Active and reactive load: payment features, how to find the capacity formula

Understanding the basic principles of electrical engineering, it is important to understand what constitutes an active and reactive load. The first type of energy is considered useful and goes directly to the needs of the consumer, for example, to heat a building, prepare food and operate electrical appliances. The second type, reactive, determines that part of the energy that is not used to do useful work.

Active and reactive power

Active and apparent power can have a range of conflicting interests on the part of customers and suppliers. The consumer is trying to save on electricity by paying bills for the consumed resources, and the supplier is looking for profitable ways to get the full amount for both types of energy. But are there ways to combine these requirements? Yes, because if you reduce the volume of reactive power to zero, then this will allow you to get closer to the maximum savings in money.

It is no secret that for some electricity consumers the indicators of full and active power are comparable. This is due to the fact that they use special devices, the load of which is carried out using resistors. Among them:

1. Incandescent lamps.
2. Electric stoves.
3. Frying cabinets and ovens.
4. Heating equipment.
5. Irons.
6. Soldering irons.

To determine the power of the loads, you can use the formula familiar from school times by multiplying the load current by the mains voltage. In this case the following units will be used:

1. Amperes (A) - indicate the amperage.
2. Volts (V) - characterize the current voltage.
3. Watts (W) - Indicate the power rating.

Recently, more and more often you can notice such a picture that a thin shiny film is located on the glazed balconies. It is created from defective capacitors that were previously used in distribution substations. As you know, capacitors are the main consumers of reactive load, which consist of a dielectric, not conducting electric current (as the main element, a polymer film or paper treated oil).

For comparison, for consumers of active power, the role of the main element is played by a current-carrying material, such as a tungsten conductor, a nichrome spiral, and others.

Capacitive loads

Trying to figure out how to find reactive power, it is necessary to understand the features and principle of operation of capacitors. The shiny surfaces that are located on the balcony are capacitor plates made of conductive material. They are distinguished by their ability to store electricity and then transmit it for consumer needs. In fact, capacitors are used as a kind of storage battery.

And if you connect the structure to a direct current source, this will allow it to be charged with a short-term pulse of electric current, which will eventually lose its power. To return the capacitor to its previous state, it is enough to disconnect it from the voltage source and connect the load to the plates. For some time, current will be supplied through the load. Ideally, the capacitor should release as much energy as it received at the beginning.

If you connect it to a light bulb, it will allow it to flash for a short time, while an unwary person may even receive a minor electric shock if he touches open contacts. Moreover, if the voltage readings are high enough, it can lead to fatal outcome - death.

When connecting capacitors to alternating current, the situation looks a little different. Since the AC voltage source is characterized by the property of constantly changing polarity, the capacitor element will constantly discharge and charge, passing the alternating current. However, its values ​​will not coincide with the source voltage, but will amount to a quarter of the period more.

The final indicators will look like this: for about half of the period, the capacitor will receive electricity from the source, and the other half will be given to the consumer. This means that the total active power indicator will be zero. However, due to the fact that a significant current constantly flows through the capacitor, for the measurement of which an ammeter is used, it is referred to as consumers of reactive power. The reactive power formula is calculated as the product of current and voltage, but in this case, the unit of measurement becomes reactive volt-ampere (VAR), and not W.

Real consumers

While figuring out how to find active power, people think about what will happen if they try to connect a capacitive and inductive load at the same time and in parallel. In this case the reaction will be carried out in the opposite way, and the final values ​​will begin to compensate for themselves.

Under certain circumstances, ideal compensation can be achieved, but it looks paradoxical: connected ammeters will react to significant currents, as well as their complete absence. But it is important to understand that ideal capacitors do not exist (the same applies to inductors), therefore idealization is a conditional picture for an expanded understanding of processes.

As for the real situation, in domestic conditions, consumers consume purely active power, as well as mixed active-inductive power. In the latter case the main consumers are the following devices:

1. Electric drills.
2. Perforators.
3. Electric motors.
4. Refrigerators.
5. Washing machines.
6. Other household appliances.

In addition, such consumers include electrical transformers of power supplies for household equipment and voltage stabilizers. With a mixed load, in addition to the useful one, the reactive one is also consumed, while its values ​​may exceed the active power indicators. Volt-ampere is used as the unit of measurement for apparent power.

In electrical engineering, there is such a thing as "cosine phi" or power factor. It indicates the ratio of active power to reactive power. When using resistive loads comparable to reactive ones, the cos φ value is 1. When capacitive and inductive loads are combined with zero active power, the value of the "cosine phi" will be zero. For mixed loads, the power factor will range from 0 to 1.

Electricity payment

Having figured out how to find the active and reactive power, how such a value can be measured and how to describe it in simple language, it remains to ask a logical question, what a real consumer pays for using electricity. There is no point in paying for full (reactive) energy. However, there are many pitfalls in this matter that lie in minor details.

As you know, a mixed load increases the current in the mains, as a result of which various difficulties arise at power plants where electricity is generated by synchronous generators. The fact is that inductive loads cause "de-excitation" of the generator, and in order to return it to initial state, you will have to spend real active energy, that is, overpay a lot of money funds. It makes sense to make reactive power paid, as this will force the client to compensate for the full component of the load.

If it becomes necessary to pay for both types of capacities separately, then the consumer can consider the installation option special capacitor banks that will start only on schedule when a certain level of consumption is reached electricity. In addition, it is possible to carry out the installation of professional equipment in the form of reactive energy compensators, which connect capacitors with an increase in the amount of power consumption. They effectively raise the "cosine phi" from 0.6 to 0.97, that is, almost to the level of 1.

In addition, according to current regulations, if the customer has used no more than 0.15 power factor, then he is exempted from the need to pay for full load. However, most individual consumers use a very small amount of electricity, so it is impractical to separate the bills for the two types of energy.

In addition, many buildings have single-phase meters that are not able to track flow. reactive electrical loads, therefore, the bill for electricity is issued taking into account the consumed active energy.

Useful Tips

It is not entirely advisable to compensate for inductive loads, since the average consumer uses a small amount of active load. And the arrangement of devices that separate the flows requires large investments and looks technically difficult.

Connected capacitors uselessly load the wiring when disconnecting loads. In some cases, meter manufacturers equip their inputs with compensation capacitors with inductive load. With the correct configuration, such elements can reduce energy loss, as well as slightly raise the voltage on the device by reducing the voltage drop on the lead wire.

In addition, reactive energy compensation will reduce the level of currents along the entire power line, which will positively affect electricity savings and prevent excessive energy losses.