Five reasons for loss of vital energy.

The loss of specific energy in a fluid flow is, of course, associated with the viscosity of the fluid, but the viscosity itself is not the only factor determining the pressure loss. But it can be argued that the amount of pressure loss is almost always proportional to the square of the average fluid velocity. This hypothesis is confirmed by the results of most experimental work and specially designed experiments. For this reason, pressure losses are usually calculated in fractions of the velocity pressure (specific kinetic energy of the flow). Then:

Pressure losses are usually divided into two categories:

pressure losses distributed along the entire channel through which the liquid moves (pipeline, canal, river bed, etc.), these losses are proportional to the length of the channel and are called pressure losses along the length; concentrated pressure losses: pressure losses at a local length of the flow (quite small compared to the length of the entire flow). This type of loss largely depends on the features of the transformation of flow parameters (velocities, shape of streamlines, etc.). As a rule, there are quite a few types of such losses and their location along the length of the flow is often far from regular. Such pressure losses are called local losses or pressure losses due to local hydraulic resistance. This type of pressure loss is also usually calculated as a fraction of the velocity head. Then the total pressure loss can be represented as the sum of all types of pressure loss:

Estimation of the magnitude of local pressure losses is almost always based on the results of experiments; based on the results of such experiments, the values ​​of loss coefficients are determined. To calculate head losses along a length, there are more or less reliable theoretical prerequisites that make it possible to calculate losses using familiar formulas.

47. Dependence for determining pressure loss along the length and local resistance. Practical application.

48. Hydraulically smooth and hydraulically rough pipes.

The pressure loss along the length of the flow can very significantly depend on the roughness characteristics of the pipe walls in which the movement occurs. The surface of the walls limiting the flow always differs from an ideally smooth surface by the presence of protrusions and irregularities. The size and shape of these protrusions depend on the wall material, its processing, operating conditions, during which corrosion is possible, solid sediment particles can fall out and settle on the walls, etc. In the following, we will not study in detail the different types of roughness, but will imagine the pipe walls as covered with uniform tubercles with an average absolute height of the roughness protrusion, denoted by Δ.

Depending on the relationship between the dimensions of the roughness protrusions and the thickness of the laminar film, all pipes can be divided into three types during turbulent motion.

If the height of the roughness protrusions Δ is less than the thickness of the laminar film (Δ<δ), то в этом случае шероховатость стенок не влияет на характер движения и соответственно потери напора не зави­сят от шероховатости, а стенки называются hydraulically smooth.

When the height of the roughness protrusions exceeds the thickness of the laminar film (Δ<δ), то потери напора зависят от шероховатости, и такие трубы называются hydraulically rough. In the third case, which is intermediate between the two above, the absolute height of the roughness protrusions is approximately equal to the thickness of the laminar film. In this case, the pipes are classified as transition region of resistance. The thickness of the laminar film is determined by the formula:

(1.87)

So, there are walls (pipes, channels) that are hydraulically smooth and rough. This division is conditional, since, as follows from formula (1.87), the thickness of the laminar film is inversely proportional to the Reynolds number (or average speed). Thus, when moving along the same surface with a constant height of the roughness protrusion, depending on the average speed (Reynolds number), the thickness of the laminar film can change. With increasing Reynolds number, the thickness of the laminar film δ the wall, which was hydraulically smooth, decreases and can become rough, since the height of the roughness protrusions will be greater than the thickness of the laminar film and the roughness will begin to influence the nature of the movement and, consequently, the pressure loss.

For subsequent practical calculations, you can take approximate values ​​for the height of the roughness protrusion for pipes: new steel and cast iron pipes - Δ ≈ 0.45 - 0.50 mm, used pipes (the so-called “normal”), Δ ≈ 1.35 mm .

Thus, knowing the height of the roughness protrusion and determining the thickness of the laminar film, it is possible, by comparing their sizes, to determine whether the wall limiting the flow in the pipe will be hydraulically smooth or hydraulically rough.

The concept of loss in electrical networks means the difference between the transmitted energy from the energy source and the recorded consumed electricity of the consumer himself. There are many reasons for electricity losses: poor insulation of conductors, very large loads, theft of unaccounted for electricity. Our article will tell you about the types and causes of electricity losses, and what methods can be adopted to prevent it.

Distance range from energy source to consumers

How to determine losses in electrical networks, as well as compensate for material damage, will be helped by a legislative act that regulates the accounting and payment of all types of losses. Decree of the Government of the Russian Federation dated December 27, 2004 N 861 (as amended on February 4, 2017) “On approval of the Rules for non-discriminatory access to electric energy transmission services and the provision of these services...” clause VI.

Loss of electricity most often occurs when transmitting electricity over long distances; one of the reasons is the voltage consumed by the consumer himself, i.e. 220V or 380V. In order to conduct electricity of this voltage directly from power plants, you will need wires with a large cross-sectional diameter; such wires are very difficult to hang on power lines because of their weight. Laying such wires in the ground will also be expensive. To avoid this, high-voltage power lines are used. For calculations, use the following formula: P=I*U, where P is the current power, I is the current strength, U is the voltage in the circuit.

If you increase the voltage when transmitting electricity, the current will decrease, and wires with a larger diameter will not be needed. But at the same time, losses occur in transformers and must be paid for. When transmitting energy with such a voltage, large losses also occur due to wear on the surfaces of the conductors, because resistance increases. The same losses are caused by weather conditions (air humidity), leakage then occurs on the insulators and on the corona.

When the electricity arrives at the final destination, consumers must convert the electricity to a voltage of 6-10 kV. From there it is distributed through cables to different points of consumption, after which it is again necessary to convert the voltage to 0.4 kV. And these are losses again. Electricity is supplied to residential premises with a voltage of 220V or 380V. It must be taken into account that transformers have their own efficiency and operate under a certain load. If the power of electrical consumers is more or less than declared, then losses will increase in any case.

Another factor in energy loss is an incorrectly selected transformer. Each transformer has a declared rated power and if more is consumed, it produces either less voltage or may even break down. Since the voltage in such cases decreases, electrical appliances increase their electricity consumption.

Household losses

After receiving the required voltage of 220V or 380V, the consumer is responsible for the loss of electricity. Losses at home occur for the following reasons:

1. Exceeding the declared electricity consumption
2. Capacitive load type
3. Inductive load type
4. Interference in the operation of devices (switches, plugs, sockets, etc.
5. Use of old electrical equipment and lighting items.

How to reduce electricity losses in houses and apartments? First, check that the cross-section of cables and wires is sufficient for the load being transferred. Typically, a cable is used for lighting lines, for socket lines - a cable with a cross-section of 2.5 sq. mm, and for particularly “gluttonous” electrical appliances - 4 sq. mm. If nothing can be done, then energy will be lost to heating the wires, which means their insulation may be damaged, increasing the chance of fire.

Second, bad contact. Switches, starters and circuit breakers help avoid loss of electricity if they are made of materials that are resistant to oxidation and metal corrosion. The slightest traces of oxide increase the resistance. For good contact, one pole must fit tightly against the other.

Third is reactive load. All electrical appliances carry a reactive load, with the exception of incandescent lamps and old electric stoves. The resulting magnetic induction leads to resistance to the passage of current through induction. At the same time, this electromagnetic induction helps the current to pass over time and adds some energy to the network, which forms eddy currents. Such currents give incorrect data to electricity meters and also reduce the quality of supplied energy. With a capacitive load, eddy currents also distort data, which can be combated using special reactive energy compensators.

The fourth point is the use of incandescent lamps for lighting. Most of the energy goes to heating the filaments and the environment, and only 3.5% is spent on lighting. Modern LED lamps are widely used; their efficiency is much higher, with LED lamps reaching 20%. The service life of modern lamps is several times different from incandescent lamps, which can last only a thousand hours.

All of the above methods of reducing the load on electrical wiring in residential premises help reduce losses in the electrical network. All methods are disclosed in detail to help household consumers who are not aware of possible losses. At the same time, professionals work at power plants and substations who also study and solve problems with electricity losses.

additional education teacher

MBOU DOD DEBC "Smolensk Zoo"

Game scenario

"We will become millionaires..."

The topic is “Energy Saving”.

Target: instilling in students an active life position and a conscious attitude to the problem of energy saving, developing creative skills, cultivating a sense of collectivism and the ability to work in groups.

Tasks:

Formation of the basics of frugality in students;

Fostering a culture of energy consumption;

Development of students’ skills to work with various sources of information; highlight the main thing, compare, generalize, draw the right conclusions.

Formation of a culture of energy consumption among students;

Formation of the economic thinking of a modern person on the scale of a family, educational institution, and the whole country.
Equipment:

Work tables for 3-4 teams of 3 people.

Chairs for fans (invitees, other class students, teachers)

A set of cards for each team with numbers from 1 to 4.

Labels with the name of lamps of various types

Plates with the names of various types of natural fuels,

Plates with the names of types of thermal energy losses,

Multimedia projector, screen, presentation slides.

Posters on the walls
Game plan

"We will become millionaires..."

Organizational moment.

Presenter (teacher)

1. Humanity faces many problems today. It's no secret that one of the leading problems is the problem of energy saving. Newspapers are screaming that uneconomical use of energy resources can lead to a global crisis. The findings are disappointing. Currently, energy resources play a decisive role not only in the world economy, but also in world politics. The world community is entering a period of shortage of fuel and energy resources and the struggle for their redistribution. In these conditions, the problem of energy saving comes to the fore. Moreover, it is becoming a global problem for all of humanity, and not just individual countries and regions. It is difficult to imagine our life without light, heat, electricity and other benefits of civilization. But if we do not change our thoughtless, ruthless and irresponsible attitude towards energy resources, how long will these benefits last for us? According to scientists, for 600 years. What will happen next?

2. An excerpt from the song “Save the Planet” is played.

3. Presenter (teacher) Today we are playing a game "We will become millionaires...", each of us today will directly touch upon the problem of energy saving, draw certain conclusions for ourselves and make fundamental decisions.

1. 
   Leading (teacher)

1. 
   Leading(teacher) Represented by the jury.

1st round

Question:

What do you understand by the word energy saving?

Response discussion time 30 seconds.

The collective answer is evaluated (1 participant answers)

ANSWER: This is simply rational use of energy. Every year, an increasing share of electricity, gas, heat, and water is spent on household needs; The use of electrified household appliances is growing on a huge scale. In big cities, tens of tons of fuel per day are wasted in vain, only because every day we forget to turn off dozens, thousands of lighting fixtures.

The same thing happens with water consumption. . Unclosed or leaking taps not uncommon. Energy saving in the house, energy saving in everyday life, ultimately depends on you and me. How to use the least amount of electricity, heat and water in your home without experiencing a shortage of them. The use of electricity for heating is in itself irrational given its high cost. Often in everyday life, in conjunction with central heating (due to its quality), they are used oil radiators. Before using them, take care to reduce heat loss in the apartment. In a home with central heating and water supply it looks like this: losses due to uninsulated windows and doors - 40%; losses through window glass – 15%; losses through walls - 15%; losses through ceilings and floors – 7%; Obviously, the use plastic windows will significantly reduce losses. Timely insulate regular windows too. Electric stoves are in second place in terms of energy consumption. Here are some rules for efficient use of electricity:
1. Use the burner at full power only for the time necessary for boiling.

2. Products that require a long cooking time should be cooked on a small burner.

3. The diameter of the cookware should be equal to or slightly larger than the diameter of the burner

4. Pots must be covered with a lid.

5. When boiling and heating water, it is better to pour as much water as necessary for the upcoming tea party. Remove scale promptly.

6. Using a pressure cooker significantly saves energy and time.

Fridge should be in the coolest place in the kitchen, away from the radiator and stove, preferably near the outer wall, but not close to it.

Home computer set to an economical operating mode (turn off the monitor, go into sleep mode, turn off hard drives, etc.).

Light curtains, light trim walls and ceilings, clean windows, moderate plantings on window sills will increase the illumination of your home.

Use wisely three lighting systems: general, local and combined.

Regular lamps incandescents used in our homes spend the lion's share of energy on heating, not lighting.
Compact fluorescent lamps as relatively inexpensive and effective.

Luminescent energy saving compact lamps pay off their high cost only if they operate reliably throughout their entire declared service life (usually 8-10 thousand hours).

Focus on quality products from domestic producers.

Always remember that The best wealth is thrift!
2 round

1. Incandescent lamps.

2. Energy saving lamps.

3. Fluorescent lamps.

4. Halogen incandescent lamps.

Questions:

1. 
   Which lamps are recommended to be used primarily for work areas with a long operating time when turned on? (3)
2. 
   These lamps are designed for directional lighting (4)
3. 
   These lamps are cheap, have poor light output, but have good thermal output (1)
4. 
   What is another name for compact fluorescent lamps, which can be used wherever they require a long operating time when turned on (2).

(team discussion 10 seconds. 1 person answers)

Questions:

1. 
   What are the advantages of energy-saving lamps??

1. 
   What are the disadvantages of energy saving lamps?

1. 
   What is the impact of energy-saving lamps on human health?

1. 
   What harmful substances are contained inside energy-saving lamps?

1. Gas.

2. Oil.

3. Peat.

4. Uranus.

Questions.

1. 
   Which energy carrier is the most common in Russia and serves as a raw material for the production of gasoline? (2)
2. 
   Which energy carrier is the oldest extracted fuel resource in Russia? (3)
3. 
   What energy carrier is used as fuel at the thermal power plant in Smolensk? (1)
4. 
   What energy carrier is the main one for generating energy at nuclear power plants? (4)

1. 
   Wind energy.
2. 
   Energy of the Earth's interior (geothermal waters).

4. Solar energy.

Questions.

1. 
   Which type of energy is the most promising for use in Russia? (1,2,3,)
2. 
   What energy source completely heats the capital of Iceland (Reykjavik)? (2)
3. 
   What energy is sourced at space stations? (4).
4. 
   What energy is the least promising for use in the Smolensk region? (2, 3).

1. 
   Losses due to uninsulated windows and doors.
2. 
   Loss through windows.

4. Losses through ceilings and floors.

Questions.

1. 
   Which of the presented energy losses is the greatest? (1)
2. 
   Which of the presented energy losses is the smallest? (4)
3. 
   What energy losses can be avoided? (1)

Tasks of the fabulous “Energy Saving”
(the speed and design acumen of teams is assessed)
Task 1: Previous meter reading in the house fabulous "Energy Saving" was 360 kWh, and the last one was 500 kWh. How much money should he pay for electricity if 1 kWh costs 100 fabulous rubles? (14,000 fabulous rubles)

Task 2:. For 1 hour of continuously burning light bulbs you need to pay 2800 rubles. How much should you pay for the light if it stays on for 10 hours? (28,000 rubles)

Task 3: One fluorescent light bulb consumes 44 kWh of energy per year. 1 incandescent lamp consumes 263 kWh of energy over the same period. How much kWh of energy will a family save if it uses three fluorescent light bulbs instead of three incandescent lamps? (657 RUR)

Task 4: In a big city at night, traffic lights flash yellow. The power of one device is small, but there are many traffic lights in the metropolis. The total power is quite large. On the other hand, you cannot turn off the traffic light - it warns rare drivers that there is an intersection ahead. What should I do?

One possible answer: Let us resolve the contradiction in time. If there are no cars, the traffic light can be turned off. It should turn on if a car approaches the traffic light. At some distance (several hundred meters), you can place a mass sensor under the asphalt, which turns on the traffic light when a car passes.

Task 5: Enormous heat losses occur in enterprises, heated warehouses, and hangars through doorways when cars enter and exit. What to do: place a special employee at the gate or ask drivers to close the door behind them?

One possible answer: heat supply problem: doors must be closed to retain heat. Doors must be open to allow forklifts to pass through. The contradiction is resolved this way: the doors are made of hard rubber or flexible but durable plastic, to which a heat-insulating material (for example, felt) is attached. They open and close themselves!

8th round

One participant per team plays. They must make up the largest number of words from a word in 2 minutes energy saving.
7. Presenter (teacher) The teacher's final word on the need to save energy.

8. Reflection

Use the unfinished sentence technique. The guys in a circle speak in one sentence, choosing the beginning of a phrase from the reflective screen on the board:

1.today I found out...,

2. it was interesting...,

3. it was difficult...,

4. I realized that...,

5. it was boring...,

6. I purchased...,

7. I learned...,

8. I did it...,

9. I was able...,

10. I was surprised...,

11. gave me a lesson for life...,

12. I wanted...

1. 
   Summing up and announcing the team of future millionaires, awarding it.

Scenario of the extracurricular activity “Energy saving is the first step towards sustainable development” Date: 05/19/2011 Venue: School No. 7, assembly hall. Goal: to cultivate in students an active life position and a conscious attitude to the problem of energy saving, the development of creative skills, the cultivation of a sense of collectivism and the ability to work in groups. Equipment: computer, projector, Whatman paper, glue, markers, templates, multimedia presentations, the film “Ecological Disasters”, illustrated models of light bulbs, drawings, photos, school model. Progress of the event. Presenter: There are guests at our event, let me introduce them..... Presenter: I also want to invite an amazing guest, and who is she to introduce herself? Queen of Thrifty Country: I am the Queen of Thrifty Country. I came to thank you for this amazing costume that you prepared for me from waste material. I'm just great in it. (spins) And now I want to find out what you have learned throughout the entire school year. Presenter: During the 2010-2011 academic year, the school purposefully worked on the theory and practice of economical use of energy resources. Let's look at the main aspects of the school's work on this issue. Please pay attention to the photographs, drawings, and leaflets made by students of our school on the topic “Energy saving through the eyes of children” as part of Sustainable Energy Day. (best on screen) In October 2010, our school took an active part in the global photography competition on the topic of energy saving. (slide on the screen), and in January, an energy saving project was drawn up as part of the Energy and Environment competition and awarded a certificate (slide). This guys is our vision of the problem, what do you think? The activity and correctness of your work today will be monitored by a competent jury consisting of: 1...... 2...... 3........ The jury will evaluate your work using green cards, the team that collects the most cards wins. The event is attended by 4 teams of students from grades 6 to 10, each team has a coordinator from grade 10. Each team has a box of useful tips on their tables, into which at the beginning of our event you need to put written down thoughts about how you would like our work on the given topic to be carried out further at school. So, our 1st competition is called “Let's save natural resources at home” (Drafting and defending a collage project) Jury evaluation. Queen of the Thrifty Country: Yes, you guys are great, and I have a special secret task for you. Attention, “black box” (the black box contains recyclable items: paper, plastic bottle, bag, scrap of material), tell the guys how these materials can be used. Presenter: Thank you, fairy, for an interesting task, we promise that we will continue to be very thrifty in the future (Fairy leaves) Jury assessment. Over the course of a number of years, our school has worked to improve the school, namely: (work with groups) 1. All the lamps in the school were changed to energy-saving ones, which not only saved light consumption, but also improved the quality of lighting (photo) 2. This year The heating system is being changed, which will make our school classrooms warmer. (photo) 3. Also, to warm the offices, the windows were taped in the winter. (photo) 4. The children and their parents installed heat-reflective film behind the radiators, which allows them to retain up to 20% of the heat. (photo) 5. The water supply system has been repaired. (photo) And in order to consolidate our knowledge about how to preserve natural resources in residential premises, we will conduct quizzes. You have red and green lights on your tables. You raise the red light if energy resources are not conserved, and the green light if they are conserved. Be careful. Grandma Arina doesn’t know the rules - She heats the house with a gas stove. In order for the house to be cozy, and the warmth to be stored in it, the doors need to be repaired, the glass needs to be inserted and closed. In my apartment, the lights are turned on everywhere, but he doesn’t notice that the sun is shining. It is necessary to change the gaskets in the taps, and then the water will not drip in vain. Dad on the sofa Dozed off a little, Our cat is watching TV instead of Dad. Turn on the light when it’s dark, With the sun - open the window. Glad Seryozha is in the bathroom with an inflatable pillow, And frogs croak from the puddle nearby. Well done guys, you were very attentive. For a number of years, the school has been monitoring classes “Ecology of nature – ecology of the soul.” In the good traditions of our school, we hold a number of environmental events. The “Plant a Tree” campaign, each class in the school took this campaign with full responsibility, the children not only planted trees, but also continue to carefully care for them (photo) “Green School” campaign. The school is our second home and we all really want to make it cozy and green (photo) “Recycled Paper” campaign. We are all already accustomed to the fact that in our school the children take this action very seriously, because the donated amount is 5 kg. waste paper can save the life of one tree (photo) And now I want to check whether your theoretical knowledge is as strong as your practical knowledge (Presentation “Ecological situations”) Water is one of the most important substances for humans. The human body is made up of more than half water. If you look at the world map, there is more blue in it. And the blue color on the maps indicates water, which no one can ever do without, and there is nothing to replace it with! Water is a good friend and helper of man! It overcomes drought, revitalizes deserts, and increases the productivity of fields and gardens. She obediently rotates the turbines of hydroelectric power stations. In nature, everything is united into an inextricable whole. Water is also the habitat of many animals. We all know such world-famous waterfalls as Victoria Falls, Neogarsky Falls, but few people know that in our Artyomovsk there is, albeit small, but still a waterfall (video) Our school has been working for many years to study the natural features of this picturesque place, namely The guys’ first scientific works (certificate) appeared there, we really hope for further support in the implementation of the “Waterfall” project. Our work does not end there, now I ask the representatives to come out and highlight the problems and thoughts on our future work. The problem of energy saving is a worldwide problem. Today we are visiting……Let’s give him the floor.. We’ll ask the chairman of the jury, the school director T.M. Belikova, to sum up the results. (rating table) Awards. We all must remember that we must take care of the nature around us, not in words, but in deeds. We need to change the consumer attitude towards it, otherwise we will soon find ourselves facing an environmental disaster and destroy ourselves. The Earth with its biosphere is the greatest miracle, and we only have one. Tomorrow will be the same as we create it today. Watching the video “Forgive the Earth”

ELECTRICAL ENERGY LOSS

1. Structure of electricity consumption for its transmission.

2. Losses, depending and independent of load.

3. Method of characteristic daily patterns.

4. Average load method.

5. Method of root-mean-square mode parameters.

6. Time of greatest losses method.

An electrical network designed for the transmission and distribution of electrical energy, like any other technical object, requires certain energy costs for its operation, which are expressed in the form of technological energy consumption for its transmission (Fig. 13.1). It consists of energy costs for the production needs of substations and technical losses of electricity associated with the physical nature of the electricity transmission process. The quality level of construction and operation of the electrical network is characterized by the efficiency coefficient:

where W o – electricity paid by the consumer; ΔW к – so-called commercial losses.

Commercial losses are associated with errors (which can be both positive and negative) of numerous electricity metering devices at power plants, in networks and at consumers, possible late payment for consumed electricity, as well as possible theft of electricity.

Note that when analyzing the network mode, losses of both active and reactive power are of interest. When moving to the analysis of energy losses, only active energy losses are important. Calculation of reactive energy has no practical significance.

Losses are usually assessed as a percentage relative to the supplied energy. The question arises: what should be the loss of electricity? Of course, they can be reduced by using, for example, wires with a larger cross-sectional area on lines. But this will lead to increased capital costs. For this reason, when choosing ways to rationally build an electrical network, the factors of capital costs and the cost of electricity losses always act as competing factors. From the above it follows that it is not always advisable to strive to reduce losses, because there is some optimal (rational) level of losses based on the conditions of a specific power system, taking into account the specified factors. Under operating conditions, you should always strive to reduce losses, if it is not associated with additional capital costs.

Experience in the operation of power systems in various countries around the world indicates that electricity losses can be within a fairly wide range (from 7 to 15%).

The task of rationalizing the level of losses is important due to the fact that they are associated with the extreme importance of additional electricity generation at power plants, which in turn requires additional fuel consumption. However, electricity losses are directly related to additional fuel consumption at thermal power plants, which are the final type of costs of power plants in the energy system, and therefore directly affect the economic performance of energy systems.

Sometimes an opinion is expressed: is it necessary to carry out calculations of electricity losses at all? After all, it would seem that they can be determined in the form of the difference in the readings of electricity meters at power plants and at consumers. However, this approach to the problem of electricity losses is unacceptable. As already noted, metering devices have errors that allow losses to be estimated only approximately. At the same time, metering devices are usually not installed along the entire energy transmission path from the power plant to consumers. For this reason, it is not possible to identify places (foci) of increased losses, including along networks of various voltages, and, as a result, to outline effective measures to reduce them. When developing such measures, and even more so when designing a network, it is extremely important to know the change in losses, which, of course, should be revealed only by calculation.

Under operating conditions, there are reported (actual for the past period) and planned losses, which must be calculated for the future, taking into account expected conditions, planned measures to reduce them, etc. In this case, electricity losses can be determined for a month, quarter or year. When designing an electrical network, annual losses are usually of interest. Obviously, in design calculations it is permissible to calculate electricity losses less accurately than in operational calculations, because the accuracy of specifying the initial information is lower. In general, the information security of calculations is closely related to the choice of appropriate calculation methods.

To identify poorly designed sections of the network, it is extremely important to study the structure of losses in the entire power transmission and distribution system. Structural analysis of losses is carried out by dividing them into groups of networks: long-distance and intersystem power transmission, main networks 110–750 kV, distribution networks 6–35 kV, networks up to 1000 V. Within each group, networks are usually divided by voltage classes. In lines and transformers, losses are divided into load-dependent and load-independent (no-load losses). The information obtained as a result of such analysis makes it possible to estimate the proportion of energy losses in all parts of the system. The accumulation of information over time makes it possible to outline ways to rationally reduce losses. The selected paths should in the future be subjected to a more detailed technical and economic analysis and assessment of their effectiveness. After implementing the planned paths, their actual impact on energy losses is determined.

If the operating mode of the network, characterized by active and reactive loads of consumers and generators of power plants, as well as voltages at network nodes, remained unchanged for time t, then electricity losses could be calculated extremely simply:

where ΔP – power losses at the specified mode parameters.

In reality, the parameters of the network mode are constantly changing, and therefore the power losses also change. Moreover, the changes are largely probabilistic in nature.

In any case, it is easiest to calculate electricity losses for one particular network element (line, transformer). In a complex network (from backbone to distribution) with numerous sections, when the regime of some section of the network is influenced by the regimes of a large number of consumers, special methods are used, based, however, on calculation methods for one section of the network.

In power lines and transformers, no-load losses and load losses occur (Fig. 13.1). No-load losses do not depend on the load of the network section and are assumed to be conditionally constant, although they are influenced by the voltage regime.

No-load energy losses in transformers are determined by the formula

No-load energy losses in overhead lines mainly consist of corona losses, as well as losses from leakage currents through insulators. Corona losses depend on the cross-sectional area of ​​the wire, operating voltage, phase design and type of weather (good, dry snow, wet, frost). Energy losses are determined based on power losses, which are found experimentally, taking into account the duration of various types of weather in the corresponding region.

Power losses from insulation leakage currents, which are in the range of 0.5 - 1 mA, are affected by the degree of contamination of the insulators, the type of weather and the number of supports per 1 km of line.

Load losses of electricity in a network element during time T with constant active resistance R and voltage U could be determined by the expression

where I is the current through the network element at time t; S – power per network element at time t. At the same time, it seems very difficult to describe the change in parameters I 2 (t) and S 2 (t) with an analytical function even over a day, and even more so over a year. For this reason, when calculating load losses of electricity, they are forced to resort to various assumptions and simplifications, on the basis of which numerous calculation methods are developed. For practical calculations based on these methods, computer programs for various purposes have been developed.

ELECTRIC ENERGY LOSS - concept and types. Classification and features of the category "ELECTRIC ENERGY LOSS" 2017, 2018.

A transformer is a device that is designed to convert network electricity. This installation has two or more windings. During their operation, transformers can convert the frequency and voltage of the current, as well as the number of phases of the network.

During the performance of specified functions, power losses are observed in the transformer. They affect the initial amount of electricity that the device produces at the output. What are the losses and efficiency of a transformer will be discussed further.

Device

A transformer is a static device. It runs on electricity. There are no moving parts in the design. Therefore, an increase in energy costs due to mechanical reasons is excluded.

When operating power equipment, electricity costs increase during non-working hours. This is due to the increase in active no-load losses in steel. In this case, a decrease in the nominal load is observed with an increase in reactive type energy. Energy losses, which are determined in the transformer, relate to active power. They appear in the magnetic drive, on the windings and other components of the unit.

Concept of losses

During operation of the installation, part of the power is supplied to the primary circuit. It dissipates in the system. Therefore, the incoming power to the load is determined at a lower level. The difference is the total reduction in power in the transformer.

There are two types of reasons due to which the energy consumption of equipment increases. They are influenced by various factors. They are divided into the following types:

1. Magnetic.
2. Electrical.

They should be understood in order to be able to reduce electrical losses in the power transformer.

Magnetic losses

In the first case, losses in the steel of the magnetic drive consist of eddy currents and hysteresis. They are directly proportional to the mass of the core and its magnetic induction. The iron itself, from which the magnetic drive is made, affects this characteristic. Therefore, the core is made of electrical steel. The plates are made thin. Between them lies a layer of insulation.

Also, the reduction in power of a transformer device is affected by the frequency of the current. As it increases, magnetic losses also increase. This indicator is not affected by changes in device load.

Electrical losses

A decrease in power can be detected in the windings when they are heated by current. In networks, such costs account for 4-7% of the total amount of energy consumed. They depend on several factors. These include:

Power losses in transformers are variable. It is influenced by the square of the current in the circuits.

Calculation method

Losses in transformers can be calculated using a certain method. To do this, you will need to obtain a number of initial characteristics of the transformer. The technique presented below is used for two-winding varieties. For measurements you will need to obtain the following data:

• Nominal system power (NM).
• Losses determined at no-load (idle) and rated load.
• Short circuit losses (SCL).
• The amount of energy consumed over a certain amount of time (PE).
• The total number of hours worked per month (quarter) (OH).
• Number of hours worked at rated load level (LF).

Having received this data, the power factor (cos φ angle) is measured. If the system does not have a reactive power meter, its compensation tg φ is taken into account. To do this, the dielectric loss tangent is measured. This value is converted to power factor.

Calculation formula

The load factor in the presented methodology will be determined by the following formula:

K = Ea/NM*OC*cos φ, where Ea is the amount of active electricity.

What losses occur in the transformer during the loading period can be calculated using the established methodology. For this, the formula is used:

P = XX * OCH * PKZ * K² * LF.

Calculation for three-winding transformers

The methodology presented above is used to evaluate the performance of two-winding transformers. For equipment with three circuits, it is necessary to take into account a number of other data. They are indicated by the manufacturer in the passport.

The calculation includes the rated power of each circuit, as well as their short circuit losses. In this case, the calculation will be made according to the following formula:

E = ESN + ENN, where E is the actual amount of electricity that passed through all circuits; ESN – medium voltage circuit electricity; ENN – low voltage electricity.

Calculation example

To make it easier to understand the presented methodology, you should consider the calculation using a specific example. For example, it is necessary to determine the increase in energy consumption in a 630 kVA power transformer. It is easier to present the source data in the form of a table.

Based on the data obtained, a calculation can be made. The measurement result will be as follows:

P = 0.38 kW*h

The % loss is 0.001. Their total number is 0.492%.

Measuring efficiency

When calculating losses, the efficiency indicator is also determined. It shows the ratio of the active type power at the input and output. This indicator is calculated for a closed system using the following formula:

Efficiency = M1/M2, where M1 and M2 are the active power of the transformer, determined by measurements on the input and output circuits.

The output is calculated by multiplying the rated power of the installation by the power factor (cosine of the angle j squared). It is taken into account in the above formula.

In transformers 630 kVA, 1000 kVA and other powerful devices, the indicator can be 0.98 or even 0.99. It shows how efficiently the unit operates. The higher the efficiency, the more economically energy is consumed. In this case, energy costs during equipment operation will be minimal.

Having considered the methodology for calculating transformer power losses, short circuits and no-load, it is possible to determine the cost-effectiveness of the equipment, as well as its efficiency. The calculation method involves using a special calculator or performing calculations in a special computer program.