Busway is challenged by breakout cables

Tradition is often challenged, for example busway has been challenged by cables, especially breakout
cables.
In fact, the two have their own advantages
in terms of product performance, application fields and economic costs.
Before the 90s of the 20th century, cables have always played an important role
in transmission and distribution in low-voltage power distribution systems.
However, since the 90s, busbar trunking systems have been gradually introduced and developed, and quickly become widely used
in construction projects.
Compared with traditional transmission equipment, it has its unique performance advantages, such as large ampacity, strong overload capacity, convenient tapping, good heat dissipation and convenient maintenance
.

Ordinary busbar duct is a transmission and distribution system
with electrical continuity that wraps several conductors in a metal shell through a reasonable and safe structure.
Ordinary busway is generally divided into two types
: dense insulation type and air insulation type.
The air-insulated type has simple structure and large transmission current; Dense insulation type compact structure and good
heat dissipation capacity.
They all have the characteristics
of strong overload capacity, convenient connection and small space occupation.
Cables are divided into single-core cables and multi-core cables
.
Single-core cables mainly use various insulating materials, and multiple strands of copper wires are wrapped in an insulating layer as a phase current conductor
.
Multi-core cable is a complete cable
formed by twisting multiple insulated cores together and wrapping the outer sheath.
The number of insulated cores of power cables is usually 1, 2, 3, 4, 5 and other cores, as well as 4+1 and 3+2 cores
.
The main advantages of cables are flexible selection and strong environmental adaptability, but they also have their inherent limitations
.
The following compares
the performance of busway and cable from several main aspects.

a) Ampacity
.
The cross-sectional area of the low-voltage cable is up to 1000mm2 and the rated current is 1600A
.
Because of its large size and weight, such a large size cable is rarely used in
practical engineering.
Cables of 400 mm2 and below are commonly used in engineering, which requires the use of multiple cables to achieve simultaneous power supply
.
The rated current of the busway can reach up to 6300A, and its strong current-carrying capacity is simply unmatched by
cables.
b) Overload capacity
.
Whether cable or busway, the overload capacity depends on the operating temperature
of the insulation material used.
The working temperature of busbar trunking insulation material is 105°C, and irradiation crosslinked flame retardant winding tape (PER) and radiation cross-linked polyhydrocarbon heat shrinkable tube
with operating temperature above 140°C have been developed.
At present, the normal working temperature of the insulation materials used in cables is generally 90 °C and 105 °C, and the maximum operating temperature of irradiated cross-linked cables is 125 °C
.
Therefore, the overload capacity of the busway is much greater than that of the cable
.

c) The installation tap busway generally adopts the plug-in installation and tap method
.
The so-called plug-in busway is to use the plug-in method to connect the power supply of the main line to the branch line, leaving a plug-in box port every few meters, so the tap is very convenient
.
The cables need to be taped in the field, the reliability is poor, and even prefabricated branch cables have their drawbacks
.
The obvious disadvantage of breakout cables is that they need to customize branch connection equipment to the factory, usually using open "C" type hoops
.
After a long time, whether this kind of hoop can ensure the tight hoop force is also a problem
.
In addition, the price of branch cable branch heads is not cheap, so prefabricated branch cables are still not widely
used so far.
When installing breakout cables, it is necessary to cut off the floor power, and there is no need to power off when installing busway, as long as the plug-in box of busway is removed under no-load conditions
.
However, to cut off the branch power of the prefabricated branch cable, it is very dangerous
to operate in a live situation.
d) Fire performance
.
The insulation and outer sheath of ordinary cables will burn.

Even flame-retardant cables burn under flame and only burn
after the flame leaves.
Fire-resistant cables do not burn, but they are expensive, and fire-resistant cables
are only used in occasions where power outages are not allowed such as fire alarm circuit systems.
The busway shell is metal and does not burn, and even if the insulation of the copper bar burns, the flame will not crisis the outside of
the busway.

Heat dissipation performance The insulation and outer sheath of the cable are both insulation and thermal insulation
.
Therefore, in order to keep the cable dissipated, when the cable is laid in the bridge, up to 2 layers are allowed to be laid, and the reason is mainly to consider the heat dissipation problem
.
The busbar duct uses air conduction to dissipate heat and dissipate heat through the steel shell in close contact, so its heat dissipation performance is much
superior to that of cables.
f) Operation and maintenance
.
Maintenance of busway is relatively simple
.
During the daily maintenance of the busway, it is usually measured to measure the temperature rise of the shell and the punching bolt, the temperature rise of the joint of the inlet box, etc.
, and the punching bolt needs to be tightened regularly if it adopts 4.
8 grade, and it does not have to be regularly strengthened
if the 8.
8 grade high-strength bolt is used.
Cables are limited by factors such as easy wear, aging and short life of their materials, and need to be regularly inspected and maintained, or even replaced
.

The selection of busway for important trunks in low-voltage distribution systems clearly has its obvious advantages
.
For low-current branch lines, the selection of cables also has its advantages of flexibility and convenience, which requires professional distribution designers to select configurations
according to actual needs.