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A new interphase distance relaying algorithm for series-compensated transmission lines is proposed in this paper. The fault impedance can be correctively calculated using the proposed algorithm without requirement of the parameters of series capacitor device. The series capacitor can be simplified as a linearized impedance during the fault period, but its parameters can be used as variables in fault loop equations. The real-time digital simulator tests show that the proposed algorithm can obtain more accurate results than other traditional distance relaying algorithms for series-compensated transmission lines. [ABSTRACT FROM PUBLISHER]

This paper proposes a simple closed-form formula of the ground-return impedance of horizontal parallel wires above a lossy ground plane. It is derived by a double logarithmic approximation of the integral term with a semi-infinite interval in Carson's ground-return impedance formula. The proposed double logarithmic approximation gives better accuracy compared to a similar approximation proposed by Pizarro and Eriksson, and this is achieved by an advanced optimization technique used for determining the coefficients in the double logarithmic approximation and also by incorporating an additional variable which minimizes errors. In this paper, it is shown, using practical examples, that the derived formula gives more accurate results compared with other existing approximate formulas. It is also shown that a graphical interpretation of the double logarithmic approximation is to replace a homogeneous lossy ground with a pair of perfectly conducting return planes located at different complex depths. [ABSTRACT FROM AUTHOR]

Those transmission lines that are on the same tower present unique problems to distance relays, especially for cross-country faults. In this paper, a novel first-zone distance relaying algorithm of parallel lines using only single-line sampling data is proposed for cross-country nonearthed faults. The relation between six phase currents and six sequence currents of parallel lines is derived. Moreover, the sequence currents of the adjacent parallel line at the relay location are expressed only by the sequence currents of the concerned line. Finally, the distance relaying algorithm using the one-end sampling data from the concerned line is presented. The computer simulations with PSCAD/EMTDC software and practical transmission-line parameters are carried out. The results show that the proposed algorithm can obtain the accurate measuring impedance for cross-country nonearthed faults and the accuracy is not affected by fault resistances, load currents, and source impedances. [ABSTRACT FROM AUTHOR]

This paper presents a new two-terminal impedance-based fault-location algorithm, which takes into account the distributed parameter line model. The algorithm utilizes unsynchronized measurements of voltages and currents from two ends of a line and is formulated in terms of the fundamental frequency phasors of symmetrical components of the measured signals. First, an analytical synchronization of the unsynchronized measurements is performed with use of the determined synchronization operator. Then, the distance to fault is calculated as for the synchronized measurements. Simultaneous usage of two kinds of symmetrical components for determining the synchronization operator makes that the calculations are simple, noniterative, and at the same time highly accurate. The developed fault-location algorithm has been thoroughly tested using signals of Alternate Transients Program-Electromagnetic Transients Program versatile simulations of faults on a transmission line. The presented evaluation shows the validity of the developed fault-location algorithm and its high accuracy. [ABSTRACT FROM AUTHOR]

This paper presents a new two-terminal impedance-based fault location algorithm, which takes into account the distributed parameter line model. The algorithm utilizes unsynchronized measurements of voltages and currents from two ends of a line and is formulated in terms of the fundamental frequency phasors of symmetrical components of the measured signals. First, an analytical synchronization of the unsynchronized measurements is performed with use of the determined synchronization operator. Then, the distance to fault is calculated as for the synchronized measurements. Simultaneous usage of two kinds of symmetrical components for determining the synchronization operator makes that the calculations are simple, noniterative and at the same time highly accurate. The developed fault location algorithm has been thoroughly tested using signals of ATP-EMTP versatile simulations of faults on a transmission line. The presented evaluation shows the validity of the developed fault location algorithm and its high accuracy. [ABSTRACT FROM AUTHOR]

This paper introduces a state-diagram-based protective algorithm for parallel circuit transmission lines using local information obtained at the relay bus. A new cross-differential technique is proposed which compares the currents in the corresponding phases of the parallel circuits in a 2-D space. A companion impedance-based algorithm is used to cover the evolving faults and some conditions in which the cross-differential technique is not able to discriminate the internal faults alone. The effect of the mutual coupling between parallel circuits on the measured impedances is adaptively compensated according to the status of the parallel circuit currents in the segmented 2-D space. The proposed state-diagram-based algorithm combines the outputs of the cross-differential and impedance-based techniques to provide a reliable response under all of the operating statuses of the parallel circuits. Extensive simulation studies using PSCAD/EMTDC software indicate that the proposed approach provides very reliable protection for the double-circuit transmission lines. It covers intercircuit and evolving faults, and is able to reliably select the faulted phases. [ABSTRACT FROM AUTHOR]

This paper puts forward a novel algorithm for locating faults on double-circuit transmission lines using two-end unsynchronized current measurements. The algorithm does not require line parameters, which is a radical step forward compared to existing approaches, which require this information, so it can be considered as a settings-free algorithm. Only the positive-sequence current phasors during the fault are processed for determining the sought distance to fault and the synchronization angle, limiting thus the amount of data needed to be transferred from each line terminal. The proposed algorithm is derived by applying the Kirchhoff's voltage law around the parallel circuits loops during the fault. The algorithm is applicable for both transposed and untransposed double-circuit lines and is independent of the fault type. Evaluation studies using reliable Alternative Transients Program-Electromagnetic Transients Program simulation data verify that the accuracy of the proposed algorithm is very high under various fault resistances, fault locations, and source impedances. [ABSTRACT FROM AUTHOR]