Low-voltage (LV) harmonics and their properties have been known since early in the 20th century. Even harmonics where for example already mentioned in 1910 [1] and the blocking of zerosequence harmonics by transformers in 1914 [2]. Early papers about harmonics addressed transformers as the source of emission. Already in 1944 it was written “it is well known that mercury-arc power rectifiers produce harmonics in the ac and dc systems” [3]. The introduction of HVDC, television and, more recently, computers and other types of consumer electronics, has resulted in a broader interest for harmonics.