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What is active and reactive power?

The calculation of the electrical energy used by a household or industrial electrical appliance is usually performed taking into account the total power of the electric current passing through the measured electrical circuit. At the same time, two indicators are outlined, reflecting the costs of full power when servicing the consumer. These indicators are called active and reactive energy. Total power is the sum of these two indicators. About what active and reactive electricity is and how to check the amount of accrued fees, let's try to tell in this article.

Full power

According to the established practice, consumers pay not the useful power that is directly used in the farm, but the complete one, which the supplier enterprise releases. Distinguish these indicators in terms of units of measurement - the total power is measured in volt-amperes (VA), and useful - in kilowatts. Active and reactive electricity is used by all electrical appliances powered from the network.

Active electricity

The active component of the total power performs useful work and is transformed into those types of energy that the consumer needs. At a part of household and industrial electrical appliances in calculations the active and full power are the same. Among such devices - electric stoves, incandescent lamps, electric furnaces, heaters, irons and ironing presses and so on.

If the passport indicates an active power of 1 kW, then the total power of such a device will be 1 kVA.

The concept of reactive power

This type of electricity is inherent in chains, in which there are reactive elements. Reactive electricity is part of the total power input, which is not spent on useful work.

The concept of reactive power is absent in DC couplers. In AC circuits, the reactive component only occurs when there is an inductive or capacitive load. In this case, the phase of the current does not correspond to the phase of the voltage. This phase shift between voltage and current is indicated by the symbol "φ".

With an inductive load in the circuit, the phase lag is observed, with capacitive one - its lead. Therefore, only a part of the total power comes to the consumer, and the main losses are due to the useless heating of devices and devices during operation.

Power losses are due to the presence of inductive coils and capacitors in electrical devices. Because of them in the chain for some time there is an accumulation of electricity. After that, the stored energy comes back into the circuit. The devices, which contain a reactive component of electric power, include portable electric tools, electric motors and various household appliances. This value is calculated taking into account a special power factor, which is denoted as cos φ.

Calculation of reactive power

The power factor lies in the range from 0.5 to 0.9; The exact value of this parameter can be found from the passport of the electrical appliance. The total power must be defined as the quotient of the active power divided by the coefficient.

For example, if the power drill card specifies a power of 600 W and a value of 0.6, then the total power consumed by the device will be 600/06, that is 1000 VA. In the absence of passports to calculate the total power of the device, the coefficient can be taken equal to 0.7.

Since one of the main tasks of the existing power supply systems is the supply of useful power to the end user, reactive power losses are considered a negative factor, and the increase of this indicator calls into question the efficiency of the electric circuit as a whole. The balance of active and reactive power in the circuit can be visually represented in the form of this amusing figure:

The value of the coefficient when accounting for losses

The higher the value of the power factor, the less is the loss of active electricity - which means that the consumed electric energy will cost a little less for the end consumer. In order to increase the value of this coefficient, in electrical engineering various methods of compensating non-target losses of electric power are used. Compensating devices are precursors that smooth the phase angle between current and voltage. For the same purpose, condenser batteries are sometimes used. They are connected in parallel to the working circuit and are used as synchronous expansion joints.

Calculation of the cost of electricity for private customers

For individual use, active and reactive electricity in the accounts is not divided - in terms of consumption, the share of reactive energy is small. Therefore, private customers with a power consumption of up to 63 A pay one account in which all consumed electricity is considered active. Additional losses in the circuit for reactive power are not separately allocated and are not paid for.

Accounting for reactive power for enterprises

Another thing - enterprises and organizations. A large number of electrical equipment is installed in industrial premises and industrial plants, and in the total supplied electricity there is a significant part of the reactive energy required for the operation of power supplies and electric motors. Active and reactive electricity supplied to enterprises and organizations needs a clear division and another way of paying for it. The basis for the regulation of the relations of the enterprise-supplier of electricity and final consumers in this case is a model contract. According to the rules established in this document, organizations consuming electricity above 63 A, need a special device that provides readings of reactive energy for accounting and payment.
The grid company sets up a reactive electricity meter and charges it according to its readings.

Coefficient of reactive energy

As mentioned earlier, active and reactive electricity in the bills for payment are allocated in separate lines. If the ratio of volumes of reactive and consumed electricity does not exceed the established rate, then the charge for reactive energy is not charged. The ratio coefficient can be prescribed in different ways, its average value is 0.15. If this threshold value is exceeded, the consumer enterprise is recommended to install compensating devices.

Reactive energy in apartment buildings

A typical electricity consumer is an apartment building with a main fuse, consuming electricity above 63 A. If such a house has exclusively residential accommodation, the charge for reactive electricity is not charged. Thus, the tenants of the apartment building see in the charges the payment only for the total electricity supplied to the house by the supplier enterprise. The same rule applies to housing cooperatives.

Particular cases of reactive power accounting

There are cases when in a multi-storey building there are also commercial organizations and apartments. The supply of electricity to such homes is regulated by separate Acts. For example, the size of the usable area can serve as a division. If in an apartment house commercial organizations occupy less than half of the useful area, then payment for reactive energy is not charged. If the threshold percentage has been exceeded, then there are payment obligations for reactive electricity.

In some cases, residential buildings are not exempt from payment for reactive energy. For example, if the house has points of connection of elevators for apartments, charging for the use of reactive electricity occurs separately, only for this equipment. Owners of apartments still pay only for active electricity.

Understanding the essence of active and reactive energy makes it possible to correctly calculate the economic effect of installing various compensation devices that reduce losses from reactive loads. According to statistics, such devices allow us to raise the value of cos φ from 0.6 to 0.97. Thus, automatic compensatory devices help to save up to a third of the electricity supplied to the consumer. A significant reduction in heat losses increases the life of devices and mechanisms in production areas and reduces the cost of finished products.

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