Double-circuit Transmission Line Research Articles

Fault Location Scheme for Cross-Country Faults in Dual-Circuit Line Using Optimized Regression Tree

In the double-circuit transmission line (DCTL), location of cross-country faults (CCFs) is more wearisome due to its intricate nature. The CCFs can occur at miscellaneous locations on dissimilar phases at the same fault inception time. Furthermore, the CCFs encompasses different fault locations which can mislead the line patrolling team and not only takes long hours to attend the fault location. Therefore, this may also cause electrical stress on the various power system components owing to tripping of circuit breaker repeatedly because of inappropriate fault clearance. In this context, an ensemble of regression tree (ERT) model-based fault location scheme is proposed using different regression trees such as Bagged Regression Trees (BGRT) and Boosted Regression Trees (BSRT). These regression tree modules have been trained with optimized hyper-parameters such as minimum leaf size, leaning cycles, and learning rate by using Bayesian optimization. A 400 kV, 50 Hz Chhattisgarh state power system (CSPS) network has been designed and simulated in MATLAB/Simulink to implement the proposed fault location scheme. Exclusive datasets have been designed at atypical fault scenarios thereby applying an exploratory signal processing technique such as Discrete Wavelet Transform (DWT). Additionally, the performance assessment has been done by comparing different error metrics. The simulation results reveal the applicability of the proposed ensemble regression tree (ERT) model for location of CCFs and it gives a research insight to adapt the same in the real power system network.

INVESTIGATION OF IMPEDANCE-DIFFERENTIAL PROTECTION’S ALGORITHM AS A FAULT LOCATOR FOR DOUBLE-CIRCUIT TRANSMISSION LINE

This paper deals with an analysis of impedance-differential protection algorithm applied to locate faults on a double-circuit transmission line. In particular, the study of fault location accuracy for the case of using the relation between currents for negative-sequence not for zero-sequence, as it was presented so far, is provided. It results from the well-known fact that zero-sequence impedances are in practice considered as quite unreliable data. Therefore, one has to limit usage of zero-sequence impedance parameters as much as possible. Such approach was applied in this paper and therefore the use of the additional relation of currents for negative-sequence is under investigation. The fault signals from ATP-EMTP simulation on the sample double-circuit transmission line was applied for evaluating the fault location accuracy. References 8, figures 4, table 1.

A precise analytical method for fault location in double-circuit transmission lines

The mutual coupling impedance between two circuits of double-circuit transmission lines degrades the performance of the fault location module and ground fault unit of distance relays. The distance measuring unit may underreach when both circuits are in operation. Meanwhile, the overreach problem may arise when one of the parallel circuits is disconnected and grounded at both sides. The appearance of the zero sequence mutual coupling impedance between two circuits causes that single line to ground faults would not be accurately determined by the fault locator module and distance measuring units. Thus, in this paper a new analytical method is presented based on the measurement of voltage and current signals at both ends of the line in service. The fault distance is calculated by analysis of the equivalent sequence network during single line to ground fault condition while the switched-off circuit is grounded at both sides. The proposed formulation for fault location is independent of the fault resistance, so that the estimation accuracy dose not decrease for high fault resistances. In order to evaluate the proposed method performance, a 230 kV double-circuit transmission line is simulated in PSCAD/EMTDC environment considering different transposition strategies. The obtained results show that the proposed method is able to locate the fault distance precisely with the maximum error of 1%, while for most of the cases the error is even much lower. Moreover, fault location, source impedance, external noise and CT saturation have ignorable impact on the estimation accuracy.

Circuit Model of Vertical Double-Circuit Transmission Tower and Line for Lightning Surge Analysis Considering TEM-mode Formation

The electromagnetic fields, which are produced by lightning currents flowing into a transmission tower and into overhead ground wires, spherically expand with time, and propagate as non-transverse electromagnetic (TEM) waves at least within the round trip time of the traveling wave along the tower. In this paper, a distributed-parameter line model of a vertical double-circuit transmission tower with an overhead line struck by lightning is composed considering the non-TEM characteristics. The surge impedances of the tower, ground wires, and phase conductors increase with time and reach their TEM-mode or steady state values with time constants determined from the configuration. In addition, the significant wave attenuation along the tower is included in the circuit model according to the propagation characteristic determined by the tower configuration. The virtual inductive grounding impedance or damping circuits for approximately representing the wave attenuation is no longer needed. The proposed model is applied to four types of transmission towers. Waveforms of voltages across insulator strings computed by the finite-difference time-domain method, which are regarded as the reference, are well reproduced by the proposed model. Computation efficiency is drastically improved by the proposed model comparing to the numerical electromagnetic field analysis.

Fault classification and fault area detection in GUPFC-compensated double-circuit transmission lines based on the analysis of active and reactive powers measured by PMUs

The paper presents a fault area detection and classification algorithm in the phasor domain for double-circuit lines compensated by a generalized unified power flow controller (GUPFC). In the first step, by defining and using a voltage index, the algorithm determines the side of the GUPFC in which the fault has occurred. In the second step, by defining and employing a current index, the algorithm will be able to identify the circuit of the line on which the fault has happened. Finally, the fault is classified. In this step, the algorithm detects the faulty phase by analyzing the loci of three-phase active and reactive powers at the line terminal. The algorithm uses the current and voltage phasors of the line terminals measured by the phasor measurement units (PMUs) in one cycle before and during the fault. The GUPFC and the test system have been modeled in MATLAB/Simulink. The presented algorithm is tested and evaluated under different conditions including different fault types and fault resistances for all normal series and shunt fault types. The results obtained from simulations verify the accurate performance of the algorithm for various fault conditions.

A new protection scheme for transmission lines utilizing positive sequence fault components

In this paper, a novel integrated approach of protective relaying methodology has been adopted for detecting faults and its location estimation in long transmission line. First, the detection algorithm has been formulated using positive sequence admittance. Subsequently, fault location algorithm has been developed using positive sequence voltage and current phasors. The proposed algorithms have been implemented on a 50 Hz, 400 kV single-circuit transmission line in MATLAB environment. A wide range of diversified and challenging cases have been simulated to test the reliability of this scheme. The results confirm the preciseness of the algorithm, as it can produce accurate results under stressed conditions, viz. high impedance fault (HIF), current transformer (CT) saturation/ capacitive voltage transformer (CVT) transient, close-in faults, swing condition, source strength variation, etc. Moreover, this scheme has also been successfully tested in series-compensated and double-circuit transmission line, which brings out the superiority of this scheme. The comparative analysis with recent protective relaying techniques institutes the potentiality and robustness of the scheme.

Adaptive fast protection technique for uncompensated/compensated double‐circuit transmission lines connected to large‐scale wind farms

The penetration of large-scale offshore wind farms in power grids has a negative effect on the operation of the conventional distance relays. In this study, a new protection technique is presented for uncompensated/compensated double-circuit transmission lines utilising one-end current measurements. The proposed protection technique does not require any information regarding the transmission line parameters, wind farms, or the compensation devices. In addition, the errors in phasor estimation due to the generated sub-harmonics and inter-harmonics by the wind generators are avoided as the current samples are directly used. Comprehensive studies are implemented on PSCAD/EMTDC software considering numerous cases of external and internal faults. In addition, the double-circuit transmission line is modelled using the frequency-dependent phase model and the mutual-coupling between both circuits are considered. The recorded results confirm the high efficacy of the proposed protection technique with respect to fault type, fault location, and fault resistance.

Fault Location in Double-Circuit Transmission Lines Compensated by Generalized Unified Power Flow Controller (GUPFC) Based on Synchronous Current and Voltage Phasors

This article proposes a fault location algorithm for double-circuit transmission lines compensated by a generalized unified power flow controller (GUPFC) in the phasor analysis domain. The suggested algorithm is able to locate the fault point in three stages at each circuit of a double-circuit line equipped with a GUPFC between two terminals. The first stage determines the faulty section with respect to the location of the GUPFC using the positive sequence voltages of two terminals of the line. In the second stage, the faulty circuit among the circuits of the double-circuit line is identified through analysis of sequence components of the line currents at the terminals. After determining the faulty section and faulty circuit of the line, the fault location is calculated at the third stage with high accuracy based on the analysis of synchronous current and voltage phasors that rule the circuitry equations in the GUPFC compensated double-circuit transmission line. Finally, the equations required for determining the fault location for 11 types of faults in these lines are presented based on the distributed parameter model of the line in sequence components considering the coupling between the two lines. The considered GUPFC, based on the detailed model method, is modeled along with the test network in MATLAB/Simulink. Moreover, the presented algorithm is programmed in MATLAB software for evaluation and test. The obtained simulation results verify the accurate performance of the presented algorithm under different fault conditions.

Adaptive neuro-fuzzy inference system based evolving fault locator for double circuit transmission lines

<p>Evolving faults are starting in one phase of circuit and spreading to other phases after some time. There has not been a suitable method for locating evolving faults in double circuit transmission line until now. In this paper, a novel method for locating different types of evolving faults occurring in double circuit transmission line is proposed by considering adaptive neuro-fuzzy inference system. The fundamental current and voltage magnitudes are specified as inputs to the proposed method. The simulation results using MATLAB verify the effectiveness and correctness of the protection method. Simulation results show the robustness of the method against different fault locations, resistances, time intervals, and all evolving fault types. Moreover, the proposed method yields satisfactory performance against percentage errors and fault location line parameters. The proposed method is easy to implement and cost-effective for new and existing double circuit transmission line installation</p>

Faults analysis of lightning stroke-caused flashover in 220 kV double-circuit transmission lines on the same tower

In this paper, four-phase simultaneous lightning stroke-caused faults have been analysed, which occurred in double-circuit transmission lines on the same tower. According to the fault patrol circumstance, lightning information data, fault recording imformation, ATP-EMTP transient simulation analysis, it can be determined that the four-phase flashover faults were caused by backflashover. The specific process was: lightning stroke top or ground line of 75# tower. The lightning current was shunted by the ground wire and the tower, and was injected into the earth through the grounding device, cause high electric potential to rise on the top of 75# tower, and backflashover overvoltage formed across the insulators of phase B and phase C, leading to insulators flashover and simultaneous trip-out.

Research on influence of split conductor induced voltage on TRV

AbstractBased on the background of Huainan–Wannan UHV AC double circuit transmission line, the mechanism of the transient recovery voltage (TRV) is analyzed in the case of a wire of split conductor failure. The simulation model is established to simulate the TRV of the circuit breaker when the multiple split conductors are in different positions, and the influence of the induced voltage on the TRV is also considered. The simulation results show that the more the number of fault split conductors is, the more serious the TRV is, and the peak and rate of rise of TRV are increased due to the induced voltage. Therefore, it is very important to consider the coupling effect on the transient characteristics of circuit breakers in practical engineering.

Current differential protection of double-circuit transmission lines in modal domain

In this paper, we present a new approach to protection of double-circuit transmission lines using modal transformation. The current differential principle is applied in the modal domain, and the relay characteristics are plotted in the alpha plane for numerical differential protection applications. Synchronized voltages and currents from both the ends are transformed to modal values. The transmission lines are modeled as equivalent $$\pi $$ model in modal domain, and line charging current is compensated. Electromagnetic transient program EMTP-ATP is used to simulate the double-circuit transmission systems, and the algorithm is implemented in MATLAB. The extensive case studies demonstrate the utility and the superiority of the proposed current differential scheme.

Impedance-Based Fault Location Algorithm for Double-Circuit Transmission Lines Using Single-End Data

Locating a fault in double-circuit transmission lines is a challenging task due to the mutual coupling effects between adjacent circuits of the line. Also, performance of impedance-based fault location schemes for double-circuit lines is adversely affected by fault resistance. Accurate fault location in double-circuit lines can be achieved if fault location schemes utilize reliable communication links. However, the communication links are not available or enabled in all transmission lines. To overcome such difficulty in fault location in double-circuit lines, a new fault location scheme is proposed for double-circuit transmission lines by using voltages and currents data extracted from single-end of the line. Only the negative-sequence current and voltage phasors during the fault are processed for calculating the fault location. The proposed fault location formula is derived by applying the Kirchhoff’s voltage law around the parallel circuits and shunt capacitances loops. Obtained formula is applicable for all types of unbalanced faults and accordingly classification of fault types and phase selection are not required. The proposed scheme is immune to the fault resistance and insensitive to mutual coupling effects. Evaluation results verify that the accuracy of the proposed algorithm is very high under various fault resistances, fault locations, and fault types.

CNN-Based Fault Phase Identification Method of Double Circuit Transmission Lines

—In order to address the problems that model-based distance protection cannot correctly identify the fault phases in the DCTL (Double Circuit Transmission Lines on the same tower), a CNN-based (Convolutional Neural Network) fault phase identification method is proposed. The proposed method only uses the current and voltage waveforms of single-ended and single-circuit of DCTL to identify the fault phases. The CNN includes two convolution layers and two pooling layers, which are used to automatically extract the features of the waveforms. Furthermore, the CNN realizes the phase identification function by the extracted features. A training set is constructed by the simulation result of PSCAD, which is used for training the CNN to fit the mapping relationship between the waveforms and the fault types. Then, a validation set is used to optimize the hyper-parameters of CNN. Finally, several test sets are used to test the performance of CNN for phase identification. Compared with the traditional model-driven methods, the CNN-based method avoids manually analyzing the fault characteristics under different fault types and constructing identification criteria. The test results show that the proposed method can greatly improve the fault phase identification accuracy of DCTL.

Distribution of Magnetic Field in 400 kV Double-Circuit Transmission Lines

A high-voltage AC double-circuit 400 kV overhead power transmission line runs from the city of Elk (Poland) to the city of Alytus (Lithuania). This international 400 kV power transmission line is potentially one of the strongest magnetic field-generating sources in the area. This 400 kV voltage double-circuit overhead transmission line and its surroundings were analyzed using the mathematical analytical methods of superposition and reflections. This research paper includes the calculation of the numerical values of the magnetic field and its distribution. The research showed that the values of the magnetic field strength near the international 400 kV power transmission line exceed the threshold values permitted by relevant standards. This overhead power line is connected to the general (50 Hz) power system and generates a highly intense magnetic field. It is suggested that experimental trials should be undertaken in order to determine the maximum values of the magnetic field strength. For the purpose of mitigating these values, it is suggested that the height of the support bars should be increased or that any individual and commercial activities near the object under investigation should be restricted.

Accurate simulation and modeling of the control system and the power electronics of a 72-pulse VSC-based generalized unified power flow controller (GUPFC)

The rapid growth and development of manufacturing technology for controlling processors and high-power semiconductor devices has led to the enhancement of flexible AC transmission system (FACTS) controllers, thus improving the performance of power systems. The generalized unified power flow controller (GUPFC) is today introduced as the most advanced generation of the FACTS family, which is based on voltage source converter (VSC). It can, hence, control all the five parameters of a power system given above. The paper, for the first time, presents the accurate modeling of different parts of the control system and power electronics of the 72-pulse VSC-based GUPFC in detail to satisfy operation constraints and improve power quality in terms of harmonic level reduction. There is no need to use active or passive filters in the proposed model for reducing harmonic level of the GUPFC. In this regard, the calculation of four main parameters, namely D_alpha, alpha, angular speed, and sigma, as inputs of the pulse-firing system for the 72-pulse VSC is performed dynamically and optimally to meet all expected constraints in terms of operation, power quality, and harmonic reduction of a network with a GUPFC. The presented modeling is implemented on a 230 kV GUPFC-compensated double-circuit transmission line in MATLAB/Simulink environment, and the desired results of the presence of the 72-pulse VSC-based GUPFC are shown to meet the desired constraints of operators.

Analysis of Six-Phase Transmission Lines for Increasing Power

In the India, especially in metropolitan areas, transmission infrastructure is congested due to a combination of increasing load demands, declining investment, and aging facilities. It is anticipated that significant investments will be required for new construction and upgrades in order to serve load demands. This paper explores higher phase order systems, specifically, six-phase, as a means of increasing power transfer capability, and provides a comparison with conventional three-phase double circuit transmission lines. Line parameters calculations performed in this thesis show that line impedances in six-phase lines have a slight difference, compared to three-phase double circuit line. The electric and magnetic fields calculations show that, ground level electric fields of the six-phase lines decline more rapidly as the distance from center of the lines increase. The six-phase lines have a better performance on ground level magnetic field. Based on the electric and magnetic field results, right of way requirements for the six-phase lines and three-phase double circuit line were calculated. The calculation results of right of way show that six-phase lines provide higher power transfer capability with a given right of way.

Fault location in UPFC compensated double circuit transmission line using negative sequence current phasors

Double-circuit transmission lines are used in modern power systems to enhance the transmission capability and to improve system reliability and safety. However, the protection of double-circuit lines is a challenging task as the presence of flexible ac transmission system (FACTS) in modern power grid impairs the performance of the conventional distance protection schemes. Moreover, the high impedance faults cannot be detected by relays as they become under-reach. This paper proposes a negative sequence current based scheme for locating faults and identifying faulty circuit/ line in double circuit transmission line compensated by UPFC at one end. In the proposed scheme the current signals are collected from both ends of the line to be protected. Then the negative sequence components of the currents are calculated. The discrimination between internal and external fault is achieved from the phase angles of the negative sequence currents and the fault location is determined from the ratio of the negative sequence currents. Prior knowledge about the type of fault is not required for fault location estimation. Extensive fault simulation studies including high impedance faults have been performed. The scheme is immune to the fault inception angle and fault resistance.

Fast adaptive reclosing in double-circuit transmission lines for improving powersystem stability based on harmonic analysis scheme

An appropriate method is proposed for identifying permanent faults from transient faults in double-circuit transmission lines. This method could be used in adaptive single phase auto-reclosures in order to diagnose between permanent and transient faults, determine extinguishing time of the secondary arc, and calculate issuing time of reclosing commands during the occurrence of transient single phase to ground faults. The proposed method is based on harmonic analysis of the adjacent healthy circuit and could be an effective solution for blocking permanent disconnection of the power flow, improving stability, and maintaining the power network synchronism. In this paper, transient and permanent faults are simulated on a typical power system, and then current harmonics of the healthy circuit terminal are extracted and finally the proposed index for identifying the fault type is applied. In the case of transient faults, this method determines the minimum time needed for a fast successful adaptive reclosing in the network and thus prevents instability and nonsynchronism in both sides of the transmission line. Results of the various simulations run in EMTP-RV verifies accurate performance of the proposed approach.

A single-end directional relaying scheme for double-circuit transmission line using fuzzy expert system

The faults occurring in different sections are difficult to identify using the traditional techniques. This paper investigates a fuzzy expert system for directional relaying, classification, and location of faults in double-circuit transmission lines. The current magnitudes measured at only one terminal of the double-circuit transmission line are used to compute discreet Fourier coefficients. Thus, this scheme does not involve any communication channel. The presented fuzzy expert system is achieved from the structure of MAMDANI system in LabVIEW software. Test case studies show the effectiveness of the presented scheme. The simulation results attest that the directional relaying, classification, and location estimation is very accurate. This scheme is adaptive to the change of fault location, fault resistance, fault inception angle, and fault type.