Abstract This paper presents a methodology for studying and specifying incremental and aggregated harmonic distortion emission limits from multiple harmonic sources that are connected to the utility network in close proximity and/or electrically are close to each other. The methodology specifically concentrates on traction loads and includes the development of combined equivalent circuits for the harmonic sources for evaluating their impact on power quality. This methodology has been used successfully to represent an electrified traction load and can be extended and applied to the assessment of multiple embedded generators such as from PV solar or wind farms.