Are harmonic recommendations according to IEEE and IEC too restrictive?

Experimental and analytical studies of the effects of voltage and current harmonics on induction machines, transformers, appliances, and relays show that the present versions of IEEE and IEC are too restrictive for low-frequency voltage and current (integer) harmonics, as they apply to residential power systems. It is recommended that not rigid but flexible guidelines are established so that different harmonic spectra are permitted which result in the same additional temperature rise in transformers and induction machines. Very restrictive amplitude limits for inter-harmonics and subharmonics should be included in the revision of the above standards due to their detrimental effects on under-frequency relays (malfunctioning), lighting equipment (flicker) and rotating machines (harmonic torques).