間高調波 — 標準的な高調波アナライザでは検出されない電力品質の乱れ
Interharmonics — frequency components that are not integer multiples of the fundamental (e.g. 75 ヘルツ, 130 Hz on a 50 Hz system) — are produced by PV inverters, wind turbines, EVの充電器, cycloconverters, and HVDC links. Their most dangerous effect: an interharmonic at 58 Hz creates an 8 Hz beat frequency — squarely in the range of peak human visual sensitivity. Field case: simultaneous PV + EV charger + microwave on one LV circuit produces stochastic interharmonics causing light flicker. Standard IEC 61000-4-7 analysers cannot correctly characterise them.