Measurements of mains impedances in the frequency range up to 20 kHz and analysis of harmonics up to 10kHz in low voltage mains

Currently there are general limits for conducted emissions only in the frequency range up to 2 kHz [1],[2] and above 150 kHz [3]. Limits for the frequency range from 2 kHz to 9 kHz are in discussion. Because of this mentioned gap in the standards there is an uncertainty how to design filters and disturbance sources like converters. For finding limits investigations are necessary on mains impedances and harmonics. There are older publications on mains impedances (e. g. [4], [5]), but they include only measurements of impedances between one phase and neutral conductor and no measurements of impedances between the phases. This is important for three-phase loads. Furthermore in [4] no measurements were made in industrial mains and the investigations were carried out more than one decade ago. Especiaily in the last years the electrical environment in the mains has changed because of the increasing number of self-commutated converters. Accordingly, much higher amplitudes for harmonics in the upper frequency range are identifiable. In this paper current investigations on mains impedances and harmonics are presented which were carried out in universities, companies and private houses. The results could be used as a base for finding limits and for designing filters and disturbance sources economicaily.