System lower-harmonic voltages — Methods of calculation and control by capacitors

A LARGE capacitor bank recently installed at Winchester, Virginia, is supplied with a series reactor to tune it to the fifth harmonic of the power frequency. This is the pioneer installation in the United States of this novel means of reducing the fifth harmonic voltage over a broad expanse of system — 33 kv in this case. The paper defines the field of application for this arrangement in comparison with other better known methods of harmonic control. A technique of system study at harmonic frequency has been developed, based on these findings. Analysis of measurements of lower system harmonics on power systems under varying conditions has shown their chief source to be transformer magnetizing current when power rectifiers are not present. This makes possible analytical determination of the harmonics of interest in the application of shunt capacitors. It involves first, the laboratory determination of the internal voltage and reactance comprising the transformer equivalent circuit, second, the setup of the actual system on the a-c network calculator, using the equivalent circuit, and third, field tests to verify the findings of the network calculator studies, and to prove the adequacy of the tuned capacitor installation. This method of analysis is presented together with confirming tests.