Standardized Impedance: Microgrid Perspective for Inrush Current Compliance

With accelerating adoption of non-linear power electronics devices as well as the trend of distributed generation and microgrids, inrush and transient switching currents are not sufficiently limited by standards. The standard reference impedance according IEC 61000-3-3 and IEC 60725 appears higher compared to what is found in practice especially in the present environment resulting in electromagnetic interference challenges with large short term peak currents. This is especially true with complex and isolated power distribution user networks. This paper shows measurements and comparisons of inrush currents for a variety of grid impedance configurations as well as the effects of switching even low wattage power electronic devices. Measurements and simulations suggests lower impedance value of microgrids resulting in higher inrush currents and risking electromagnetic compatibility.