Every person whose work is related to electrical engineering should have a good understanding of what the term “installed power” means. During installation, this allows you to select the power source in the most rational way , as well as properly perform the necessary matching calculations.
In the definition given by the Soviet Energy Dictionary of 1984, the installed capacity of any electrical installation is understood as the largest active component of all its capacities, allowing the entire installation to work for a long time in normal mode without overload, according to the passport data. However, in this case it is hardly possible to speak of a clear definition. In fact, everything is quite simple.
Imagine a situation familiar to many when it becomes necessary to replace home wiring. It would seem that there are no difficulties. But this is not so. One of the key points is the selection of the conductor cross section. It is carried out according to the permissible current or, which is also true (although with some reservations), according to the power value. For example, the room houses one incandescent lamp, an electric kettle and a microwave. Installed power is the sum of all the active components of each appliance, that is, 100 W + 1200 kW + 2000 kW = 3300 kW. Any reactive load, if any, must be accounted for separately (apparent power in kilovolt-amperes). Electric motors and fluorescent lamps are the most common such consumers. So, the first moment - the installed capacity is not actually consumed, since it is not at all necessary that all electrical appliances must be turned on at the same time.
In the case of the supplying power system, the sum of all its constituent generating capacities (current sources) is taken into account . An example is the network of substations in production. It is important to note the power utilization factor. It represents the ratio of electric energy produced during the accounting period of time to its design value. For example, over a month, generators generated 10 MW of energy per consumer, despite the fact that the theoretical output limit is 100 MW. It is obvious that generating capacities are used irrationally and are idle. Indirectly, this means "extra" costs for the acquisition and maintenance of electrical equipment. At the same time, this coefficient is also necessary in the calculations to take into account the necessary time: scheduled current repairs (with shutdown), fuel loading (for nuclear power plants and thermal power plants), etc.
In the above wiring example, a demand factor for electrical equipment is used. In fact, this is a corrective value that allows us to take into account in the calculations the fact that almost never all electric consumers are involved at a time. For a single device, its power must be multiplied by a coefficient, which will give the actual value. The coefficient is selected according to the tables depending on the characteristics of consumers. Using this solution allows you to significantly (sometimes more than twice) reduce the cost of equipment and related materials, simplify subsequent maintenance.
For example, in the case of calculation of lighting networks, this coefficient is taken equal to:
- 1.0 for emergency lines (which is quite understandable - power consumption is relatively low, and operation is short-term).
- 0.6 - warehouse type premises. As a rule, the inclusion of light is necessary only when using buildings.
- 0.8 - domestic premises in the industries. Significant corrections are made by the specifics (sometimes the light is on around the clock), but on average the calculation from 0.8 is correct.
- 0.95 - buildings with large spans. Sometimes even on a sunny day there is a need for backlighting, etc.