Economic effect due to reduction of reactive power losses

If we take a consumer who uses active power for transformation into useful work, along with the active power, reactive power will be inevitably passing through electric lines, without which no electric motor can work. But this does not mean that reactive power shall be obtained from the generators constantly; it may be obtained by means of automatic compensating system instalation at the substations.

In the fig. 1 there is an example of two inductive users (electric motors), that receive equal active power, but with different power factor φ1, φ2:

• S1 - user 1;
• S2 - user 2.

One can see that the first user loads the network with two times bigger reactive power than the second one, operating with better power factor. Correspondingly, when paying for actual energy consumption, the first user pays for one unit of manufactured product by 5-15% more, depending on its network arrangement.

Besides, in case of reactive power undercompensation (cos φ < 0,97), local overheating leads to the failure of contacts and standard insulation (for example, electric motor windings etc.), which reduces equipment lifetime.

For example, a capacitor system payback period may be estimated as follows:

T = З/(З₂ – З₃),

where:

• З – capacitor system price, ruble;
• З₂ – electricity costs without compensation, ruble /month;
• З₃ – electricity costs when using capacitor systems, ruble /month.

Technical-and-economical effect, expected as a result of capacitor system application, is shown in the table below.

Conditions of compensating device economic efficiency are determined on the basis of minimum reduced expenditures, when calculating which the following parameters shall be considered:

• Costs of compensating devices (C.D.), switching apparatus for these devices, C.D. power adjustment devices etc.;
• Decrease of transformer substation and electric network cost due to reduction of current load.