Development of the internal power supply system of the administrative building of small storeys

Introduction

A modern administrative building cannot be imagined without a reliable and safe power supply system, so a well-designed building system is a guarantee of its durability

The power supply system shall be reliable, economical and safe. At the same time, the correct determination of electrical loads in the process of designing components of the power supply system plays an important role.

The solution of these tasks is not complete without comprehensive consideration of the issues of power supply safety, therefore, the task of modernizing the power supply using modern technologies and materials while increasing the level of safety is very urgent.

The issues of power supply of enterprises and civil buildings are reflected in the works: Knyazevsky B.A., Lipkin B.Yu., Postnikov N.P., Rudakov R.M. These works can serve as the basis for the development of more modern power supply systems.

The present work solves the current task of designing the power supply system of the administrative building of a small floor that meets not only the requirements of increased electrical safety but also the requirements of reliability and economy

Electrical Load Analysis

1.1Analysis of electric power consumer characteristics and power supply category

The main consumers of the electricity of the administrative building are consumer electric receivers, computer equipment, ventilation equipment, air conditioning and lighting. Lighting installations operate in a long-term mode with a power factor. The building of a small building with the number of working more than 50 people in terms of reliability belongs to consumers of the second category to receivers of the first category include server, electric receivers of fire protection devices, security alarms and elevators.

Protection against electromagnetic fields, static electricity, radiation

When working with PC, a person is exposed to various man-made radiation. The main source of radiation is

monitor. Samtron 55E monitors, 17 developed by Samsung Electronics ″ are installed in the considered office premises. Monitors meet the requirements of the TSO99 standard, which regulates the interaction of PCMs with the environment and is aimed at reducing the harmful effect of radiation to a technically possible level.

To reduce the influence of electrostatic fields arising from the design of the electron beam tube, the surface of the screen is coated with quartz with anti-electrostatic properties. Additionally, it is recommended to wipe the monitor screen periodically, thereby removing a significant part of the electrostatic charge.

Keep in mind that the maximum values of electromagnetic field intensity are observed near the rear cover of the monitor, and take this into account when placing workplaces in the room.

To reduce X-rays, salts of heavy metals are usually added to the screen glass of the monitor.

Installed monitors meet ergonomics and safety requirements, so no additional protection measures are provided.

Lightning protection

This administrative building belongs to structures of category II. As protection against direct lightning strikes of buildings and structures of category II with a non-metallic roof, it can be made either by separate or installed on the protected object rod or cable lightning ducts, or by lightning screen. The roof slope of the building is not more than 1:8, so a lightning screen can be used. Lightning screen shall be made of steel wire with a diameter of not less than 6 mm and laid on the roof on top or under non-combustible or difficult to burn insulation or waterproofing. Grid cell spacing shall not exceed 6x6 m. Grid nodes shall be welded. The metal elements protruding above the roof (pipes, shafts, ventilation devices) shall be connected to the lightning screen, and the protruding non-metallic elements shall be equipped with additional lightning receptacles also connected to the lightning screen. Current leads from the lightning intake grid shall be routed to the earthing terminals at least 25 m later along the perimeter of the building.

Metal structures of buildings and structures (columns, trusses, frames, fire ladders, etc., as well as reinforcement of reinforced concrete structures) should be used as current leads, provided that continuous electrical communication is provided in connections of structures and reinforcement with lightning receptors and earthing connectors, performed, as a rule, by welding. Current leads laid on the external walls of buildings should be located no closer than 3 m from the entrances or in places inaccessible for people to touch .

The functions of grounding conductors, protection against direct lightning strikes in all possible cases should be performed by reinforced concrete foundations of buildings and structures.

If foundations cannot be used, artificial earthing connectors shall be provided; In large area buildings, the outer ground loop can also be used to equalize the potential inside. To protect buildings and structures from secondary lightning events, the following measures shall be provided:

a) metal bodies of all equipment and apparatus installed in the protected building (structure) shall be connected to the grounding device of electrical installations, or to the reinforced concrete foundation of the building.

b) bridges shall be made inside the building between pipelines and other extended metal structures in places of their mutual approach for distances less than 10 cm every 30 m.

c) normal tightening of at least 4 bolts for each flange shall be provided in flange connections of pipelines inside the building.

To protect external installations from secondary lightning manifestations, the metal bodies of the devices installed on them must be connected to the grounding device of electrical equipment or to the ground conductor for protection against direct lightning strikes .

Protection against high potential drift through underground communications shall be performed by connecting them at the entrance to the building or structure to the ground conductor of the protection against direct lightning strikes .

Protection against skid of high potential by external ground (above ground) communications must be performed by connecting them at the entrance to the building or structure to the ground conductor for protection against direct lightning strikes, and at the communication support closest to the entry - to its reinforced concrete foundation. If it is impossible to use the foundation, an artificial grounding conductor shall be made, consisting of one vertical or horizontal electrode with a length of at least 5 m.

To protect against high potential drift, the following conditions shall be met through overhead transmission lines, telephone, radio and alarm networks. Air lines with a voltage of up to 1 kV, telephone networks, radio, alarm should be entered into buildings only by cables with a length of at least 50 m with metal armor or a shell or laid in metal pipes.

At the entry into the building, metal pipes, armor and cable shells, including with insulation coating of the metal shell (for example, AAIIv, AAIIp), must be connected to the reinforced concrete foundation of the building or to an artificial grounding electrode.

At the point of transition of the overhead line to the cable, the metal armor and cable sheath, as well as the pins or hooks of the overhead line insulators, shall be connected to the grounding conductor. Pins or hooks of insulators on the overhead line support closest to the cable transition point shall be connected to the same grounding conductor.

In addition, closed air spark gaps of 2-3 mm length or a low-voltage valve arrester shall be provided at the point of transition of the overhead line into the cable between each core cable and the grounded elements. for example, PBH0.5. According to PUE of the room, intended for operation of computer facilities, refers to the category of rooms without increased danger, since electrical safety is provided by the design of electrical installations, as well as technical methods and protective equipment. Technical methods and means of ensuring electrical safety are divided into two groups: providing protection against accidental contact with current-carrying parts and protecting against shock when touching metal non-flowing parts, which may be energized as a result of insulation damage.

To ensure electrical safety, grounding is provided in premises equipped with computer equipment.

According to the PUE, at least one of the following measures should be used for protection against shock in case of insulation damage: grounding, suspension, protective shutdown, low voltage, double insulation, potential equalization.

Fire safety

Fire and explosion hazard production category - D in accordance with

The process of software design, as well as PC operation according to SNiP 2.01.0285, belongs to category D for explosion and fire hazard. The building has fire resistance rating not lower than the third, in accordance with SNiP 2.09.0285.

The causes of fire in premises with PC are most often electrical (short circuit, overloads, high transient resistance; spark, electric arc).

To prevent fire, provide:

training of employees; Conducting briefings, lectures and subsequent certification;

correct operation of machinery, equipment, buildings and territories;

observance of fire rules and norms in the installation of heating and ventilation systems;

prohibition of smoking in non-designated places.

A fire alarm is used to detect the beginning of the fire. For example, smoke photovoltaic detectors - sensors such as IDF - M, triggered by a change in the luminous flux of smoke particles can be used. They send an alarm to the fire alarm station when smoke occurs at the location of the detector. Detectors above workplaces are installed.

Hand-held carbon dioxide fire extinguishers, such as OU5, are used as primary fire extinguishers. Carbon dioxide is not electrically conductive and is suitable for extinguishing electrical installations under voltage.

People are evacuated through the door, which opens in the direction of leaving the building.

Conclusion

The following results are obtained in the work:

Analysis of consumer characteristics and category of power supply was carried out. It was established that in the building there are electric consumers operating in a long-term load mode. The building belongs to the second category of power supply requiring two transformer substations.

Electrical load calculation methods have been analyzed. It has been found that it is most appropriate to use the demand factor method to solve this problem.

Power supply system is designed. The design process included the following steps:

3.1. Calculation and selection of electrical devices, cables and wires for power supply diagram

3.2. Selection and substantiation of electric energy meters and current transformers of the input switchgear.

3.3. Calculation of short-circuit currents

Economic calculation was made, which included the following steps

4.1. Evaluation of cost-effectiveness of different types of lighting fixtures

4.2. Estimated calculation of electrical works

Occupational and environmental protection issues have been worked out and included the following steps.

5.1. Protection against electromagnetic fields, static electricity, radiation

5.2. Lighting Network Calculation

5.3. Lightning protection

5.4. Calculation of grounding devices

5.5. Fire safety