Protection Of Parallel Transmission Lines Research Articles

A new approach to eliminate impacts of high-resistance faults by compensation of traditional distance relays’ input signals

Ground impedance measuring elements of digital distance relays, responsible for line to ground faults, are highly prone to underreach in case of high-resistance faults. To tackle this problem for the distance protection of parallel transmission lines, this paper presents an effective approach by compensating the input signals to the existent traditional distance relays. For this objective, the fault distance is estimated innovatively within a short duration by analyzing the line sequence networks in time domain. The fault distance is employed to generate the signals compensating the under-operation distance relays’ instantaneous input signals measured by instrument transformers, in a way as to eliminate the high fault resistance-caused underreach. The proposed approach would not threaten the relay security in normal operating conditions, irrelevant-circuit and external faults. Further, it would not interfere with the relay phase elements. Performance of the proposed approach is examined through comprehensive simulation studies conducted in PSCAD/ EMTDC for a variety of influencing situations and the results would reveal that the proposed approach is able to fully prevent underreach incidents arising from high-resistance faults, without having a significant impact on the relay response time.

A New Intelligent Method for Parallel Transmission Lines Protection

In many countries, the parallel lines are widely used in transmission systems due to economic and technical benefits. Distance relays have poor performance on the protection of parallel transmission lines because of the mutual coupling effect. The distance relay may underreach when both lines are in-service. On the other hand the over reach problem may arise when only one line is in-service and another line is disconnected and grounded at both sides. Therefore, a new intelligent method is presented to protect parallel lines comprehensively in different operating modes. In the first stage, considering the status of circuit breakers as well as measured current signals at both sides of parallel lines, the fault types are identified by allocating a probabilistic neural network (PNN). Then, in the second stage, the fault location is estimated by assigning an artificial neural network (ANN) to each type of fault. The results obtained from the simulation of a part of the power system including 230-kV parallel lines, show that the proposed method can accurately detect all fault types and also it can precisely locate the fault points with an accuracy of 98.8%.

Protection of parallel transmission lines including inter-circuit faults using Naïve Bayes classifier

Parallel transmission lines are difficult to protect due to mutual coupling between circuits. This paper proposes a Naïve Bayes classifier (NBC) based fault detection and classification technique for protection of parallel transmission line involving inter-circuit faults. NBC is a good classification tool for larger data sets as the training process takes less time with greater accuracy. Input given to the fault detection module is the fundamental components of three phase current signals of both circuits. Input given to the fault phase identification and fault classification module is the fundamental component of three phase current signals and zero sequence currents of both the circuits. Seven separate classifiers are designed for fault phase identification for A1, B1, C1, A2, B2, C2 and G. From fault phase identification module faults are classified. Accuracy of the proposed method is 100% for fault detection and 99.99% for classification of fault from all the tested fault cases. Response time of the proposed method is within 10ms for all the fault cases studied.

Traveling‐wave‐based protection of parallel transmission lines using Teager energy operator and fuzzy systems

This study proposes an intelligent traveling-wave (TW)-based protection algorithm for parallel transmission lines. In the proposed algorithm, Karenbauer's phase to modal transform is applied on three phase current signals. Teager energy operator is then applied on the modal components to extract TWs. First extracted TW of each modal component along with well-designed fuzzy systems are used for internal fault identification and fault type classification. In order to find the fault location, the time difference between the first and the second TWs and the TW propagation speed are utilised. Test signals are generated in PSCAD/EMTDC software and the algorithm is implemented in MATLAB. Results show that the proposed algorithm is an ultra-high-speed algorithm for the reliable protection of parallel transmission lines.

Time domain complete protection scheme for parallel transmission lines

Abstract In this paper, time domain relaying schemes for complete protection of parallel transmission lines using wavelet and artificial neural network (ANN) are presented. Four different ANN networks are designed for detection of the fault, fault section identification, classification of fault and location of fault in time domain. The 3rd level approximate discrete wavelet transform (DWT) coefficients of signals of one end are used as input to ANN network. Proposed method is tested with varying fault location, inception angle, fault type and fault resistance. The test results show that the fault is detected and located within 5 ms time accurately. This scheme offers primary protection as well as backup protection to the lines.

Non-communication protection of parallel transmission lines using breakers open-switching travelling waves

This study presents a protective algorithm for discrimination and classification of short-circuit faults on parallel circuit transmission lines. The proposed algorithm is composed of two stages. In the first stage, the cross-differential technique is employed to identify close-in internal faults. The second stage is assigned to discriminate remote faults occurring at the end part of the protected transmission line. This stage is based on the travelling waves generated by the open switching of the transmission line circuit breakers. Using these travelling waves, the algorithm can quickly identify operation of remote end circuit breakers and discriminate between internal and external faults. The proposed algorithm also classifies the faulted phases. Moreover, it covers inter-circuit faults, in which phases of both parallel circuits get involved in the fault. Extensive simulation studies were performed to evaluate the proposed algorithm performance. It is concluded that this algorithm provides a fast and reliable scheme for protection of parallel transmission lines.

Adaptive Protection of Parallel Transmission Lines Using Combined Cross-Differential and Impedance-Based Techniques

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.

Comprehensive Adaptive Distance Relaying Scheme for Parallel Transmission Lines

Reach accuracy of a distance relay is adversely affected by prefault system conditions, ground fault resistance, shunt capacitance, and mutual coupling of parallel lines. This paper presents a comprehensive adaptive relaying scheme for stand-alone distance protection of parallel transmission lines under a single-line-to-ground fault condition taking into account all of these factors. The proposed adaptive scheme is based on the back-propagation neural network used for training and adaptation. The relay acts as a stand-alone relay, which does not require a separate communication channel for real-time data transmission during faults. The simulation results show significant improvement in the relay selectivity.

New adaptive digital distance relaying scheme for double infeed parallel transmission line during inter-circuit faults

Presence of various types of inter-circuit faults between parallel transmission lines combined with the effect of mutual coupling and fault-resistance makes the protection of parallel transmission lines quite complicated. The authors have proposed a new adaptive digital distance relaying scheme which takes care of all the abnormalities of the conventional ground distance relays and measures the correct value of impedance during phase-to-phase and phase-to-phase-to-ground inter-circuit faults. The impact of fault-resistance and mutual coupling phenomena has been considered during such types of inter-circuit faults. The proposed adaptive scheme is based on the derivation of the compensated value of impedance using symmetrical component theory without the need of remote end data. To validate the proposed scheme, numerous computer simulations have been carried out on an existing 400 kV parallel transmission line network using MATLAB/SIMULINK software. The simulation results demonstrate the effectiveness of the proposed scheme giving an average percentage error of 0.579 . The results indicate that the proposed technique is highly accurate and robust for a wide variation in system and fault conditions.

Ultra-high-speed protection of parallel transmission lines using current travelling waves

This study presents a protective algorithm for discrimination and classification of short-circuit faults in parallel circuit transmission lines. The proposed algorithm is based on the initial fault-induced current travelling waves (TWs) detected by the relay using the wavelet transform. In the case of internal faults on any of the parallel circuits, the detected current TWs in the corresponding phases of the parallel circuits are different, whereas, for external faults, the initial current TWs are almost similar. This feature is used to discriminate between internal and external faults. A fault-type classification algorithm is also proposed to identify the faulted phases. The proposed algorithm only uses the initial current TWs caused by the fault and provides an ultra-high-speed protective technique. It also covers inter-circuit faults, in which phases of both parallel circuits get involved in the fault. The obtained simulation results using the PSCAD/EMTDC software show that the proposed algorithm is able to discriminate the internal faults and to select the faulted phases very rapidly and reliably. It is able to identify faults in just ∼1 ms.

Time–frequency transform approach for protection of parallel transmission lines

A new approach for protection of parallel transmission lines is presented using a time-frequency transform known as the S-transform that generates the S-matrix during fault conditions. The S-transform is an extension of the wavelet transform and provides excellent time localisation of voltage and current signals during fault conditions. The change in energy is calculated from the S-matrix of the current signal using signal samples for a period of one cycle. The change in energy in any of the phases of the two lines can be used to identify the faulty phase based on some threshold value. Once the faulty phase is identified the differences in magnitude and phase are utilised to identify the faulty line. For similar types of simultaneous faults on both the lines and external faults beyond the protected zone, where phasor comparison does not work, the impedance to the fault point is calculated from the estimated phasors. The computed phasors are then used to trip the circuit breakers in both lines. The proposed method for transmission-line protection includes all 11 types of shunt faults on one line and also simultaneous faults on both lines. The robustness of the proposed algorithm is tested by adding significant noise to the simulated voltage and current waveforms of a parallel transmission line. A laboratory power network simulator is used for testing the efficacy of the algorithm in a more realistic manner.

Experimental test results for a parallel transmission lines protection scheme using wavelet transform

A scheme for the protection of parallel transmission lines using wavelet transform (WT) has been implemented and results of experimental tests on a physical power system model are described. The relaying scheme depends on the three line voltages and the six line currents of the two parallel lines at each end. Fault detection, fault discrimination and calculation of the phasors of the measured signals are done using WT. The performance of the proposed scheme has been investigated by a number of online tests. The results show that all types of shortcircuit faults can be correctly identified in less than one cycle of the fundamental frequency.

A new digital directional transverse differential current protection technique

Recently, several papers have discussed the protection of parallel transmission lines connected to common buses. The main purpose of this paper is to discuss problems associated with parallel line relaying schemes, which depend upon the theory of transverse differential protection relaying, and to present a new advanced technique to overcome these problems. The suggested technique relies on current incremental signals in corresponding phases instead of current magnitude. This method eliminates many of the associated problems typically encountered in this area. The possibility of applying the suggested technique on parallel three-terminal power transmission lines was investigated and satisfactory results were recorded. The voltage signal and the communication channel have been excluded from this study.

Power system fault detection and state estimation using Kalman filter with hypothesis testing

An algorithm for detecting power system faults and estimating the pre and post-fault steady state values of the voltages and currents is described. The proposed algorithm is based on the Kalman filter and hypothesis testing. It is shown that a power system fault is ideally suited for single sample hypothesis testing. The performance of the proposed technique is examined in connection with the protection of parallel transmission lines. The proposed technique avoids many problems of parallel line protection. The simplicity and the avoidance of complicated software and hardware in addition to the stability of the relay under different switching conditions are some of the features of the proposed technique. Studies performed on a long double-circuit transmission line with and without series compensation show a trip time in all cases of around 5 ms. >