Title :
Mitigation of resonance using digital models and direct measurement of harmonic impedances
Author :
Martinich, T.G. ; Neilson, J.B.
Author_Institution :
British Columbia Hydro, Burnaby, BC, Canada
Abstract :
A 12 kV 4800 kVAr power factor correction shunt capacitor bank for a 22 MW paper mill in the British Columbia Lower Mainland operated without problems for almost twenty years, until May of 1997. After that time, the 0.49 Ohm series reactor in the capacitor bank suffered repeated overloading and failures. Fifth harmonic current in the bank was measured by mill personnel and found to be, at times, 60 percent of the fundamental component, where only 5 percent was expected. It was suspected that the capacitor bank was involved in a resonance. Since no significant modifications or additions to the mill had taken place since 1984, the customer believed that changes to the utility subtransmission system must have been responsible for the sudden onset of problems. This paper describes the process of developing a digital model for the mill and its low voltage systems, including equivalents for a large number of induction motors, which was interfaced to a detailed pre-existing model of the utility supply. Furthermore, the results of a unique set of field tests to directly measure the harmonic driving point impedance of the mill and the utility network are presented. The measured impedances are used to fine tune the mill motor diversity factor assumed for the digital model of the induction motor loads. Using the models of the mill and external network thus established, the reason for the 1997 reactor failures is shown to be inappropriate rating of the original tuning reactors. A process is described for selecting a new reactor rating which will avoid further harmonic problems as well as meet customer operating requirements
Keywords :
capacitor storage; electric impedance measurement; industrial power systems; paper industry; power factor correction; power system harmonics; reactors (electric); resonance; 12 kV; 22 MW; 4800 kVAr; British Columbia Lower Mainland; customer operating requirements; digital models; field tests; fifth harmonic current; harmonic driving point impedance; harmonic impedances measurement; induction motor loads; induction motors; low voltage systems; measured impedances; mill motor diversity factor; paper mill; power factor correction shunt capacitor bank; reactor failures; resonance mitigation; series reactor; tuning reactors inappropriate rating; utility network; utility subtransmission system; Capacitors; Current measurement; Impedance measurement; Induction motors; Inductors; Milling machines; Paper mills; Power factor correction; Resonance; Shunt (electrical);
Conference_Titel :
Power Engineering Society Summer Meeting, 2000. IEEE
Conference_Location :
Seattle, WA
Print_ISBN :
0-7803-6420-1
DOI :
10.1109/PESS.2000.867523