Emission levels above 2 kHz — Laboratory results and survey measurements in public low voltage grids

The research presented in this paper is aimed at the higher frequency (HF) voltage distortion in public low voltage (LV) grids in the range between 2 kHz and 40 kHz. The particular focus lies on the emission caused by modern photovoltaic (PV) inverters. Based on laboratory measurements, the general characteristics of the emission spectrum of these inverters are discussed and a suitable evaluation method is proposed. The next part presents the results of a long term measurement campaign recording voltage distortion levels at 25 sites up to 40 kHz. Grids without PV installations show very low distortion levels. In grids with PV the level is closely linked to the location of the inverter in relation to the measurement site. In general, the lowest distortion levels were recorded at the transformer LV bus bar. The highest levels were reached at the point of connection (POC) of an inverter. At all sites no customer complaints are known due to HF voltage distortion. The last part of the paper presents a case study, where the connection of a machine with inverter technology caused HF distortion levels, which led to multiple device malfunction and noise in household appliances and subsequently to customer complaints.