This standard is concerned with conducted disturbances in the frequency range from 0 kHz to9 kHz, with an extension up to 148,5 kHz specifically for mains signalling systems. It gives compatibility levels for public low voltage a.c. distribution systems having a nominal voltageup to 420 V, single-phase or 690 V, three-phase and a nominal frequency of 50 Hz or 60 Hz.The compatibility levels specified in this standard apply at the point of common coupling. Atthe power input terminals of equipment receiving its supply from the above systems the severity levels of the disturbances can, for the most part, be taken to be the same as the levels at the point of common coupling. In some situations this is not so, particularly in the case of a long line dedicated to the supply of a particular installation, or in the case of a disturbance generated or amplified within the installation of which the equipment forms a part.Compatibility levels are specified for electromagnetic disturbances of the types which can be expected in public low voltage power supply systems, for guidance in:– the limits to be set for disturbance emission into public power supply systems (includingthe planning levels defined in 3.1.5).– the immunity limits to be set by product committees and others for the equipmentexposed to the conducted disturbances present in public power supply systems.The disturbance phenomena considered are:– voltage fluctuations and flicker;– harmonics up to and including order 50;– inter-harmonics up to the 50th harmonic;– voltage distortions at higher frequencies (above the 50th harmonic);– voltage dips and short supply interruptions;– voltage unbalance;– transient overvoltages;– power frequency variation;– d.c. components;– mains signalling.Most of these phenomena are described in IEC 61000-2-1. In cases where it is not yet possible to establish compatibility levels, some information is provided.