A comparative assessment of the treatment of harmonic resonance for calculating harmonic emission limits in US and Europe

Harmonic resonance is a common phenomenon in electricity systems across the world. In recent years, the increa sed usage of capacitors in transmission and distribution systems, coupled with the increased usage of Distributed Energy Resources (DERs) and energy efficient equipment has made the phenomenon of resonance more frequent, and in some cases, more severe. Although resonance was likely considered while deriving harmonic limits in standards such as IEEE 519, it is not clear how or what level of allowance was made in this standard, to accommodate resonance and which risk it involves that target levels (e. g. planning levels) are underutilized or exceeded under realistic conditions. This stands in some contrast to Europe, where IEC standards like IEC 61000-3-6 and different grid codes clearly describe the system studies and operational practices required to account for harmonic resonance in the system. This paper seeks to compare and contrast the approaches used to tackle the phenomenon of resonance in calculating harmonic emission limits, in both the US and Europe. In addition to a detailed discussion of the contrasting approaches used to account for resonances, this paper uses an actual system example to bring out the pros and cons of each approach, for both radial and meshed networks.