The term installation configuration, when applied to prefabricated busbar systems and cables – transmission and distribution of energy in the installation, essentially refers to the geometric requirements of conductor routing to be taken into account.
Installation advise for prefabricated busbar systems and cables (in the photo: example of high power distribution; credit: Edvard CSANYI)
Adaptability requirements can also be added to these considerations, in particular at the level of the connection of the points of use which must have the required flexibility (for example, frequent disconnections or modifications).
- Note from the conductor
- Cable trays or prefabricated bar systems?
- Dimension and size of the distribution system
- radius of curvature
- Mechanical resistance
- Specific installation conditions
- Installation flexibility level
- Connections and junctions
1. Note from the conductor
To design an energy transport system with prefabricated busbar or cable systems, it is necessary to have a global vision of the routing to be carried out, paying particular attention to changes in direction, obstructions (partitions, firebreaks, doors, etc.), or obstacles (pillars, walls, etc.), which must be avoided without interrupting the continuity of the conductors.
With this approach, it is recommended that a site inspection be performed prior to the project to assess routing issues. If this is not possible, a study will be made “on the model”.
The choice of a cable tray or prefabricated The busbar system must be compatible with the required routing, without forgetting to check that the accessories necessary for changes of direction, obstacles, changes in level, and crossings are actually available.
In addition, it is necessary to take into consideration the characteristics of the floor tiles or walls (for example, reinforced concrete), the difficulty of fixing the supports, as well as the size and weight of the cable trays or systems. of prefabricated busbars.
1.1 Cable trays or prefabricated bar systems?
These two systems are used in infrastructure for the transmission and distribution of electrical energy, regardless of the destination:
- Industrial or commercial sites,
- Establishments in the service sector or
- Residential buildings.
The most classic uses of the conductor system or insulated cables that are supported by mechanical devices: cable ladders, ducts, cable trays, and conduits that can offer multiple configurations, shapes, and construction options allowing them to be adapted to different environments and environments
The existence of many types of conductors suitable for the majority of stresses (temperature, immersion, chemicals, vegetation, fire, UV, etc.) means cable trays can be installed in almost any environment. The limit of this system is the result of maximum operating current (multiple conductors) or electrical requirements (short circuit and magnetic radiation).
Prefabricated bar systems are both an alternative and a complementary system. The conductors are grouped and isolated in the same housing, which supports and protects them.
These integrated systems, perfectly calculated from an electrical and electromagnetic point of view, allow very high power flow and offer very high levels of protection against specific constraints: IP, fire, electromagnetic radiation Their integration into the building infrastructure requires a preliminary examination to ensure the selection of the optimal solutions. specific rules must be followed for installation and assembly.
Prefabricated busbar systems are generally classified into the “high power”, “medium power” and “low power” categories. They allow all types of energy transport, from the power source to the point of end-use (workstations, machines, lighting, etc.).
Cable trays and prefabricated busbar systems are two different systems, each with its own advantages. Of course, their use may also depend on current practices. Of course, the two systems are complementary and can be installed at different levels or for different uses on the same site.
The section and number of cables to be installed can also be an important variable for consideration. The larger the number of cables and their cross-section, the closer the supports must be. The minimum bend radius must also be taken into account.
With a comprehensive approach to conductor routing, it is also necessary to take into account other building services that may constitute interference:
- Smoke pipes or ventilation,
- Air conditioner,
- Fire systems and
- Other networks in general.
Certain sensitive sites (airports, data centers, high-tech industries, etc.) require a second conduit for the transport and distribution of energy, which must be separated for the safety of goods and people, in order to ” ensure continuity and/or separation in the event of a fire risk.
1.2 Dimension and size of the distribution system
The height and width of the sheath chosen must be suitable to contain the wire harnesses, possibly in several layers.
NOTE! It is not recommended that more than 50% of the total duct section be filled!
It might be necessary, for example, to choose narrow cable runs or trunks with high sides for longer distances, or wide trunks or troughs with low sides to install cables in a reduced number of layers.
In all cases, there must be a study to facilitate the installation of ducts and the laying of cables. If the available space is limited, it is worth considering a “prefabricated busbar system” solution that generally offers more compactness.
1.3. radius of curvature
The minimum bend radius can be a limitation on the installation and this should be taken into account. It depends on the cross-section of the cables and the number of cables that must be installed without constraint. It is recommended to provide a minimum bending radius at least equal to 6 or 8 times the outer diameter of the largest cable.
Prefabricated busbar systems have special parts (elbows) which allow less cumbersome changes of direction than those possible with cable ducts and cable trays.
1.4. Mechanical resistance
The conduit must be able to support the weight of the cables it contains. The maximum load certified by the manufacturer should be checked and strictly adhered to. Heavy-duty conduits may allow a reduction in the number of brackets, while light conduits will require many attachment points.
The number, type, and quality of brackets (wall and/or ceiling brackets) must be calculated when looking at the total cost of the installation.
Prefabricated bar systems are self-supporting solutions that give more rigidity to the installation. It is particularly important to check the availability of all the parts and accessories.
1.5 Specific installation conditions
In addition to the sizing, shape, and mechanical strength requirements linked to the routing of the conductors, each installation situation generally requires the study and implementation of special precautions.
In the majority, these precautions are related to local environmental conditions, classified in the broadest sense by standardization bodies as “external influences”. These conditions, defined by standard IEC 60364-5-52, characterize mechanical stresses (shocks, vibrations, earthquakes, etc.), climatic stresses (temperature, humidity, etc.) to which are added a certain number of specific constraints, such as wind, sun, corrosion, risk of fire, etc.
2. Level of the flexibility of the installation
The choice of an energy transport system in a building must also allow possible modifications, developments, and extensions of the installation.
If these requirements exist, it is necessary to choose solutions offering good installation flexibility and continuity of service. The system chosen must be able to direct power where it is needed, without having to cut the power for long periods.
Ease of installation is also important to minimize the time required to modify the system and ensure quick and safe maintenance. From this perspective, the choice must take into account the operations that may affect the production costs or the management of the system.
of the prefabricated busbar system
As the installation evolves, prefabricated busbar systems guarantee continuity of service by allowing connections and disconnections with power on. On the other hand, it may be less expensive to install cable ducts or cable trays in installations that do not require any particular modification or maintenance.
The choice of a distribution system is not limited to a single solution. Depending on the complexity and size of the building, the power used, the location configuration, and environmental conditions, prefabricated busbar systems, trunking, or cable trays can be used together.
3. Connections and junctions
The electrical installation must be designed and installed taking into account the need for modification and extension. This means that a flexible system must be installed which must allow connections to power future uses.
Prefabricated cables and busbar systems must be dimensioned to take into account possible extensions and must allow new junctions. With a “cable” solution, connection equipment, such as distribution boxes and panels, must be installed at predefined points on the trunk line.
This equipment, which could potentially be equipped with protection or isolation devices, could supply the starting points of the additional lines.
With the “prefabricated busbar system” solution, the bars used as main lines are equipped with connection points. In this case, to supply new lines, it suffices to install the junction boxes directly on the busbar. If necessary, these junction boxes will be fitted with protection or isolation devices.
Similar precautions will be taken at the terminal circuits to ensure maximum flexibility in the event of a change in the layout of the workstations and/or an extension.