Power supply for lighting installations. luminous flux ripple
The forms of government depend on who is recognized as a citizen, or on the number of those in power. It is impossible, according to Aristotle, to recognize as citizens all who are useful to the state. Not only slaves should be eliminated from among the citizens, but also those who, due to lack of prosperity, leisure, education, are not able to come to reasonable decisions on their own. These are foreigners, artisans, merchants, sailors.
Aristotle does not give civil rights to women.
Citizens are those "who participate in legislative and judicial activities." There may not be complete equality between them. A full citizen is one who can be elected to any position. A sign of a good citizen can be a practical knowledge of the organization and life of the policy, both as a subject and as an official.
Aristotle divides the states into three groups according to the number of those participating in government: where one person rules, a few and a majority. But he adds ethical to the numerical criterion. Depending on whether the ruler thinks about the common good or cares only about his own interests, the forms of government are right and wrong (perverted).
Based on the combination of these two criteria, Aristotle identifies and characterizes six forms of government. The correct power of one person is called a monarchy, and the wrong one is called tyranny. The correct government of the few is the aristocracy, and the wrong is the oligarchy. The correct rule of the majority is called polity, and the wrong rule is called democracy.
Monarchy is a real concentration of power in the hands of one person. Aristotle has no fondness for this form. He prefers the rule of the best laws to the rule of the best husband. For a monarchy to be correct, a king must be a great man.
Wrong monarchy (tyranny) Aristotle considers the worst form of government.
The philosopher gives preference to the aristocracy - the power of a limited number of the best morally and intellectually persons. In order for the aristocracy not to degenerate, a group of very good people is needed, which is rare. In the absence of outstanding rulers, the aristocracy degenerates into an oligarchy.
Under an oligarchy, the rich rule. A high property qualification drives the majority of the population out of power. Lawlessness and arbitrariness reign. There is complete inequality in the oligarchy. Aristotle considers this to be unfair. But, according to the philosopher, the opposite principle is also unjust - complete equality, which is characteristic of democracy.
The rich and the poor are essential elements of the state. Depending on the predominance of one or the other, the corresponding political form is established. The hallmark of oligarchy is not so much the power of the minority as the power of wealth. Democracy is characterized by the predominance of the poor in the power structure.
Aristotle identifies several types of democracy. All citizens, regardless of their property status, can participate on an equal footing in the exercise of supreme power, or there may be a low property qualification.
The worst kind of democracy is when people rule without relying on laws, making every decision they make into law. Lawlessness makes this type of power related to tyranny and oligarchy.
Aristotle is selective about democracy. The philosopher approved of moderate census democracy. Such democracy, according to Aristotle, was in Greece during the reign of Solon at the beginning of the 6th century BC. This ruler divided all citizens, depending on their condition, into four categories.
Aristotle condemned the order established in Greece under Pericles, since he did not recognize equalizing justice. The Thinker believed that most poor people have neither the education nor the leisure to do the affairs of government. Their poverty creates conditions for bribery, for group squabbles.
Democracy is an unstable form of government, but Aristotle puts it above the oligarchy and even the aristocracy, because he believes: in a multitude of people there is in everyone a particle of either talent or wisdom.
Polity is a variant of majority rule. It combines the dignity of oligarchy and democracy, this is the golden mean towards which Aristotle was striving. Only persons with average income are recognized as citizens. They participate in the assembly of the people, elect magistrates. The pure form of polity is rare because it requires a strong middle class.
According to Aristotle, the cause of coups, a violent change of forms of government is the violation of justice, the absolutization of the principle underlying the form of government. For example, in a democracy, this is the absolutization of equality. Aristotle connects coups with social contradictions. The reasons for the coups are the strengthening of one of the classes, the weakness of the middle class.
In his writings, the philosopher gives advice on how to strengthen different forms of government. But he considers the establishment of polity to be the best way to ensure stability.
Like all of Aristotle's philosophy, his doctrine of justice bore the stamp of the thinker's gravitation towards materialism. By justice, he understood, on the one hand, the moral quality of a person - virtue, and on the other, a social category that testifies to the nature of social relations. For him, justice as a social category acts as the most important prerequisite for the social institutions he approves. Aristotle drew his ideas about such justice from the real life of the Athenian slave-owning democracy with its developed exchange relations. It is this circumstance that explains his clear division of justice into two types: equalizing and distributing (rewarding). Justice of the first kind is one of the manifestations of the direct relationship of equivalents, for its essence is manifested "in the equalization of what constitutes the subject of exchange." 12 The materialistic guess about the economic content of the category of justice is undoubtedly the merit of Aristotle, which was pointed out by K. Marx. K. Marx. Capital, vol. I. M., Gospolitizdat, 1963, pp. 68-70. At the same time, Aristotle in his doctrine of justice, naturally, could not but reflect the class relations of inequality that developed in the Athenian state. A reflection of this inequality was his concept of distributing justice, which should pay “according to merit,” that is, to express the ratio of unequal measures determined by the greater or lesser social merit of people. Aristotle included virtue and wealth among such virtues. In his opinion, giving equal to unequal people would be an injustice and therefore he justified the social inequality inherent in Athenian democracy.
The literature indicated that with the division of justice into equalizing and distributing, Aristotle connected the difference between private and public law (equalizing justice operates in the sphere of private law, distributing - in the sphere of public law) and used the doctrine of justice to substantiate his political theory. S. F. Kechekian. Methodological questions of the history of political studies. "Voprosy filosofii", 1962, No. 2, p. 95. It should be noted, however, that, as it seems to us, the ancient philosopher distinguished between law and justice, did not always consider them identical. So, Aristotle spoke about justice (calling it "truth" and emphasizing that the latter is the same justice in a special manifestation), which does not insist on the letter of formal law, even in cases where the law speaks in favor of the person's self-interest. It is this justice that makes one voluntarily yield to the internally just claim of another person. 15
Aristotle's doctrine of justice corresponded to the socio-political views of the broadest circles of Athenian slaveholders and did not go beyond their class ideology. But his analysis of justice as an objective category, of course, had a progressive character, which was especially revealed later, in the era of the struggle of the bourgeoisie against feudalism.
An even more decisive opposition to Plato's idealistic approach to justice was the doctrine of Epicurus, who acted as a consistent enemy of Platonism. 16 Epicurus viewed justice as a social category, the origin of which he associated with the presence of human society. "Justice originating from nature," he said, "is a contract about the useful — with the aim of not harming each other and not enduring harm." His statement about the contractual origin of justice, as well as the fact that animals “have nothing fair and unjust”, is convincing evidence that he completely excluded the divine principle in justice, seeing only the earthly origin of the latter. This was also evidenced by his desire to emphasize its objective and universal nature (justice is the same for all) and an indication of the dependence of the concept of justice "on" the individual characteristics of the country and any other circumstances. " Epicurus belongs to the progressive idea of the need for the law to comply with the benefits of earthly communication of people, which is the main criterion of justice. He clearly understood the difference between the formal requirement of the law and justice, which, in his view, was the most important principle of human community.
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FEDERAL EDUCATION AGENCY
State educational institution of higher professional education
"NORTH-WEST STATE CORPORATE TECHNICAL UNIVERSITY"
Department of Power Supply
ELECTRICAL INSTALLATION
LIGHTING
TRAINING AND METODOLOGY COMPLEX
Power Engineering Institute Specialty 140211.65 - power supply Direction of bachelor's degree training 140200.62 - power industry St. Petersburg Publishing house SZTU 2008 Approved by the editorial and publishing council of the university UDC 621.3 (075) Kostin, A.L. Pinegin. SPb .: Publishing house of North-West Technical University, 2008 .-- 128 p.The educational and methodological complex was developed in accordance with the state educational standard of higher professional education.
Considered at a meeting of the Department of Power Supply on November 10, 2008, approved by the Methodological Commission of the Power Engineering Institute on November 10, 2008.
Reviewers: Department of Power Supply, SZTU (Head of Department GZ Zaitsev, Candidate of Technical Sciences, Prof.); A.L. Vinogradov, Cand. tech. Sciences, Assoc. Department of Electrical Engineering and Electromechanics, SZTU.
Compiled by V.N. Kostin, Cand. tech. Sciences, prof., A.L. Pinegin, Cand. tech. Sciences, Assoc.
North-West State Correspondence Technical University, Kostin V.N., Pinegin A.L., Information about the discipline 1.1. Foreword The discipline "Installations of electric lighting" is studied by students of the specialty 140211.65 - "Power supply" in one semester and includes the following sections:
- basic information about lighting;
- lighting engineering part of lighting installations;
- electrical part of lighting installations.
The process of studying the discipline includes lectures, laboratory work and consultations. As an intermediate control of knowledge, control questions, test tasks, the performance of control work are provided, as a final control of knowledge, a test.
The purpose of studying the discipline "Installations of electric lighting"
is the acquisition by students of basic knowledge in the field of lighting engineering, element base, design and calculation methods for lighting installations.
As a result of studying the discipline, the student must master the basics of knowledge, formed at several levels:
have an idea of the basics of lighting technology;
know the basic equipment of lighting installations;
be able to design electric lighting for various objects;
own methods of calculating electric lighting.
Place of discipline in the educational process. In accordance with the curriculum, the discipline under study belongs to the cycle of specialization disciplines.
The theoretical and practical foundations of the discipline are courses: "Physics", "Theoretical Foundations of Electrical Engineering", "Power Engineering". The acquired knowledge will be used in the study of disciplines "Power supply systems", "Installation and operation of equipment for power supply systems", as well as in diploma design.
tests by discipline sections;
test;
2.1. Work program (discipline volume 74 hours) Aims and objectives of the discipline, its place in the educational process. A brief overview of the development of lighting technology. The role of artificial lighting. Tasks in the field of lighting engineering and lighting.
Section 1. Basics of information about lighting (26 hours) Topic 1.1. Lighting units, basic concepts and relationships. Radiant energy. Radiant stream. Luminous flux - part of the radiant flux perceived by human vision.
The distribution of the luminous flux in space. Luminous intensity, solid angle. Illumination of the surface. The brightness of the luminous surface.
Reflection, absorption and transmission of the light flux by the surface.
Units of measurement of light engineering quantities.
Topic 1.2. Basics of light measurements (4 hours) Physical receivers of optical radiation. Photoelectric, photochemical and thermal radiation detectors.
Illumination measurement. The device and the schematic diagram of the luxmeter. The use of a corrective light filter.
Measurement of luminous flux. Photometric ball (ball photometer). Ball photometer device.
Topic 1.3. Systems and types of lighting (6 hours) Natural lighting. Artificial lighting. Artificial lighting systems. General uniform lighting system. General localized lighting system. Local lighting. Combined lighting system. Work and emergency lighting. Security lighting. Evacuation lighting. Security and emergency lighting.
Topic 1.4. Lighting rationing (6 hours), p. 465 ... 466; , with. 250 ... 254; , with. 35 ... Lighting standards for industrial and public buildings and structures, residential premises, areas outside buildings. SNiP 23-05-95 "Natural and artificial lighting".
Object visibility conditions. The smallest size of the object of discrimination.
Category (sub-category) of visual work. The background and contrast of the object with the background.
Safety factor and its value.
Standardization of emergency lighting.
Illumination and brightness of road and street coverage.
Section 2. Lighting engineering part of lighting installations (28 hours) Topic 2.1. Characteristics and selection of light sources (8 hours) Main light sources. Incandescent lamps. Halogen lamps.
Low and high pressure fluorescent lamps, sodium lamps.
Lighting and electrical characteristics of light sources.
Luminous flux, luminous efficacy, color discrimination, rated voltage and power, service life, criticality to environmental conditions.
Designs and characteristics of various light sources. Advantages and disadvantages. Application area. Schemes for switching on various light sources. Start-control equipment.
Selection of light sources.
Topic 2.2. Characteristics and selection of luminaires (10 hours), p. 266 ... 268; , with. 256 ... 261; , with. 26 ... Design and purpose of luminaires. The main lighting parameters of the lamps. The nature of the light distribution (curves of the distribution of luminous intensity). The ratio of the luminous flux emitted by the luminaire into the lower hemisphere to the total luminaire flux (Kf coefficient). The efficiency of the luminaires.
Areas of application of luminaires with different light distribution and different Kf coefficient.
Luminaire marking. Protection of luminaires from dust and water.
Eye protection against glitter. Protective corner of the luminaire.
Features of the use of lamps in explosive and fire hazardous premises.
Topic 2.3. Lighting calculation methods (10 hours) Location of lamps in the room. Basic geometric dimensions. Estimated height. The optimal ratio of the distance between the luminaires to the design height. Features of the placement of lamps with tubular fluorescent lamps.
Lighting calculation tasks.
Lighting calculation methods. The utilization rate method. Point method. Specific power method.
Features of calculating illumination by tubular fluorescent lamps.
Section 3. Electrical part of lighting installations (20 hours) Topic 3.1. Power supply of lighting installations (8 hours) Voltages and power sources of electric lighting. Power supply for working and emergency lighting fixtures, indoor and outdoor lighting fixtures.
Supply lines. Group lines. Lighting points and group lighting panels.
Redundant power supply of lighting installations.
The greatest length and the greatest number of lamps in a group line.
Protection of group lines from short-circuit currents.
The main options for placing single-phase light sources in a group lighting network.
Construction and placement of lighting panels.
Trace group lines.
Lighting network constructions. Wires, cables, busbars.
Compensation of reactive power in lighting installations.
Topic 3.2. Calculation of electrical lighting networks (10 hours), p. 273 ... 274; , with. 271 ... 276; , with. 59… Calculation of lighting loads. The values of the demand coefficient Ks.
Selection of conductor cross-sections. Permissible heating and mechanical strength of the conductors. Conditions of operation of protective devices at short circuit. Power quality requirements. Section of the neutral working conductor.
Normally permissible and maximum permissible values of the voltage deviation at the terminals of the light source. GOST 13109-97. Calculation of voltage losses in the lighting network.
Adaptation of a specialist in modern conditions. Promising directions in lighting engineering. Further improvement of knowledge in the discipline.
1. Introduction. Section Basic information about the ratio 1.2 Basics of lighting 1.3 Systems and types 1.4 Standardization 2 Section 2. The lighting part of lighting installations 2.2 Characteristics and selection of lamps 2.3 Methods for calculating lighting 3 Section 3. Electrical part of lighting installations. Conclusion 3.1 Power supply of lighting installations 3.2 Calculation of electrical seSad. tei lighting 1 Introduction. Section Basic information about the ratio 1.2 Basics of lighting 1.3 Systems and types 1.4 Rationing 2 Section 2. The lighting engineering part of lighting installations 2.1 Characteristics and selection of light sources 2.2 Characteristics and selection of luminaires 2.3 Methods for calculating lighting 3 Section 3. Electrical part of lighting installations. Conclusion 3.1 Power supply of lighting installations 3.2 Calculation of electrical seSad. tey lighting information about lighting lighting installations lighting installations Topic 1.1. Lighting units, basic concepts and relationships Topic 1.2. Basics of light Theme 2.2. Characteristics and Topic 1.3. Systems and types Topic 2.3. Calculation methods Topic 1.4. Rationing 2.4. Time schedule for studying the discipline 1 Introduction. Section 1. Basic information about lighting Topic 1.4. Lighting rationing 2 Section 2. Lighting engineering part of lighting installations Topic 2.1. Characteristics and selection of light sources 3 Section 3. Electrical part of lighting installations Topic 3.1. Power supply of lighting installations - Topic 3.2. Calculation of electrical lighting networks Practical classes in the discipline under study are not provided for by the curriculum.
2.5.1.1. Laboratory work (part-time education) Number and title Topic 2.1. Characteristics and source selection - Work No. 1. Light sources 2 light nicknames light nicknames tillers Number and title Topic 2.1. Characteristics and source selection - Work No. 1. Light sources 2 nicknames of light from tillers 2.6. Point-rating system for assessing knowledge All stages of the study of the discipline are evaluated in points. The maximum number of points a student can score is 100 and is shown in the table below.
When passing tests in sections of the discipline, one point is given for each correct answer (75 test questions).
For each correctly solved task of the control work, points are given (2 tasks). For a fundamental error in a task, the student does not receive points for this task.
For the correct execution of the report of the completed laboratory work, 5 points are given (3 laboratory work). No points will be awarded for fundamental errors in the laboratory work and in the preparation of the report.
To receive a credit in a discipline without an interview with a teacher, you must score at least 80 points.
3. Information resources of the discipline Main:
1. Kudrin, B.I. Power supply of industrial enterprises: textbook for universities / B.I. Kudrin. - 2nd ed. - M .: Intermet Engineering, 2006 .-- 670 p.
Additional:
2. Fedorov, A.A. Textbook for course and diploma design for the power supply of industrial enterprises / A.A. Fedorov, L.E. Starkov. - M .: Energoatomizdat, 1987 .-- 368 p.
3. Knorring, G.М. Reference book for the design of electric lighting / G.М. Knorring. - L .: Energy, 1976 .-- 320 p.
4. Shevkoplyasov P.M. Electrical equipment of lighting installations / P.M. Shevkoplyasov. - L .: SZPI, 1987 .-- 67 p.
3.2. Basic lecture notes for the discipline Installations of artificial lighting are, perhaps, the most massive of all engineering devices. The implementation and installation of these installations requires significant material costs, but these costs are paid off by the possibility of normal life for people in the absence or inadequacy of natural light.
Labor productivity, quality of manufactured products, safety of work, safety of human vision and the architectural appearance of the premises largely depend on the features of the device of artificial lighting.
The discipline "Installations of electric lighting" deals with the construction and design of lighting installations.
The project for the installation of artificial electric lighting consists of two parts - lighting and electrical.
In the lighting engineering part of the lighting project, the following tasks are solved:
- choose the types of light sources and fixtures;
- outline the installation height of the lamps and their placement;
- determine the quality characteristics of lighting installations.
In the electrical part of the lighting project, the following tasks are solved:
- determination of the calculated lighting loads;
- selection of the power supply scheme for the lighting installation;
- the choice of rational stress;
- selection of the cross-section and brand of wires for supply and group lines;
- the choice of methods of laying the network.
In the first section of the discipline, students get acquainted with the basic lighting engineering units, systems and types of lighting, lighting rationing.
The second and third sections of the discipline are devoted to the design of lighting installations and are aimed at preparing students for the implementation of the diploma project.
Section 1. Lighting Basics This section covers three topics:
- lighting units, basic concepts and relationships;
- systems and types of lighting;
- lighting rationing.
When working with theoretical material, you should answer the self-test questions at the end of the section. As an intermediate control of knowledge in the first section, you should pass test # 1.
With an effective study of the material in this section, you can score 25 points out of 100 possible.
1.1. Lighting units, basic concepts and relationships As a result of the transformation of energy supplied to bodies (thermal or electrical), in a number of cases, electromagnetic radiation arises, which is quantitatively characterized by power - a radiant flux. That part of the radiant flux that is perceived by human vision as light is called the luminous flux F.
A number of units of measurement have been adopted to characterize lighting devices and lighting conditions.
The luminous flux is measured in lumen (lm).
The luminous flux can be differently distributed in space. The intensity (density) of the luminous flux in any direction is characterized by the luminous intensity I, determined by the ratio of the luminous flux to the solid angle within which it spreads:
The unit of measurement for the solid angle is the steradian (sr). One steradian (1 sr) is a volumetric angle that has a vertex in the center of the sphere and “cuts out” a section on its surface, the area of which is equal to the square of the radius of this sphere (Fig. 1.1).
Rice. 1.1. To the definition of the unit of the solid angle (= 1 sr) The total solid angle of the space surrounding the point is 4 sr.
The unit of luminous intensity is the candela (cd) - the luminous flux of 1 lm, emitted by a point light source in a solid angle of 1 sr (1 cd = 1 lm / 1 sr).
A point light source refers to a source that is small compared to the distance to the source.
The luminous flux Ф, falling on a surface with an area S, creates the illumination of this surface. The unit of illumination is lux (lx). A surface has illumination lx if a luminous flux of 1 lm falls on 1 m2 of the surface (1 lx = 1 lm / 1 m2).
The illumination of the surface does not depend on its light properties.
In many cases, the illumination of a point on the surface is calculated by the intensity of the light source, with which it is associated with the expression where r is the distance between the light source and the illuminated surface, m;
- the angle between the direction of the luminous intensity and the normal N to the illuminated surface (Fig. 1.2).
The brightness of a luminous (illuminated) surface in a certain direction is called a value equal to the ratio of the luminous intensity I in the direction to the area S of the projection of the luminous surface onto a plane perpendicular to this direction (Fig. 1.3):
The unit for luminance is candela per square meter (cd / m2).
The light flux falling on any body is partially reflected, partially absorbed and partially passes through this body. Quantitatively, the reflection, absorption and transmission of the light flux by the body are estimated by the corresponding coefficients.
The reflectance is defined as where F is the luminous flux incident on the surface;
Fotr - luminous flux reflected from the surface.
The absorption coefficient is equal to where Фпол - the luminous flux absorbed by the body.
The transmittance is equal to where Fprosh is the luminous flux that has passed through the body.
According to the law of conservation of energy, therefore, the magnitude of the light flux reflected, absorbed and transmitted through a body depends on the properties of this body, in particular on color, material, structure, etc.
Table 1.1 shows the values of the coefficients of reflection, absorption and transmission for some common materials.
Reflection, absorption and transmission coefficients of some For light measurements, physical optical receivers (FPIs) are used:
- photovoltaic: photocells, photoresistors, photomultipliers;
- photochemical - various photographic materials;
- thermal - thermoelectric converters.
Each of the FPI converts the absorbed radiation energy into another type of energy: electrical (current, voltage), chemical (blackening of photographic material under the influence of absorbed radiation), etc.
In laboratory conditions and in operational practice, luxmeters are used to measure illumination. The schematic diagram of the luxmeter is shown in Fig. 1.4, a.
The light meter consists of a photocell 1 connected to a galvanometer 2. The galvanometer can be shunted by resistors R1 and R2 using switches 3. The sensitive part of the photocell can be covered with special nozzles 4. The use of shunts and nozzles allows you to change the limits of illumination measurements.
Rice. 1.4. Schematic diagram of the luxmeter (a), measurement of the luminous flux Measurement with a portable luxmeter is carried out as follows.
The photocell is located in the plane, the illumination of which is measured. The desired illumination is determined by the deflection of the galvanometer needle.
Luxmeters are periodically checked and calibrated using a light source whose characteristics are known.
Measurements with a light meter are quite accurate when the spectral composition of the radiation from the source used to calibrate the light meter is close to the spectral composition of the sources from which the illumination is measured. If the indicated spectral compositions are very different, it is necessary to use a photocell with a corrective light filter. For example, if the calibration was carried out using an incandescent lamp, and the illumination must be measured from a fluorescent light source, measurements without a correcting filter may have errors in excess of 10%.
Measuring the illumination generated by lighting installations in industrial plants using a portable light meter is a fairly simple and quick action. Illumination measurement error is no more than ± 10%. For periodic monitoring of the illumination conditions of workplaces in industry, such an error is quite acceptable.
A spherical photometer - a photometric sphere (Ulbricht sphere) - is used to measure the luminous flux of light sources. Its schematic section is shown in Fig. 1.4, b.
The ball photometer is a hollow ball, the inner surface of which is painted with white paint that diffusely reflects light. The ball has a door that allows the light source (I) to be placed inside the ball. The door is part of a ball surface, the inner side of the door is painted with white diffused light reflecting paint.
The ball has a small opening, closed by milky glass (MC).
A screen (E) will be placed inside the ball, which protects the milk glass from direct streams of the light source. Behind the milk glass is a photocell (PV), in the circuit of which a galvanometer (G) calibrated in lumens is included, showing the measurement result.
To create normal lighting conditions in residential, public and industrial premises, two types of lighting are used - natural and artificial.
Natural lighting is the illumination of premises with rays of daylight through skylights (windows). Such lighting is most favorable for the human eye, but this lighting is uneven throughout the day.
Artificial lighting requires energy consumption, electrical safety, and has the worst spectral characteristics. However, such lighting is necessary due to the unevenness or insufficient natural lighting during the day.
Below we will only talk about artificial electric lighting.
For electric lighting, gas-discharge lamps (fluorescent, mercury, sodium, xenon) and incandescent lamps should be used.
When arranging lighting installations, three lighting systems can be used:
- general uniform illumination, when the luminous flux is distributed without taking into account the placement of equipment;
General localized lighting, when the luminous flux is distributed taking into account the located equipment;
- combined lighting, when local lighting of workplaces is added to the general lighting.
Local lighting is created by luminaires that concentrate the luminous flux directly at the workplace.
The quality and efficiency of a lighting installation largely depends on the correct choice of lighting system.
The general lighting system is used to illuminate the entire room as a whole, including work surfaces.
A general lighting system with uniform placement of luminaires is used when technological equipment in production facilities is evenly located over the entire area with the same conditions for visual work.
The combined lighting system is used in rooms with delicate visual work requiring high illumination. In this case, some of the luminaires illuminate only workplaces (local lighting), while the other illuminates the entire room.
To power the general lighting system, a voltage of no higher than 220/380 V AC with neutral earthing must be used.
To power the luminaires of local stationary lighting with incandescent lamps, a voltage of no higher than 220 V for rooms without increased danger and not higher than 42 V for rooms with increased danger and especially dangerous must be used.
Artificial electric lighting is subdivided into working and emergency.
Emergency lighting is divided, in turn, into safety lighting and evacuation lighting.
Work lighting is arranged in all rooms without exception and creates standardized illumination on work surfaces.
In some cases, in addition to the work lighting, emergency lighting is required, which provides minimal illumination in the workplace when the work light is suddenly turned off.
For emergency lighting, it is allowed to use incandescent lamps that instantly ignite at low temperatures (below +5 ° C) and fluorescent. The latter are allowed to be used in rooms with a minimum temperature of +5 ° C and when powered in all modes with alternating current with a lamp voltage of at least 90% of the nominal value.
Work and emergency lighting in industrial and public buildings must be powered from various independent sources. It is allowed to power the working and emergency lighting from different transformers of one two-transformer substation, provided that the transformers are powered from different independent sources.
Luminaires of emergency lighting should differ from luminaires of working lighting in standard sizes or specially applied signs.
Safety lighting should be provided in cases where the shutdown of working lighting and the associated disruption of equipment and machinery maintenance may cause:
- explosion, fire, poisoning of people;
- long-term disruption of the technological process;
Disruption of the operation of such facilities as power plants, communication centers, radio and television broadcasts, control rooms, pumping installations for water supply, sewerage and district heating, etc .;
- violation of the regime of children's institutions, regardless of the number of children in them.
Evacuation lighting should include:
- in places dangerous for the passage of people;
- in the aisles and on the stairs, serving for the evacuation of people, when the number of evacuees is more than 50 people;
- along the main aisles of industrial premises, in which more than 50 people work;
- in stairwells of residential buildings with a height of 6 floors or more;
In industrial premises with people constantly working in them, where the exit of people from the premises during an emergency shutdown of normal lighting is associated with the risk of injury due to the continuation of the operation of production equipment;
In the premises of public and auxiliary buildings of industrial enterprises, if the premises can accommodate more than 100 people at the same time;
- in industrial premises without natural light.
Security lighting should be provided along the boundaries of areas protected at night.
Emergency lighting is lighting of premises during off-hours.
Lighting standards for industrial and public buildings and structures, residential premises, as well as areas outside buildings are established by SNiP 23-05-95 "Natural and artificial lighting" (see Tables 1.2, 1.3).
The standardized illumination values are given at the points of its minimum value on the working surface indoors for discharge light sources, for outdoor lighting - for any light sources.
Normalized values of illumination in lux, differing by one level, should be taken on a scale: 0.2: 0.3; 0.5; 1; 2; 3; 4; 5; 6; 7; ten;
15; 20; 30; 50; 75; 100; 150; 200; 300; 400; 500; 600; 750; 1000; 1250; 1500;
2000; 2500; 3000; 3500; 4000; 4500; 5000 lx.
Table 1.2 shows the Enorm norms for lighting residential, public and administrative premises. The amount of illumination depends on the characteristics of visual work, the size of the object of discrimination and the relative duration of visual work, which determine the category (A, B, ... H) and sub-category (1, 2) of visual work.
Table 1.3 shows the standards for lighting industrial premises. The amount of illumination depends on the characteristics of visual work and the size of the object of discrimination, which determine the category of visual work (I ... VIII). Each category is divided into sub-categories of visual work (a, b, c, d), characterized by the contrast of the object with the background (small, medium, large) and the characteristics of the background (dark, medium, light).
During the operation of the lighting installation, the illumination on the working surfaces decreases due to a decrease in the luminous flux over time due to contamination of lamps, lighting fixtures and reflective surfaces (walls and ceilings). Therefore, to ensure the standardized illumination Enorm, the calculated illumination Ep is taken taking into account the safety factor:
Safety factors values:
Kz = 1.3 ... 1.7 for incandescent lamps;
Kz = 1.5 ... 2.0 for gas-discharge lamps.
Emergency lighting should create illumination at workplaces equal to 5% of the illumination standard for work lighting with a general lighting system, but not less than 2 lux.
Safety lighting should create on work surfaces in industrial premises and on the territories of enterprises that require maintenance when the work lighting is turned off, the lowest illumination in the amount of 5% of the illumination standard for work lighting from general lighting, but not less than 2 lux inside buildings and at least 1 lx for the territories of enterprises.
Evacuation lighting should provide the lowest illumination on the floor of the main aisles (or on the ground) and on the steps of stairs:
- indoors - 0.5 lux;
- in open areas - 0.2 lux.
Table 1.4 shows the standards for the lighting of streets, roads and squares of the urban area.
Lighting of residential, public and administrative premises Distinguishing objects with a fixed and non-fixed line of sight:
c) average accuracy more than 0.5 V Survey of the surrounding space with short-term discrimination of objects:
a) with high rooms with light b) with normal rooms with light c) with low rooms with light a) with large b) with small crowds a) with large b) with small crowds Illumination of premises of industrial enterprises visual Very high accuracy High accuracy Medium accuracy Low accuracy Very low accuracy Working with materials General monitoring of the production process:
permanent;
periodic with the constant presence of people;
periodic with periodic presence of people General observation of engineering communications Notes. 1. Illumination when using incandescent lamps should be reduced on the illumination scale:
One step with a combined lighting system, if the standardized illumination is 750 lux or more;
- one stage with a general lighting system for categories I-V, VI;
- by two steps with a general lighting system for categories VI and VIII.
2. The background of the surface is considered light if the reflection coefficient of this surface is 0.4; medium - if 0.20.4; dark - if 0.2.
local significance single cars From tab. 1.4 it can be seen that for streets, roads and squares, in addition to illumination, the brightness of the road surface is also normalized.
The standardization of brightness is adopted due to the pronounced directionality of the reflection of modern road surfaces. The brightness of the road surface is selected from the conditions that ensure the timely detection of obstacles by drivers and the adoption of the necessary measures.
1. Explain the basic terms of lighting technology: luminous flux, luminous intensity, illumination, brightness.
2. What are the main units of measurement used in lighting engineering?
3. What is the unit of measure for luminous flux?
4. What is the unit of measure for luminous intensity?
5. What is the unit of measure for illuminance?
6. What is the unit of measure for brightness?
7. Give the definition of steradian.
8. What happens to the light flux falling on the body?
9. What determines the magnitude of the light flux reflected, absorbed and transmitted through the body?
10. Which of the known materials have the highest and lowest reflectivity?
11. What are the main lighting systems.
12. What voltage is used for electric lighting?
13. What types of artificial electric lighting are subdivided into?
14. How is the supply of working and emergency lighting provided?
15. When is the safety lighting provided?
16. When is evacuation lighting foreseen?
17. What document regulates lighting standards?
18. On what factors does the standard illumination of industrial premises depend?
19. On what factors does the regulatory illumination of administrative and residential premises depend?
20. For what purpose is the safety factor introduced when calculating the illumination?
Section 2. Lighting technology of lighting installations This section deals with three topics:
- characteristics and selection of light sources;
- characteristics and selection of luminaires;
- methods for calculating lighting.
When working with theoretical material, you should answer the self-test questions at the end of the section. As an intermediate control of knowledge in the first section, you should pass the test number 2.
If you have any difficulties on questions for self-examination and test tasks, you should refer to the theoretical material of the supporting synopsis or the literature indicated in the bibliographic list.
Laboratory works No. 1, 2 and 3 are performed on the theoretical material of this section.
The solution of task 1 of the control work should be carried out after working out the theoretical material of topics 2.1 and 2.2.
With an effective study of the material in this section, you can score 45 points out of 100 possible.
2.1. Characteristics and selection of light sources Light sources are divided into three broad classes:
- incandescent lamps;
- low pressure gas discharge lamps;
- high pressure gas discharge lamps.
Each of these classes has specific design features. Light, electrical and technical characteristics are the same for all classes. Electrical specifications include rated voltage and power; to luminous characteristics - luminous flux, luminous efficacy and color rendering; to technical characteristics - service life, coefficient of performance (COP).
The luminous efficacy of the lamp is equal to the ratio of the luminous flux F to the electrical power consumed by the source P. The greater the luminous efficacy, the more economical and perfect the light source is.
Incandescent lamps. Incandescent lamps (LN) are widely used as light sources in everyday life and at work.
The LN design is shown in Fig. 2.1, a. The main elements of the LN are a glass bulb 1, a tungsten coil 2 and a base 3. When current flows through the lamp, the tungsten coil heats up, emitting light and heat. Strong heating of the coil causes the tungsten to evaporate. To slow down this process, the flasks are either vacuum-filled or filled with an inert gas (argon).
LN are included in the electrical network directly without special starting equipment. LN connections to the network are made through the base.
Rice. 2.1. The design of an incandescent lamp (a), a halogen incandescent lamp (b), a fluorescent lamp (c) The main advantages of an LN are:
- low cost;
- simplicity of construction and maintenance;
- small size;
- independence of work from environmental conditions.
The disadvantages of LN include:
- of the light sources considered below, the lowest efficiency (about 2%);
- of the light sources considered below, the lowest luminous efficiency (10 ... 15 lm / W);
- the predominance of the yellow-red part of the spectrum in the emission spectrum;
- short service life (about 1000 hours);
- a large dependence of the service life on voltage.
With an increase in voltage by 10%, the service life of the LV is reduced by 3 ... 4 times.
Incandescent halogen lamps. Incandescent halogen lamps are comparable in structure and function to incandescent lamps.
The device of a quartz halogen (KG) lamp is shown in Fig. 2.1, b.
A tungsten spiral 4 is placed in a quartz tube 5, fixed on holders 6. Tungsten leads 3 are connected to leads 1 using a molybdenum foil 2 soldered into quartz.
The quartz flask is filled with xenon with the addition of halogens. The tungsten halides formed during lamp operation prevent the evaporation of the tungsten coil.
The advantages of CG in comparison with conventional LN are:
- higher luminous efficiency (up to 25 lm / W);
- 2–3 times longer service life;
- smaller dimensions with the same power;
- better color rendering (the light is "whiter" due to the higher heating temperature of the coil).
The main application of KG is found in general and local lighting fixtures, spotlights, car headlights, etc.
Fluorescent lamps. These lamps are classified as low pressure discharge lamps. Fluorescent lamps (FL) are widely used to illuminate industrial premises, public and residential buildings.
The design of a tubular LL is shown in Fig. 2.1, c. The lamp consists of a glass tube 1, tungsten electrodes in the form of spirals 2, located at both ends of the lamp and connected through the base 3 with the contact pins 4.
The glass tube is filled with an inert gas (argon) with mercury vapor.
The inner surface of the tube is coated with a special phosphor compound. Under the action of an electrical discharge, mercury vapor emit ultraviolet rays, which cause the phosphor to emit light.
This phenomenon is called luminescence.
Rice. 2.2. One-lamp (a) and two-lamp (b) switching circuits for the LL.Inclusion of the LL in the network requires a ballast (ballast), which ensures the ignition of the lamps and their normal operation.
The LL switching circuits are shown in Fig. 2.2.
To turn on the lamps 1, the electrodes are preheated to a temperature that provides thermal emission (ionization of the space around the electrodes), sufficient to ignite the discharge. Heating is carried out by short-term inclusion of electrodes in the current circuit, which is achieved by closing the contact of the starter 3. Upon subsequent opening of the contact, an overvoltage pulse occurs due to the inductance energy of the inductor 2. This pulse applied to the lamp with the electrodes not yet cooled down ignites a discharge in it. Choke 2 limits the lamp current after it is turned on. Capacitors 4 are designed to compensate for reactive power consumed by choke 2.
One of the disadvantages of LL is the pulsation of the luminous flux with twice the frequency of the network. Ripples cause the appearance of a stroboscopic effect. Therefore, a two-lamp switching circuit is more often used (Fig. 2.2, b), in which a capacitor 5 and a discharge resistor 6 are connected to the circuit of one of the chokes 2. As a result, the currents in the lamps are shifted in phase and the total luminous flux of the two lamps becomes more constant.
Advantages of fluorescent lamps:
- high luminous efficiency (up to 75 lm / W);
- long service life (up to 10,000 hours);
- Better color rendering than incandescent lamps.
Disadvantages of fluorescent lamps:
- unit power limited by the length of the lamp;
- the complexity of switching on, requiring special control gear;
- pulsation of the luminous flux;
- the dependence of the characteristics on the ambient temperature.
For conventional fluorescent lamps, the optimum ambient temperature is 18 ... 25 C. When the temperature deviates, the luminous flux and luminous efficiency decrease. At temperatures below +10 C, ignition is not guaranteed.
The following letters are used in the marking of fluorescent lamps: L - fluorescent, D - daylight, B - white light, HB - cold white light, TB - warm white light, C - improved color rendering, A - amalgam.
Fluorescent compact lamps. If you "twist" the LL tube into a spiral, you get a compact fluorescent lamp (CFL). According to its parameters, CFL is close to traditional LL.
CFLs are manufactured with an electronic trigger built into the base of a conventional incandescent lamp. One of the types of CFLs is shown in Fig. 2.3, a.
CFL consumes five times less electricity at the same luminous flux and has eight to ten times longer service life than LN.
The cost of CFL is noticeably higher than that of traditional LL and LN.
It is obvious that in the near future CFLs will significantly replace the usual incandescent lamps.
Arc mercury fluorescent lamps. In contrast to low-pressure gas-discharge tubular LL, mercury arc fluorescent lamps (DRL) belong to high-pressure gas-discharge lamps.
Rice. 2.3. Compact fluorescent lamp (a), arc mercury fluorescent lamp (b), sodium lamp (c) The DRL design is shown in Fig. 2.3, b. The lamp consists of a quartz discharge tube 1 with main tungsten electrodes 3 and additional (ignition) electrodes. The quartz tube is filled with high pressure mercury vapor and placed in a glass flask 2.
The inner surface of the flask is covered with a phosphor layer. To maintain the stability of the properties of the phosphor, the glass bulb is filled with carbon dioxide.
Under the influence of ultraviolet radiation that occurs during the discharge in the mercury-quartz tube, the phosphor glows, giving the light a bluish tint, distorting the true colors. To eliminate this drawback, special components are introduced into the composition of the phosphor, which partially correct the color rendering.
DRL lamps are connected to the network either with a choke (Fig. 2.4, a), or with a transformer (Fig. 2.4, b).
The main area of application of DRL is outdoor lighting, lighting of industrial premises with high ceilings (7 and more meters).
Rice. 2.4. DRL starting circuits with a choke (a) and a transformer (b) Advantages of DRL lamps:
- high luminous efficiency (up to 55 lm / W);
- long service life (up to 10,000 hours);
- uncritical to environmental conditions (except for very low temperatures).
Disadvantages of DRL lamps:
Unsatisfactory color rendering, which excludes the use of lamps in cases where the objects of discrimination are human faces or painted surfaces;
The duration of the switch-on process (about 7 minutes) and re-ignition (about 10 minutes for the lamp to cool down) after a short power interruption;
- pulsations of the luminous flux (more than that of LL);
- a significant decrease in luminous flux by the end of the service.
Metal halide lamps (MGL). These are high pressure mercury lamps with additives of metal iodides and halides. These compounds disintegrate at the center of the discharge arc, and metal vapors can stimulate the emission of light, whose intensity and spectral distribution depend on the vapor pressure of the metal halides.
Arc mercury metal halide lamps (for example, DRI - arc mercury iodide lamp) outwardly differ from DRL lamps in the absence of a phosphor on the bulb. They are characterized by a high luminous efficacy (up to lm / W) and a significantly better spectral composition of light, but their service life is much shorter than that of DRL lamps, and the switching circuit is more complicated, since it contains, in addition to the choke, an ignition device.
Frequent short-term activation of high-pressure lamps will shorten their service life. This applies to both cold and hot starting of lamps.
The luminous flux is practically independent of the ambient temperature. However, at very low temperatures (down to -50 ° C), special ignition devices must be used.
Sodium lamps. These lamps are currently the most economical light sources available. The most widespread are high-pressure sodium lamps of the DNaT type (arc sodium tubular).
The designs of sodium lamps are different (cylindrical, elliptical, etc.). In fig. 2.3, c shows a DNaT lamp of a cylindrical design. A discharge tube made of polycrystalline alumina is placed inside the cylindrical flask 2. These lamps use a vapor discharge of sodium, mercury and xenon ignition gas.
To ignite the DNaT lamp, special starting devices are used. In low-power lamps, the starting device is located in the lamp base (position 3 in Fig. 2.3, c).
Advantages of sodium lamps:
- have the highest luminous efficiency among gas-discharge lamps (up to 130 lm / W);
- long service life (up to 15000 hours).
- slight decrease in luminous flux during the service life.
The disadvantage of sodium lamps is their extremely yellow light and low color rendering, which makes them suitable for indoor use only in combination with other types of lamps.
HPS lamps are used to illuminate large areas (streets, squares, etc.) and successfully replace DRL.
Selection of light sources. The above characteristics and applications of light sources indicate that different light sources can be used for the same object.
Characteristics of visual work Illumination, Approximate types Color control with very high requirements for more LDC, LDC UV, (LHE) for color discrimination Comparison of colors with high requirements for more LBTsT, LDC, LDC UV for color discrimination Differentiation of colored objects with non-500 and more LB , (LHB), MGL High requirements for color differentiation Requirements for color discrimination are absent - 500 or more LB, (LHB), MGL When choosing a light source, one should give preference to gas-discharge lamps. Incandescent lamps can be used for emergency lighting, for example.
The type of light source is determined by the characteristics of visual work, the requirements for the comfort of lighting, color discrimination and illumination.
2.2. Characteristics and selection of luminaires The luminaire consists of fittings and a diffuser and redistributes the luminous flux of the light source installed in the luminaire.
The main lighting parameters of the lamps:
- the nature of light distribution (curves of the distribution of luminous intensity);
The distribution coefficient of the luminous flux Кф, equal to the ratio of the luminous flux emitted by the luminaire into the lower hemisphere Fnizh, to the total flux of the luminaire Fsv:
Efficiency is the ratio of the luminous flux of the luminaire Фсв to the flux of the installed light source Фл:
The nature of the light distribution shows the change in the luminous intensity of the luminaire when the control point moves in the meridional plane.
Luminous intensity is expressed in relative units. The unit of luminous intensity is taken to be its maximum value in the considered meridional plane.
By the nature of light distribution, luminaires with point light sources (LN, DRL, etc.) are divided into seven types (Fig. 2.5).
In rooms where the ratio of height to area is large, it is advisable to use lamps with concentrated or deep light distribution (K or G). Such lamps direct the bulk of the light flux directly to the work surfaces, which increases the efficiency of their use.
to use luminaires with a wider light distribution (D, L, M), which makes it possible, even with significant distances between the luminaires, to ensure a uniform distribution of illumination over the working surface.
it is advisable to use it when it is necessary to have good lighting of the walls of the room (for example, at exhibitions, in museums, etc.).
Luminous intensity (p.u.) Fig. 2.5. Typical light distribution (luminous intensity curves) of luminaires - reflected light O (Kf 20%).
Each group has its own area of application.
Direct light luminaires are used in rooms with dark, poorly reflecting ceilings and walls, such as foundries, blacksmiths, mechanical and other workshops, where a lot of dust, smoke, soot and various vapors are emitted. Direct light fixtures produce rather harsh shadows that are not smoothed out by the light reflected from the walls and ceiling.
Due to the fact that the largest part of the light flux is directed directly to the illuminated surfaces, direct light luminaires are the most economical in terms of energy consumption.
Luminaires of mainly direct light are installed in workshops with walls and ceilings that reflect light well. These luminaires have a metal body with a small reflector. The lamp is covered with light-diffusing glass.
Luminaires with predominantly direct light give rather soft shadows, which is of great importance for many workshops and types of work, especially in the absence of local lighting.
Luminaires of diffused light are used in those workshops where it is necessary to create high levels of illumination with diffused light (office and household premises with light ceilings and walls).
Luminaires of predominantly reflected light and luminaires of reflected light are required in cases where even slight shadows are undesirable due to the nature of the operation.
Indirect luminaires are less economical than direct or diffused luminaires.
Luminaires with linear fluorescent lamps, as a rule, are multi-lamp and can be direct light, mainly direct light and diffused light.
An increase in the efficiency of a luminaire is achieved by using reflectors with a high reflectance, diffusers with a high transmittance, and other design features. The more perfect the luminaire, the smaller the proportion of the luminous flux is absorbed in the armature and the higher its efficiency. Real luminaires have an efficiency in the range of 40 ... 90%, and, as a rule, the lower value is characteristic of diffused luminaires, and the upper value is characteristic of direct light.
The general structure of the alphanumeric designation of the luminaire is as follows:
where 1 is the letter denoting the light source:
H - incandescent lamps for general use;
R - mercury lamps of the DRL type;
L - tubular fluorescent lamps;
And - quartz halogen incandescent lamps;
G - DRI type mercury lamps;
F - sodium lamps, etc.;
2 - a letter indicating how to install the luminaire:
C - suspended;
P - ceiling;
B - wall-mounted;
K - console, etc.
3 - a letter denoting the main purpose of the luminaire:
P - for industrial enterprises;
O - general purpose;
U - for outdoor lighting;
B - for household premises;
4 - two-digit number (01-99) indicating the series number;
5 - a number indicating the number of lamps in the luminaire (for single-lamp luminaires, the number 1 and the "x" sign are not set);
6 - a number indicating the power of one lamp (W);
7 - three-digit number (001-099), indicating the modification number;
8 - a letter denoting the climatic version of the luminaire:
U - for areas with a temperate climate;
T - for areas with a tropical climate;
CL - for areas with a cold climate;
UHL - for areas with a temperate and cold climate;
O - general climatic (for all regions), etc.
An example of a designation for a luminaire type:
ZhKU40-250-001 is an outdoor lighting fixture, console series 40 with a 250 Watt HPS lamp, modification 001.
The protection class of the luminaire against dust and water is indicated by the Latin letters IP (International Protection) and two numbers.
The first digit indicates dust protection:
2 - dustproof;
5 - dustproof;
6 - dustproof.
The second number indicates protection against water:
0 - waterproof;
2 - drip-proof;
3 - rainproof;
4 - splash-proof;
5 - jet-proof;
7 - waterproof.
For some luminaires, the protection designation does not have IP letters, and a stroke is added to the first digit indicating the degree of protection against dust (for example, 5'4).
In accordance with the requirements of the PUE, lamps with a protection class of at least IP53 must be used in fire-hazardous rooms P-I, P-II, and at least IP23 in rooms P-III. In explosive rooms B-I and B-II, explosion-proof and explosion-proof luminaires should be used, respectively.
An important function of the luminaire is to protect the eyes from glare. The degree of protection against glitter is characterized by the size of the protective angle (Fig.
2.6), which is understood as the angle formed by the horizontal line passing through the light source and the straight line passing through the edge of the reinforcement.
Rice. 2.6. Protective angle of a luminaire with an incandescent lamp (a) and To ensure a protective angle in luminaires with tubular fluorescent lamps, longitudinal and transverse shielding strips are used, which together form a shielding grid.
Some types of luminaires are shown in fig. 2.7, 2.8 and 2.9.
Rice. 2.7. Industrial suspended luminaire NSP, RSP, ZhSP, GSP:
used with different types of lamps: incandescent, mercury, sodium, metal halide, compact fluorescent; used for general lighting of industrial premises Fig. 2.8. Console lamp RKU, GKU, RKU:
used with different types of lamps (DNaT, DRI, DRL); It is used to illuminate areas (squares, streets and roads with different traffic intensities, pedestrian and walking areas, etc.). Fig. 2.9. Fluorescent lamp LPO, LPP:
LPO type - used for lighting public buildings, shops, offices, hospitals, schools, canteens of industrial premises, etc.;
LPP type - used to illuminate industrial premises of large areas with high ceilings (more than 3 m) The efficiency, quality and ease of use of the lighting installation depend on the solution of this issue.
The main dimensions taken for a typical arrangement of luminaires in a room are shown in Fig. 2. Fig. 2.10. The layout of the lamps in the section of the room (a), in the plan of the room (b), in the plan of the room with fluorescent lamps (c) All dimensions are taken in meters:
A, B, H - length, width and height of the room;
hc is the distance from the ceiling to the luminaire;
hр is the height of the working surface (as a rule, hр = 0.8 m);
hп = Н - hc is the distance from the floor to the luminaire;
h = hп - hр = Н - hс - hр - design height (vertical distance between the working surface and the lamps);
L is the distance between luminaires or their rows;
Lа, Lв - the distance between the lamps in the direction along and across the room, if Lа Lв;
l is the distance from the wall to the extreme rows of fixtures.
Of these dimensions, A, B, H and hp are given. The value of hc is taken in the range from 0 to 1.5 m. The distance l is recommended to be taken (0.3 0.5) L.
It is advisable to place luminaires with tubular fluorescent lamps in rows parallel to the wall with windows or to the long side of the room (Fig. 2.10, c). The rows are preferably continuous to avoid fan-shaped shadows.
The main requirements when choosing the location and number of luminaires are the efficiency and availability of luminaires for maintenance. Here, the ratio of the distance between the luminaires (rows of luminaires) to the calculated height is important:
A decrease in this ratio leads to an increase in the cost of the lighting installation and complications in its maintenance, and an excessive increase leads to uneven illumination and an increase in energy consumption.
In,,, the optimal values of the value are given, which ensure the uniformity and efficiency of illumination (see Table 2.2).
The task of calculating lighting is to determine the number of luminaires and the power of light sources required to ensure the specified level of illumination.
The main calculation methods are discussed below.
The utilization factor method is designed to calculate the overall uniform illumination of horizontal surfaces.
When calculating using this method, the luminous flux of the lamp in each luminaire, necessary to create a given standardized illumination Enorm, is determined by the formula where Kz is the safety factor (Kz = 1.3 ... 1.7 for incandescent lamps; Kz = 1, ... 2.0 for gas discharge lamps);
S is the area of the illuminated surface, m2;
z - coefficient of minimum illumination (approximately you can take z = 1.1 - for fluorescent lamps, z = 1.15 - for incandescent lamps and DRL);
N number of luminaires (planned before calculation);
the utilization factor of the luminous flux of the light source.
According to the value of Ф, a standard lamp is selected so that its flux differs from the calculated value of Ф by -10% ... + 20%. If it is impossible to select a light source with such an approximation, the number of luminaires is corrected.
When calculating the illumination made by tubular fluorescent lamps, the number of rows n is initially outlined, which in formula (2.4) corresponds to N. Then the flux Ф should be understood as the flux of lamps of one row.
If the luminous flux of lamps in each lamp is Fnom, then the number of lamps in a row is determined by the formula The total length of lamps in a row is compared with the length of the room, while the following cases are possible:
The total length of the luminaire exceeds the length of the room; in this case, it is necessary to use more powerful lamps (for which the flux is greater per unit length) or to increase the number of rows of lamps;
- the total length of the luminaires is equal to the length of the room; in this case, the problem is solved by installing a continuous row of lamps;
The total length of the luminaires is less than the length of the room; in this case, a row is taken with gaps between the luminaires evenly distributed along it. It is recommended that the distance between luminaires in a row lt should not exceed 0.5h.
The utilization factor of the luminous flux is a function of the room index i, which is determined by the formula where A is the length of the room, m;
B is the width of the room, m;
h - design height, m.
The values of the utilization factor for different types of luminaires are given in the reference materials. Table 2.3 shows the values of the utilization factor for luminaires with typical curves of luminous intensity (KSS) at different reflectivity of the ceiling p, walls with and floor p. The approximate values of the reflection coefficients of the surfaces of the premises are given in table. 2.4.
The point method is used to calculate the illumination of arbitrarily located surfaces and for any distribution of light sources. The reflected light component is taken into account approximately.
Let us consider the point calculation method using the example of point light sources (LN, DRL, DRI - their geometric dimensions are much less than the distance to the illuminated surface) and luminous lines (the length of the emitter exceeds half the design height h).
For point light sources, it is assumed that the lamp flux in each luminaire is 1000 lm. The illumination generated from each luminaire is called conditional and is denoted by e. The illumination e depends on the light distribution of the luminaires and the geometric dimensions d and h (h is the design height; d is the distance from the projection of the luminaire onto the design surface to the control point).
KCC KCC KCC Note. With a room index of i5, the values are the same as for i = 5.
Whitewashed ceiling, whitewashed walls in dry rooms 0, Whitewashed walls, whitewashed ceilings in damp rooms, clean concrete ceiling Concrete ceiling in dirty rooms, walls in light wallpaper 0, Walls and ceilings with a lot of dark dust, unplastered red bricks, walls in dark wallpaper As control points, you should take those where the illumination is minimal. With general uniform illumination of large rooms, the main control points are the center a of the corner field and the middle b of its long side (Fig. 2.11).
To determine the value of e, the spatial isoluxes of the conditional horizontal illumination, given in the reference materials, are used. On these isoluxes there is a point with given values of d Fig. 2.11. The choice of control points (a and b) and the nearest lamps (1 ... 8) The total effect of the nearest lamps (positions 1 ... 8 in Fig.
2.11) creates a conditional illumination e at the control point. The action of more distant lamps and the reflected component of illumination are taken into account by the coefficient (= l, l ... 1.2). Then, to obtain the illumination Ea at the control point a, taking into account the safety factor K3, the lamps in each luminaire must have a luminous flux, lm. According to this flux, a lamp is selected, the flux of which should differ from the calculated one by -10 ... + 20%. If it is impossible to choose a lamp with such a luminous flux, the location of the lamps is adjusted.
Let us consider the point method as applied to the case of luminaire arrangement with luminous lines (tubular fluorescent lamps). The characteristic of the luminous lines is the linear density of the luminous flux of the lamps, lm / m, which is determined by dividing the total flux of the lamps in the F line by its length lsl.
Lines with discontinuities lt uniformly distributed along their length are considered in the calculation as continuous if lt 0.5h, and Lw.l means the length of a line with discontinuities. For extended lines with such discontinuities, we can consider where Ф is the flux of lamps in a solid element of length l SL.
At lt 0.5h, for each continuous section of the line, Ф "and the illumination created by this section are determined separately.
The calculated graphs of linear isolux, given in the reference materials, make it possible to determine the relative illumination (illumination at Ф "= 1000 lm / m and h = 1 m) of the points lying opposite the end of the lines.
The illumination of other points is determined by dividing the lines into parts and supplementing them with imaginary segments, the illumination from which is then subtracted (Fig. 2.12).
With general uniform illumination, the control points are usually selected in the middle between the rows of luminaires.
Rice. 2.12. Illumination of points that do not lie opposite the end of the line When calculating from the graphs of the linear isolux according to the plan and section, the dimensions L d.l and p are determined (Fig. 2.13), the ratios p "= p / h and L" = Lw.l / h and for a point on the graph with coordinates p "and L" is defined.
Lines for which the condition L "4 is satisfied can be considered in calculations as infinitely long.
Summing the values from the nearest rows of luminaires or parts of the rows illuminating the points gives e, the coefficient is taken according to the reference data, and the linear flux density, lm / m, is determined by the formula Knowing F ', you can compose the lines. In this case, two methods are used:
The total flow of lamps in the line is found, the length of the line L s.l, after which the placement of lamps in the line is performed in the same way as discussed above;
If the line is long enough and it can be considered as an extended line with breaks, then, taking the possible values of the flux of the lamps F, we find where lw is the length of the luminaire.
Based on the calculations performed, a suitable option is selected.
The power density method is used to calculate the overall uniform illumination of rooms.
Power density is an important energy indicator of a lighting installation, used to assess the cost-effectiveness of solutions and determine the lighting load in the early stages of design.
The method under consideration cannot be used in the design of lighting installations for industrial premises with a complex characteristic of visual work (categories 1 and 2 in Table 1.3), as well as installations that require high quality lighting and correct color rendering.
Specific power of the lighting installation - quotient from the division of the total power of the light sources installed in the room by the area of the room:
where N is the number of light sources;
Р1 - power of one light source (lamp), W;
S is the area of the room, m2.
When calculating using the power density method for the illuminated room, first select the type of luminaire and the estimated height h. When the room is illuminated with point light sources (LN, DRL, etc.), the number of lamps N is outlined. For a given value of the standardized illumination, the specific power Rud is found from the reference data.
Determine the power of one lamp:
For tubular fluorescent lamps, the number of rows N is first outlined and the total required power of all lamps in the Pp row is found:
and then determine the number of fixtures and lamps in each row.
1. What classes are light sources divided into?
2. Name the light and electrical characteristics of light sources.
3. Give the design of the incandescent lamp.
4. Name the advantages, disadvantages and scope of incandescent lamps.
5. Give the design of the halogen incandescent lamp.
6. Name the advantages, disadvantages and scope of halogen incandescent lamps.
7. Give the design of the fluorescent lamp.
8. Explain the term "luminescence".
9. Name the advantages, disadvantages and scope of fluorescent lamps.
10. Give the circuits for connecting fluorescent lamps to the network.
11. Give the design and characterize compact fluorescent lamps.
12. Give the design of an arc fluorescent mercury lamp.
13. Name the advantages, disadvantages and scope of arc mercury fluorescent lamps.
14. Give the circuits for connecting arc mercury fluorescent lamps to the network.
15. Characterize metal halide lamps.
16. Give the design of the sodium lamp.
17. Name the advantages, disadvantages and scope of sodium lamps.
18. What factors determine the choice of the light source?
19. What are the elements of the lamp?
20. What are the main lighting characteristics of the lamps?
21. How do luminaires differ in terms of light distribution?
22. Give the areas of application of luminaires with different types of light distribution.
23. How is the efficiency of a luminaire determined?
24. How are luminaires classified in terms of the ratio of the luminous flux emitted into the lower hemisphere to the total flux of the luminaire?
25. Indicate the area of application of the luminaires for direct, diffused and reflected light.
26. How is the protection class of the luminaire against dust and water indicated?
27. Give an example of designation of the type of luminaire.
28. Explain the term "protective corner" of the luminaire.
29. Give an example of the placement of lamps on the plan and section of the room and explain the main dimensions.
30. How is it advisable to place lamps with tubular fluorescent lamps?
31. What relationship determines the efficiency of the lighting installation, the quality of lighting and the availability of the luminaires for maintenance?
32. What are the main methods for calculating lighting.
33. Indicate the field of application of the utilization factor method.
34. Designate the area of application of the point calculation method.
35. Designate the area of application of the power density method.
36. Give the algorithm for calculating the illumination using the method of utilization in relation to point light sources.
37. Give an algorithm for calculating the illumination using the utilization factor for tubular light sources.
38. Give the algorithm for calculating the illumination by the point method in relation to point light sources.
39. Give an algorithm for calculating the illumination by the point method as applied to tubular light sources.
40. Give an algorithm for calculating the illumination by the specific power method.
Section 3. Electrical part of lighting installations This section covers two topics:
- power supply of lighting installations;
- calculation of electric lighting networks.
When working with theoretical material, you should answer the self-test questions at the end of the section. As an intermediate control of knowledge in the third section, test №3 should be passed.
If you have any difficulties on questions for self-examination and test tasks, you should refer to the theoretical material of the supporting synopsis or the literature indicated in the bibliographic list.
The solution of task 2 of the control work should be carried out after working out the theoretical material of topics 3.1 and 3.2.
With an effective study of the material in this section, you can score 30 points out of 100 possible.
3.1. Power supply for lighting installations Voltages and power supplies. The choice of voltage for the lighting installation is determined by the general requirements adopted for the power supply of the facility, as well as by the requirements of electrical safety.
For industrial, public and residential buildings, as well as for open areas, a voltage of no higher than 380/220 V AC with grounded neutral should be used.
In rooms with increased danger and especially dangerous when used for lighting luminaires with incandescent lamps, a voltage of no higher than 42 V should be used.
Luminaires for working lighting and emergency lighting in industrial and public buildings and in work areas in open spaces must be powered from different independent power sources. It is allowed to supply working and emergency lighting from different transformers of the same transformer substation (TP) when the transformers are powered from different independent sources. In public buildings, in the absence of independent sources, emergency lighting may be powered from a transformer that is not used to power the working lighting.
The power supply for the outdoor lighting of the facility must be separated from the power supply for the indoor lighting.
Power supply of lighting is performed, as a rule, by independent lines from RU-0.4 kV TP. Typical power supply circuits for lighting objects are shown in Fig. 3.1.
Rice. 3.1. Typical power supply schemes for lighting objects:
1 - supply lines;
2 - group lines;
3 - main lighting point;
4 - group lighting panel Electricity from the transformer substation is transmitted by supply lines to the lighting main points, and from them - to the group lighting panels. Direct power supply of light sources is carried out from group shields by group lines.
The lighting power circuit and the number of its links are mainly determined by the power required for lighting and the size of the object. In the simplest case, group shields (or shield) can be powered by lines extending directly from RU-0.4 kV TP.
The issues of power supply redundancy for lighting installations are resolved in the complex of the facility's power supply project. Two-transformer TP with ATS device provide the ability to continue lighting operation in case of emergency shutdown of one of the transformers.
Supply and group lines are carried out according to radial, main and mixed schemes (Fig. 3.1). The choice of power supply scheme is determined by:
- requirements for uninterrupted power supply of lighting installations;
Technical and economic indicators (reduced costs, consumption of non-ferrous metal and electricity);
- ease of control and ease of operation of the lighting installation.
Technical and economic calculations established that the maximum length of three-phase four-wire group lines at a voltage of 380/220 V is no more than 100 m, and two-wire ones - no more than 40 m.Each group line, as a rule, should contain no more than 20 incandescent lamps per phase, DRL, DRI, DNaT, and when using multi-lamp fluorescent lamps - up to 50 lamps.
The group lines of lighting networks must be protected by fuses or circuit breakers for an operating current of not more than 25 A. A.
Circuit breakers in lighting networks have become more widespread. They are conveniently assembled in a panel, safe to operate, combine protection and control functions, and operate repeatedly.
In lighting networks, unlike power networks, single-phase electrical receivers are connected to a three-phase circuit. In fig. 3.2 shows three options for the distribution of lighting lamps between phases in a three-phase circuit.
The upper option is optimal from the point of view of voltage losses in the line, since the centers of gravity of the loads of different phases are the same, but this option is not the best in terms of attenuating the ripple of illumination and, in addition, if one or two phases are accidentally disconnected, a random distribution of illumination along the line is created.
The middle option is used most often. It is better than the others, it provides a decrease in illumination ripple and, when one or two phases are turned off, it gives a relatively uniform distribution of illumination along the line.
The lower option is used in cases where the lighting of the room must be turned on in sections.
Group lighting panels (SCHO), located at the junction of supply and group lines, are designed to install protection devices and control group electrical networks.
When choosing a SCHO, the environmental conditions in the premises, the installation method, the types and number of devices installed in them are taken into account.
By the type of protection against external influences, the SCHO have the following designs:
- protected;
- closed;
- splash-proof;
- dustproof;
- explosion-proof;
- chemically resistant.
SCHO structures allow open installation on walls (columns, structures, etc.) and recessed in wall niches.
The placement of the switchboard should be carried out near the center of electrical loads, while it is necessary to ensure the availability of maintenance of the switchboard.
When placing SCHO, you should choose rooms with more favorable environmental conditions. You should not place the SCHO in hot and damp workshops of the enterprise, as well as in fire-hazardous rooms. It is forbidden to install the SCHO in hazardous areas.
Multicast tracing is subject to a number of regulatory requirements and best practices:
Lines should be laid along the shortest possible routes, with open wiring parallel to the walls of the premises, with hidden wiring in the shortest direction;
It is advisable to combine the traces of lines going in the same direction, even if this somewhat lengthens the length of the lines;
- if possible, you should lay lines along the walls, and not along the ceilings;
- lines laid openly on the ceiling should be laid perpendicular to the side with windows;
- the number of wall passes and the number of branch boxes should be limited;
- in premises with trusses, it is advisable to lay lines across the trusses in the form of crossovers between the trusses;
In fire-hazardous premises, transit laying of lines that are not related to the electrical receivers of this premises is prohibited.
Implementation of lighting networks. Electric lighting networks are made with insulated wires, cables, busbars.
Wires and cables are used with copper and aluminum conductors, busbars - with aluminum busbars.
Outdoor power lines are predominantly cabled in earth trenches or cable structures. Less commonly, overhead lines with bare or insulated (SIP) wires are used.
Indoor lighting networks are carried out with open and hidden electrical wiring. In residential and public buildings, hidden electrical wiring is preferable due to their aesthetics.
The most common methods of open wiring:
Direct laying of wires and cables along walls and ceilings using special fixing fittings;
- gasket in perforated steel trays;
- laying in pipes if necessary to protect wires and cables from mechanical damage;
- cable guides, in which the wire (cable) is attached to a pre-tensioned cable (wire);
- wiring with lighting busbar (SCO).
Busbars are used in industrial premises, public and administrative buildings. Bus ducts SHOS2 and SHOS3 are single-phase, bus ducts SHOS4 and SHOS5 are three-phase.
Bus ducts SHOS2 and SHOS4 two- and four-wire are used for electrical networks with a solidly grounded neutral. The neutral conductor is shorted to the metal housing of the busbar trunking and forms a combined (PEN) conductor.
Bus ducts SHOS3 and SHOS5 are made in three- and five-wire.
Here, the neutral working and zero protective conductors are separated (N and PEN). The working neutral conductor (N) is located in the bus duct body, the metal body plays the role of the protective conductor (PEN).
The SCO bus duct provides the possibility of plug connection (without removing the voltage from the line) of single-phase receivers of electrical energy for a rated current of up to 10 A.
The busbar consists of typical elements: sections (straight, lead-in, flexible); end caps; plugs and fixing structures.
The connection of the sections is detachable and dismountable. One end of the section is provided with a receptacle with tightening screws, and at the other end, the protruding rails form the plug. After the plug of one section is inserted into the socket of the other section, the plug contact is tightened with screws.
The laying of a lighting network with a busbar is the most industrial way, but by no means cheap and aesthetic.
Reactive power compensation. Incandescent lamps have a power factor cos = 1. The inclusion of gas-discharge lamps in the network through ballasts (ballasts), which have inductive elements (chokes), leads to a decrease in the power factor to 0.6.
To increase the power factor to cos = 0.9 ... 0, static capacitors are used.
For fluorescent lamps, capacitors are supplied in a control gear set (capacitors 4 in Fig. 2.2), that is, there is an individual compensation for reactive power.
For other gas-discharge lamps (DRL, DRI, DNaT), both individual and group reactive power compensation are used. With group compensation of reactive power, capacitors are connected to the beginning of the group line.
3.2. Calculation of electrical lighting networks Calculation of lighting loads. Each section of the lighting network is characterized by a certain value of the power transmitted through it.
The estimated capacity of the site is determined through the installed capacity of the electrical receivers Rust, the power loss in the ballast and the demand coefficient Kc:
The installed power is determined as the sum of the nominal powers of all lamps Pnom supplied from the considered section of the lighting network.
The value of the KPRA factor, taking into account the power losses in the ballast, is taken:
- CPRA = 1.1 for DRL and DRI lamps;
- CPRA = 1.2 for fluorescent lamps.
In accordance with the PUE, the demand coefficient Kc for calculating the group lighting network of buildings, all links of the emergency lighting network and the outdoor lighting network is taken equal to 1.0.
For power supply lines, the demand coefficient is taken in the range of Кс = 0.8 ... 1.0. The range of demand factor values takes into account that not all light sources may be switched on during peak hours. The larger the object and the more rooms it contains, the lower the Kc value.
The calculated lighting current load is calculated using the following formulas:
For a three-phase network with a neutral wire - for a two-phase network with a neutral wire - for a single-phase network where Rpo1, Rpo2, Rpo3, - the calculated load of one, two and three phases, respectively;
Unom and Unom f - nominal line and phase voltage of the network.
The power factor is taken taking into account the reactive power compensation cos = 0.9 ... 0.95.
Selection of conductor cross-sections. The cross-sections of the conductors of the lighting network must meet the conditions:
- permissible heating of the conductor;
- mechanical strength;
- tripping of protective devices in case of short circuit;
- standardized quality of electricity at the clamps of light sources.
Checking the cross-sections of conductors for the permissible heating is carried out according to the expression where Iadd is the long-term permissible current for the selected conductor cross-section, which ensures the permissible heating of the conductor, is determined from the reference materials.
The mechanical strength of the conductors is necessary so that during installation and operation there is no excessive sagging or wire breakage. The smallest permissible conductor cross-sections in terms of mechanical strength are:
- for copper wires 1 mm2;
- for aluminum wires 2.5 mm2.
According to the PUE, the selected conductor cross-sections must be consistent with the protective devices. In relation to the long-term permissible current of the conductor, protection devices must have a multiplicity of no more than:
3 for the rated current of the fuse-link;
4.5 for the setting current of a circuit breaker with only an electromagnetic release (cut-off);
1 for the rated current of the thermal release of the circuit breaker.
The cross-section of the neutral working conductor of three-phase supply and group networks with compensated ballasts should be selected according to the rated current of the most loaded phase, that is, it is taken to be equal to the cross-section of the phase wire. For network sections with uncompensated ballasts, the section of the neutral protective conductor is taken equal to 50% of the section of the phase conductor.
Calculation of voltage losses in the lighting network. One of the important indicators of the quality of electricity at the terminals of the light source is the steady-state value of the voltage deviation from the nominal voltage Unom. Normally (maximum) permissible voltage deviations at the terminals of the light source are standardized by GOST 13109-97 and are +5% (+10%).
Deviations from the nominal voltage are due to voltage losses in the electrical network, determined by the load and the resistance of the conductors. Therefore, the selected cross-sections of the conductors of the lighting network are subject to verification by voltage deviation, that is, the conditions are subject to verification where U is the total voltage loss from the power source to the most distant light source;
U is the voltage of the power supply to the lighting network.
The value of U is calculated by the expression where Ui is the voltage loss in the i-th section of the lighting network.
The voltage loss in the i-th section of the lighting network in volts is determined by the formula where Рi is the power flowing through the i-th section, kW;
r0 - active resistance of 1 km of wire, Ohm / km;
li — length of section i, km;
Unom is the rated voltage of the lighting network, kV.
It is often expedient to present the voltage loss in the i-th section of the lighting network as a percentage. In this case, formula (3.8) changes to the form When calculating group lighting networks, the design load is often represented as uniformly distributed over a certain length l2 (Fig. 3.3, a).
Rice. 3.3. Representation of the distributed load concentrated For the convenience of using formulas (3.7 and 3.8), the distributed load is represented as equivalent concentrated in the middle of the section l (Fig. 3.3, b).
In practical calculations, the cross-section of the conductors of the lighting network is selected, as a rule, according to the permissible heating (long-term permissible current), and then the conditions of mechanical strength, operation of protective devices in case of short-circuit and permissible voltage loss are checked. If any condition is not met, the preselected section is increased.
1. What voltages are used to power lighting networks?
2. Give a typical power supply scheme for lighting an object.
3. What sources should be used to power the work lighting and emergency lighting fixtures?
4. Explain the terms "supply line" and "group line"
5. How are the issues of redundant power supply of lighting installations resolved?
6. How many lamps can be connected to one group line?
7. What devices protect lighting networks from short-circuit currents?
8. Why is the power factor of discharge lamps less than unity?
9. What are the most common methods of open wiring.
10. What conductive materials are used in lighting networks?
11. What elements are the lighting networks made of?
12. How is the estimated capacity of a section of the lighting network determined?
13. What are the values of the demand coefficient for the supply and group networks?
14. What conditions should the conductor cross-sections of the lighting network meet?
15. What are the smallest allowable conductor cross-sections in terms of mechanical strength?
16. What multiplicity should have protective devices in relation to the long-term permissible current of the conductor?
17. Give the formula for calculating the voltage loss in the section of the lighting network.
18. What are the normally permissible and maximum permissible values of the voltage deviation at the terminals of the light source?
19. What are the requirements for the conductor cross-sections of the lighting network?
20. What is the sequence for choosing a cross-section in an electric lighting network?
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Estimated lighting power R r.o determined taking into account the power losses in the control gear (ballast):
P p.o = P nom.o to ballast, (12.6)
where P nom.o = P nom.i × N- nominal (installed) power of the lighting network ( N- number of lamps; R number i- rated power of one lamp); k ballast- coefficient taking into account losses in ballast.
The values of the coefficient taking into account the losses in the ballast are taken: for lamps of the DRL and DRI types k ballast= 1.1; for LL with starter switching circuits k ballast= 1.2; for LL with starterless switching circuits k ballast= 1.3-1.35. In most reference books (textbooks), the design capacity is determined by introducing the demand coefficient k with... However, to calculate the group lighting network of the building and all links of the emergency lighting network, as well as to calculate the outdoor lighting network, it should be taken k with= 1.
Power supply of working lighting, as a rule, is carried out by independent lines from the substation switchboards. In this case, electricity from the substation is transmitted by supply lines to the main lighting panels, and from them - to the group lighting panels. Power supply of light sources is carried out from group panels by group lines. Emergency lighting fixtures, including for the continuation of work, as well as others, in particular for evacuation, must be connected to an independent power source.
The electrical network of lighting installations consists of supply and group lines. The supply lines are performed according to radial, main, and radial-main schemes (Fig. 12.2). Radial supply lines are used with loads on group panels of more than 200 A. The most common are mixed radial-trunk networks. The choice of the scheme of supply and group networks should be determined by: requirements for the uninterrupted operation of the lighting installation; technical and economic indicators (minimum given indicators, consumption of non-ferrous materials and electricity); ease of control and ease of operation of the lighting installation.
When choosing the route of the lighting network and the places of installation of the main and group shields, take into account: ease of use (availability); exclusion of the possibility of damage during the production of work; aesthetic requirements; reducing the length of the route.
Technical and economic calculations established that the maximum length of three-phase four-wire group lines at a voltage of 380/220 V can be taken no more than 80 m, and two-wire - no more than 35 m. It is not recommended to connect more than 20 incandescent lamps per phase to group lines, and at using multi-lamp fluorescent lamps - up to 50 lamps.
Placement of shields should be carried out near the center of electrical loads, while it is necessary to ensure the availability of their service. Shields should not be installed in hot and damp workshops of enterprises, as well as in fire-hazardous rooms. Installation of shields in hazardous areas of all classes is prohibited.
For many years, lighting networks have been made from aluminum-based wires. The minimum cross-section of insulated wires with aluminum conductors had to be at least 2.5 mm 2. Currently, given the unreliability, fragility, fire hazard of aluminum, copper should be used.
If a number of electrical receivers are connected to the line along its length, then the current load will decrease with distance from the source. Therefore, electrical lighting networks, based on economic feasibility, are built with a decreasing size of the cross-section of wires in the direction from the power source to the electrical receivers.
In practice, for calculating the cross-sections of lighting networks, provided the lowest consumption of conductive material is used, a simplified technique is used, derived on the basis of mathematical analysis and a number of accepted assumptions:
S = M drive / (C∆U add), (12.7)
where S- cross-section of the wire of this section, mm 2; M priv- reduced power moment, kW · m; WITH- coefficient depending on the power supply circuit (three, two- or single-phase) and the grade of the conductor material; ΔU add,%, Is the permissible voltage loss in the lighting network from the power source to the most distant lamp ( ΔU add= 2.5%). Reduced power moment
M priv = ∑М + ∑аm, (12.8)
where M- the sum of the moments of this and all subsequent sections in the direction of energy transfer with the same number of wires in the line as in this section; Σаm- the sum of the moments of all branches that have a different number of wires in the line than in this section (a is the coefficient of the reduction of the moments, depending on the number of wires in the section and in the branch).
When choosing wire cross-sections for the first sections of the network, the nearest standard cross-sections should be taken S cc... According to the selected standard section of this section S i cт and its actual moment M i determine the actual voltage loss ΔU phi:
∆U ph i = M i / (CS icc). (12.9)
Subsequent sections are calculated similarly, taking into account the remaining (or available) voltage losses on them:
∆U rasp.p = ∆U add - ∆U ph i (12.10)
After determining the cross-sections, the sections are checked by heating:
I pi< I доп i , (12.11)
where I pi- rated current of the i-th section; I addi Is the permissible current selected on the i-th section of the section.
The calculated current is determined by the following formulas: for a single-phase (two-wire) lighting network
I p = P p ∙ 10 3 / U f cosφ ; (12.12)
for a two-phase (three-wire) network when the lamps are turned on for phase voltage
I p = P p ∙ 10 3 / 2U f cosφ ; (12.13)
for a three-phase (four-wire) network
I p = P p ∙ 10 3 / √3U f cosφ ; (12.14)
where P p- design power, kW.
The value of the power factor for different types of lamps is as follows: cosφ= 1 - for networks with incandescent lamps; 0.95 - for networks with LL and compensated ballasts; 0.6 - for networks with DRL lamps.
In the last decade, low-voltage overhead networks have become widespread, made as a self-supporting system of insulated wires (SIP). The self-supporting insulated wire is used in cities as a mandatory laying, as a highway in rural areas with a low population density, as a branch to consumers. The methods of laying the self-supporting insulated wire are different: pulling on the supports; stretching along the facades of buildings; laying along facades.
The construction of self-supporting insulated wire (unipolar armored and non-armored, tripolar with insulated or bare carrier neutral) generally consists of a copper or aluminum conductor stranded core surrounded by an internal semiconductor extruded screen, then - with XLPE, polyethylene or PVC insulation. The tightness is ensured by powder and compounded tape, on top of which there is a metal shield made of copper or aluminum in the form of spirally laid threads or tape, using extruded lead. On top of the cushion of cable armor made of paper, PVC, polyethylene, armor is made of aluminum in the form of a mesh of strips and threads. The outer protection is made of PVC, polyethylene or helogen-free mixtures. The gasket spans, calculated taking into account its temperature and wire cross-sections (at least 25 mm 2 for highways and 16 mm 2 on the branches to the inputs for consumers, 10 mm2 for a steel-aluminum wire) are from 40 to 90 m.
Self-test questions
1. List the advantages and disadvantages of different indoor light sources.
2. Name the areas of application of different types of fixtures.
3. What determines the number of lamps in the room?
4. How is the lighting installation supplied with electricity?
Literature: .
Power supply- a set of measures to provide electricity to its various consumers. A power supply system is a complex of engineering structures that carry out power supply tasks, or a set of electrical installations designed to provide consumers with electrical energy.
The power supply network is characterized by the fact that it connects geographically remote points of sources and consumers. This is carried out using a power line - special engineering structures consisting of electric current conductors (wire - bare conductor or cable - insulated conductor), structures for placement and laying (supports, overpasses, channels), insulation means (suspension and support insulators) and protection (lightning protection cables, arresters, grounding).
A rational and reliable solution to the issue of organizing power supply in a building or office is necessary for almost all operated premises. The task of building a power supply system that meets modern requirements for reliability and quality, taking into account the development prospects, is far from always simple and usually involves several options for solutions, depending on operational requirements and economic indicators.
The creation of a power supply system includes the following main stages:
supply of the necessary equipment,
performance of electrical installation and commissioning works (),
warranty and post-warranty.
The development of the power supply system begins with the analysis of consumers, the examination of the facility, and the study of possible options for connecting to the existing power supply system of the facility. Careful work at the preliminary design stage allows you to optimize the problem of power supply for a specific facility, to ensure its uninterrupted operation and easy scaling of the system in the future.
A very important stage is the choice of electrical equipment.
Electrical work in a typical operated premises (office, administrative, production, warehouse, retail, etc.) consists of the following main parts:
installation of metering and distribution boards (with circuit breakers, residual current devices, electricity meters);
installation of electrical wiring in the room, installation and connection of electrical devices (pantographs).
Switchboards
Electrical switchboards are assembled from standardized modules. The devices installed in the switchboard (circuit breakers, differential switches, relays, contactors, meters, transformers, timers, thermostats, etc.) have overall dimensions that are multiples of the size of one module, the boards are available for both wall-mounted and built-in installation, have a wide range of standard sizes, housings are made of plastic or steel with a special polymer coating.
Circuit breakers
The circuit breakers have a tripping mechanism that provides tripping for protection against short-circuit currents and tripping with a time delay for overload current. The machines can be single-phase and three-phase.
Differential circuit breakersAutomatic differential switches (difavtomats) are designed for use of a single-phase or three-phase electrical network in a power supply system with a grounded neutral. Difautomat reacts to differential (residual) current (AC type) and provides:
increasing the level of safety during the operation of household and similar electrical appliances by people;
prevention of fires due to ignition of insulation of current-carrying parts of electrical appliances from the differential (residual) current to the ground;
automatic shutdown of a section of the electrical network (including apartment) in case of overload (T3) and short-circuit current (MT3).
Electricity meters
Electricity meters are electrical meters for metering alternating current energy in single-phase and three-phase 220 / 380V networks with a nominal frequency of 50 Hz. Counters can be single-rate and two-rate (main - day zone and preferential - night, Saturday and Sunday).
Wiring
Electrical wiring is a collection of wires and cables. According to the method of installation, electrical wiring is divided into open (along the surface of walls, ceilings and other building structures), hidden (inside walls or ceilings, in foundations, under the floor along ceilings) and combined (in cable ducts and trays). When choosing cable products, the class of the room (according to the airbag, PUE) and the degree of flammability of the building materials on which the wiring is mounted are also taken into account. Depending on these factors, the choice of brands of wires and cables for rooms is made.
Reliability, durability and safety of wiring is largely determined by the choice of material for wires and cables. In modern construction, it is not recommended to use wires and cables with conductors made of aluminum, since this metal is susceptible to corrosion, its crystal structure changes over time, and hence its electrically conductive properties. An increase in internal resistance ultimately leads to energy losses, heating of wires and connections. Copper, in comparison with aluminum, has significantly higher quality characteristics, therefore, when carrying out electrical work, copper-based wires and cables are increasingly used.
The easiest way to install is open wiring. It is convenient because any part of it is easily accessible for repair and connection of new pantographs. Installation is carried out quickly, as it is associated only with the fastening of the cable to the supporting structures (walls, ceilings, false ceilings, etc.) and with the punching of walls and partitions. The disadvantage of this method is low aesthetics and, in this regard, open wiring in modern rooms is used very rarely. Nevertheless, in utility rooms and in the individual residential sector (in summer cottages, etc.), it is used quite often. Open wiring of wires on combustible bases is carried out on a layer of sheet asbestos. With open wiring, switches and sockets are installed on plastic sockets attached to the wall.
Concealed wiring the most common and safe to use, as it is located in the thickness of a non-combustible material (there are no mechanical influences, air access to it is difficult). The main disadvantage is the inability to connect new pantographs without opening the walls. Covered wires are brought out to the surface of walls or floors (for connection to current collectors) through insulating plastic tubes. The connection and branching of hidden wiring wires is carried out by welding, crimping, soldering or clamps in branch boxes. With hidden wiring, it is allowed to branch off the wires in the lead-in boxes of switches, sockets or lamps.
Wiring in cable ducts(boxes, trays) is located at the junction of the open and hidden ways of laying wires. On the one hand, all the advantages of open wiring are retained, on the other hand, wiring in cable channels is safer and more elegant. In addition, in the presence of a dividing wall, wires of low-current systems (computer networks, television cables, telephone wires, etc.) can be laid in the cable duct, if there is a dividing wall. This type of wiring is used almost everywhere today. For the laying of computer networks, fire and burglar alarms, this method is standard. Cable ducts are produced in the form of hollow boxes of various cross-sections, 2 meters long, as well as in the form of a hollow plinth with internal partitions for cable laying. The cable channels are fastened to self-tapping screws and anchors, straight and corner joints are carried out using special fittings.
Mounting products
For wiring in cable channels, plastic boxes and metal trays are used. For hidden wiring, there is a whole range of installation products for flush mounting of any configuration - junction boxes for various types of walls, junction boxes with terminal blocks inside for branching or contact connections, PVC pipes or corrugated pipes for laying wires in walls. For open wiring in basements and attic rooms, a metal hose is used. With open wiring behind suspended ceilings and under a raised floor, the cable and wires are laid in a corrugated pipe (PVC).
Wiring accessories
Wiring accessories - sockets, switches, switches with an infrared sensor, switches, electrical connectors, sockets, dimmers, dimmers (electronic controls), etc. The material for the installation products is shock-resistant plastic or polycarbonate, the frame design of the wiring products allows you to make a set of several functionally different devices in a single block.
Lighting
The creation of artificial lighting of premises is realized by the selection of lamps with a power sufficient to illuminate the premises of a specific area. Luminaires are lighting fixtures with a lamp installed in it. Luminaires are classified according to several characteristics - according to the distribution of the luminous flux, according to the angle of radiation, according to the purpose of the luminaire and according to the type of light source (lamp) used in the luminaire. The most widely used:
incandescent lamps (glow is created by heating a tungsten coil),
fluorescent lamps (gas discharge lamp, the glow is created by exciting the phosphor layer with ultraviolet radiation that occurs during the discharge),
gas-discharge lamps (glow is created directly from an electric discharge in gas, metal vapors or in their mixture),
halogen lamps (gas-filled tungsten filament lamp).
Measurement of parameters of the power grid
The project should provide for the measurement of the parameters of the installed electrical network, such as:
insulation resistance;
phase-zero circuit resistance;
possible short circuit current (PSC);
checking the presence of a circuit between the earthing switch and the grounded element;
loading of circuit breakers;
RCD check;
ground loop tests (spreading resistance).
For detailed information on the performance of electrical work, electrical measurements and our other services, please contact our office by phone
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