Abstract: The invention describes a method, system, device, and computer-readable medium having computer-executable instructions for classifying faults on an electrical power line. In particular, the invention permits the classification of crossover faults, using a local measurement technique. The inventive method includes providing a first electrical power transmission line and a second electrical power transmission line, and monitoring the first electrical power transmission line to identify a crossover fault occurring between the first and the second electrical power transmission lines.

Abstract: The invention describes a method, system, device, and computer-readable medium having computer-executable instructions for classifying faults on an electrical power line. In particular, the invention permits the classification of crossover faults using a local measurement technique. The inventive method includes providing a first electrical power transmission line and a second electrical power transmission line, and monitoring the first electrical power transmission line to identify a crossover fault occurring between the first and the second electrical power transmission lines.

Abstract: The invention describes a method, system, device, and computer-readable medium having computer-executable instructions for classifying faults on an electrical power line. In particular, the invention permits the classification of crossover faults using a local measurement technique. The inventive method includes providing a first electrical power transmission line and a second electrical power transmission line, and monitoring the first electrical power transmission line to identify a crossover fault occurring between the first and the second electrical power transmission lines.

Abstract: The invention describes a method, system, device, and computer-readable medium having computer-executable instructions for classifying faults on an electrical power line. In particular, the invention permits the classification of crossover faults, using a local measurement technique. The inventive method includes providing a first electrical power transmission line and a second electrical power transmission line, and monitoring the first electrical power transmission line to identify a crossover fault occurring between the first and the second electrical power transmission lines.

Abstract: A method and apparatus for over current backup protection is provided. The method generates a set of root mean square (rms) values from samples that are taken from the system current. Several rms current values are averaged to generate an estimated rms over current value. The estimated over current value is compared with a predetermined threshold value. If the estimated current is above the predetermined threshold value, a fault protection mechanism, such as opening a circuit breaker, is activated. A generator protection unit having digital signal processing capabilities executes the inventive method to provide protection from over current episodes.

Abstract: A protective relay system comprises current and voltage transducers 10, filters 12, and a multiplexor 14, the latter outputting an interleaved stream of analog phase current and voltage signal samples, as well as neutral current samples. The analog multiplex output by the multiplexor 14 is digitized by an analog-to-digital converter 16. The output of the analog-to-digital converter 16 is fed to a digital signal processing block 18. The multiplexor necessarily introduces a time-skew between the successive samples for each channel and also introduces a time-skew between the respective channels. The system corrects the sample-to-sample time-skew for each channel, and then derives current and voltage phasors from the time-skew corrected data.

Abstract: A method and system for detecting the peak of respective half-cycles of a sinusoidal waveform. The sinusoidal waveform is rectified and only sample points above a first threshold are analyzed. The peaks of each half-cycle are only accepted if they are above a second, greater threshold. Peaks below the second threshold are not accepted. The peaks themselves are detected by starting a counter at the first sample in the rectified waveform which is above the first threshold value. Once the rectified waveform descends below the first threshold, the counter is stopped and the maximum value of the previous k samples is the peak value, where k is the counter value for the successive samples above the first threshold. The peak value so determined is rejected if it is less than the second threshold value. On the other hand, when the peak value is above the second threshold, it is averaged with the last valid peak value (above the second threshold).

Abstract: A method for estimating phasors and tracking the frequency of a signal during frequency ramping is provided. The method uses a variable N-point DFT periodically to compute one or more phasors based on data acquired from one or more sampled signals. The period between DFT computations is a predetermined number of sample periods. After each DFT computation, the change in phasor angle between the current phasor estimate and the most previous phasor estimate is determined and used to estimate the instantaneous frequency of the signal. The current instantaneous frequency estimate and the most previous instantaneous frequency estimate are averaged to compute an average cycle frequency. In addition, a number of discrete frequencies and corresponding DFT windows based on a fixed sampling rate and a predetermined fundamental frequency of the signal are defined and used in estimating the instantaneous frequency.

Abstract: A new method of compensating for errors in phasor estimation due to oscillations caused by discrete fourier transforms used to estimate signal frequency is provided. The method uses a variable N-point DFT to compute one or more phasors based on data acquired from one or more sampled signals. At each sampling interval the change in phasor angle between the current sampling interval and the previous sampling interval is determined and used to estimate the instantaneous frequency of the signal. A non-oscillating phasor indicative of the instantaneous magnitude, angular frequency, and phase angle of the signal is generated based on the instantaneous frequency estimate. Instantaneous frequencies are averaged over a cycle of the signal to generate an average cycle frequency. In addition, a number of discrete frequencies and corresponding DFT windows based on a fixed sampling rate and a predetermined fundamental frequency of the signal are defined and used in estimating the instantaneous frequency.