Time-frequency diversity measurements in power systems

Conducted interference is rapidly increasing due to the widespread use of power electronics. This is causing an increase of interference cases, and is limiting the possibility of using the mains wiring for low-frequency power line communication, such as the mains communication system between smart meters. Increasing the mains communication signal amplitude would result in more interference, while decreasing the emission level of the power electronics via filtering would also decrease the wanted communication signal amplitude. By using low-cost digitisers for measurements of conducted emission in time domain and fast fourier transform to the frequency domain time-frequency spectrograms can be generated. These show that conducted interference is mainly cyclo-stationary and at fized frequencies, showing open areas, or slots, in time-as well as frequency-domain. These slots can be used for the mains communication. This requires smarter EMC standards, and not in frequency domain only.