Characteristics: Harmonics not divisible by 3 (5th, 7th, 11th, 13th, etc.) arise from three-phase harmonic generators such as 6- or 12-pulse frequency converters, power converters (for DC drives), inverters (e.g. of photovoltaic systems), arc and induction furnaces, three-phase welding systems, or a very large number of switching power supplies in a network area.

Effects: Harmonics of these orders increase overall the total current and stress the overall network and the equipment connected to it, without causing an effective power at the consumer. They cause iron losses in transformers and motors. The consequences are poor efficiency, overheating of components, increased risk of fire and – due to the unnecessarily high energy consumption – lead to a noticeably worse CO₂ balance. Harmonics cause pendulum torques in motors and overvoltages, they influence the disconnection characteristics of circuit breakers and lead to unplanned false tripping. All in all, this results in grid standard violations in combination with the loss of warranty claims against machine manufacturers, failure of control systems, reduced service life of devices and systems, flat-topping, increased noise emissions from transformers and consumers, increased power losses and thus temperature increases on electrical transmission equipment such as lines and transformers.