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Reactive energy: what it is and how much it costs


IS reactive energy that which is absorbed by motors, transformers, fluorescent lamps and so on without producing work (only active energy produces work).

The problem is that thereactive energy of the user causes greater consumption and commitment on the lines of the electricity company, which charges the relative higher costs to the user through penalties for low power factor Cosfi (Cosfi = cosine of the phase angle between current and voltage).

L'reactive energy it is measured in kvarh and there are no penalties if the cosfi = 0.9, that is, if the kvarh are less than 50% of the kWh consumed. If the cosfi is between 0.9 and 0.8, that is, if the kvarh are between 50% and 75% of the kWh consumed, there are penalties for each recorded kvarh. When the cosfi is less than 0.8, ie if the kvarh are higher than 75% of the kWh consumed, the penalties on each recorded kvarh are even greater.

In order not to pay the penalties, the only way is to install power factor correction capacitors in parallel with the user in order to produce the quantity of reactive energy the equipment needs to function.

To avoid the damage of the phase shift for the electricity supplier, the energy distribution body has imposed a series of contractual clauses (the tariff measures of CIP n ° 12/1984 and n ° 26/1989) which oblige the user to rephasing your system. In detail, for low voltage systems and with power greater than 15 kW:

  • if the average monthly power factor is less than 0.7, the user is obliged to re-phase the system;
  • if the average monthly power factor is between 0.7 and 0.9 there is no obligation to re-phase the system but the user pays a penalty for reactive energy;
  • if the average monthly power factor is greater than 0.9, there is no obligation to re-phase the system and no fee is paid reactive energy.

The penalty mechanism therefore stimulates the user to rephasing at least up to a cosfi = 0.9. However, the same user could have the advantage of a higher power factor correction due to the benefits deriving from the lower voltage drops and drops in his own system. In any case, the power factor correction must be carried out so that the user's system does not, under any circumstances, reactive energy capacitive type to the network.



Video: Difference between Real, Reactive and Apparent Power (October 2021).