International reference standards for harmonics and flicker testing define differing applicable supply voltage levels and operating frequencies. CLEPA proposes maintaining baseline requirements for UN R10.08 unchanged, testing according to standardized parameters of reference IEC standards. Contracting Parties with diverging local grid configurations should define tailored national requirements or propose harmonized evaluation methods directly within relevant IEC standard committees, as direct application or mathematical conversion of limits for diverging grids lacks standardized metrological foundation in IEC publications.