Abstract: An electrical power system includes a transmission line for transmitting electrical power, series capacitance compensation series-coupled to the transmission line adjacent one end thereof, where the series compensation includes a capacitance having a value (−j XCAP), and a protective relay at the one end of the transmission line for monitoring line voltages and line currents on the transmission line. Upon sensing a fault, an impedance Z of the line is calculated based on the monitored line voltages and line currents. The calculated impedance Z is adjusted according to the value of the capacitance of the series compensation (−j XCAP) to result in a modified impedance ZMOD, and the phasor angle Of ZMOD is examined to determine the direction of the sensed fault. The fault is in a first direction if the phasor angle is between X and X+180 degrees and is in a second direction opposite the first direction if the phasor angle is between X+180 and X+360 degrees.

Abstract: A fault is located in a power distribution system having a line frequency. The power distribution system includes a plurality of phases, at least one feeder, and each feeder includes at least one segment. The fault is located by detecting a faulted phase from the plurality of phases of the power distribution system. A measurement signal having a measurement frequency is injected into the detected faulted phase, the measurement frequency being a different frequency than the line frequency. The fault location is determined for a selected segment based on at least one measured residual current corresponding to the injected signal and a predetermined relative impedance of the power distribution system.

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: 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 system and method for clustering data from a server computer and sent to a client computer. The server computer obtains a requested cluster size for the client computer. The requested cluster size includes the optimal size cluster the client computer can handle and the largest manageable cluster size that can be handled by the client. Fuzzy logic computations are performed on the data to determine an optimal cluster size and an optimal point at which to split the data for the particular client. Part of the cluster computations are based upon the affinity of individual data items to adjacent data items in the clustered list. The server computer also checks the affinity between the item with the largest score and the first item in the next cluster. If this affinity is higher than other affinity scores within the cluster, the cluster split is moved accordingly. Once an optimal cluster is determined, the data is transmitted from the server computer to the client computer.

Abstract: A recloser trips on one phase for single-phase only fault conditions, two phases for two-phase fault conditions, or all three phases for three-phase fault conditions. During power delivery, the recloser monitors the three phases of a power line (e.g., phases A, B, and C). If a fault is detected on one phase, then a timer is started and subsequently decremented. If the timer finishes counting down while the fault is still present, then it is determined if any of the other two phases are timing a fault. If so, then those phases having a fault are tripped. Thus, only the faulted phase(s) is (are) tripped.

Abstract: A recloser trips on one phase for single-phase only fault conditions, or all phases for multi-phase fault conditions. During power delivery, the recloser monitors the three phases of a power line (e.g., phases A, B, and C). If a fault is detected on one phase, then a timer is started and subsequently decremented. If the timer finishes counting down while the fault is still present, then it is determined if any of the other two phases are timing a fault. If so, then all three phases are tripped; otherwise, only the faulted phase is tripped.

Abstract: An improved high impedance fault (HIF) detection system comprises an analyzer located at a circuit breaker or substation with feeders, wherein the analyzer analyzes current and/or voltage waveforms to detect a HIF on the feeder or on one of a plurality of laterals coupled to the feeder; a plurality of remote outage detectors located respectively at corresponding customer sites, each remote outage detector including a mechanism to detect a loss of potential or power at the corresponding site; and a computer in communication with the analyzer and the remote outage detectors.

Abstract: A system and methods that enable a restoration scheme for power distribution systems that is independent of power distribution system component configuration, the number of power distribution system components, and component settings are provided. In a power distribution system, a number of intelligent reclosers having restoration control modules are deployed that execute a restoration scheme. The intelligent reclosers constantly poll cooperating power distribution lines to determine changes in current or voltage provided by the power distribution lines. In the event of a power distribution system fault, the reclosers act in accordance to a predefined restoration scheme to reanimate the unaffected portions of the failing power distribution system.

Abstract: A recloser is adaptively controlled so that it will operate in a manner responsive to prevailing conditions such as time of day, day of week, and/or load current. A protection setting group is stored in a memory accessible by the recloser controller, and contains a set of instructions for controlling the recloser based on the prevailing conditions. The prevailing conditions are continuously monitored, and the control of the recloser is based on the prevailing conditions and the protection setting group.

Abstract: An accurate impedance measurement method for a power system transmission line is disclosed for improving various protection functions, i.e., distance protection and/or fault location estimation. The method is less sensitive to harmonics and other transient problems introduced to power systems by series capacitance and the like, and is easily incorporated into existing protective relays. In the method, a number (n) of current and voltage samples (Ik, Vk) representative of values of current and voltage waveforms are measured, respectively, at successive instants of time on a conductor in a power system. The number n is an integer greater than I and the index k takes on values of 1 to n. Resistance (R) and inductance (L) values are computed in accordance with an equation in which R and L are related to sums of differences in values of successive current and voltage samples. A prescribed power system function is then performed based on the computed R and L values.

Abstract: A reach-measurement method is used in connection with a series-compensated line of a power system. The series-compensated line includes an installed series capacitance having a bus side and a line side, and a non-linear protection device parallel to the installed series capacitance. The series-compensated line has a line current, a bus side voltage, and a line side voltage. The series capacitance and the non-linear protection device have a capacitance voltage thereacross equal to the bus side voltage minus the line side voltage. In the method, a number (n) of line current samples are measured, where such samples are representative of values of a line current waveform at successive instants of time on the series-compensated line. Capacitance voltage values are computed based on the measured line current samples in accordance with an equation which takes into account the non-linear protection device parallel to the installed series capacitance.

Abstract: An automatic power restoration device has a modifiable end point. The end point is indicative of the operational parameters of the automatic power restoration device. A user can modify the end point and thus the operational parameters of the automatic power restoration device. The end point can be modified according to the protection characteristics of other fault protection devices within a power system.

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: As a variation of the non-orthogonal filter, a phasor estimate is computed by using an N-point window. An aspect of the sub-window cosine filter is to repeat the basic cosine filter for only selected points of the window. In the end, a least-squares fit is used to obtain an estimate for the phasors components. Previous cosine techniques use a data window whose length is greater than 1 cycle while the present invention requires only 1 cycle.

Abstract: A high sample rate cosine filter eliminates DC components by summing them such that they sum to zero. A non-orthogonal cosine filter is also provided. When the cosine filter is applied for N=4 samples per cycle, the samples are separated by 90 degrees. However, at higher sampling rates, it is not necessary to wait for 90 degrees to estimate the phasor value. Non-orthogonal components are used to estimate the phasor value. The time delay associated with the cosine filter is reduced in the process.

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).