Harmonic power flow analysis for the measurement of the electric power quality

The number and power of loads that pollute, from an electric point of view, the electric network are constantly increasing. Their connection to the electric network causes a significant distortion in the line current and, when their overall power is no longer negligible with respect to the network power, also some distortion in the line voltage, thus deteriorating the electric supply quality. The paper proposes a method, based on the evaluation of the harmonic powers, to identify whether the source producing harmonic distortion in the line currents and voltages of a three-phase system is a polluting load connected after the metering section or is the distortion of the line voltages. Some parameters are also defined in order to quantify the effects of the polluting load on the power quality. A Virtual Instrument is also described, realized to implement the proposed method and to verify it experimentally. The instrument accuracy is discussed