Abstract: Techniques for distance protection of a transmission line include determining a fault inception time from a voltage and/or current, determining rate of change sample values indicative of a rate of change of the voltage and/or of a rate of change of the current for at least one sample time that is dependent on the fault inception time, and using the rate of change sample values to generate a phase classifier for fault classification of a zone classifier for faulted zone identification.

Abstract: Fault location determination in a power transmission system is described. Samples of voltage and current measured are obtained for each phase at a terminal. A first equivalent reactance value based on the samples of voltage and current is calculated. Further, based on the calculated equivalent reactance value a first fault location is determined.

Abstract: The present subject matter describes fault detection during power swing in a power transmission system. Voltage and current measurements are obtained for each phase at a terminal of the power transmission system. Based on measurements obtained, a value of change in an impedance angle for each phase-to-ground loop and each phase-to-phase loop for each sampled value of voltage and current is calculated, where the value of change in the impedance angle is a difference between impedance angles of two samples separated by a predetermined interval. Further, the average values for change in impedance angle based on a predetermined number of values of the change in the impedance angle for each phase-to-ground loop and each phase-to-phase loop is calculated. The average values calculated are compared with a threshold of change in impedance angle and based on the comparison a fault in one or more of the phase-to-ground loops or phase-to-phase loops is detected and classified.

Abstract: Examples of operating an Intelligent Electronic Device (IED) during power swings, are described. In an example, voltage measurements for a phase is received and sampled. Root mean square (RMS) values of the voltage samples is calculated based on the voltage measurements. Delta quantities for each phase are calculated based on the RMS values. Each of the RMS values and delta quantities are associated with respective sampling instants. In response to a delta quantity being greater than a predefined threshold, a peak delta quantity is detected. A time interval between a sampling instant associated with the peak delta quantity and a sampling instant associated with a first delta quantity is determined. Based on a comparison of the time interval with a threshold time, a disturbance condition may be detected as a power swing and consequently, fault detection at the IED may be blocked.

Abstract: Examples of operating an Intelligent Electronic Device (IED) during power swings, are described. In an example, voltage measurements for a phase is received and sampled. Root mean square (RMS) values of the voltage samples is calculated based on the voltage measurements. Delta quantities for each phase are calculated based on the RMS values. Each of the RMS values and delta quantities are associated with respective sampling instants. In response to a delta quantity being greater than a predefined threshold, a peak delta quantity is detected. A time interval between a sampling instant associated with the peak delta quantity and a sampling instant associated with a first delta quantity is determined. Based on a comparison of the time interval with a threshold time, a disturbance condition may be detected as a power swing and consequently, fault detection at the IED may be blocked.

Abstract: The present disclosure relates to methods and devices for calculating winding currents at a delta side for a transformer. The transformer has two or more windings, with a first winding being a delta connected winding. The method includes obtaining line currents measured with measurement equipment associated with lines connected with the windings. The method further includes calculating zero sequence currents for at least a second winding, from the line currents of a corresponding line. The method further includes calculating zero sequence currents for the first winding, based on the zero sequence currents for at least the second winding, a phase displacement between the windings, and a turns ratio associated with the windings. The winding currents is calculated from the zero sequence currents of the first winding, and the line currents of a corresponding line.

Abstract: The present disclosure relates to methods and devices for calculating winding currents at a delta side for a transformer. The transformer has two or more windings, with a first winding being a delta connected winding. The method may comprise obtaining line currents measured with measurement equipment associated with lines connected with the windings. The method may further comprise calculating zero sequence currents for at least a second winding, from the line currents of a corresponding line. The method may further comprise calculating zero sequence currents for the first winding, based on the zero sequence currents for at least the second winding, a phase displacement between the windings, and a turns ratio associated with the windings. The winding currents may be calculated from the zero sequence currents of the first winding, and the line currents of a corresponding line.