This paper presents a new definitions for three-phase power using combination of the p-q theory and wavelet multiresolution analysis. Different definition for three-phase power may cause significant changes in the measurement equipment topology. The simple phase shift using the Clarke method between current and voltage for reactive power measurement is discussed. Computer simulations have verified the efficiency of this method and experimental results are presented- Based in the principle of multiresolution analysis in the alpha-beta-0 reference frame, the perturbation power Sd is defined. It is a physical parameter that shows the source of pollution in the system, because it is a signed power (perturbation power flow). It can be powerful help for fault diagnosis in electrical machines.