Peter Minns

Power Quality: Overview and monitoring

ldquoPower qualityrdquo (PQ) is a generic term often used in relation with unwanted disturbances of the electricity supply. In recent years, there has been an increased number of PQ related problems. This is mainly due to the rapid growth in the use of equipment that generate PQ disturbances and also increase of equipment that are sensitive to these disturbances. This increased concern about PQ issues from both suppliers and consumers of electricity has increased the demand for advanced PQ monitoring systems. Each PQ disturbance has a unique wave shape resembling its characteristics. Therefore PQ disturbances could be identified by monitoring the voltage/current signal waveform and analysing its features. PQ monitoring instruments can vary from a simple true r.m.s. meter to advanced techniques that are capable of automatically capturing and classifying PQ events. This paper presents an overview of the characteristics, effects and causes of PQ events and addresses recent trends in PQ monitoring.

Effects of frequency deviation on the accuracy of harmonic analysis and mitigation

Different signal processing techniques are available for automatic detection and diagnosis of power quality disturbances. This paper describes the results of a comparison of the effects of frequency deviation on the accuracy of a number of widely used techniques for signal harmonic analysis, together with a means of mitigation of these effects.