Categories: Featured Articles » Novice electricians
Number of views: 66725
Comments on the article: 15

Is reactive electricity available?

 

Is reactive electricity available?For power engineers of enterprises and large shopping centers, there is no doubt that reactive energy exists. Monthly bills and quite real money that goes to pay reactive electricity, convince of the reality of its existence. But some electrical engineers seriously, with mathematical calculations, prove that this type of electricity is fiction, that the separation of electric energy into active and reactive components is artificial.

Let's try and we will sort this issue out, especially since the creators speculate on ignorance of the differences between different types of electricity “Unique” and “revolutionary” energy-saving devices. Promising huge interest energy saving, they knowingly or unknowingly replace one type of electrical energy with another.


Let's start with the concepts of active and reactive electricity. Without going into the jungle of formulas of electrical engineering, you can determine active energy as the one that does the work: heats food on electric stoves, illuminates your room, cools the air using an air conditioner. And jet electricity creates the necessary conditions for such work. There will be no reactive energy, and the engines will not be able to rotate, the refrigerator will not work. The voltage of 220 volts will not come into your premises, since no power transformer can operate without the consumption of reactive electricity.

If the current and voltage signals are simultaneously observed on an oscilloscope, then these two sinusoids always have a shift relative to each other by an amount called phase angle. This shift characterizes the contribution of reactive energy to the total energy consumed by the load. By measuring only the current in the load, it is impossible to isolate the reactive part of the energy.

Given that reactive energy does not do work, it can be generated at the place of consumption. For this, capacitors are used. The fact is that coils and capacitors consume various types of reactive energy: inductive and capacitive, respectively. They shift the current curve with respect to voltage in opposite directions.

Due to these circumstances a capacitor can be considered a consumer of capacitive energy or an inductive generator. For a motor that consumes inductive energy, a nearby capacitor can become its source. Such reversibility is possible only for reactive circuit elements that do not perform work. For active energy, such a reversibility does not exist: its generation is associated with fuel costs. After all, before you complete the work, you need to spend energy.

In domestic conditions, power transmission organizations do not charge a fee for reactive energy, and a household meter only considers the active component of electrical energy. A completely different situation at large enterprises: a large number of electric motors, welding machines and transformers, which require reactive energy to operate, create an additional load on the power lines. In this case, the current increases and the heat loss of already active energy.

In these cases, the consumption of reactive energy is taken into account by the meter and is paid separately. The cost of reactive electricity is less than the cost of active, but with large volumes of its consumption, payments can be very significant. In addition, fines are imposed for the consumption of reactive energy in excess of the agreed values. Therefore, the generation of such energy at the place of its consumption becomes economically beneficial for such enterprises.

To do this, either individual capacitors or automatic compensation units are used, which monitor the volume of consumption and connect or disconnect capacitor banks. Modern compensation systems significantly reduce the consumption of reactive energy from an external network.

Returning to the question in the title of the article, we can answer it in the affirmative. Reactive energy exists. Without it, the operation of electrical installations in which a magnetic field is created is impossible. Not committing visible work, it is, nevertheless, a prerequisite for performing work performed by active electric energy.

See also: Options for reactive energy compensation in the home using the Saving Box

See also at bgv.electricianexp.com:

  • What is reactive power and how to deal with it
  • Options for reactive energy compensation in the home using the Saving Box
  • Energy saving appliances: myth or reality?
  • 10 advantages of electronic energy meters compared to induction ...
  • The most common schemes for switching on single-phase and three-phase electric meters ...

  •  
     
    Comments:

    # 1 wrote: | [quote]

     
     

    Sorry, but the conclusion that reactive energy exists is completely wrong. There is no such energy in nature. What is this described correctly. It is possible to mislead some inaccurate names that have been used for a long time. For example, a counter of reactive energy seems to imply the presence of such energy. In fact, it only calculates the losses of active energy that arise due to a phase shift between the voltage and current sinusoids. It turns out that the maximum power is consumed not at the peak voltage, but at a certain drop, due to which the current consumption increases. This unnecessarily loads energy networks. A separate fee is charged in order to push the consumer with a reactive load to compensate for losses and thus contribute to a more rational operation of the entire energy system.

     
    Comments:

    # 2 wrote: | [quote]

     
     

    The Mercury-200 type apartment meter clearly says “active-watt-hour meter” and we do not pay for any reactive power. If that is what it is for production. And for apartments, there is no need to buy any devices to reduce power consumption. You just bred for money. Moreover, they offer it only through online stores. If this were true, then they would be sold in normal stores. People be vigilant and think a little bit with your head.

     
    Comments:

    # 3 wrote: | [quote]

     
     

    All of these savings are drawn in by the same crooks as politicians! To benefit from the already skinny pockets of the working and unemployed people ...

     
    Comments:

    # 4 wrote: | [quote]

     
     

    Oh, woe to the experts in electrical engineering. Have you ever heard of such a phenomenon as current resonance. To those who have heard, but continue to remain in the tank, I inform you of a “terrible secret”: if inductance is replaced in the parallel-resonant circuit with a net delay and active resistance, then such a device will not consume power from the network at all. In view of the poor tuning for resonance and the absence of a control controller, only 50% savings are obtained instead of 100%. I feel sorry for those to whom empty boxes sucked in. And the commentators who imagined themselves Engineers need to select diplomas, if they have them.

     
    Comments:

    # 5 wrote: MaksimovM | [quote]

     
     

    Andrew, you, most likely, are a "woe expert" of electrical engineering. A perpetual motion machine does not exist, a device cannot be created that does not expend energy for its work. Here there is a phenomenon when the meter does not work correctly - it does not take into account the consumed electric energy.Several times I came across a situation where the operation of automatic compensating devices, compensation devices for capacitive currents of earth faults led to the fact that metering devices stopped, although in fact there was electricity consumption.

    As for household consumers, then, as noted above, payment is for the consumed active component of electric energy. Therefore, even if one actually realizes the compensation of the reactive component of electricity in everyday life, it still will not lead to savings. Therefore, they sell empty boxes, which are also useless.

    Most likely, you yourself are engaged in the implementation of such energy-saving devices, and here are the false arguments. In order to make sure that the idea of ​​such devices is a hoax, it is enough to read a lot of reviews from people who were led by ads and bought these useless devices.

    At the expense of the payment for reactive electric energy described in the article, it is not entirely true. Power plants produce active electrical energy and, accordingly, tariffs for consumed kWh are set for payment. Accordingly, bills for electricity consumed by consumers come precisely for the active component, for the amount of kWh consumed, and this does not depend on what kind of enterprise it is or how much it consumes electric energy. If the consumer is a transit substation or a large enterprise that receives power from several sources, then when taking into account the consumed electric energy, energy flows, usually its active component, are also taken into account.

    Accounting for the reactive component of electricity is carried out to calculate the modes of operation of the electric network, the selection and further organization of the work of compensating devices. The consumer pays for the active component of electricity, and reactive, depending on the configuration of the electrical network, can compensate on the spot. Although in most cases, the compensation of the reactive component of electricity is either not performed at all or is carried out at large junction substations that supply several large consumers.

     
    Comments:

    # 6 wrote: Vladimir | [quote]

     
     

    Reactive energy / power are electrical engineering terms.
    Reactive means imaginary: in reality there is no such energy / power.
    This is not energy - this is the reaction of the circuit to the passage of current through it.
    If the circuit is inductive, then the reaction of the circuit is the creation of a magnetic field.
    If the circuit is capacitive, then the reaction of the circuit is the creation of an electric field.
    Both chains have a common name - reactive chains.
    Energy is not expended in creating an electric and magnetic field!
    For example, with the help of a permanent magnet you can attract iron objects, - this connection to the network is not required; a magnet is a source of magnetic field, not energy!
    And all would be fine, but there’s a “trouble” - there is still an active chain: the reaction of this chain is the generation of heat, the creation of mechanical work, etc.
    When current flows through the active circuit, work is done, which means that energy is expended.
    The active circuit includes wires (this is where the dog is buried!), Which supply energy to the consumer. And even if the consumer is a purely reactive load (that is, it does not consume energy at all!), Its imaginary (reactive) current creates a very real heat generation on the active circuit (supply wires), and this is a waste of energy, which is measured in joules (J) or in kilowatt-hours - 1 kWh = 3600 kJ - in these units is measured active energy - it is measured by ordinary household electric meters.

     
    Comments:

    # 7 wrote: MaksimovM | [quote]

     
     

    Vladimir, reactive energy has a significant effect on the electrical circuit as a whole. The reactive component is considered individually, not as active losses.When choosing electrical equipment, full power is taken into account, that is, not only the active component, but also the reactive one. When accounting for the amount of electricity consumed, the separately active, separately reactive component is also taken into account.

    Inductive and capacitive loads are considered as opposite to each other in the direction of the current vector in the electrical circuit. Reactive power in electrical networks is, in fact, an inductive component. If you add a capacitive component to the electric network, it will reduce the inductive, that is, reactive power, since it is directed towards it in the opposite direction. According to this principle, reactive power compensating devices in electrical installations work — the inductive load that flows in the electrical networks is compensated by adding capacity — by switching on the batteries of static capacitors or synchronous compensators.

    Regarding the creation of an electric and magnetic field. Take, for example, a power transformer in which electricity is first converted into a magnetic field, and then into an electric field. In the process of converting electricity, both magnetic losses and electrical losses occur, which are indicated in the passport data of any power transformer. These losses are indicated in watts, that is, they can be considered as real energy spent on creating a magnetic and electric field.

    It is incorrect to compare the permanent magnet with the processes of creating a magnetic and electric field. If we take an electromagnet and use its magnetic field to attract iron objects, then energy will be expended in creating this magnetic field, the magnitude of which is directly proportional to the mechanical work that the electromagnet performs.

     
    Comments:

    # 8 wrote: | [quote]

     
     

    Andrew, I realized that I wrote?

     
    Comments:

    # 9 wrote: | [quote]

     
     

    Economists in the form in which they are (2 schemes) - fraud. MAI-78 Radio engineer.

     
    Comments:

    # 10 wrote: | [quote]

     
     

    "Reactive energy exists. Without it, the operation of electrical installations in which a magnetic field is created is impossible." "What? What? What ?. What kind of nonsense are you carrying sir.

     
    Comments:

    # 11 wrote: | [quote]

     
     

    Good afternoon, tell me, a 3-phase induction motor is installed at the enterprise, current clamps showed a current value of 25 A in phases (Inom = 55A). I need to mathematically estimate how much electricity a three-phase meter wraps around (CE 303 Energomera - stands at the input, many receivers are connected to it) per hour of operation of this particular engine. Will the calculation be correct?
    Meter reading = 1.73x380x25x1 hours of operation = 16.4 kWh?
    Does the meter measure total power or does it separate the active component from the reactive? Is it possible to hold a mat. calculation that it approximately coincided with indications?

     
    Comments:

    # 12 wrote: MaksimovM | [quote]

     
     

    Dmitriy, the electric meter CE 303 Energomera measures separately the active and reactive components, and in different directions. The plus sign shows the value of power that was consumed by consumers connected to this electric meter. With a minus sign, power flows are recorded, which can be in the case of consumers being supplied by several lines or transit lines connected in parallel - this power value is not taken into account in this case.

    The readout of the active power P + is taken from the meter, that is, the number of kilowatt hours, for which the consumer, powered by this electric meter, also pays. When fixing the readings of the electric meter, it is also necessary to take into account the correction factor, which is calculated depending on the transformation coefficient of the current transformers to which this electric meter is connected.

    As for the calculations, it is accordingly necessary to determine the active power consumption of a three-phase asynchronous electric motor.The formula for calculating the consumed active power in a three-phase network in the case of a symmetrical phase load:

    P = 3 * U * I * cos = 1.73 * U * I * cos

    Your mistake is that you did not take into account the value of cos. This value is usually indicated in the motor data sheet. If you do not multiply by cos, then in the end we get not the active power, but the full one. In addition, in the above formula, the values ​​of the line voltage of the network and the linear load current are substituted. The linear voltage is 380 V, you correctly set, and the current, which was determined by current-measuring clamps, is phase, and the value of the linear current must be substituted into the formula. In this case, it all depends on the method of connecting the windings in the electric motor. If the windings are connected according to the “star” scheme, then the linear current is equal to the phase current and we substitute the value 25 A in the above formula. If the motor windings are connected with a “triangle”, to determine the linear current it is necessary to multiply the phase current by 3, in this case 25 * 1.73 = 43.25 A.

    That is, to determine the active power consumption, you need to know the wiring diagram of the motor windings and the value of the power factor - cos.

    And it should be mentioned that in the calculation it is necessary to take not the nominal voltage of the electric network - 380 V, but the actual one, which was in the power supply at the time of measuring the load current. Almost always, the real voltage in the network differs from the nominal values.

    The resulting value of the consumed active power is multiplied by the number of hours the engine is running and compared with changes in meter readings over a similar period of time.

     
    Comments:

    # 13 wrote: | [quote]

     
     

    MaksimovM thanks for the answer, I have approximately determined this same cosine using the formulas and engine performance (dependence of the cosine on the load on the shaft), it turned out 0.45

    The rated motor current is 55 A, cos = 0.91, star connection.

    Measured current = 25 A (the motor is significantly underloaded, close to idle).

    Approximate meter readings: P = 1.73 * 390 * 25 * 0.45 * 1 hour = 7.5 kW * h.

     
    Comments:

    # 14 wrote: ananim | [quote]

     
     

    I turned on the 150 microfarad capacitor to the dimmer, my meter in the house showed about 300 watts of active, okay, let the losses go back and forth, but the meter on the column counted 1.5 kW of active !!! there were no loads except the dimmer and conder, and how to understand this?

     
    Comments:

    # 15 wrote: Trainee | [quote]

     
     

    I don’t understand, but I want to understand. This is how thermal energy differs from mechanical energy is understandable, but here they flow along one wire and different.