How can we convert kVarh to kWh

Blind work

Lexicon> Letter B> Blind work

Definition: the time integral of reactive power

Counter-term: real work

English: reactive energy

Categories: electrical energy, physical principles

Unit: kvarh

Author: Dr. RĂ¼diger Paschotta

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Original creation: 01/06/2013; last change: 15.05.2021


If a consumer draws a constant reactive power from an AC line for a certain period of time, this corresponds to a total of one Blind workwhich is the product of reactive power and duration. More generally, reactive energy is the time integral of reactive power. It is also called Reactive energy designated.

Reactive energy is energy that only shuttles back and forth between the grid and the consumer, i.e. it cannot be used to drive machines or for heating purposes. So a machine can NotWork to the extent that it involves blind work; for that would be Real work necessary. The reactive work only loads the power grid without producing any useful effect. This effect does not occur with direct current networks - only with alternating current or three-phase current.

A common unit of reactive work is the kvarh: 1 kvarh means 1 kvar (= 1000 var) over an hour, or e.g. B. 2 kvar over half an hour. Different symbols are used for reactive work, e.g. B. W.b, W.q or E.b.

Some industrial electricity tariffs include a contribution for reactive work in the electricity bill (especially if there is a high proportion of reactive work, e.g. more than 50% of the real work), while small consumers do not pay for it. The electricity meter must of course also be able to record reactive energy for a calculation, which is not the case for simple household electricity meters. For such industrial consumers there is an incentive to keep the drawn reactive power small or to use it for as short a time as possible. This is possible, for example, by using appropriate devices for reactive power compensation. The energy supply companies benefit from the lowest possible reactive work because their lines are then correspondingly less stressed, i.e. lower line capacities have to be kept ready.

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See also: reactive power, electricity tariff, work
as well as other articles in the categories of electrical energy, physical principles