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The way in which power factor correction can enable large industrial consumers to increase the level of active power in cables and transformers, or reduce the cost of an installation for the same power, is explained. Stages in the definition and setting-up of a power factor correction installation are outlined. Criteria observed by Electricite de France in measuring and charging for reactive power used by 'green tariff' consumers (at medium voltages up to 10 MVA) are illustrated by a typical bill for a winter month. For 'yellow tariff' consumers at low voltages from 36 to 250 kVA, only one meter is used and a current limiter is set to the subscribed apparent load; excess current operates a circuit-breaker more or less quickly as a function of the extent and duration of overload (a distinction is drawn between 'long' and medium' users, at 2000 hours of consumption per year). Three possible criteria for phase correction are distinguished: centralised correction with a single battery (or capacitor bank), grouped load correction with several automatically-adjusted batteries, and direct load correction via a contactor and fuse with a closely-connected capacitor.