How to choose cable protection pipe

The use of cable protection pipes in large-scale power grid construction and transformation is increasing day by day, and the choice and use of cable protection pipes and the selection and use of power cables are the same as the major events related to the operation safety of urban distribution networks, and must be cautious
.
Therefore, it is particularly important
to carry out correct technical analysis and reasonable selection of cable protection tubes.

The types of cable protection pipes mainly include the following categories: organic polymer material cable protection pipes, such as PE carbon corrugated pipes, PVC pipes, etc
.
Metal material cable protection pipe, such as plastic coated steel pipe, galvanized steel pipe, etc
.
Resin-based fiber reinforced composite cable protection pipes, such as FRP pipes
.
Cement-based fiber reinforced composite cable protection pipes, such as low-friction fiber cement pipes, vinylon cement pipes, etc
.

PE carbon bellows

PE carbon corrugated pipe is high-density polyethylene and modified carbon as the main material, using the withdrawal molding process to produce threaded pipe, with good strength and aging resistance, bendable, no joints, good waterproof and other characteristics, compared with other polyethylene pipes, has better strength and aging resistance, corrosion resistance, has a small density, generally less than 1.
0 g/c
.

Advantages: Flexibility: can bend freely around obstacles, easy to construct
.
Due to its low weight and corrugated structure
.
The carbon bellows can be made of any length, and there is no joint between the two working wells, and there is good waterproof performance
.

Long life: high strength, corrosion resistance, acid and alkali
resistance.

Convenient and practical: light texture, easy handling, steel wire leads, long single length, few interfaces, short construction period, low comprehensive cost
.

Wide range of uses: urban network transformation, high and low voltage cable buried protective wire, telecommunication cable, highway, substation, water conservancy project, etc
.

Disadvantages: carbon bellows has a high thermal expansion coefficient, generally about 10 times the expansion coefficient of concrete, calculated by 100 m, when the temperature in the pipe rises by 40 °C, the free state carbon bellows can be extended by 0.
00015×100×40 = 0.
6 m
.
The heat deflection temperature of carbon bellows is generally 60~80 °C, the heat resistance temperature is low, the pressure load is low under higher working temperature conditions, and it is easy to age
.
The carbon bellows has a low oxygen index, which is not conducive
to the waterproofing of the cable.
In addition, the thermal resistance coefficient of carbon bellows is high, and the heat generated during cable operation is not easy to dissipate, which is not conducive
to improving the current carrying capacity of the cable.

PVC pipe

Advantages: PVC pipe is made of polyvinyl chloride as the main raw material, and filled with a variety of different fillers modified into extruded pipe, from the pipe structure is divided into double-wall corrugated and ordinary pipe
.
PVC pipe has smooth appearance, small friction coefficient of inner wall, no damage to the cable when laying through the pipe, and has the characteristics
of light weight, high strength, easy transportation, investment saving, convenient construction, and wide application industry.

Disadvantages: The heat deflection temperature of PVC pipe is 75~85 °C, and its heat resistance improves with the increase of filler, but it can burn slowly and has poor
fire performance.
The oxygen index of the existing chlorinated polyvinyl chloride PVC-C casing can reach 40, the linear expansion coefficient of PVC pipe is 0.
00008 K-1, the thermal resistance coefficient of encapsulated concrete is high, and the heat generated when the cable is running is not easy to dissipate, which is not conducive
to improving the current carrying capacity of the cable.

Plastic-coated steel pipe

Advantages: Plastic-coated steel pipe is a new type of pipe made of ordinary steel pipe coating, which has excellent mechanical properties and good heat resistance, fire resistance and heat dissipation performance of steel pipe, and overcomes the shortcomings
of steel pipe not corrosion resistance.
Plastic-coated steel pipe has a high cost and is more suitable for use in special requirements such as shallow soil crossing and excessive load
.

Disadvantages: Plastic-coated steel pipe, like steel pipe, cannot be used as a threading pipe of single-core cable, so as to avoid that when the large-load current is high, the plastic-coated steel pipe wall induces a large zero-sequence current and seriously heats up and endangers the cable insulation
.

FRP pipe

Advantages: FRP pipe is an organic compound composed of medium alkali fiber untwisted roving gauze and unsaturated polyester resin as the main components, which is obtained by layering on the core mold to form the required thickness and demolding after curing
.
It has the characteristics of high strength, corrosion resistance and aging resistance, as well as good insulation performance, no combustion in case of fire, good heat resistance and long service life
.
The inner wall of the pipe is smooth, the cable will not be scratched when threading the cable, the weight of the body is light, the installation and construction are simple and convenient, and one person can move, which can greatly shorten the construction period and reduce the installation cost
.
In addition, the tube also has a certain water resistance and can be laid in wet or long-term in water
.
Ordinary inorganic composites are not water-resistant and can only be laid under dry conditions
.

Disadvantages: the performance of FRP pipe depends on the raw materials used, if the raw materials are selected appropriately, high-quality fiberglass cable pipe has all the advantages of organic materials and inorganic materials, if the selection of raw materials is not suitable, the use of high alkali glass fiber has all the shortcomings of organic materials and inorganic materials at the same time, chemical properties and mechanical stability are extremely poor, aging speed is very fast, used for cable laying, will leave great hidden dangers
to the quality of the project.

Low friction fiber cement pipe

Advantages: low-friction fiber cement pipe is a kind of protective pipe made of inorganic water hard cement material as the base material, rolled under pressure by copying process, and coated with a film layer on the inner wall of the pipe
.
It is a heat-resistant, fireproof material
.
The product does not destroy the structure at a temperature of 300 °C, there is no softening, shrinkage and deformation, and has good heat dissipation, corrosion resistance and durability, and its heat dissipation effect is close to the heat dissipation effect
of direct burial underground.
Since the main component of the pipe is cement, cement and fiber mixed and coagulated to form a hard cement stone, buried in the underground soil heat dissipation effect, not subject to natural weathering erosion, suitable for acid, alkali, salt, organic matter and other environments laying
.
The pipe has high strength and lower price, suitable for encapsulation, direct burial, crossing and other construction methods, the construction is relatively simple and convenient
.
Low friction fiber cement pipe has good rigidity, convenient connection between pipes, straight pipelines, small friction coefficient of inner wall, which is conducive to smooth cable penetration and protection from external forces
.

Disadvantages: Because the low-friction fiber cement pipe is a rigid material, the tensile strength is significantly lower than the compressive strength, and the weight is heavy, and the transportation loading and unloading is inconvenient
.