Schemes of electrical networks of residential buildings are performed based on the following:
The power supply of apartments and power consumers, including elevators, should, as a rule, be carried out from the common sections of the ASU. Their separate power supply is performed only in cases where the magnitude of the voltage change at the terminals of the lamps in the apartments when the elevators are turned on is higher than those regulated by GOST 13109-98;
Distribution power lines for smoke exhaust and air overpressure fans installed in one section must be independent for each fan or cabinet from which several fans are powered, starting from the ASU fire-fighting device panel.
Lighting of stairs, floor corridors, lobbies, entrances to the building, license plates and indicators of fire hydrants, lights of light fences and intercoms is powered by lines from the ASU. At the same time, the power lines of intercoms and lights of the light fence must be independent. The TV signal amplifiers are powered from group attic lighting lines, and in non-attic buildings - from independent lines from the ASU.
To power the electrical receivers of residential buildings with a height of 9-16 floors, both radial and main circuits are used. On fig. 1.5. the main circuit with two switches on inputs is given. At the same time, one of the supply lines is used to connect the electrical receivers of apartments and general lighting of common premises; the other is for connecting elevators, fire fighting devices, evacuation and emergency lighting, etc. Each line is designed taking into account the allowable overloads in emergency mode. A break in the power supply according to this scheme does not exceed 1 hour, which is enough for an electrician for the necessary switching to the ASP.
Metering of electricity consumed by general house consumers is carried out using three-phase meters, which are installed on branches and connected to the corresponding busbar sections.
Rice. 1.5. circuit diagram power supply of residential buildings
height 9-16 floors with two switches on the inputs:
1, 2 - transformers; 3 - fuses; 4 - switches;
5, 6 - ASU; 7, 8 - supply lines
In apartment-type residential buildings, one single-phase meter is installed for each apartment. It is allowed to install one three-phase counter. Estimated apartment meters are recommended to be placed together with protection devices (fuses, circuit breakers) and switches (for meters) on common apartment shields. To safely replace the meter, a knife switch or a two-pole switch located on the apartment shield must be installed in front of it.
The group apartment network is designed to power lighting and household electrical appliances.
Group lines are single-phase and, under significant loads, three-phase four-wire, but at the same time there must be reliable insulation of conductors and devices, as well as an automatic protective shutdown device.
Three-phase lines in residential buildings must have a cross section of neutral conductors equal to the cross section of phase conductors if the phase conductors have a cross section of up to 25 mm 2, and for large cross sections - at least 50% of the cross section of the phase conductors. The cross sections of zero working and zero protective conductors in three-wire lines must be at least the cross section of the phase ones.
Rice. 1.6. Schematic diagrams of risers,
The norms regulate the number of sockets installed in apartments. AT living room apartments and hostels must be installed at least one socket for a current of 10 (16) A for every full and incomplete 4 m of the perimeter of the room, in the corridors of apartments - at least one socket for every full and incomplete 10 m 2 of the corridor area.
In the kitchens of apartments, at least four sockets for a current of 10 (16) A should be provided.
A double socket installed in a living room is considered one socket. A double outlet installed in the kitchen counts as two outlets.
If there is an outlet in the bathroom, the installation of an RCD for current up to 30 mA should be provided.
On fig. 1.7 shows a diagram of a group apartment network with an electric stove. For safety reasons, the body of the stationary electric stove and household appliances zero, for which a separate conductor is laid from the floor shield. The cross section of the latter is equal to the cross section of the phase conductor.
Rice. 1.7. Schematic diagram of a group apartment network:
1 - switch; 2 - electricity meter; 3 - automatic switch; 4 - general lighting; 5 - socket for 6 A;
6 - 10 A socket; 7 - electric stove; 8 - storey shield
Electricity of the net public buildings
Power supply schemes and electrical equipment of public buildings have a number of features:
Significant share of power consumers;
Specific modes of operation of these electrical receivers;
Other lighting requirements for a number of rooms;
Possibility of embedding TS in some of the public buildings.
Public buildings are very diverse, so in this manual only some of the most common public buildings are considered.
Calculations and operating experience have shown that with a power consumption of more than 400 kVA, it is advisable to use built-in substations, including complete substations (KTP). This has the following advantages:
Saving non-ferrous metals;
Exclusion of laying external cable lines up to 1 kV;
There is no need to install separate ASUs in the building, since the ASU can be combined with a switchgear ( Switchgear) 0.4 kV substation.
Substations are usually located on the first or technical floors. It is allowed to place transformer substations with dry-type transformers in basements, as well as on the middle and upper floors of buildings, if freight elevators are provided for their transportation.
It is allowed to install both dry and oil transformers on built-in transformer substations. In this case, there should be no more than two oil transformers with a power of each up to 1000 kVA. The number and power of dry-type transformers and transformers with non-combustible filling are not limited. Water should not get into the places where the TP is located.
For consumers of the 1st category of reliability, as a rule, two-transformer transformer substations are used, but single-transformer transformer substations can also be used, subject to redundancy (jumpers and ATS for low voltage).
For consumers of the II and III categories, in terms of the reliability of power supply, single-transformer transformer substations are installed.
The distribution of electricity in public buildings is carried out according to radial or main schemes.
Radial circuits are used to power high-power electrical consumers (large refrigeration machines, pump motors, large ventilation chambers, etc.). With a uniform placement of electrical receivers of low power throughout the building, trunk circuits are used.
In public buildings, it is recommended to carry out the supply lines of power and lighting networks separately. As in residential buildings, at the inputs of the supply networks to the building, an ASU is installed with protection, control, electricity metering devices, and in large buildings with measuring instruments. At the inputs of isolated consumers (trading enterprises, post offices, etc.), additional separate control devices are installed. Where appropriate for operating conditions, circuit breakers are used that combine the functions of protection and control.
Luminaires for evacuation and emergency lighting are connected to a network independent of the working lighting network, starting from the switchboard of the transformer substation or from the ASU. With a two-transformer transformer substation, working and evacuation lighting is connected to different transformers.
Electric receivers of small, but equal or close in value to the installed capacity, are connected in a "chain", which saves wires and cables, as well as reducing the number of protection devices at distribution points.
Group switchboards of the lighting network according to architectural conditions are located on stairwells, in the corridors. Group lines extending from the shields can be:
Single-phase (phase + zero);
Two-phase (two phases + zero);
Three-phase (three phases + zero).
Preference should be given to three-phase four-wire group lines, providing three times the load and six times less voltage loss compared to single-phase group lines.
There are norms for the arrangement of group lighting networks. As in residential buildings, it is allowed to connect up to 60 fluorescent lamps or incandescent lamps with a power of up to 65 W inclusive per phase. This applies to group lighting lines for stairs, floor corridors, halls, technical undergrounds, basements and attics. The distribution of loads between the phases of the lighting network should be as uniform as possible.
On fig. 1.8. a simplified diagram of the power supply of a public building for power receivers of the third category in terms of reliability is given.
Rice. 1.8. circuit diagram
public building power supply
from a single-transformer substation:
1 - supply line to the ASU; 2 - feeding
lines to RP; 3 - RP power receivers; 4, 6 - lines; 5 - group shields
working lighting; 7 - shield of evacuation lighting
The building is powered by a single-transformer transformer substation, from the 0.4 kV shield of which the supply line 1 goes to the ASU of the building. Supply lines 2 depart from the ASU to distribution points of power receivers 3, lines 4 - to group panels of working lighting 5 and lines 6 - to the panel of evacuation lighting 7.
To supply responsible consumers in large cities, two-transformer transformer substations with an AVR device on the low voltage side are widely used. Schemes of such a TP are shown in fig. 1.9 (with ATS on contactors) and in fig. 1.10 (with ATS on the circuit breaker).
The distribution of electricity to power distribution boards, points and group panels of the electric lighting network is carried out according to the main schemes.
Fig.1.9. Schematic diagram of the power supply of a public building
from a two-transformer substation with ATS on contactors:
1 - contactor stations; 2, 3 - outgoing lines to building entrances
Radial schemes are performed for connecting powerful electric motors, groups of electrical receivers for general technological purposes (built-in catering units, premises computer centers etc.), electrical receivers of the 1st category of power supply reliability.
Rice. 1.10. Schematic diagram of public power supply
buildings with a built-in transformer substation and a subscriber switchboard with ATS on a sectional circuit breaker:
1 - automatic switch; 2 - sectional automatic switch; 3 - line to the distribution network of the power network, shields for evacuation and emergency lighting; 4 - line to group shields of working lighting
It is recommended to power the working lighting of premises where 600 or more people can stay for a long time (conference rooms, assembly halls, etc.) from different inputs. At the same time, 50% of fixtures should be connected to each input.
Because electricity represents a great danger to life, the design and construction of multi-storey buildings and industrial facilities must be carried out in compliance with all requirements for the installation of electricians. Since all electrical wiring of industrial and commercial buildings is laid with high-quality cables, it can only be carried out by a qualified specialist. The quality with which the design and execution is carried out depends not only on the safety of electrical appliances, which a large number of has any apartment building, lighting, but also the lives of many people.
Requirements for electrical wiring
There are certain requirements that must be observed when designing and wiring in a new building. They must be respected:
- During the installation of power cables.
- For the purpose of lighting and other circuits that have a voltage not exceeding 1 kW DC and alternating current and are laid inside and outside the objects in the installation wire, in which all sections are insulated, as well as cables that do not have armor, have plastic and rubber insulation up to 16 mm2.
Laying unarmored cables, wires with and without protection through non-flammable walls and ceilings. Through walls and ceilings exposed to fire, installation must be carried out in steel pipe. Openings in walls and openings in ceilings apartment building must have a frame that will prevent their destruction during use. At the points where the cable and wire pass through walls, ceilings, or goes outside, there should be no holes between cables, wires, ducts, openings and other structures. The gaps are easily sealed with a mixture that has fireproof properties and is easily removed, if necessary. Gaps must be closed on both sides of pipes, ducts and other things.
When laying metal pipes in an open manner, the passage through fire barriers should be sealed with non-combustible material after the electrical wiring in the new building has been completed.
When installation cables with a diameter of 4 mm2 or less are exposed, they can be fixed to the wall sheathing or plaster on rollers. Brackets and hooks should only be attached to the main wall material. When the rollers are fastened with wood grouses, washers made of metal and elastic material should be placed under the heads of the wood grouses; if the rollers are fastened to metal, the washers must be elastic.
To ensure the reliability of electrical installation, long and safe service life of electrical wiring, during installation, it should be taken into account that:
- Exposed electrical wiring is laid along the wall under the ceiling, directly on the ceiling, using trusses.
- Open wiring of unprotected cables on building foundations is laid on rollers and insulators, at a height of at least 2.5 m. You can reduce the distance to 2 m in places where there is no increased danger, and when the voltage is 42 V - in any room.
- AT industrial premises the supply to switches, starting devices, socket outlets is protected from physical damage to a height of 1 meter from the floor or service platform. For the domestic sector, residential, public buildings and electrical premises of organizations that have a commercial bias, the electrician does not protect all descents from physical impact.
- When placing wiring in other ways, such as: in a pipe, duct, cable, protected wire - there are no norms for the height of the gasket. The organization of their protection is carried out only where there is a high probability mechanical damage in particular, these are passageways.
- In the open, the wires are laid in such a way that they are not very noticeable in the residential area against the rest of the background. To do this, if it is an apartment building, the wires are laid at the level of the eaves, along the slope of doors and windows.
- When crossing industrially protected and unprotected wires with a water or heating pipeline, a distance of at least 5 cm should be observed, with a hidden laying. When flammable compounds pass through the pipeline - 10 cm or more. When it is not possible to comply with the required indentation, it is required to provide additional protection wires from physical damage.
- When laying cables parallel to pipelines, it is required to keep a distance of at least 10 cm, and from a pipeline with a flammable composition - 400 or more.
- The joints of the wire and their branches should be connected by welding, soldering, crimping in sleeves or using clamps in junction boxes.
Competent design already includes all these requirements.
Requirements for electrical installation in a production room
Since industrial wiring may include self-contained power devices, generators, laying high voltage line, assembly of a transformer substation, etc., therefore, you should adhere to certain rules mounting:
- In such buildings, in order for the electrical installation of industrial facilities to be carried out in accordance with all the rules, it is mandatory to have an electrical panel equipped with a central switch.
- Power for lighting each room should be separate.
- Each electrical appliance should have its own circuit breaker in order to increase the overall safety of the production line.
- A prerequisite is the wiring of the cable in metal pipe and special trays.
- In any workshop, the installation of a ground bus is mandatory, and all machines must be grounded with a hard wire that is connected to the bus.
- The work and maintenance of all electrical appliances must be carried out in accordance with all PUE standards, the rules for protection against static electricity and other things, including a lightning rod. This must be taken into account when designing.
Video about installation in a new building
In multi-apartment buildings, energy input and distribution systems generally depend on the building itself (the amount of electrical equipment in it to ensure its life). Let's try to understand the devices of such systems.
Energy distribution in an apartment building with a TN-C system
TN-C is an outdated system, but it is actively used in old houses. This is a four-wire system consisting of three voltage phases and a combined neutral and working conductors (L1, L2, L3, PEN). In this system PEN conductor is not subject to splitting and in this form and comes to the consumer. It is also worth noting that quite often the phase wires are given the name A, B, C.
As a result, with such a power supply system, with a single-phase connection, the consumer is connected with two wires (L, PEN), and with a three-phase connection with four (L1, L2, L3, PEN).
A power cable comes from the substation to the house, laid underground. The cable enters the input box connected to the switchboard:
Vertically laid risers will already depart from it. On each floor, floor shields will be connected to the risers, from which the apartments will be supplied with electricity.
Inputs can be made different ways, it directly depends on the number of storeys and the size of the house, on the cable laying system (in the collector or in the ground). Why is that? Yes, because the load of a house with 100 apartments will be significantly lower than a house with 500 apartments. Moreover, the power supply requirements of, for example, a five-story building are relatively small - there are no elevators in the house and there is no need to install additional pumps to maintain water pressure, which can not be said about a 30-storey building, where it is impossible to leave elevators and water supply pumps without power.
It is for these reasons that in big houses can enter not one, but two or more power supply cables. Distribution execution electrical energy between common house loads (elevators, entrance lighting, pumps) and apartments, the task is rather complicated and time-consuming. The distribution is carried out using complete electrical devices, the mounting methods, dimensions and installation locations of which are coordinated with the structures of the houses.
Let's look at options for connecting apartments to risers in multi-apartment buildings with a TN-C system. The riser has four wires - three phases and one PEN conductor, indicated in the diagram as A, B, C and PEN:
Between the phases (A-B, C-B, C-A), the voltage will be 1.73 or more than between any of the phases and the neutral conductor (zero). From here we calculate the voltage between phase and neutral - 380 / 1.73 \u003d 220 V. Two wires enter each of the apartments - phase and neutral. The current in both of these wires will be exactly the same.
They try to connect the load (in our case, apartments) evenly to different phases. In figure a), out of six apartments, two are connected to each phase. Uniform connection makes it possible to reduce and avoid phase imbalance.
In houses of old construction, combined electrical cabinets were sometimes used instead of floor shields. An example of such a cabinet is shown below:
This cabinet has compartments with separate doors. In one compartment there are plates with apartment numbers, switches and circuit breakers. In the other, meters, in the third, low-current devices such as telephones, television antenna networks, twisted pair intercom, internet and other devices.
In such a floor shield, each apartment includes one switch and two automatic switches (the first for the general lighting line, and the second for socket outlets). In some versions of electrical cabinets, the presence of socket outlet with protective contact for connecting various machines (e.g. harvesters).
Energy distribution in an apartment building with a TN-C-S system
In a residential area, electrical wiring consists of an electrical input, a group electrical network, distributing energy from the switchboard throughout the room and, in fact, the switchboard itself. For each group of consumers, electrical wiring is carried out with a cable with a certain cross section and circuit breakers with previously calculated ratings.
Input and distribution devices
As mentioned earlier, the power cable coming from the substation goes to the VU (input device) or ASU (input switchgear). For apartment building their main difference from each other will be the availability of equipment for the ASU to distribute energy throughout the building.
So, ASU is a set of protective devices (fuses, circuit breakers, and so on), devices and devices for electricity metering (electricity meters, ammeters, and so on), electrical equipment (tires, circuit breakers, and other devices) and also building construction installed at the entrance to a building or residential premises, which include protective devices and metering devices (electricity meters) of outgoing electrical wiring lines.
You also need to remember that re-grounding lines are suitable for both the WU and the ASU, which means that the splitting of the incoming PEN conductor can only be done here.
When using the TN-C-S system, the combined PEN conductor coming from the substation must be split. The TN-C-S system will take place only after splitting from the side of the transformer substation. In modern floor shields, three-phase automatic machines and difautomatic devices are usually installed.
After the ASU or VU, electricity is supplied to the storey switchboards of an apartment building. When using the TN-C-S system, five wires (L1, L2, L3, N, PE) go to consumers.
And who will be interested a little about the VRU:
Power supply schemes for residential buildings can be divided into three categories to ensure the reliability of power supply. The first category of reliability is characterized by the presence of two supply cables connected to two different transformers. If one of the network elements (cable or transformer) fails, the load is connected to the operating power supply element using an automatic transfer switch (ATS). In this case, the time to turn on backup source nutrition should be minimal. Can be used as a backup power source rechargeable batteries or local power plants. Power supply in the first category is carried out for hospitals, hazardous production facilities, a number of public buildings.
The power supply scheme of an apartment building of the second reliability category also provides for the presence of two supply cables and two transformers. The standby source is switched on by the duty personnel. It is used in residential buildings with more than 5 floors ( gas stoves).
Most simple option is the third category - one power cable for powering a residential building, extending from a transformer substation. When emergency interruption in the supply of electricity should not exceed one day. This type of power supply is used in 5-storey (gas stoves) and 9-storey ( electric stoves).
Consider the power supply scheme of an apartment building. The power supply scheme is presented in the form of the second category of reliability. Zero position of the switch - both cables are disconnected; "1" position - the main cable is connected; "2" position - the reserve cable is connected. Connection of electrical receivers is carried out through automatic switches (QF1 ... QF4 - power supply for apartments, QF5 and QF6 - power supply for entrance lighting circuits).
The connection of all electrical receivers occurs through various electrical protection and control devices located in electrical cabinets. As a rule, electrical equipment is divided into functional groups. Each functional group pull out their control cabinet. The following groups are distinguished:
1. Introductory devices and electricity metering units.
2. Reversing knife switch with current protection elements.
3. Circuit breakers outgoing lines.
It is not difficult to notice that a fairly large number of various switching equipment and protection devices are located in control cabinets. Each device is, first of all, a mechanism that has a certain mechanical and electrical durability. Therefore, each of these devices is not durable and its use not in the nominal operating modes leads to premature failure. In this case, both a separate electrical receiver (apartment, entrance) and a group of electrical receivers may suffer.
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