A METHOD AND RELATED DIGITAL INSTRUMENT FOR THE MEASUREMENT OF THE ELECTRIC-POWER QUALITY

The ever increasing number and power of polluting loads (non-linear, t ime-variant loads, ...) connected to the electric power network causes a significant distortion in the line current and, as their overall po wer is no longer neglible with respect to the network power, also some distortion in the line voltage. This causes a deterioration of the el ectric power quality that may disturb the other connected loads. The a vailability of an instrument able to quantify the deterioration of the power quality due to the harmonic distortion, to assess whether or no t this deterioration is caused by a polluting load connected after the metering section and to quantify the effects of such a load on the po wer quality represents hence an important point for the correct operat ion of the electric power system. This paper proposes a measurement me thod, based on the evaluation of the harmonic powers, for the identifi cation of the source producing pollution in a three-phase system. Some parameters are also defined in order to quantify the electric power q uality and the deteriorating effects of a polluting load. A digital in strument is also described, realized by means of Virtual Instrument te chniques to implement the proposed method and to verify it experimenta lly. The measurement accuracy is discussed.