Virtual Instrument for Measurement of Power Quality in Unbalanced Three Phase System

This paper proposes a power quality index that integrally assesses the quality of the power transferred in a three phase system considering power factor, harmonic distortion and unbalanced condition. The development of a data acquisition system that provides real time measurement of power quality index is also presented here. The proposed power quality index allows explanation of the results obtained when static VAr compensators (SVC) are used in customer installations to balance the unbalanced voltage. In the process of balancing the supply voltage, it introduces harmonics in the network and in turn improves the power factor of the network. The proposed data acquisition system simultaneously collects the on line signals pertaining to the calculation of three factors viz. Harmonic Distortion factor, Unbalanced factor and Representative Quality Power Factor. Fuzzy logic is used for combining three factors into a single power quality index.