NOTE 1 This differs from the approach of IEC 62053‑23, where reactive power and energy is defined only for sinusoidal signals. In this standard reactive power and energy is defined for all periodic signals. Reactive power and energy is defined in this way to achieve proper reproducibility of measurements with meters of different designs. With this definition, reactive power and energy reflects the generally unnecessary current possible to compensate with capacitors rather than the total unnecessary current.

NOTE 2 IEC 61869‑2:2012 describes transformers having a measuring range of 0,05 I_n to I_max for accuracy classes 0,2, 0,5, 1 and 2, and transformers having a measuring range of 0,01 I_n to I_max for accuracy classes 0,2 S and 0,5 S. As the measuring range of a meter and its associated transformers have to be matched and as only transformers of classes 0,2 S / 0,5 S have the current error and phase displacement characteristics suitable to operate a class 0,5 S / 1 S meter respectively as specified in this standard, the measuring range of the transformer operated meters will be 0,01 I_n to I_max. Reactive meters intended to be used together with non-S transformers are, therefore, not covered by this standard.