In the 1990s, direct cables played an important role in the transmission and distribution of low-voltage distribution systems. However, since the 1990s, systematic research on busbar trunking has gradually been introduced and developed, and has quickly been widely used in power supply and distribution design engineering. Compared with traditional transmission technology equipment management, it has its own unique performance development potential, such as high current carrying capacity, strong overload capacity, easy tapping, good heat dissipation, and convenient maintenance.

1. Performance characteristics of ordinary bus ducts and cables

A multi-core cable is a complete cable made up of multiple insulated wire cores twisted together and wrapped with an outer sheath. The insulation cores of power system cables are usually 1, 2, 3, 4, 5 cores, and 4+1 and 3+2 cores. The main characteristics of cables are flexibility and adaptability to the environment, but they also have inherent limitations. Below, we will compare the performance of bus ducts and cables from several main aspects.

a) Current carrying capacity

The cross-sectional area of the low-voltage control cable structure for current carrying capacity is 1000mm2, and the rated working current is 1600A. Due to the large volume and weight of such large cables, they are rarely used in practical engineering. In general engineering, cables of 400mm2 and below are commonly used, and multiple cables are required to achieve simultaneous power supply. The rated working current efficiency of the bus duct can reach 6300A, and its strong current carrying capacity is the foundation of the cable.

b) Overload capacity

Whether it is a cable or a bus duct, its overload capacity depends on the operating temperature of the insulation material used. The working environment temperature for the insulation structure material of the bus duct is 105 ℃. We have developed radiation cross-linked flame-retardant winding tape (PER) and radiation cross-linked polyolefin heat shrink tubing for students working at temperatures above 140 ℃. The normal operating temperature for insulation materials used in mesh cables is 90 ° C and 105 ° C, while the normal operating temperature for irradiated cross-linked cables is 125 ° C. Therefore, the overload protection capability of bus ducts has a much greater impact than the overload problem capability of cables.

C) Installation of bus duct

The installation of bus ducts generally adopts a plug-in installation method. The so-called plug-in bus duct refers to the use of a plug-in method to branch the power supply of the main line to the branch line. There is a plug-in box opening every few meters, so branching is very convenient. However, cables require on-site splicing and have poor reliability, and even prefabricated branch cables have their drawbacks. The obvious disadvantage of branch cables is that they require customized branch connection technology equipment from the enterprise factory, usually using data open "C" type clamps. Over time, whether this type of clamp can ensure sealing is also a question. In addition, the price of branch cable heads is expensive, so prefabricated branch cables have not yet been widely used. When installing a branch network cable, it is necessary to cut off the power supply on the floor. When installing the bus duct, there is no need to cut off the working power supply. Simply remove the plug box of the bus duct under no-load conditions. However, it is very important and dangerous to cut off the branches of prefabricated branch cables for power supply when operating live equipment.

d) Fire resistance

The insulation layer and sheath of ordinary cables will burn out. Even flame-retardant cables can burn under flames, and we only increase combustion when the flames can leave. Fire resistant cables do not burn, but they are expensive. Fire resistant cables are only used in places where power is not allowed to be cut off, such as fire alarm circuit systems. The casing of the bus duct is made of metal and will not burn. Even if the insulation material of the copper busbar burns, the flame will not threaten the outside of the busbar duct.

e) Heat dissipation performance

The insulation layer and outer sheath of the cable are both insulation layers. Therefore, in order to maintain the heat dissipation of a cable, it is allowed to lay two layers when the cable is laid in the cable tray. The main reason is to consider heat dissipation issues. The busbar trunking adopts air conduction for heat dissipation, and the heat dissipation is achieved through tightly contacting steel shells, so its heat dissipation performance is better than that of cables.

f) Operations and Maintenance

The maintenance of bus ducts is relatively simple. In the daily maintenance of bus ducts, it is usually necessary to measure the temperature rise of the shell and core bolts, as well as the temperature rise of the incoming box joints. If the core bolts are of grade 4 and grade 8, they need to be tightened regularly. If high-strength bolts of grade 8.8 are used, they do not need to be tightened regularly. However, due to limitations such as material wear, aging, and short lifespan, cables require regular inspection, maintenance, and even replacement.

2. Installation and construction

Although cable laying can be flexibly and conveniently installed in the direction of the line, cable companies in engineering are generally supported by cable trays. Therefore, during cable construction, cable trays need to be installed first, and then cables need to be laid gradually. The installation of bus ducts does require professional installation techniques, but only by following the product standard installation procedures can they be installed in one go. In addition, the bus duct structure is designed to be compact, occupying less space, making it easy to arrange piping and wiring space, and convenient to install and use. Of course, for low current lines below 400a, the use of cables is flexible due to the small cross-sectional area and small number of cables selected.

3. Power supply system

The busbar power supply system is usually a main line led from the distribution center, providing flexible power supply in a decentralized form, while cable power supply is limited by factors such as difficulty in tapping, low current carrying capacity, and difficulty in decentralized control. It is usually a 'point-to-point' power supply. Especially in the power supply control system of high-rise management buildings, bus ducts are more prominent than cables. The traditional wired power supply method requires separate installation on each floor and a large number of cables. This technology intensive installation method has poor heat dissipation, occupies a large space, makes it difficult to inspect and learn from accidents, and makes maintenance management challenging. Bus duct power supply enterprises can adopt a single central bus duct system and set up a plug-in box with corresponding information capacity on each floor for effective diversion. This method makes the branching extremely flexible, with each branch having a plug-in box to protect the shunt variable capacitance. Therefore, the use of bus ducts is safe, simple, and reliable.

4. Economic cost

Compared to cables, bus ducts generally use better materials and relatively complex processes, so the expected investment cost is generally higher than that of cables. However, in the long run, more bus ducts will be used. However, the service life of bus ducts is generally 30-40 years, while the service life of ordinary cables is only about 15 years. As long as the busbar trunking system is installed and operated according to specifications, there is no need to replace components, only routine inspections of the surrounding environment. However, cable companies often experience issues such as joint aging and insulation layer detachment, which require replacing a certain section of the cable. In addition, many powerful bus duct manufacturers have introduced aluminum conductor bus ducts in the market, which have been widely used in large buildings. The procurement cost of this type of busbar trunking is much lower than that of traditional cable trays, but its performance is higher than other cables. For users who lack bulk investment funds, this type of bus duct can be used.