VOLTAGE DISTORTION IN DISTRIBUTION FEEDERS WITH NONLINEAR LOADS

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 characteri stic for different types of ac to de converters such as the input de s upply used for adjustable-speed-drives, battery chargers, PC's, TV's a nd electronically ballasted Eights, The analysis is based on the deter mination of the most harmonic susceptible busses and their response to each harmonic frequency. A new expeditive method that takes into acco unt the background harmonic voltage phasor, and an equivalent bus impe dance was developed and used to compute the maximum non-linear loads t hat yields VTHD = 5%, (Voltage Total Harmonic Distortion). The main co nclusion of this work is that when mitigation methods are not used, fo r a 15kV class feeder with a maximum 10MVA installed load, the fetal n onlinear residential load should not exceed 300kW if the ITHD < 30% (C urrent Total Harmonic Distortion), and 100kW if ITHD > 100%.