more power signals, regardless whether or not an event of interest was identified. This algorithm referred to as PQZip empowers a processor with a memory that is sufficient to store the waveform, under normal power conditions, over a long period of time, of at least a month, two months or even a year. The compression is performed in real time, as the signals are acquired; it calculates a compression decision before all the compressed data is received. For instance should one parameter remain constant, and various others fluctuate, the compression decision retains only what is relevant from the constant data, and retains all the fluctuation data. It then decomposes the waveform of the power signal of numerous components, over various periods of the waveform. It concludes the process by compressing the values of at least some of these components over different periods, separately. This real time compression algorithm, performed independent of the sampling, prevents data gaps and has a typical 1000:1 compression ratio. Aggregated data compression A typical function of a power analyzer is generation of data archive aggregated over given interval. Most typically 10 minute or 1 minute interval is used as specified by the IEC/IEEE PQ standards. A significant archive sizes are created during an operation of such instrument. As Kraus et al. have demonstrated the compression ratio on such archives using Lempel–Ziv–Markov chain algorithm, bzip or other similar lossless compression algorithms can be significant. By using prediction and modeling on the stored time series in the actual power quality archive the efficiency of post processing compression is usually further improved. This combination of simplistic techniques implies savings in both data storage and data acquisition processes. Standards The quality of electricity supplied is set forth in international standards and their local derivatives, adopted by different countries: EN50160 is the European standard for power quality, setting the acceptable limits of distortion for the different parameters defining voltage in AC power. IEEE-519 is the North American guideline for power systems. It is defined as "recommended practice" and, unlike EN50160, this guideline refers to current distortion as well as voltage. IEC 61000-4-30 is the standard defining methods for monitoring power quality. Edition 3 (2015) includes current measurements, unlike earlier editions which related to voltage measurement alone. See also Dynamic voltage restoration References Literature Power quality Power engineering de:Versorgungsqualität