Reactive power compensation for the home. Reactive power compensators. General questions of theory

Saving energy resources is one of the main tasks of modern civilization. More and more articles appear on the Internet about saving electricity by compensation. Indeed, for industrial enterprises, this process is relevant, as it saves money. Quite a lot of people are beginning to wonder if industrial enterprises save on the reactive component, is it possible to save on this in everyday life, by compensating for the reactive component in the workshop, in the country or in the apartment.

I will probably disappoint you - this is impossible to do, for several reasons:

1. , which are installed for private consumers, keep records of only active power;
2. Accounting for the reactive component is carried out only at large industrial enterprises; for private consumers, this accounting is not kept;
3. Such energy does absolutely no useful work, but only heats wires and other devices;

Yes, in domestic conditions it is possible to install filters, this will reduce the total current in the circuit, reduce the voltage drop. When starting high power devices (vacuum cleaners, refrigerators), household reactive power compensators reduce the starting current. It is quite simple to assemble a reactive power compensator with your own hands at home. To do this, it is necessary to calculate the reactive power for a single-phase device:

To do this, you need to measure the voltage and current of the circuit. How to find cos? Very simple:

P - active power of the device (indicated on the device itself)

f - network frequency.

We select capacitors for a household reactive power compensator by capacitance, voltage, type of current. Capacitors are hung in parallel with the load.

Reducing the total current will reduce heat and allow maximum utilization of circuit power. But, at industrial enterprises, cosφ is strictly regulated, and in most cases it is controlled automatically, that is, when a device is taken out of operation, cosφ is still maintained in the specified range. Imagine that you have calculated in your apartment, made a compensator and connected it to the circuit. But after a while, the consumer (for example, a refrigerator) turned off and the network balance was disturbed. Now you do not compensate, but generate reactive energy back into the grid, thereby negatively affecting the work of other consumers. In order to maintain balance, you must constantly monitor the operation of various devices. In everyday life, automating this process is too expensive and makes no sense, since this will not allow you to return the money even for the compensator.

It can be concluded that reactive power compensation in everyday life is meaningless, since it will not save money, and the installation of an unregulated compensator can lead to overcompensation and, as a result, only worsen the network power factor cosφ.

If you want to save energy, you should use the old reliable ways:

1. Buy household appliances of class A or B;
2. Turn off the lights and household appliances (with the exception of the refrigerator) when you leave the house;
3. Replace incandescent light bulbs with energy saving ones. They both last longer and consume less;
4. If you use an electric kettle, boil as much water as needed, this will significantly reduce the energy consumed by it;
5. Clean the vacuum cleaner filter to improve traction and reduce energy consumption;
6. Insulate rooms to minimize the use of electric heaters.

The video shows a do-it-yourself household reactive power compensator

The video uses a household compensator in the form of a block of capacitor banks

The load of enterprises is divided into active, inductive and capacitive, all these types of capacities depend on the type of operating equipment.

The existence of reactive energy has a negative impact on electrical networks, creates electromagnetic fields in electrical devices.

The existence of a reactive current creates an additional load, leading to a decrease in the quality of electricity, resulting in an increase in the cross sections of the current conductors.

Purpose of the reactive power compensation device

The main purpose of the device is to reduce the action, it serves to increase and maintain at a certain standard level the value of the power factor in three-phase distribution networks. The main purpose of the UKRM is the accumulation of reactive power in capacitors. This action helps to unload the electrical network from reactive power flows, voltage stabilization occurs, and the share of active power increases.

Main functions of UKRM

1. Reducing the consumed load current by 30-50%.
2. Reducing the constituent elements of the distribution network, increasing their service life.
3. Increasing the reliability and capacity of the electrical network.
4. Reduction of thermal losses of electric current.
5. Reducing the impact of higher harmonics.
6. Phase unbalance reduction, network interference smoothing.
7. Minimizing the cost of inductive power.

The reactive power compensation unit UKRM has a number of advantages due to the use of capacitors, supplemented by the third level of safety in the form of a polypropylene segmented film impregnated with a special liquid, ensuring reliable use, durability, low cost when performing maintenance and repair work.

The presence in the capacitor unit UKRM of specialized thyristor high-speed starters operating with a time advance for switching phase capacitors that operate when cosφ changes, extends their uptime.

To ensure the regulation of cosj in automatic mode with the transfer of information to a PC with control in the network of higher harmonics of current and voltage, controllers with contactor switching are used.

To improve the quality of the work of the UKRM, the installation has an odd harmonic filter and a thermoregulation device; an indication system has been thought out to detect faults.

All equipment is placed in a block-container equipped with ventilation and heating with automatic control. The devices provide comfortable and convenient service at low temperatures down to -60 ° C.

The modular type of construction contributes to the gradual increase in the capacity of the UKRM.

Protection of capacitor installations

For the safe operation of the device, protections are provided:

1. Interlocks that provide protection against contact with live parts under voltage.
2. Protection that protects the installation from a short circuit of the capacitor.
3. From exceeding the norm of electric current.
4. From overvoltage.
5. From the imbalance of currents in the phases of the device.
6. Electromagnetic blocking, which protects against erroneous activation of switching devices UKRM.
7. Mechanical blocking of the switching on of the grounding knives in a running installation.
8. The presence of a contact switch that turns off the unit when the doors are opened when the equipment is turned on.
9. Thermal protection, including forced cooling when the temperature of the capacitor banks rises.
10. Thermal sensor that turns on heating in the installation when the temperature drops.

Advantages of the UKRM capacitor unit

1. Availability of three-phase fireproof environmental capacitors.
2. Application in the device of special fuses and resistance arresters with linings made of a polymeric metallized film with mineral impregnation.
3. Reactive power controllers and digital analyzers with remote control.
4. To improve seismic and vibration resistance, special polymer insulators are used.

Types of UKRM

There are several types of UKRM installations used in 6-10 kV networks, these are:

1. Unregulated installations, made in a modular construction, consisting of several fixed steps, switching takes place in manual mode in the absence of load currents.
2. Automatic or adjustable, the basic device is designed for automatic regulation of stages, each of which consists of three capacitors connected in a star, switching operations are carried out automatically using an electronic unit that determines the power and on-time.
3. Semi-automatic installations are used to reduce the cost of the reactive power compensation device, the price becomes affordable while maintaining the quality of the device. To do this, the device uses both regulated steps and fixed ones.
4. High-voltage installations with filters used to protect against non-linear harmonic distortion of protective anti-resonance chokes. Such installations are used in conjunction with devices that generate a phenomenon in the network of higher harmonics, these are: devices that provide soft start and frequency converters.

In modular KRM installations, the stages are structurally combined into a module

Features of connecting UKRM

The most optimal connection of a reactive power compensation device is to install the device in close proximity to the consumer (individual compensation). In this case , the cost of a reactive power compensation installation, consisting of the sum of the cost of implementation and further maintenance, is a significant amount.

When combining loads into a single complex for the consumption of reactive power, it is advisable to apply group compensation. In this case, the use of the price of a reactive power device becomes the most acceptable when put into operation, but less profitable for users due to a decrease in active losses in the electrical network that affect cost savings.

It is possible to connect the KRM device as a separate equipment with an individual cable gland, or as part of a low-voltage switchgear, for example, as part of the main switchboard.

Calculation UKRM

To select the UKRM, the total total power of the capacitor banks of the electrical installation is calculated, according to the formula:

Qc = Px (tg(1)-tg(f2)).

Where P is the active power of the electrical installation
Indications (tg (f1) -tg (f2)) are found according to cos (f1) and cos (f2)
The value of cos(φ1) of the power factor before installing the UKRM
The value of cos(φ2) of the power factor after the installation of the UKRM is set by the power supply company.

The power formula looks like this:

k- tabular coefficient corresponding to the values ​​of the power factor cos (f2)

The power of the UKRM is determined specifically for all sections of the electrical network, depending on the nature of the load and the method of compensation.

Only after a full analysis of the indicators obtained during the diagnostics of the data, it becomes possible to choose regulated or unregulated MCRM.

The degree of power splitting by steps, the time and speed of repeated operation of the steps are indicated, the need to use reactive power compensation in the capacitor installation to reduce the non-sinusoidality factor in the supply network, filter out odd harmonics, and also the absence of the resonance effect is revealed. This ensures power quality.

It is necessary to know that it is impossible to make full compensation of reactive power up to unity, this leads to overcompensation, which can occur as a result of a non-constant value of the active power of the consumer, as well as as a result of random factors. The desired value of cosph2 is from 0.90 to 0.95.

Reactive power and energy degrade the performance of the power system, that is, loading generators of power plants with reactive currents increases fuel consumption; losses in the supply networks and receivers increase, the voltage drop in the networks increases.

Reactive current additionally loads power lines, which leads to an increase in the cross-sections of wires and cables and, accordingly, to an increase in capital costs for external and on-site networks.

Reactive power compensation, at present, is an important factor that allows solving the issue of energy saving in almost any enterprise.

According to estimates of domestic and leading foreign experts, the share of energy resources, and in particular electricity, is about 30-40% in the cost of production. This is a strong enough argument for a manager to seriously approach the analysis and audit of energy consumption and development of methods for reactive power compensation. Reactive power compensation is the key to solving the issue of energy saving.

Reactive power consumers

Main consumers of reactive power- , which consume 40% of all power together with household and own needs; electric ovens 8%; converters 10%; transformers of all stages of transformation 35%; power lines 7%.

In electrical machines, a variable magnetic flux is associated with windings. As a result, reactive emfs are induced in the windings when an alternating current flows. causing a phase shift (fi) between voltage and current. This phase shift typically increases and decreases at light load. For example, if the cosine phi of AC motors at full load is 0.75-0.80, then at light load it will decrease to 0.20-0.40.

Lightly loaded transformers also have low (cos phi). Therefore, if reactive power compensation is used, then the resulting cosine phi of the power system will be low and the electrical load current, without reactive power compensation, will increase with the same active power consumed from the network. Accordingly, when reactive power is compensated (using automatic capacitor units KRM), the current consumed from the network is reduced, depending on the cosine phi by 30-50%, respectively, the heating of the conductive wires and the aging of the insulation are reduced.

Besides, reactive power along with active power is taken into account by the electricity supplier, and therefore payable at the current tariffs, and therefore constitutes a significant part of the electricity bill.

Structure of reactive power consumers in power grids (according to installed active power):

Other converters: AC to DC, industrial frequency current to high or low frequency current, furnace load (induction furnaces, arc steel furnaces), welding (welding transformers, units, rectifiers, spot, contact).

The total absolute and relative losses of reactive power in the elements of the supply network are very large and reach 50% of the power supplied to the network. Approximately 70 - 75% of all reactive power losses are losses in transformers.

So, in a three-winding transformer TDTN-40000/220 with a load factor of 0.8, reactive power losses are about 12%. At least three voltage transformations occur on the way from the power plant, and therefore the reactive power losses in transformers and autotransformers reach large values.

Ways to reduce the consumption of reactive power. Reactive power compensation

The most effective and efficient way to reduce the reactive power consumed from the network is the use of reactive power compensation units.(condensing units).

The use of capacitor units for reactive power compensation allows:

• unload power lines, transformers and switchgears;

• reduce electricity bills

• when using a certain type of installation, reduce the level of higher harmonics;

• suppress network interference, reduce phase unbalance;

• make distribution networks more reliable and economical.
  

Using electricity, we use active and reactive energy. Only active energy can be useful, it is always transformed into the benefits that people need. Reactive energy lingers in networks, it participates in the creation of electromagnetic fields. Such processes can be observed in transformers, electric motors and other types of equipment in demand. Unused energy does not disappear without a trace, it creates an additional load on the entire network, thereby provoking the loss of active energy. As a result, the user receives double losses, which could have been avoided by using a regulator and a reactive power compensator.

Losses in networks occur for various reasons, but the main problem is reactive energy in conductive networks. Reactive power compensation for business owners and representatives of housing and communal services is mandatory to be carried out by installing reactive power regulators, because energy consumption at large-scale facilities reaches the maximum level.

The assortment of the company "RUSELT"

RUSELT is engaged in the development and production of certified products that meet European quality and reliability standards. TU 3114-017-55978767-09 confirms our competence and responsibility. The company presents models of ukrm:

• KRM-0.4 - used for automatic and manual power control (from 20 to 1000 kvar);
• KRM-F - perform the function of compensation and filtering (from 20 to 1000 kvar);
• KRM-MINI (KRM-M) - applicable for networks, have a controlled type (20, 30, 40 kvar).

Why are compensators used?

There are a number of advantages of using compensators and reactive power controllers:

• reduction of electricity costs up to thirty percent;
• extending the service life of transformer and other special equipment, maintaining the integrity of the equipment;
• reduction of electrical load in networks and connection cables;
• extending the service life of switching equipment;
• exclusion of fines and other penalties from state bodies;
• reducing the risk of network interference.

The RUSELT manufacturer uses modern equipment technologies to save energy resources. We strive to meet the needs of consumers, therefore we are expanding and improving the range of products.

Intrusive advertising on the Internet and even on state television channels through a TV shop persistently offers the population a device for saving electricity in the form of "novelties" in the electronics industry. Senior citizens receive a 50% discount on the total price.

"Saving Box" - this is the name of one of the proposed devices. They have already been written about in the article. It's time to continue the topic on the example of a specific model, explaining in more detail:

what is reactance;

how active and reactive power is generated;

how reactive power compensation is carried out;

on the basis of which reactive power compensators and a device for saving electricity work.

People who buy such a device receive a parcel with a beautiful box by mail. Inside there is an elegant plastic case with two LEDs on the front side and a plug for installation in a socket on the back.

A miracle device for saving electricity (click on the picture to enlarge):

The attached photo shows the characteristics declared by the manufacturer: 15,000 W at a mains voltage of 90 to 250 V. Let's evaluate them from the point of view of a practicing electrician using the formulas below the pictures.

At the lowest specified voltage, such a device should pass a current of 166.67 A through itself, and at 250 V - 60 A. Let's compare the calculations obtained with the loads of AC welding machines.

The welding current for steel electrodes with a diameter of 5 mm is 150 ÷ ​​220 amperes, and for a thickness of 1.6 mm, 35 ÷ 60 A is enough. These recommendations are in any electric welder's handbook.

Remember the weight and dimensions of the welding machine, which welds with 5 mm electrodes. Compare them to a plastic box the size of a mobile phone charger. Think about why steel electrodes of 5 mm melt from a current of 150 A, but the contacts of the plug of this “device”, and all the wiring in the apartment, remain intact?

To understand the reason for this discrepancy, I had to open the case, showing the "insides" of the electronics. There, in addition to the board for illuminating the LEDs and the fuse, there is another plastic box for props.

Attention! In this scheme, there is no device for saving electricity or compensating for it.

Is it cheating? Let's try to figure it out with the help of the basics of electrical engineering and existing industrial power compensators operating in energy enterprises.

Power supply principles

Let's consider a typical scheme for connecting electricity consumers to an alternating voltage generator, as a small analogue of the apartment's power supply network. For clarity, its characteristics of inductance, capacitance and active load are shown , and . We will assume that they operate in a steady state when the current of the same value I passes through the entire circuit.

Wiring diagram (click on picture to enlarge):

Here, the energy of the generator with voltage U will be distributed by its constituent parts to:

inductance winding UL;

capacitor plates UC;

active resistance of heating element UR.

If we represent the quantities under consideration with a vector form and perform their geometric addition in the polar coordinate system, then we get an ordinary voltage triangle, in which the value of the active component UR coincides in direction with the current vector.

UX is formed by adding the voltage drops across the inductor UL and the capacitor plates UC. Moreover, this action takes into account their direction.

As a result, it turned out that the generator voltage vector U deviated from the direction of the current I by an angle φ.

Once again, pay attention to the fact that the current in the circuit I does not change, it is the same in all sections. Therefore, we divide the components of the voltage triangle by the value I. Based on Ohm's law, we obtain a resistance triangle.

The total resistance of the inductance XL and capacitance XC is commonly called the term "reactance" X. The impedance Z applied to the generator terminals of our circuit consists of the sum of the active resistance of the heating element R and the reactive value X.

Let's perform another action - multiplying the vectors of the voltage triangle by I. As a result of the transformations, a power triangle is formed. Active and it creates a total applied value. The total energy produced by the generator S is spent on active P and reactive Q components.

The active part is consumed by consumers, and the reactive part is released during magnetic and electrical transformations. Capacitive and inductive powers are not used by consumers, but load conductors with generators.

Attention! In all 3 right-angled triangles, the proportions between the sides are preserved, and the angle φ does not change.

Now we will understand how reactive energy manifests itself and why household meters did not take it into account.

What is reactive power compensation in industry?

In the energy sector of the country, and more precisely, the states of the whole continent, a huge number of generators are engaged in the production of electricity. Among them there are both simple home-made designs of master enthusiasts, and the most powerful industrial installations of hydroelectric power stations and nuclear power plants.

All their energy is summed up, transformed and distributed to the final consumer through the most complex technologies and transport routes over vast distances. With this method of transmission, electric current passes through a large number of inductances in the form of windings of transformers / autotransformers, reactors, barriers and other devices that create an inductive load.

Overhead wires, and especially cables, create a capacitive component in the circuit. Its value is added by various capacitor units. The metal of the wires through which current flows has active resistance.

Thus, the most complex energy system can be simplified to the circuit we have considered from a generator, inductance, active load and capacitance. Only it still needs to be combined into three phases.

The task of the energy industry is to provide consumers with high-quality electricity. In relation to the final object, this implies the supply of electricity to the input shield with a voltage of 220/380 V, a frequency of 50 Hz with the absence of interference and reactive components. All deviations of these values ​​are limited by the requirements of GOST.

In this case, the consumer is not interested in the reactive component Q, which creates additional losses, but in obtaining active power P, which does useful work. To characterize the quality of electricity, the dimensionless ratio P to the applied energy S is used, for which the cosine of the angle φ is used. Active power P is taken into account by all household electric meters.

Electric power compensation devices normalize electricity for distribution among consumers, reduce reactive components to normal. At the same time, phase sinusoids are also "aligned", in which frequency interference is removed, the consequences of transient processes during circuit switching are smoothed out, and the frequency is normalized.

Industrial reactive power compensators are installed after the inputs of transformer substations in front of switchgears: the full power of the electrical installation is passed through them. As an example, see a fragment of a single-line electrical circuit of a substation in a 10 kV network, where the compensator receives currents from the AT and only after it has been processed, electricity flows further, and the load on energy sources and connecting wires decreases.

Let's return for a moment to the "Saving Box" device and ask the question: how can it compensate for power when located in the final outlet, and not at the entrance to the apartment in front of the meter?

Look at the photo how impressive industrial expansion joints look. They can be created and work on different element base. Their functions:

smooth regulation of the reactive component with fast unloading of equipment from power overflows and reduction of energy losses;

voltage stabilization;

increasing the dynamic and statistical stability of the scheme.

The fulfillment of these tasks ensures the reliability of power supply and reduces the cost of the construction of current leads by normalizing temperature conditions.

What is reactive power compensation in an apartment?

Electrical appliances of the home electrical network also have inductive, capacitive and active resistance. For them, all the ratios of the triangles considered above are valid, in which there are reactive components.

It should only be understood that they are created during the passage of current (taken into account by the meter, by the way) through the load already connected to the network. The generated inductive and capacitive voltages create the corresponding reactive power components in the same apartment, additionally load the wiring.

Their value does not take into account the old induction counter. But separate static accounting models are able to fix it. This allows you to more accurately analyze the situation with current loads and thermal effects on the insulation during the operation of a large number of electric motors. The capacitive voltage generated by household appliances is very small, as is its reactive energy and meters often do not show it.

In this case, compensation of the reactive component consists in connecting capacitor units that “extinguish” the inductive power. They should be connected only at the right time for a certain period of time and have their own switching contacts.

Such reactive power compensators have significant dimensions and are more suitable for production purposes, they often work with an automation kit. They do not reduce the consumption of active power in any way, they cannot reduce the payment for electricity.

Conclusion

The capabilities and technical characteristics of the "Saving Box" declared by the manufacturer do not correspond to reality, they are used for advertising based on deception.

It is high time for the consumer rights protection society and law enforcement agencies to take measures to stop sales of low-quality products in the country, at least through state information channels.