Showing papers by "Surya Santoso published in 2001"

Understanding Power System Hannonics

Abstract: Harmonics – Past to Present Power systems are designed to operate at frequencies of 50 or 60Hz. However, certain types of loads produce currents and voltages with frequencies that are integer multiples of the 50 or 60 Hz fundamental frequency. These higher frequencies are a form of electrical pollution known as power system harmonics. Power system harmonics are not a new phenomenon. Concern over harmonic distortion has ebbed and flowed during the history of electric power systems. Steinmetz published a book in 1916 that devoted considerable attention to the study of harmonics in three-phase power systems. His main concern was third harmonic currents caused by saturated iron in transformers and machines, and he was the first to propose delta connections for blocking third harmonic currents. Later, with the advent of rural electrification and telephone service, power and telephone circuits were often placed on common rights-of-way. Harmonic currents produced by transformer magnetizing currents caused inductive interference with open-wire telephone systems. The interference was so severe at times that voice communication was impossible. This problem was studied and alleviated by filtering and by placing design limits on transformer magnetizing currents. Today, the most common sources of harmonics are power electronic loads such as adjustable-speed drives (ASDs) and switch-mode power supplies. These loads use diodes, silicon-controlled rectifiers (SCRs), power transistors, and other electronic switches to chop waveforms to control power or to convert 50/60Hz AC to DC. In the case of ASDs, the DC is then converted to variable-frequency AC to control motor speed. Example uses of ASDs include chillers and pumps. Due to tremendous advantages in efficiency and controllability, power electronic loads are proliferating and can be found at all power levels – from low voltage appliances to high voltage converters. Hence, power systems harmonics are once again an important problem.

Signature analysis to track capacitor switching performance

Abstract: Although capacitor switching transient events are one of the most common disturbance events on distribution systems, information on whether the capacitor bank is energized properly or as desired is often not available. The capacitor switching performance tracker is designed to examine capacitor switching transient events and determine the condition relative to the events. The module identifies if the root cause of the event is due to energizing a capacitor bank. It then determines the relative location of the bank, i.e., upstream or downstream from the monitoring location, and examines if the kVAr generated from the capacitor bank is added properly to the system and if the kVAr is distributed evenly among all phases. By determining the kvar changes, it is possible to identify unsuccessful energization, blown fuses, or even failed capacitor cans on one of the phases.

IEEE Power Engineering Society

Abstract: Harmonic distortion is not a new phenomenon. Concern over harmonic distortion emerged during the early history of AC power systems. Widespread applications of power electronic-based loads continue to increase concerns over harmonic distortion. Harmonic problems have sparked research that has led to much of the present-day understanding of power quality problems. The current-drawn by electronic loads can be made virtually distortion-free (i.e., perfectly sinusoidal), but the cost of doing this is significant and is debate between equipment manufacturers and electric utility companies in standards-making activities. This paper discusses the history of harmonics in power systems. It then defines harmonic distortion and discusses harmonic sources. System response characteristics to harmonics and the impact of harmonics are also discussed. Control of harmonics is also discussed.