Conducted emissions
Conducted emissions consist a part of electromagnetic interference in circuits that mainly create issues in delivered power quality, owing to interference caused by harmonics arising due to linear & non linear loads present in the electric system mainly due to increasing presence of switched mode power supply and other consumer electronics.
The electric grid progresses towards becoming increasingly nonlinear system and newer issues in power quality are being addressed.
When loads like motors and generators that have DC magnetic fields, the conducted emission are non linear and difficult to predict.
Electric power quality in AC mains is well developed and established with empirical data gathered over a century.
For alternating current technology has been well established in the modern world, the parameter for measuring conducted emissions is well understood and is called total harmonic distortion (%THD).
It measures power quality of AC mains for different voltage levels as described in common EMC test standards.
Much of research covering DC harmonics suggest use of a percentage low frequency sinusoidal disturbance (%LFSD).
The percentage of root of squared summations of these deviations gives a total %LFSD value, which is a near equivalent of the %THD value in AC systems.
Other issues with power quality in DC mains are to do with frequency range for conducted emissions in the electromagnetic spectrum.
It is primarily understood that due to the presence of electronic switching non-linear loads, the filter circuits tend to push emissions away into higher frequency bands.
The current research suggest that much effort is being given to understand measurement methods for supraharmonic emissions in order to further standardize DC power quality to include short circuits, voltage variations and other factors as well.
