Published Paper Details:

An issue that has been plaguing protection engineers for a considerable amount of time is the extraction of negative phase sequence components from three-phase alternating current voltages and currents. In this research, a unique numerical three-phase filtering approach is presented for the purpose of extracting the negative phase sequence components from sampled three-phase observations. In order to calculate either the absolute value of the negative phase quantity or the relative value of the negative phase sequence to the positive phase sequence measured at the operating point, the mathematical algorithm has been designed to be appropriate for use in a numeric relay. This is because the method has been developed to be suitable for use in its intended application. The purpose of this study is to illustrate the capabilities of the method by presenting findings that indicate that the amount of negative phase sequence components can often be retrieved within thirty milliseconds after a disturbance by using a simple post-extraction smoothing filter. A notional sampling rate of 1200 samples per second was used in this example, together with an automated frequency tracking method, in order to ensure that the sampling clock and the power system frequency remained in perfect sync with one another.