Harmonic allocation using IEC/TR 61000-3-6 at the distribution/transmission interface

IEC Technical Report 61000-3-6 gives principles to be applied to ensure acceptable harmonic levels in power systems. Detailed analysis methods have been developed to apply these principles to both distribution and transmission systems. At the transmission/distribution interface, it is found that transmission harmonic allocations can be as little as one third of the allocation which would be given to an equivalent distribution load. Possible adverse consequences are discussed and several modifications to avoid this mismatch are given. The recommended modification is a hybrid approach combining aspects of both the distribution and transmission allocation methods.