This standard contains the German version of the 2nd edition of the European Standard EN 61000-4-30 and is identical with the 2nd edition of the International Standard IEC 61000-4-30. It defines the methods for measurement and interpretation of results for power quality parameters in 50/60 Hz a.c. power supply systems. The measurements are described for each relevant parameter as in-situ-measurements regardless of the compliant instrument being used and its environmental conditions. The parameters considered in this standard are power frequency, the magnitude of the voltage, flicker, voltage dips, swells, interruptions and rapid voltage changes, transient voltages, supply voltage unbalance, harmonics, interharmonics, mains signalling. In relation to the previous edition a further measuring equipment class is introduced so that three classes A, S and B are now specified.