The calculation of the electrical energy used by a household or industrial electrical device is usually made taking into account the total power of the electric current passing through the measured electrical circuit. At the same time, two indicators are distinguished that reflect the costs of full power when servicing the consumer. These indicators are called active and reactive energy. Gross power is the sum of these two figures. About what active and reactive electricity is and how to check the amount of accrued payments, we will try to tell in this article.
Full power
According to established practice, consumers do not pay for the useful capacity, which is directly used in the economy, but for the full capacity, which is supplied by the supplier. These indicators are distinguished by units of measurement - total power is measured in volt-amperes (VA), and useful power is measured in kilowatts. Active and reactive electricity is used by all mains-powered electrical appliances.
Active electricity
The active component of full power does useful work and is converted into the types of energy that the consumer needs. For some household and industrial electrical appliances, the active and apparent power in the calculations are the same. Among such devices are electric stoves, incandescent lamps, electric furnaces, heaters, irons and ironing presses, etc.
If the active power of 1 kW is indicated in the passport, then the total power of such a device will be 1 kVA.
The concept of reactive electricity
This type of electricity is inherent in circuits that include reactive elements. Reactive electricity is the portion of the total power delivered that is not used for useful work.
In DC circuits, the concept of reactive power is absent. In AC circuits, the reactive component occurs only when an inductive or capacitive load is present. In this case, there is a mismatch between the phase of the current and 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, a phase lag is observed, with a capacitive load, it is ahead of it. Therefore, only a part of the full power comes to the consumer, and the main losses occur due to useless heating of devices and devices during operation.
Power losses occur due to the presence of inductive coils in electrical devices andcapacitors. Because of them, electricity accumulates in the circuit for some time. The stored energy is then fed back into the circuit. Appliances whose power consumption includes a reactive component of electricity include portable power 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 electricity
Power factor ranges from 0.5 to 0.9; the exact value of this parameter can be found in the passport of the electrical appliance. The apparent power must be defined as the quotient of active power divided by a factor.
For example, if the power of an electric drill is 600 W and the value is 0.6, then the total power consumed by the device will be 600/06, that is, 1000 VA. In the absence of passports for calculating the total power of the device, the coefficient can be taken equal to 0.7.
Since one of the main tasks of existing power supply systems is to deliver useful power to the end consumer, reactive power losses are considered a negative factor, and an increase in this indicator casts doubt on the efficiency of the electrical circuit as a whole. The balance of active and reactive power in a circuit can be visualized in the form of this funny picture:
The value of the coefficient when taking into account losses
The higherthe value of the power factor, the less will be the loss of active electricity - which means that the final consumer of the consumed electrical energy will cost a little less. In order to increase the value of this coefficient, various methods of compensating for non-target losses of electricity are used in electrical engineering. Compensating devices are leading current generators that smooth out the phase angle between current and voltage. Capacitor banks are sometimes used for the same purpose. They are connected in parallel to the working circuit and are used as synchronous compensators.
Calculating the cost of electricity for private customers
For individual use, active and reactive electricity is not separated in the bills - in terms of consumption, the share of reactive energy is small. Therefore, private customers with power consumption up to 63 A pay one bill, in which all consumed electricity is considered active. Additional losses in the circuit for reactive electricity are not separately allocated and not paid.
Reactive electricity metering for businesses
Another thing is enterprises and organizations. A huge number of electrical equipment is installed in industrial premises and industrial workshops, and in the total incoming electricity there is a significant part of reactive energy, which is necessary for the operation of power supplies and electric motors. Active and reactive electricity supplied to enterprises and organizations needs a clear separation and a different waypayment for it. In this case, the standard contract serves as the basis for regulating relations between the electricity supplier and end consumers. According to the rules established in this document, organizations consuming electricity above 63 A need a special device that provides reactive energy readings for metering and payment. The network operator installs a reactive electricity meter and charges according to its readings.
Reactive Energy Factor
As mentioned earlier, active and reactive electricity in the invoices for payment are allocated in separate lines. If the ratio of the volumes of reactive and consumed electricity does not exceed the established norm, then the payment 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 compensatory devices.
Reactive power in apartment buildings
Typical consumer of electricity is an apartment building with a main fuse that consumes more than 63A. Thus, residents of an apartment building see in charges only payment for the full electricity supplied to the house by the supplier. The same rule applies to housing cooperatives.
Special cases of reactive power accounting
There are cases when there are both commercial organizations and apartments in a multi-storey building. The supply of electricity to such houses is regulated by separate Acts. For example, the division can be the size of the usable area. If commercial organizations occupy less than half of the usable area in an apartment building, then payment for reactive energy is not charged. If the threshold percentage has been exceeded, then there are obligations to pay for reactive electricity.
In some cases, residential buildings are not exempt from reactive power charges. For example, if the building has elevator connection points for apartments, the charge for the use of reactive electricity occurs separately, only for this equipment. Apartment owners still pay only 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 load. According to statistics, such devices allow you to raise the value of cos φ from 0.6 to 0.97. Thus, automatic compensating devices help save up to a third of the electricity provided to the consumer. A significant reduction in heat losses increases the life of devices and mechanisms at production sites and reduces the cost of finished products.
