Main distribution board (MSB): features

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The main distribution board (MSB) is a distribution device that is responsible for receiving and further distributing energy throughout the building. Main switchboards can also be connected to networks with a solidly grounded neutral type of grounding:

TN-C;
TN-S;
TN-CS.

Main switchboard

It can also be used to protect lines from overload, current leakage and short circuits. The device may contain emergency automation, as well as electricity metering devices. To purchase high-quality switchboard equipment, follow the link elektrika.ru. In this store you can expect low prices and high-quality equipment.

Design

The panel structure must necessarily include the following parts: introductory, sectional, linear panels. Input machines will be installed in the water panel, which are responsible for receiving electricity from transformers and other metering devices. In a sectional panel, specialists usually install an automatic switch, which allows powering several sections of one input. ATS can also be placed here. This device is used for backup power supply.

Automatic reserve input

The main switchboard circuit can be varied, as it depends on the number of incoming and outgoing lines. Most switchboards can have a circuit with two inputs and two outputs. When using such a scheme, the input will be from 2 transformers, and the output will go through the sectional panel to the distribution buses. Many electricians consider the main advantage of the main switchboard to be that all sections are collapsible.

The main characteristics that you need to pay attention to during purchase include:

Nominal points of input and output lines.
Rated mains voltage.
Grounding system.
Degree of protection according to GOST.

Each distribution board can be equipped with the following metering devices:

automatic switches;
control and measuring instruments;
metering devices;
load switches;
automatic entry of reserve.

If you install the correct devices in the main switchboard, then you can use it to replace the ASU. The main difference between the main switchboard and the ASU is the strength of the maximum input current.

Automatic switches in main switchboards

What are the similarities and differences between the main switchboard and the ASU?

The main distribution board (MSB) and the input distribution device (IDU) perform almost the same functions:

reception and distribution of electrical energy received from external sources;
protection of power lines from overloads and short circuits;
electricity metering and automatic switching on of backup power (these options may not be available on some products).

The functional similarity of these switchgears is emphasized by the definition of clause 7.1.4. PUE, which states that the ASU can serve as the main distribution board.

However, there is a fundamental difference between these distribution devices. The input-distribution device is always located at the facility's power input, while the main switchboard, in addition, can be located on the territory of the supply substation, performing the functions of a low-voltage switchgear.

Main switchboards and ASUs, as a rule, also differ in design. The main switchboard is a set of several voluminous cabinets - panels; the equipment of the input distribution device (IDU) is usually located in one cabinet of a relatively small volume. ASUs consisting of several cabinets are much less common.

The difference in technical characteristics is significant, since the maximum operating current of the input switching devices ASU, given in GOST R 51732-2001, is 630 amperes. Certain models of main distribution boards, mass-produced by Russian manufacturers, are designed for an operating current of 4000 amperes or more. This circumstance allows us to classify the main switchboard as a group of switchgears located at a higher level of the hierarchy than the ASU.

Marking of electrical panels

The wires of all internal circuits must be color coded. It must have a sharp contrast and be resistant to abrasion. Terminals for PE and N conductors that extend from distribution and group circuits should be marked with serial numbers. If connecting wires to the device terminals is difficult, then intermediate clamps must be provided. The clamps must also be marked with serial numbers.

A sign with information must be placed on the door on the outside of the main switchboard. Typically the nameplate contains the following information:

Manufacturer's name.
Type designation.
Device protection level.
Rated current of the ASU.
Weight.
Identification of all technical conditions.
Date of manufacture.
Additional Information.

Marking in the main switchboard

Installation technology

Power supply to the main switchboard today is carried out through the main busbar and is produced from the low side of the transformer. The electrician should also remember that the main switchboard sections should be powered by mutually redundant lines.

Before starting installation, you must first place the circuit breakers on the mounting panel. Then it is necessary to adjust the placement of the copper busbars in the busbar holders of the device. The easiest way to install equipment is when the main switchboard is located on the table. All automatic input elements must be placed on a DIN rail. When locating high-power circuit breakers, they should be located one below the other. Thanks to this arrangement, the amount of work required to disconnect the tires will be significantly reduced.

Main switchboard wiring diagram

PE and N busbars are usually installed on insulators and subsequently fastened together along the entire length. In the future, holes are made in them to disconnect the cable lines. To exclude the possibility of further electric shock, plastrons are installed, which are made of non-flammable material. If you are interested, read about the distribution panel assembly diagram.

Features of the electrical panel

Often home renovations need to be combined with electrical wiring repairs. If you do it with a large margin of safety, then this may ultimately cause a fire.

If, on the contrary, you make it unbearable to loads, then the plugs on the electrical panel in a private house will have to be constantly changed. Therefore, both the shield and the wiring must be carefully calculated for the current and voltage.

What is current strength

Any electrical appliance has an indicator indicating current and power consumption. If there are no current values on it, but only power consumption and voltage, then you need to divide the power by the voltage value.

When calculating the electrical panel in a private house, it is necessary to take into account the current strength. The maximum current value in an apartment is determined as the sum of the power consumption of all switched on devices, divided by a voltage of 220 Volts. If the wiring is designed for low current, then with a small load they can burn out.

It is necessary to calculate not the nominal, but the peak load, because in any apartment sometimes a vacuum cleaner or iron is turned on. So, for example, if a computer of 400 W, a lamp of 100 W, a table lamp of 75 W, a TV of 150 W, as well as a “stray load” of a heater of 2 kW, a vacuum cleaner of 1.8 kW, are constantly turned on in a room, then the peak consumption of the room will be 5.5 kW or 25 amperes.

What is the shield for?

Many home owners do not know what an electrical panel is for. Its main purpose is to protect against network overloads that can cause a fire.

If the wiring has a low cross-section, then under heavy loads it may not withstand and catch fire. If there are oversized circuit breakers on the electrical panel, then if high-power appliances are turned on in the house for a long time, the sockets may burn out.

If you increase the cross-section of the wiring, then the apartment, in fact, will also be left without protection: the machines may not respond to high load parameters. In a word, the shield must have optimally selected plugs, which must match both the power consumption and the cross-section of the wiring.

What types of wires are there?

Standard wires are connected to the panel. Copper wiring has four standard types of cross-section - from 1.5 mm 2 to 6 mm 2. The permissible current strength of the thinnest wire is 15 amperes, the thickest is 34 amperes. The aluminum wire must have a much larger cross-section. It is not recommended to use soft cables, as there may be problems with the safety of the wiring.

Be careful: shields in a private house and sockets are not suitable for wires smaller than one and a half square meters. mm. There is also no need to take machines smaller than 10 amperes.

What needs to be installed in the panel

The panel must provide for the division of wiring into several lines. If there is one line in the house, then in the event of an accident the entire house will be de-energized. By dividing the wiring into several parts, it will be easier to determine the location of the accident.

Several circuit breakers need to be installed in an electrical panel in a private home. For example, for each room you need to install a separate machine. Ideally, there would also be an automatic for lighting. The machines receive power through one large machine. This is necessary so that you can quickly turn off the power to the entire room. The machine is numbered in position from left to right.

Installation and replacement of the shield

You can install the electrical panel yourself. The simplest procedure in this case is to replace the machines.

The meter can be seen on the panel, as well as a batch switch and automatic machines. The batch switch looks like a device with four contacts and a rotary handle. From the main electrical wires, phase and zero come to the panel.

Before replacing machines, you need to check their nominal value and buy the same one. In no case should you install a machine with a larger rating, as this leads to accidents if many powerful devices are turned on simultaneously on one machine.

Replacing the machines is done with the package switch completely turned off. However, you need to be careful, otherwise if you move incorrectly you can be left without light. Remember that you cannot repair or install a packet switch yourself. To do this, you need to call a qualified electrician.

If a short circuit occurs when installing machines, you need to check the condition of the wire insulation and, if necessary, replace it with electrical tape.

Plastic enclosures for the electrical panel can be purchased at the store. As a rule, they have a ready-made DIN rail. The product package also includes grounding pads and a zero. You should not buy cases with plastic slats, as they break and do not provide the necessary safety.

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Safety requirement when installing main switchboards

General labor protection requirements

Only persons over 18 years of age are allowed to work in the distribution panel. Also, before working in the main switchboard, they must undergo a medical examination, induction training, initial training, as well as training and internship. The electrical safety level must be at least group 3.
The work of a specialist must be defined by a work or job description.
It is necessary to comply with internal labor regulations.
Individual or collective protective equipment should be used correctly.
If a situation arises that threatens people's lives, you must inform your superior. A specialist who works with the shield must undergo regular medical examination.
During work in the cabinet, hazardous or harmful production factors may occur.
The employee must be provided with special clothing, shoes and other personal protective equipment.
As a result of injury, work must be stopped immediately and the supervisor must be informed.

Requirements before starting work

You should select the necessary tool to begin the work. Tools must be visually inspected to ensure they are in good working order.
Wear special clothing.
Before carrying out work, inspect your workplace.

Requirements in emergency situations

If faulty equipment occurs, the employee must notify his superiors.
If the smell of gas is detected, work must be stopped immediately.
Gas removal work should be carried out by professionals.
If you are injured, you should stop working and contact a medical facility.
If an accident occurs, then the victim needs to provide first aid.

Requirements while working

Before starting work, the worker must make sure that there is no extraneous voltage.
Warning signs must be placed on the outside of the internal door of the ShR type cabinet.
The inlet hole, which is located in the cabinet, must be hermetically sealed.
Before using a blowtorch, make sure there is no gas in the cabinet well.
Smoking in the control cabinet during work is prohibited.

Requirements upon completion of work

The workplace should be put in order.
Close the closet.
Gather all the tools.
Inform management about any shortcomings you find in the shield.

Signs on the main switchboard