Adopts IEC 61000.4.30, Ed.2.0 to specify the methods for measurement and interpretation of results for power quality parameters in 50/60 Hz a.c. power supply systems. The power quality parameters considered in This Standard are power frequency, magnitude of the supply voltage, flicker, supply voltage dips and swells, voltage interruptions, transient voltages, supply voltage unbalance, voltage harmonics and interharmonics, mains signalling on the supply voltage and rapid voltage changes.