with two other procedures: one is filling, which ensures the completeness and stability of the cables after cabling; One is binding to ensure that the cable core is not loose.
6. The protective layer
In order to protect the insulation core from being armored, it is necessary to properly protect the insulation layer. The inner sheath is divided into extruded inner sheath (isolation sleeve) and wound inner sheath (cushion layer). The wrapping cushion replaces the binding belt and is carried out synchronously with the cabling process.

7. Armoured
For laying underground cable, it may bear certain positive pressure during work. Internal steel tape armored structure can be selected. When cables are laid under both positive pressure and tension (such as in water, vertical shafts or in soil with a large drop), the structural type with internal steel wire armor should be selected.
8. Outer sheath
The outer sheath is the structural part that protects the insulation layer of electric wire and cable from environmental factors. The main function of the outer sheath is to improve the mechanical strength of the wire and cable, prevent chemical corrosion, moistureproof, waterproof immersion, prevent the cable from burning capacity. According to the different requirements of cable extrusion machine directly extrusion plastic sheath.

Procurement and selection of crosslinked cables

Crosslinking cable quality is high, the power frequency breakdown strength can reach 50 kv/mm, tan6 was only 5 x10-4, dielectric constant is 2.3, is the ideal cable insulation, at the same time, the working temperature of crosslinking cable up to 90 c, good heat resistance and weather resistance, and high mechanical properties and chemical properties such as corrosion resistance, in the middle and lower cable products basically have all crosslinking cable. Although the technology of crosslinked cable is different, its insulation quality is completely the same. The selection of different types of cables in common use is introduced as follows:

(1) 1 kv three core aluminum core is 70 mm ‘cross-linked polyethylene insulated PVC sheathed steel pin cables, models for YJLV22-0.6/1, 3 x70: the types of crosslinking insulation (YJ) can use any kind of crosslinking process, but to use warm water network it best, such as using dry crosslinking, the equipment investment is large, slow production, such as cable again, in the vast product line cable will be fine, or break, if use irradiation crosslinking, due to the bending times too much will make the compression of the cable conductor is impaired, press the copper conductors are easier to damage. When purchasing, it should be taken into consideration that dry crosslinking should be avoided for aluminum cable with small cross section; For large section or copper core cable can not be used to crosslink, warm water crosslink has greater flexibility.

(2) 10 kv three core copper 120 mm ‘crosslinked polyethylene insulated PVC sheathed steel tape armoured cable, models for YJV22-8.7/10, 3 x 120:10 kv level cable is larger, especially copper core cable, can’t irradiation crosslinking process, except for the bending times too much easy to damage the cable, and the insulation cimc tired space charge decreased insulation quality. At present, dry crosslinking technology is the most suitable for the production of 10kV cable, which has stable product quality and reasonable price. However, if the cable quantity is small and the specifications change a lot, dry crosslinking scrap rate is very high, and it is easy to break the cable with a small section, so warm water crosslinking should be used. Warm water crosslinking belongs to the category of low temperature crosslinking, with no insulation thermal stress and good insulation quality. To eliminate the misunderstanding of “certain water content” of warm water crosslinking, with the development of new warm water crosslinking materials, it has a very good development prospect in the field of medium and low voltage cables.
(3)10KV aluminum core 70mm overhead insulated cable, models jKLYj-6 / lO, 1×70:, this type of cable is also in the production of three technologies, using the cross linking technology of amplitude lighting. In order to eliminate space charge, after the cable conductor is grounded for a long time, the cable can be safely used in the overhead cable line of semi-insulated system. The comparison between dry crosslinking and warm water crosslinking is consistent with the above 10kV cable production.
Henan Huaxing wire and cable Co., LTD., 20 years focus on the production and customization of industrial equipment supporting cables, mainly produces power cables, control cables, flame retardant cables, fire-resistant cables, low-smoke halogen-free cables, high-temperature resistance, waterproof and other dozens of series, thousands of specifications of low-voltage cables. The products strictly comply with international standards (IEC), national standards (GB) and Machinery Ministry standards (JB), the implementation of strict production process testing and rigorous factory testing, products through CCC certification and ISO9001 quality management system certification. It is your first choice to buy wires and cables.