Impact of induction motor loads in system loadability margins and damping of inter-area modes

Induction motors constitute almost half of the total load in interconnected power systems. Static and dynamic data-files for large interconnected power systems do not usually contain ample representation of aggregate induction motor loads due to unfavorable cost-effectiveness: the low gains obtained in the quality of the results do not justify the larger effort required in preparing models more sophisticated than constant current models to hundreds or thousands of load buses. Modern power system analysis software should be suited to carry out cost-effective sensitivity analysis of motor load content in large interconnected systems. This paper describes the positive results in system loadability studies obtained with the modeling of induction motor loads in the Rio de Janeiro Area of the Brazilian interconnected system. Other results described in the paper show that the damping of the Brazilian North-South inter-area mode (about 0.2 Hz) is dependent on the percentage of induction motor loads that have been dynamically represented.