Fault locating for traveling-wave accelerators based on transmission line theory

Radio-frequency(RF)breakdown analysis and location are critical for successful development of high-gradient traveling-wave(TW)accelerators,especially those expected to generate high-intensity,high-power beams.Compared with commonly used schemes involving dedicated devices or complicated techniques,a convenient approach for breakdown locating based on transmission line(TL)theory offers advantages in the typical constant-gradient TW-accelerating structure.To deliver such an approach,an equivalent TL model has been constructed to equate the TW-accelerating structure based on the fun-damental theory of the TL transient response in the time domain.An equivalence relationship between the TW-accelerating structure and the TL model has been established via analytical derivations associated with grid charts and verified by TL circuit simulations.Furthermore,to validate the proposed fault-locating method in practical applications,an elaborate analysis via such a method has been conducted for the recoverable RF-breakdown phenomena observed at an existing prototype of a TW-accelerating-structure-based beam injector constructed at the Huazhong University of Science and Technology.In addition,further considerations and discussion for extending the applications of the proposed method have been given.This breakdown-locating approach involving the transient response in the framework of TL theory can be a conceivable supple-ment to existing methods,facilitating solution to construction problems at an affordable cost.

Accurate Fault Location Modeling for Parallel Transmission Lines Considering Mutual Effect

:A new accurate algorithms based on mathematical modeling of two parallel transmissions lines system(TPTLS)as influenced by the mutual effect to determine the fault location is discussed in this work.The distance relay measures the impedance to the fault location which is the positive-sequence.The principle of summation the positive-,negative-,and zero-sequence voltages which equal zero is used to determine the fault location on the TPTLS.Also,the impedance of the transmission line to the fault location is determined.These algorithms are applied to single-line-to-ground(SLG)and double-line-to-ground(DLG)faults.To detect the fault location along the transmission line,its impedance as seen by the distance relay is determined to indicate if the fault is within the relay’s reach area.TPTLS under study are fed from one-and both-ends.A schematic diagrams are obtained for the impedance relays to determine the fault location with high accuracy.

Fault Location Method for STATCOM Connected Transmission Lines Using CCM

Determining the fault location using conventional impedance based distance relay in the presence of FACTS controllers is a challenging task in a transmission line. A new distance protection method is developed to locate the fault in a transmission line compensated with STATCOM with simple calculations. The proposed protection method considers the STATCOM injected/absorbed current to correct the fault loop apparent impedance and accordingly calculates the actual distance to the fault location. The comprehensive equations needed for apparent impedance calculation are also outlined and the performance is evaluated and tested with a typical 400 KV transmission system for different fault types and locations using MATLAB/SIMULINK software. The evaluation results indicate that the new protection method effectively estimates the exact fault location by mitigating the impact of STATCOM on distance relay performance with error less than 0.3%.

One-End Data Method for Fault Position Estimate of Two-Parallel Transmission Lines

An accurate numerical algorithm for three-line fault involving different phases from each of two-parallel lines is presented. It is based on one-terminal voltage and current data. The loop and nodel equations comparing faulted phase to non-faulted phase of two-parallel lines are introduced in the fault location estimation modal, in which the faulted impedance of remote end is not involved. The effect of load flow and fault resistance on the accuracy of fault location are effectively eliminated, therefore an accurate algorithm of locating fault is derived. The algorithm is demonstrated by digital computer simulations and the results show that errors in locating fault are less than 1%.

T-Shaped Transmission Line Fault Location Based on Phase-Angle Jump Checking

In order to effectively solve the dead-zone and low-precision of T-shaped transmission line fault location,a new T-shaped transmission line fault location algorithm based on phase-angle jump checking is proposed in this paper.Firstly,the 3-terminal synchronous fundamental positive sequence voltage and current phasors are extracted and substituted into the fault branch distance function to realize the selection of fault branch when the fault occurs;Secondly,use the condition of the fundamental positive sequence voltage phasor at the fault point is equal to calculate all roots(including real root and virtual roots);Finally,the phase-angle jump check function is used for checking calculation,and then the only real root can be determined as the actual fault distance,thereby achieving the purpose of high-precision fault location.MATLAB simulation results show that the proposed new algorithm is feasible and effective with high fault location accuracy and good versatility.

Correlation Analysis Algorithm for Transmission Line Fault Location Based on Travelling Wave

This paper introduced correlation method to locate transmission line fault.First it described the principle of transmission line fault location based on traveling waves.The principle of correlation analysis is introduced,then the method using correlation analysis in fault location is given.Transmission line model is established with EMTP-ATP.Basing on the model,some kinds of fault are simulated.The feasibility of this algorithm is proved based on simulation results.By comparing with the classical wavelet analysis,this paper gave the advantages of this algorithm in two cases:noise influence suppression and accuracy of near distance fault location.Experiment is established to simulate transmission line grounding fault.The experiment result showed the correlation algorithm's validity.All the analysis result indicated that the correlation algorithm have a high precision.

Modern Travelling Wave Based Fault Location Techniques for HVDC Transmission Lines

The modern travelling wave based fault location principles for transmission lines are analyzed.In order to apply the travelling wave principles to HVDC transmission lines,the special technical problems are studied.Based on this,a fault locating system for HVDC transmission lines is developed.The system can support modern double ended and single ended travelling wave princi- ples simultaneously,and it is composed of three different parts:travelling wave data acquisition and processing system,communication network and PC based master station.In the system,the fault generated transients are induced from the ground leads of the over-voltage suppression capacitors of an HVDC line through specially developed travelling wave couplers.The system was applied to 500 kV Gezhouba-Nanqiao(Shanghai)HVDC transmission line in China.Some field operation experiences are summarized,showing that the system has very high reliability and accuracy,and the maximum location error is about 3 km(not more than 0.3%of the total line length). Obviously,the application of the system is successful,and the fault location problem has finally been solved completely since the line operation.

Online One-End Fault Location Algorithm for Parallel Transmission Lines

Fault location and distance protection are essential smart grid technologies ensuring reliability of the power system. This paper describes an accurate algorithm for locating faults on double-circuit transmission lines. The proposed approach is capable of identifying the faulted circuit of a parallel transmission line by checking the estimated fault location and fault resistance. Voltage and current measurements from only one of the terminals of the faulty line are used. No pre-fault data are required for the estimation. The lumped parameter line model considering shunt capacitance is utilized for the derivation of the algorithm. It’s assumed that line parameters are known and transmission lines are fully transposed. The method is applicable to all types of faults. It’s evinced by evaluation studies that the proposed algorithm can correctly determine the faulted circuit in most cases. For exceptional cases, the current waveforms during the fault can be used to help identify the faulted circuit. The proposed algorithm generates quite accurate fault location estimates, and may be suitable for distance relaying.

Fault location of two-parallel transmission line for double phase-to-earth fault using one-terminal data

An accurate algorithm for fault location of double phase-to-earth fault on transmission line of direct ground neutral system is presented. The algorithm, which employs the faulted phase network and zero-sequence network as fault-location model in which the source impedance at the remote end is not involved, ef-fectively eliminates the effect of load flow and fault resistance on the accuracy of fault location. The algorithm achieves accurate location by measuring only one local end data and is used in a procedure that provides automatic determination of faulted types and phases, and does not require the engineer to specify them. Simulation results showed the effectiveness of the algorithm under the condition of double phase-to-earth fault.

Fault location for parallel transmission lines using one-terminal current traveling waves

With proper phase module transformation,parallel lines can be decomposed to the same directional net and the reverse directional net. The propagation characteristics of traveling waves in the reverse directional net were analyzed,and the refraction coefficient at the fault point for a single phase fault was derived. In addition,the module selection was discussed. Simulation results show that satisfying accuracy can be achieved with the proposed method. Moreover,it is immune to fault types,fault resistances,and outside system parameters.

A Novel Fault Location Algorithmfor Double-Circuit Transmission Lines based on Distributed Parameter

Anewfault location algorithmfor double-circuit transmissionlines is described inthis paper.Theproposed method uses data extractedfromtwo ends of the transmissionlines andthus eliminates the effects ofthe source impedance andthe fault resistance.The distributed parameter model and the modal transformationare also employed.Depending on modal transformation,the coupled equations of the lines are converted intodecoupled ones.Inthis way,the mutual coupling effects between adjacent circuits of the lines are eliminatedandtherefore an accurate fault location can be achieved.The proposed methodis tested via digital simulationusing EMTP in conjunction with MATLAB.The test results corroborate the high accuracy of the proposedmethod.

Fault location of untransposed double-circuit transmission lines based on an improved Karrenbauer matrix and the QPSO algorithm

Some double-circuit transmission lines are untransposed,which results in complex coupling relations between the parameters of the transmission lines.If the traditional modal transformation matrix is directly used to decouple the parameters,it can lead to large errors in the decoupled modal parameter,errors which will be amplified in the fault location equation.Consequently,it makes the fault location results of the untransposed double-circuit transmission lines less accurate.Therefore,a new modal transformation method is needed to decou-ple the parameter matrix of untransposed double-circuit transmission lines and realize the fault location according to the decoupled modal parameter.By improving the basis of the Karrenbauer matrix,a modal transformation matrix suitable for decoupling parameters of untransposed double-circuit transmission lines is obtained.To address the dif-ficulties in solving the fault location equation of untransposed double-circuit transmission lines,a new fault location method based on an improved Karrenbauer matrix and the quantum-behaved particle swarm optimization(QPSO)algorithm is proposed.Firstly,the line parameter matrix is decomposed into identical and inverse sequence compo-nents using the identical-inverse sequence component transformation.The Karrenbauer matrix is then transformed to obtain the improved Karrenbauer matrix for untransposed double-circuit transmission lines and applied to identi-cal and inverse sequence components to solve the decoupled modal parameter.Secondly,based on the principle that voltage magnitudes at both ends are equal,the fault location equation is expressed using sequence compo-nents at each end,and the QPSO algorithm is introduced to solve the equation.Finally,the feasibility and accuracy of the proposed method are verified by PSCAD simulation.The simulation results fully demonstrate that the innova-tive improvement on the basis of the traditional modal transformation matrix in this paper can realize the modal transformation of the complex coupling parameters of the untransposed double-circuit transmission lines.It causes almost no errors in the decoupling process.The QPSO algorithm can also solve the fault location equation more accu-rately.The new fault location method can realize the accurate fault location of untransposed double-circuit transmis-sion lines.

A cumulative standard deviation sum based method for high resistance fault identification and classification in power transmission lines

High resistance fault poses an enormous challenge to the existing algorithms of fault detection and fault classification.In this paper,the standard deviation and accumulation method are employed to perform the fault detection and classification.It is primarily built in two stages.Firstly,the standard deviations for the measured current’s signals of the local and remote terminals is computed to extract the fault feature.Secondly,the cumulative approach is used to enlarge the fault feature to perform the high resistance fault.The proposed scheme is known as Standard Deviation Index(SDI),and it is obtained for the three phases and zero sequence.The proposed algorithm has been tested through different fault circumstances such as multiple faults locations,fault resistances,and fault inception time.Moreover,far-end faults with high-resistance,faults happened nearby the terminal,faults considering variable loading angle,sudden load change,different sampling frequency,bad signaling and a fault occurred in the presence of series compensation are also discussed.The results show that the proposed scheme performed remarkably well regarding the fault with resistance up to 1.5kΩand can be detected within a millisecond after the fault inception.Additionally,the computational simplicity that characterizes the processes makes it more efficient and suitable for domain applications.

Detection and Classification of Transmission Line Transient Faults Based on Graph Convolutional Neural Network

We present a novel transient fault detection and classification approach in power transmission lines based on graph convolutional neural network.Compared with the existing techniques,the proposed approach considers explicit spatial information in sampling sequences as prior knowledge and it has stronger feature extraction ability.On this basis,a framework for transient fault detection and classification is created.Graph structure is generated to provide topology information to the task.Our approach takes the adjacency matrix of topology graph and the bus voltage signals during a sampling period after transient faults as inputs,and outputs the predicted classification results rapidly.Furthermore,the proposed approach is tested in various situations and its generalization ability is verified by experimental results.The results show that the proposed approach can detect and classify transient faults more effectively than the existing techniques,and it is practical for online transmission line protection for its rapidness,high robustness and generalization ability.

Experimental studies on impedance based fault location for long transmission lines

In long transmission lines,the charging current caused by the shunt capacitance decreases the accuracy in impedance based fault location.To improve the accuracy of fault location,this paper presents a novel scheme,where two Digital Fault Recorders(DFRs)are installed in a line.They can send the transient data of the faults to the both ends of a line.To estimate the distance of a fault,impedance based fault location methods are applied with transient fault data of both ends protection relays and both DFRs installed in a line.To evaluate the proposed scheme,a laboratory setup has been developed.In the lab,several faults have been simulated and associated voltages and currents are injected to a relay IED to compare experimental results.

A fault locating method for multi-branch hybrid transmission lines in wind farm based on redundancy parameter estimation

In order to solve the problem of‘‘abandoned’’wind caused by short circuit faults in a wind farm,a wind farm fault locating method based on redundancy parameter estimation is proposed.Using the characteristics of the traveling wave,transmission equations containing the position of the fault point are constructed.Parameter estimation from statistical theory is used to solve the redundant transmission equations formed by multiple measuring points to locate the faults.In addition,the bad data error detection capability of the parameter estimation is used to determine bad data and remove them.This improves locating accuracy.A length coefficient is introduced to solve the error enlargement problem caused by a transmission line sag.The proposed fault locating method can solve the fault branch misjudgment problem caused by the short-circuit faults near the data measuring nodes of thewind farm based on the proposed fault interval criterion.It also avoids the requirements to the traveling wave speed of traditional methods,thus its fault location is more accurate.Its effectiveness is verified through simulations in PSCAD/EMTDC,and the results show that it can be used in thefault locating of hybrid transmission lines.

Single Ended Fault Location Estimation for EHV Transmission Systems

A novel numerical algorithm for fault location estimation of single-phase-to-earth fault on EHV transmission lines is presented in this paper. The method is based on one-terminal voltage and current data and is used in a procedure that provides the automatic determination of faulted types and phases, rather than requires engineer to specify them. The loop and nodal equations comparing the faulted phase to non-faulted phases of multi-parallel lines are introduced in the fault location estimation models, in which source impedance of remote end is not involved. Precise algorithms of locating fault are derived. The effect of load flow and fault resistance,on the location accuracy, are effectively eliminated. The algorithms are demonstrated by digital computer simulations.

A New Principle of Fault Identification of on the Same Tower Based on Traveling Wave Reactive Powers

In order to improve the reliability of fault identification of the double-circuit transmission lines on the same tower, a new algorithm for fast protection of double-circuit transmission lines on the same tower based on the reactive powers of traveling wave is proposed. With the implementation of S-transform, the initial traveling wave reactive powers are calculated and the change characteristics of reactive power under different fault conditions are studied. The protection criterion is constructed by analyzing the ratio of the reactive powers of the same end on double-circuit transmission lines and the ratio of the reactive powers at both ends on the same line. According to the ratio of reactive power on the same side of the line and both ends of the same line, it is possible to identify whether the faults of the double-circuit line of the same tower occurred in or out of the protection zone. A large number of simulation results show that the protection performance is sensitive and reliable, and quick to respond. The criterion is simple and is basically not affected by fault initial angles, fault types, and transitional resistances.

基于波形群灵敏角特征的输电线路故障单端行波辨识与测距

针对输电线路单端行波测距难以可靠、有效辨识第二个波头的不足,该文提出基于波形群灵敏角检测的单端行波辨识与测距方法。首先,对线路故障波过程的解析和规律分析,发现波头局部波形呈现灵敏角和非轴对称性的特点。进而提出利用Radon变换变角度投影检测最灵敏角并判别最灵敏角两侧非轴对称特性,实现单端故障初始行波及多次同极性行波群的可靠辨识。最后,基于多次同极性行波到达时差构造多测距算式,输出最合理测距结果。所提方法将时域波头辨识转化为波形图像空间域最灵敏变化方向和几何轴对称性的检测,抗干扰能力强,大幅提升检测可靠性和后续波头的识别能力,提升单端测距算式冗余性。大量实测和仿真数据测试表明,算法有效、可靠、直观,适用范围广,为单端行波分析故障测距及扩展应用提供了新思路。