The need for power system studies increase with the use of adjustable speed drive

The author reviews the various system studies that are performed on industrial power systems and discusses the advantages and information obtained from these studies. Case studies of applications are used to illustrate some findings from the studies of systems with adjustable-speed drives. It is noted that system studies for short-circuit protective device coordination, load flow, and motor starting have long proved valuable. More recently, the influence of nonlinear loads, in particular adjustable-speed drives, on the power system with the application of power factor improvement capacitors has given rise to problems with harmonic currents and voltages. This study provides two solutions to power system problems: the improvement of the power factor of the plant load and the control of the resonant point in the system which in turn controls the flow of the harmonic current produced by static power converters as used in adjustable-speed drives