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This paper presents a new protection algorithm for double circuit transmission lines using the sum of ratios of modal currents. Relay-operating characteristics is proposed using the complex ratio of modal currents. The proposed algorithm estimates modal domain line parameters and identifies the faulty phases for single pole-tripping applications even during inter-circuit faults. The scheme is sensitive to high resistance internal faults and also detects internal faults with outfeed. The proposed scheme is immune to mutual coupling and is found robust to uncertainties in parameter estimation due to measurement inaccuracies. The scheme is tested for its effectiveness to deal with current transformer saturation and synchronisation error. The scheme protects series compensated double circuit transmission lines even in the presence of current inversion. Exhaustive case studies in electromagnetic transient program (EMTP)/alternate transient program are performed on 400 kV, 300 km, double circuit transmission lines and the proposed protection algorithm is implemented in MATLAB. The results confirm the superiority of the proposed scheme. [ABSTRACT FROM AUTHOR]

This paper introduces a new noniterative fault-location algorithm for long transmission lines compensated by a series flexible ac transmission systems (FACTS) device. In the proposed algorithm, synchronous voltage and current samples from both ends of the transmission line are used and the distributed parameter line model in the time domain is applied. Due to the difficulties in the modeling of the series FACTS devices during a fault, the presented method does not use the model of the series devices. In this paper, the fault-location problem is converted to an optimization one in which the location and resistance of the fault are the decision variables. The proposed method includes three stages. Two fault locations are obtained, corresponding to the first two stages. In stage three, the obtained results from stages 1 and 2 are compared, and the correct fault location is selected. The proposed algorithm is a noniterative one and it is suitable for transmission lines compensated by any series FACTS device which could have the overvoltage protection and can be in any operating mode. The performance of the proposed algorithm is evaluated under different structural and fault conditions. The simulation results confirm the accuracy of the proposed algorithm. [ABSTRACT FROM AUTHOR]

Bridging the gap between the theoretical modeling and the practical implementation is always essential for fault detection, classification, and location methods in a power transmission-line network. In this paper, a novel hybrid framework that is able to rapidly detect and locate a fault on power transmission lines is presented. The proposed algorithm presents a fault discrimination method based on the three-phase current and voltage waveforms measured when fault events occur in the power transmission-line network. Negative-sequence components of the three-phase current and voltage quantities are applied to achieve fast online fault detection. Subsequently, the fault detection method triggers the fault classification and fault-location methods to become active. A variety of methods—including multilevel wavelet transform, principal component analysis, support vector machines, and adaptive structure neural networks—are incorporated into the framework to identify fault type and location at the same time. This paper lays out the fundamental concept of the proposed framework and introduces the methodology of the analytical techniques, a pattern-recognition approach via neural networks and a joint decision-making mechanism. Using a well-trained framework, the tasks of fault detection, classification, and location are accomplished in 1.28 cycles, significantly shorter than the critical fault clearing time. [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]

In this paper, a fuzzy-logic-based algorithm to identify the type of faults for digital distance protection system has been developed. The proposed technique is able to accurately identify the phase(s) involved in all ten types of shunt faults that may occur in a transmission line under different fault resistances, inception angle, and loading levels. The proposed method needs only three line-current measurements available at the relay location and can perform the fault classification task in about a half-cycle period. Thus, the proposed technique is well suited for implementation in a digital distance protection scheme. [ABSTRACT FROM PUBLISHER]

Lines with several taps are frequent and involve a large number of small towns and customers. With the need for costs reduction, this solution has been adopted in Brazilian utilities, with measurements only at the two terminal substations of the main line. The relevance of the problem is related to the long time for fault location when there are several secondary tap lines, depriving a large number of customers of energy during this period. Since there is not yet an adequate approach for this configuration, without additional hardware and measurements in tap lines, this paper presents a low-cost solution focusing on the synchronization of data measurements and the fault location in the main line or in the tap lines. The algorithm can handle the critical condition of zero-sequence infeed of star-delta transformers connected to tap lines, detecting the faulty section through the superposition theorem and finally obtaining the fault distance. Simple and accurate enough expressions were developed for fault location in order to help computer implementation of the algorithm. The algorithm also enables fault location in double-circuit main lines with several tap lines. The results, considering various line configurations and fault types, are presented, showing the accuracy and efficiency of the proposed method. [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 article presents a novel phasor domain approach to determine the location of faults in non-homogeneous transmission lines. Best implementation requires synchronized voltage and current phasor measurements at all terminals of the transmission line. The overall non-homogeneous transmission line model with fault is established by systematically combining the generalized compact models of all homogeneous line sections. The location of the fault is introduced as an additional state of the overall model. The derivation procedure of the model is without further assumptions, resulting in full consideration of three phase line asymmetry as well as distributed parameters of non-homogeneous transmission lines. Afterwards, the location of the fault is identified using the state estimation algorithm. Extensive numerical experiments in a two-terminal and a multi-terminal non-homogeneous transmission line demonstrate that the method has higher accuracy than existing fault location methods, independent of fault types, locations and impedances. [ABSTRACT FROM AUTHOR]

A universal wavefront positioning correction method on traveling-wave-based fault-location algorithms is proposed. According to the location accuracy analysis for the faults of which the fault positions change successively, it is noted that the real fault distance generally cannot be divided exactly by the distance corresponding to an integer sampling interval. It will lead to unavoidable truncated error when the discrete sampling points of traveling-wave-based fault-location algorithms are applied. Furthermore, it is disclosed that the fault-location error can be limited within a single sampling interval by the simple wavefront identification method in the event of low sampling rate. In view of the aforementioned two scenarios, an appropriate correction strategy in the event of the appropriate sampling rate is put forward. The fault-location accuracy can be improved greatly with the aid of the proposed correction strategy. The effectiveness of the proposed correction strategy is verified with various typical EMTDC-based simulation test results. [ABSTRACT FROM AUTHOR]