The assembly of the switchboard is critical to the reliability of an electrical installation. It must comply with well-defined standards governing the design and construction of low voltage devices.
Switchboard assembly is the creation of a point at which the input power source is disconnected into separate circuits, each of which is controlled and protected by fuses. This design is divided into several functional blocks, each of which contains all the electrical and mechanical elements that contribute to the performance of the declared function. For example, assembling a 380v switchboard in a private house is necessary in order to create a key link in the reliability chain.
Therefore, the design type must be perfectly adapted to its application. Its design and construction must comply with applicable standards and practices.
Switchboard box assembly provides triple protection:
- First of all, it is the safety of measuring instruments, relays, fuses, etc.
- The switchboard assembly must include protection against mechanical influences, vibrations and other external factors that may affect the operational integrity (electromagnetic interference, dust, moisture, parasites, etc.).
- Protection of human life from the possibility of direct and indirect electric shock.
Types of switchboards
Load requirements determine the device models to be installed.
Switchboard assemblies 380V and below may vary depending on the application and design principle adopted (especially busbar arrangement).
Main types:
- Main low voltage model - MLVS.
- Engine control centers - MCC.
- Sub-distribution switchboards.
- Final models.
And the last three-phase switchboard assembly is designed for specific applications (eg heating, elevators, industrial processes). It can be located:
- Near the main low voltage facility.
- Next to attached items.
- Sub-distribution and final switchboards. usually spread over the entire area.
Two technologies
Distinguish:
- Universal distribution boards in which various devices, fuses, etc. are attached to the chassis at the rear of the case.
- Functional models for specific applications based onon a modular and standardized design.
Universal
The switchgear, as noted above, is usually located on the chassis at the rear of the case. That is why the assembly of the switchboard with your own hands is very simplified. But it should be borne in mind that the display and control devices (meters, lamps, buttons, etc.) are installed on the front panel.
The placement of components inside the case requires very careful consideration, considering the dimensions of each element, the connections that must be made to it, and the clearances needed to ensure safe and trouble-free operation.
Functional switchboards
As a rule, these are models designed for specific applications. Consist of functional modules that include separation devices, along with standard accessories for mounting and assembling the switchboard, and connection, which ensures a high level of reliability and large capacity for changes at any moment in the future.
Many benefits
The use of functional switchboard assemblies has spread to all levels of low voltage devices, from main to end, due to their many benefits:
- Modularity of the system, which allows you to integrate all kinds of functions in one model, including protection, maintenance, operation and modernization.
- Self-assembly of the switchboard and its structure is fast. That's whythat this model, unlike others, simply includes the addition of functional modules.
- Of course, assembling a private house switchboard can be even faster. This is due to the fact that for the average user, the developers are trying to simplify the design as much as possible.
- Finally, these models are subjected to type tests which ensure a high degree of reliability. Assembling a switchboard with your own hands has really become not only faster, but also safer.
Schneider Electric's Prisma G and P range of functional units require up to 3200 A and offer:
- Flexibility and ease of construction.
- IEC 61439 certification and safe service guarantee.
- Saving DIY switchboard assembly time step by step, from design to installation, operation and modifications or upgrades.
- Easy adaptation, for example to suit specific work habits and standards in different countries.
Fixed
There are three main technologies used in basic switchboards. Fixed - these units cannot be isolated from the power supply, so any intervention for maintenance, modifications, etc. requires the entire device to be turned off. However, plug-in or plug-in models can be used to minimize outage time and increase availability for the rest of the installation.
Disabled
Each function blockmounted on a plug-in board and provided with means of isolation on the input side (busbars) and disconnection at the output side (circuits). Thus, the entire device can be removed for maintenance without a general shutdown.
Retractable
The assembly of the metering switchboard and related accessories in this case is a little more complicated. This is because the devices, for completeness of functions, are mounted on a retractable horizontal chassis. This model tends to be complex and often involves motor control.
Insulation is possible on both the inlet and outlet sides by pulling out the drawer completely, allowing a faulty unit to be quickly replaced without shutting down the rest of the switchboard.
Standards
Compliance with applicable benchmarks is essential to ensure an adequate degree of reliability.
The IEC 61439 (Low Voltage Switchgear and Control) series of standards has been developed to provide end users with a high level of confidence in terms of the safety and availability of electricity.
Reliability aspects include:
- Harmless to humans (risk of electric shock).
- Fire protection.
- Explosion hazard.
Availability of power supply is a major issue in many sectors of activity, which can lead to significant economic consequences in the event of a long interruption associated with the failure of the distribution board.
Standardsestablish design and verification requirements, so failure should not be expected in the event of malfunction, disturbance, or operation in harsh environmental conditions.
Compliance with standards should ensure that the switchboard operates accurately, not only in normal conditions, but also in difficult ones.
Three elements of IEC 61439-1 and 61439-2 contribute significantly to reliability:
- Clear definition of functional units.
- Dividing shapes between adjacent blocks according to user requirements.
- Well-defined screening tests and routine checks.
Standard structure
The IEC 61439 series of standards consists of one basic postulate (IEC 61439-1) containing general rules and several related abstracts detailing which of them apply (or are not used, or should be adapted) for specific types, for example, assembling a switchboard in an apartment:
- IEC / TR 61439-0: Guidance for identification.
- IEC 61439-1: General rules.
- IEC 61439-2: Power Distribution and Control Assemblies.
- IEC 61439-3: Boards intended for use by the general public.
- IEC 61439-4: Particular requirements for devices for construction sites.
- IEC 61439-5: Assembly of electrical switchboards in public networks.
- IEC 61439-6: Busbars.
- IEC / TS 61439-7: Assemblies for special applications such as marinas, campsites, marketplaces, stationscharging electric vehicles.
The first edition of these documents was published in 2009 and revised in 2011.
Requirements based on end user expectations
Various applications included in the standards have been introduced in order to meet the many expectations:
- Ability to operate the electrical installation.
- Ability to withstand great stress.
- Current capability.
- Withstand short circuit.
- EMC.
- Protection against electric shock.
- Maintenance and modification capabilities.
- Possibility of installation on site.
- Protection against fire risk and environmental conditions.
Clear definition of responsibilities
Distribution boards are qualified as assembly boards, including switching devices, control, measuring, protective, regulating equipment, with all internal electrical and mechanical connections and structural elements. Assembly systems include mechanical and electrical components (enclosures, rails, functional blocks, etc.).
The original manufacturer is the organization that has carried out all the design and associated assembly verification in accordance with the standard. He is responsible for the design tests listed in IEC 61439-2, including many electrical tests.
Verification can be controlled by a certification body that licenses the original manufacturer. These documentsmay be passed to the specifier or end user upon request.
The builder is usually the organization that takes responsibility for the completed design. The model must be completed according to the instructions. If the assembly manufacturer is based on the original inventor's guidance, they must re-survey the design.
If there are deviations, they must be presented to the original creator for review. At the end of assembly, normal testing must be performed by the distributor.
The result is a fully tested model, for which the original manufacturer has performed design checks, and the final manufacturer has carried out routine inspections.
This procedure provides better reliability to the end user compared to the "Partly Type Checked" approach offered by the previous IEC60439 series.
Design Requirements
In order for an assembly system or switchboard to meet standards, different requirements apply. These requirements are of two types:
- Construction.
- Productive.
The design of the assembly system must meet these requirements under the responsibility of the original manufacturer.
Installation of switchboard
This is one of the most important works that should be carried out only according to the instructions provided. This document must be enclosed with the goods at the time of purchase. With a good and understandableschemes, such installation turns into a purely technical task and does not present any difficulty. In this case, at the very beginning, it is necessary to ensure the correctness of all connections of individual user groups and the reliability of connections. To get started, you should unpack everything and prepare the necessary additional tools.
The assembly of the shield itself is carried out only after wiring in the room or office in accordance with the instructions provided. The ends of the products of each group are marked, inserted from below into a pre-mounted shield and bifurcated or rastered, depending on the need.
Power input is from above. DIN rails are formed in the shield. Then, zero and ground tires and a sorting box for the phase cable are installed. Safety devices are mounted from top to bottom and from left to right with their synchronous connection according to the diagram. Zero wires are inserted into the N tire, and those operating the safety ground - into PE.
During the installation of the shield, it is necessary to observe the color ratio of the products to its multifunctional purpose: white - phase, blue - zero, yellow-green - safety ground. This kind of procedure will make it possible to eliminate many errors.
Depending on the characteristics of the internal connection and the installed circuit, the sorting board may contain a common protection device, RCD, switches, zero and main grounding tires, a flow meter and other equipment.
Without exception, all innovative devices have a specific width,multiple of one value - module (18 millimeters). Thus, a unipolar apparatus is 18 mm, i.e. one segment, a bipolar 36 millimeters - two, etc. A single-phase RCD has a width of 2 modules, a three-phase one - 4. This design makes it possible to choose a steel shield according to the number of segments and type contacted devices.
Integrated sorting devices are formed in a niche and then smeared with cement. The depth of the collection must also be set according to the scale of the shield, taking into account the wall thickness.
Grounding and neutral busbars are brass plates with holes and screws to securely connect wires. They can be installed in a special heat-insulating block housing with a DIN-rail mounting perspective.
When installed in apartment rooms, modular panels make it possible to preserve the aesthetics of interior decoration. In order to mount devices in the rear wall of the sorting element, specialized iron contour profiles are formed - DIN rails.
Dimensional scales of safety devices of different manufacturers may vary both in width and elevation. Therefore, when obtaining these devices, it is necessary to focus not only on industrial properties, but also on their rectilinear scales. This will enable the safety panels to be applied effectively to provide an aesthetic outdoor style.
Already after the installation of equipment and execution in the electrical connection panel, an iron or plastic panel is installed on top of it,hiding device terminals, cable and DIN rail and protecting against contact with current-carrying parts. Slots are made in the panel, providing visibility of devices and access to their controls. The vacant part of the slot is covered with plastic plugs.
When assembling the sorting board, all wires are first introduced into it, which must be marked by all means. This eliminates most of the errors made during assembly. For the purpose of marking, as a rule, masking tape with numbers or multi-colored electrical tape is used.
For branching of phase wires, you can use sorting structures that make it possible to connect conductors of different cuts and guarantee protection from touching the current-carrying share thanks to a replaceable cover. The body of this unit is made of a flame retardant material that is stable to heat and has excellent electrical insulation properties.
When communicating wires, special attention must be focused on the correct connection of the RCD. The most popular error is considered to be its connection to a group in the circuit of which there is a combination of a zero working conductor with open conductive parts of the electrical installation.
Short sequence
Installation of the sorting board contains the following procedures:
- installation of a metal box of the required volumes;
- marking the supply wires with the prescription of the category and section number, and connecting them with the correspondingappliances;
- Introduction of pre-marked devices into the stand and butchering their ends;
- establishing the order of placement of safety parts in accordance with the scheme for distributing consumers into groups;
- fixing DIN rails and connecting one by one according to the diagram;
- marking each device with the prescription number of the category for which it is specialized in order to avoid possible errors;
- control of the accuracy of all connections according to the marking of input wires and protection devices of all groups.
After the installation is completed, the bundles of the same name must be tightened with special ties and placed in the free areas of the shield.
The readiness of the RCD to operate can be tested using the control key, which is supplied with each safety shutdown device. When it is pressed, an electric leakage current is formed into the ground, which should activate the inclusion of the working device.
