This technical report outlines principles which are intended to be used as the basis for determining the requirements for connecting large distorting loads (producing harmonics and/or interharmonics) to public power systems. The primary objective is to provide guidance for engineering practices which will ensure adequate service quality for all connected consumers. Since the guidelines outlined in this report are necessarily based on certain simplifying assumptions, there is no guarantee that this approach will always provide the optimum solution for all harmonic problems. The recommended approach should be used with flexibility and judgment as far as engineering is concerned, when applying the given assessment procedures in full or in part.