The voltage of three real-life 13.8kV feeders supplying customers with non-linear loads was analyzed by means of computer simulations. Three classes of non-linear loads were considered. Each class is characteristic for different types of ac to de converters such as the input de supply used for adjustable-speed-drives, battery chargers, PC's, TV's and electronically ballasted Eights, The analysis is based on the determination of the most harmonic susceptible busses and their response to each harmonic frequency. A new expeditive method that takes into account the background harmonic voltage phasor, and an equivalent bus impedance was developed and used to compute the maximum non-linear loads that yields VTHD = 5%, (Voltage Total Harmonic Distortion). The main conclusion of this work is that when mitigation methods are not used, for a 15kV class feeder with a maximum 10MVA installed load, the fetal nonlinear residential load should not exceed 300kW if the ITHD < 30% (Current Total Harmonic Distortion), and 100kW if ITHD > 100%.
