Busbar trunking system according to DIN EN 61439-1 / -6
Under busway systems refers to fixed installations for power distribution and transmission: These are usually protected internal insulated conductors by an outer casing against contact and damage. The technical requirements of a busbar trunking system are defined in the standard DIN EN 61439 (low-voltage switchgear assemblies ), with part 6 (DIN EN 61439-6 / VDE 0660-600-6) explicitly defining, operating conditions, construction requirements, technical features and requirements for evidence for the busbar trunking system.
Typical applications for busbar trunking systems are low-voltage power supplies in industrial applications (e.g. production facilities, workshops) or large buildings (e.g. high-rise buildings, airports)
history
The first use of busbar trunking systems is attributed to the American automotive industry in the period before the Second World War: In the course of industrial production, a higher amount of electrical energy was required, which was transported to the machines with the help of busbar trunking. The well-known manufacturer here is Bulldog, which introduced a rail system to the US market in 1932.
After the Second World War, this technology was used on the European market: The first busbar trunking systems were introduced on the European market by Hein Moeller in 1950 and have been produced in Germany by the Klöckner-Moeller company since 1954 . In France, Telemecanique established itself around the same time with the Canalis system in this area.
In 1993, busbar trunking systems were defined by DIN EN 60439-2; the following DIN EN 61439-6 has been in force since 2013. (This standard must be read in conjunction with DIN EN 61439-1 (VDE 0660-600-1).)
Areas of application
Busbar trunking systems are suitable for transporting energy as well as distributing electrical energy. Transport is the term used to describe the connection between two electrical components (e.g. transformer to switchgear). Energy distribution refers to the output of electrical energy from one or more electrical sources (e.g. low-voltage switchgear ) to decentralized consumers (e.g. motors). For this purpose, changeable tap-off units are attached to the rail system in which switching and / or protective devices are located, which are used to protect the consumers.
The rated current range for busbar trunking systems is in the range from 25 A to 6300 A or more. The nominal voltage is limited by DIN EN 61439-1 / -6 to 1000 V AC / 1500 V DC.
providers
In addition to well-known electrical companies such as Schneider Electric (France; Canalis systems) and Siemens (Germany; Sivacon 8PS systems), numerous medium-sized manufacturers such as EAE (Turkey), Pogliano BusBar Srl (Italy), E&I (Ireland) also offer busbar trunking systems DIN EN 61439-1 / -6. There are many local manufacturers worldwide, especially in Asia.
Structure of a busbar trunking system
A busbar trunking system consists of a conductor system (usually aluminum or copper bars) that contains busbars in a duct, trough or similar housing, which are kept at a distance by insulating material. In principle, there are three different variants:
Air-insulated systems
The conductors (with or without an insulating material coating) are located at a sufficient distance from one another in a busbar housing. This technology is common for low and medium currents (e.g. Schneider Electric: System KN; EAE: System KO), but is also used in the area of high currents (e.g. Siemens: System LD).
Depending on the system's degree of protection, heat is dissipated via convection or heat radiation from the housing.
Sandwich systems
Here, the conductor rails are electrically isolated from one another by thin plastic films, but are mechanically placed on top of one another. The housing presses the system together, there are only small air gaps within the rail block. Heat is dissipated via the housing, which is often designed like a heat sink.
Solid-insulated systems
The conductor rails are embedded in an insulating material: This consists of an insulating but thermally conductive material, for example an epoxy resin mixture. Air pockets in the system are rare. The heat is also dissipated here via the radiation via the outer surface, which often consists of the identical insulating material used.
Functional units of a busbar trunking system
ladder
The current conductors are used to transmit electrical energy. These conductors are made of metallic materials (copper or aluminum). The conductor surface can be refined to improve the contact, tin is often used for this, in rare cases silver. In the case of copper conductors, tin-plating can also be dispensed with, but measures to reduce the contact resistance are necessary here (e.g. cleaning of the contact surfaces). Aluminum conductors are not used without surface finishing due to oxidation. Tin is often used for this purpose, but it requires a nickel (or copper) intermediate layer. When treating the surface, it must be ensured that no function- critical whiskers can form.
The number of conductors depends on the application and network type. Different cross-sections can also be used for external conductors, neutral conductors and protective conductors. The housing can also be used for the protective conductor.
isolation
In order to electrically separate the conductors from one another and from the housing, insulation is necessary. This can consist of directly adjacent insulation materials (e.g. plastic films such as Mylar, insulation coatings such as epoxy) or sufficient air gaps. A combination of both is often used. The standard DIN EN 61439-1 / -6 defines these technical details.
In the event of a short circuit (see also rated short-time withstand current, DIN EN 61439-1, Chapter 5.3.4), the insulation must separate the rails safely and permanently from one another; for this purpose, appropriate tests are made and technical properties are assigned to the conductor rail system.
casing
The housing serves as the external protection of the conductors against contact and mechanical damage. A metallic housing must be included in the protective measure so that a short-circuit to the body triggers the upstream protective device.
Connection point
The busbar elements are mechanically and electrically connected to one another via connection points. Two functional principles are common here:
- Connection via terminal unit: The open ends of two busbar trunking systems are connected to one another using a separate connector
- Direct connection: The two open ends of two busbar trunking systems are contacted directly
To ensure a good electrical connection, surface pressure is applied; this can be done by screw connections or spring-clamp connections. It is necessary to maintain the surface pressure here; this is usually done using spring technology.
Sufficient torque is ensured by means of shear bolts (or nuts) or torque specifications.
Features of a busbar trunking system
Due to the design of a busbar trunking system, there are properties that differ from those of an installation with lines ('cables').
planning
Basically, the installation of a busbar trunking system requires increased planning effort. The spatial conditions must be known prior to installation in order to determine the course of the busbar trunking system. This is how this strand is divided into the individual geometric rail components. This requires detailed knowledge of the installation space at an early stage.
The conductor rail must also be planned electrically so that the maximum connected load is defined in order to determine the electrical properties of the system and to select the system. This level of detail is only required at a later point in time for line installations.
The current carrying capacity of busbar trunking systems are tested and specified by the manufacturer through type tests. In the case of electrical cables, these must be determined taking into account the type of installation, ambient temperature, maximum permissible limit temperature ...
Space requirement
Due to the geometrical design of the busbars, they can be laid close to the building contour. They have the advantage over cables, especially when changing direction, that they do not require bending radii, but can be laid with the same contours and are therefore more space-saving. When cables are laid, these bending radii are 4 to 6 times the outer diameter of a cable and, if they are laid in parallel with the specified spacing, can result in a significant space requirement.
At low currents, busbar trunking systems usually take up more installation space than a comparable installation with low-voltage lines; at high currents, this ratio is reversed, as cables usually allow lower permissible conductor temperatures.
Fire behavior
Electric cables contain a large proportion of flammable insulation, shielding and sheathing materials. Depending on the type of cable, these can mainly consist of various elastomers and polymers. The latter can contain halogens such as chlorine, fluorine and bromine to prevent the formation of a fire, which in turn cause corrosive combustion gases and can thus have a toxic effect.
In general, in the event of a fire, these plastics give off heat of combustion, the so-called fire load , which can be stated in kWh / m.
Due to their construction, busbar trunking systems often contain a lower proportion of plastic, metallic materials are also dominant for the outer housing parts. As a result, the fire load is usually lower with this type of energy transfer.
The most important components of a busbar trunking system
Feeds (according to DIN EN 61439-6: busbar trunking unit for feed)
The infeeds are the elements where the power is fed to the power rail. Typical components here are
- Transformer connection elements for connection to the low-voltage side of the transformer, usually via flexible strips (laminated or braided)
- Distribution or switchgear connections for direct connection to a low-voltage switchgear, usually via solid busbars
- Cable feeds for connection to cables that are fed, for example, from sub-distributors or other busbar trunking systems
In the case of a connection between transformer and switchgear, the transformer connection element is used for the supply, the distributor connection piece in turn for the outlet of the electrical energy.
Busbar boxes (according to DIN EN 61439-6: busbar trunking unit)
Busbar boxes, which can take various forms, are connected to the feeds. In addition to the straight rail elements, which have a usual maximum length of around 3m, various angles and direction change pieces are pronounced that adapt to the building contour and also offsets, e.g. B. at obstacles, make it possible. The straight trunking units can have tap-off points which enable tap-off units to be received and thus the energy can be drawn from the busbar trunking system.
The expansion element is a special form of a trunking unit: This can compensate for the thermal expansion of the power rails in the longitudinal direction during operation and thus prevent possible damage. (Alternatively, the expansion can also be compensated for using special terminals, for example in the terminals of the Schneider Electric KN system)
Tap-off units
The power is taken from the busbar trunking system via tap-off units: A tap-off unit must be placed in a corresponding tap-off point: Here, the tap-off unit is connected to the trunking unit both mechanically and electrically. This can partly be done with the help of integrated (e.g. EAE System KX) or separate (e.g. Siemens System LI) plug-in aids. In terms of the normative, leading (when plugging in) or lagging (when pulling) the PE conductor in front of the outer conductors is mandatory for the electrical connection.
Protection devices (e.g. fuseless: miniature circuit breaker, circuit breaker or fused: fuse switch disconnector, switch disconnector with fuses) are installed and wired in the tap-off unit. Please note that the primary wiring of these devices must be short-circuit proof.
In addition, further components can be installed in the tap-off unit.
According to the definition of the standard, tap-off units are only approved for tapping and not for supplying energy. This is particularly important with regard to contact safety and the ignition of blown gases on live parts.
equipment
Various accessories are offered for busbar trunking systems: In addition to specific fastening systems and covers, safety-relevant components are also available: A busbar trunking system for fire protection walls can be run with tested fire protection elements. A test according to the fire resistance classes according to DIN EN 13501 is required for this.
Trends in busbar trunking
In recent years, busbar trunking systems have seen an increase in the degree of protection according to DIN EN 60529. In the meantime, IP55 has become an industrial standard, in some cases systems are offered in IP66 or IP68.
In addition, the rated currents of the busbar trunking systems are constantly increasing (6300 A is a usual maximum).
Busbar trunking systems for special applications (e.g. data centers: Arnord Mardix, System Databar; wind power: Siemens, System LDM) are increasingly being offered. These should better meet the special requirements of these applications.
In busbar trunking systems, the current paths can also be used to transfer data; this is done with the help of Powerline Communication ( PowerLAN , PLC). Control lines to the tap-off units are no longer necessary.
Individual evidence
- ↑ Klöckner-Moeller Post 2/56, pages 1 to 22 .
- ↑ DIN EN 61439-6 VDE 0660-600-6: 2013-06 - Standards - VDE VERLAG. Retrieved January 14, 2020 .
- ↑ L. Heinhold, R. Stubbe (Ed.): Cables and lines for heavy current, 5th edition 1999, ( ISBN 3-89578-088-X ) page 103ff .
- ↑ DIN EN 50565-1 (VDE 0298-565-1): 2015-02. Retrieved January 14, 2020 .
- ↑ DIN VDE 0298-4 (VDE 0298-4): 2013-06. June 24, 2013, accessed January 14, 2020 .
- ↑ L. Heinhold, R. Stubbe (Ed.): Cables and lines for heavy current, 5th edition 1999, ( ISBN 3-89578-088-X ) page 28 .
- ↑ Schneider Electric: 'Busbar trunking systems from 20 A to 1000 A', ZXKCanalis 11/2017, page 140 .
- ↑ DIN EN 61439-1 (VDE 0660-600-1): 2012-06, EN 61439-1: 2011, chap. 8.4.3.2.3 .
- ↑ DIN EN 61439-6 (VDE 0660-600-6): 2013-06, EN 61439-6: 2012, chap. 3.111 .