During-fault Voltage Research Articles

New technique for fault location in distribution systems using sincrophasor voltages

This paper proposes a new fault location technique for distribution networks using synchrophasor voltages from Phasor Measurement Units (PMUs). The proposed method has the ability to work with data acquired from a minimum of only two PMUs. Fault point is calculated using the bus admittance matrix along with the pre- and during-fault voltage phasors. At first it is obtained the bus nearest to the fault, then an iterative process is employed to find the exact fault point. The main innovative aspects of the presented approach are: (i) the technique is able to indicate the faulted branch, not only the nearest bus, (ii) current phasors are not necessary, (iii) no fault type classification is required. The performance of the proposed method is validated using a real 134 bus feeder modeled in ATP-EMTP. The results demonstrate a robust performance against several faults conditions.

A New Method for Fault Location in Distribution Networks Based on Voltage Sag Measurements

This paper presents an innovative method for fault location in distribution networks based on classical circuit analyses. Two synchronized and few nonsynchronized pre- and during-fault voltages are required at few buses along with the impedancematrix. A new impedance matrix manipulation procedure is proposed so that the distribution system is investigated in partitions across multiple subsystems. This procedure allows the fault location process to be performed by solving systems of determined equations, making the method more technically accessible. The fault is located by analyzing the voltage sag at the terminal-bus of each subsystem separately. The proposed method is validated on the IEEE 33-bus, 12.66 kV distribution system with/without distributed generation (DG). Simulation results show the robustness and accuracy of the method under several pre- and during-fault scenarios and measurements errors.

An Improved Sparse-Measurement Based Fault Location Technology for Distribution Networks

In this article, a sparse-measurement-based fault location method for all fault types in the distribution networks with/without the distributed generators access is proposed. The pre- and during-fault voltage samplings at a few buses are needful to estimate the fault position via a compressed sensing algorithm. Besides, the principles of the sparse meter allocation are theoretically deduced, which are of directive significance for the practical implementation of the proposed method. Furthermore, the method possesses feasibility for the fault resistance of smaller than 50 Ω and metering noise of lower than 1%. The performance of the method is tested on a 12.66 kV, 69-bus distribution network model established in the real-time digital simulator. Simulation results verified that the proposed method is of a good performance for various scenarios.

Analytical expressions for characterising voltage dips and phase‐angle jumps in electricity networks

Voltage dips/sags are one of the major concerns for electricity consumers as well as utility service providers. Therefore, the characterisation of voltage dips/sags is required. This study presents a set of mathematical expressions for characterising different types of voltage dips/sags and their associated phase-angle jumps, which are typically found due to faults and/or disturbances in electricity networks. The expressions are derived analytically from the model of the power network containing generators, transmission and/or distribution lines, transformers etc. Four types of voltage dips, namely, A, B, E, and G, which are associated with four major types of faults including balanced three-phase faults, single line-to-ground, double line-to-ground, and line-to-line faults, are considered to derive the analytical expressions. Dynamic simulation results, using a test distribution system, approve the validity as well as the accuracy of the developed expressions. The influence of fault-types and fault-locations is investigated from the mathematical expressions; further, validation is conducted through a simulation study. The analytical expressions, presented in this study, are a valuable tool in the planning stage since the expressions can be employed to characterise during-fault voltage dips at different buses in electricity network without conducting a large number of repeated dynamic simulations.

A New Fault Location Technique in Smart Distribution Networks Using Synchronized/Nonsynchronized Measurements

This paper proposes a new impedance-based technique to locate all fault types in distribution networks with/without distributed generators. A new procedure to form an impedance matrix using only series impedances of the distribution lines is introduced. The impedance matrix along with the prefault and during-fault voltage phasors at few buses is used to estimate the injection fault current via the least-squares technique. Linear least-squares estimator is utilized if microphasor measurement units ${({\mu} \rm{PMUs)}}$ are installed along the network. However, a nonlinear least-squares problem solved by the trust-region-reflective algorithm is used when only the voltage magnitudes are provided by smart meters. The operation of the standard protective devices in the distribution networks is used to reduce the computational burden of the proposed method. Also, a generalized measurement placement algorithm is studied using the discovered features of the impedance matrix. In addition, the Sobol's sensitivity analysis is conducted to quantify the importance of different input factors on the fault location accuracy. The effectiveness of the proposed method is validated on a real 134-bus, 13.8 kV distribution network under several fault scenarios and noisy measurements.

Characterization of Phase-Angle Jump in Radial Systems Using Incremental Voltage Phasors

A methodology for characterizing the phase-angle jump associated with voltage sags in radial systems using incremental voltage quantities is presented in this paper. The incremental voltage phasor is defined as the difference between the pre-fault and the during-fault voltage phasors at the point of common coupling. The characteristics of this phasor are stated for different fault conditions as a function of system impedances. Both fault impedance and source neutral grounding impedance are considered in the analysis. Furthermore, the vector representation of phasors and impedance diagrams are employed as a graphical aid for understanding the incremental quantities behavior as a function of the system parameters. An algorithm for fault classification is also presented. Finally, the theoretical analysis is confirmed using real data provided by the Department of Energy and the Electric Power Research Institute. The results of this paper can be useful in future works for fault classification and fault location.

Impact of Distributed Generation on the Voltage Sag Performance of Transmission Systems

In this paper, we analysed the growing penetration of generating units from renewable energy sources in transmission power systems. Among the possible effects of the interaction of distributed generation (DG) with transmission systems, we considered the abnormal operating conditions caused by short circuits in the transmission systems and the resulting voltage sags that occur in the network. A systematic method is presented for analysing the voltage sag behaviour of any transmission system in which large DG units are connected to the transmission system by means of High Voltage/Medium Voltage (HV/MV) stations. The method proposed for obtaining the voltage sags is the fault position method (FPM), from which we derived a graphical visualization of the during-fault voltage (DFV) matrix as a valuable tool to obtain an immediate measure of the propagation of voltage sags in the network. The results obtained were based on a portion of a real transmission system. The system that we considered is an actual portion of the Italian transmission system, and all of the quantities we used were obtained from the data of the Transmission system operator (TSO).

Calculation of current limiting reactance of hybrid SFCL for low voltage ride-through capability enhancement in DFIG wind farms

This paper presents a new approach for the low voltage ride-through capability enhancement of doubly-fed induction generator (DFIG) wind farms using a hybrid superconducting fault current limiter (SFCL) of the first peak current limiting type, which has the advantage of a fast recovery time. A design for the hybrid SFCL, focusing on current limiting reactor (CLR) reactance calculation, is proposed in this paper to determine an appropriate value for the CLR reactance that satisfies the grid code requirements of the DFIG wind turbines. High-temperature superconductors (HTS) such as Bi-2212, YBCO, Bi-2223, Ti-2223, and Hg-1223 are investigated for use in the hybrid SFCL. The recovery time and first peak current reduction effectiveness are the criteria for selecting the HTS. In the proposed method, a during-fault voltage from the grid code requirement is used as an input parameter to compute the reactance of the CLR. Based on the results of the base-case simulations conducted on the DIgSILENT PowerFactory software, the Bi-2223 HTS with the first peak of fault current less than 4.5 kA and recovery time of 2.5 s is selected for adoption in the hybrid SFCL. The calculated results of the proposed method are compared with the simulation results of the hybrid SFCL, in terms of the DFIG wind turbine fault ride-through capability enhancement, to demonstrate that the performance of the proposed method satisfies the grid code requirements.

Fault location in distribution systems with DG based on similarity of fault impedance

This paper presents a new method for locating a fault in distribution systems using the similarity of fault impedance. A four-step approach is proposed to locate the fault in the networks. First, pre- and during-fault voltages from smart feeders along the primary feeders are measured. Second, three-phase impedance to calculate fault current corresponding to voltage deviation from each smart meter is achieved. Third, a relation between fault current and fault impedance for each type of fault is extracted. Finally, based on the similarity of the estimated fault impedance for each bus, an error index is calculated. Moreover, an auxiliary process is utilized to analyze the estimated fault impedance. The proposed method uses both smart meters and phasor measurement units to obtain voltage sag. Distributed generation and loads are modeled as constant impedances and then they are considered in the three-phase impedance matrix. The suggested approach is evaluated in the IEEE 34-bus test distribution network, which is simulated in the PSCAD/EMTDC environment. The obtained numerical results confirm the acceptable accuracy of the proposed methodology for all types of faults with various fault resistances.

A Novel Method for Single and Simultaneous Fault Location in Distribution Networks

This paper introduces a novel method for single and simultaneous fault location in distribution networks by means of a sparse representation (SR) vector, Fuzzy-clustering, and machine-learning. The method requires few smart meters along the primary feeders to measure the pre- and during-fault voltages. The voltage sag values for the measured buses produce a vector whose dimension is less than the number of buses in the system. By concatenating the corresponding rows of the bus impedance matrix, an underdetermined set of equation is formed and is used to recover the fault current vector. Since the current vector ideally contains few nonzero values corresponding to fault currents at the faulted points, it is a sparse vector which can be determined by $\ell^{{{1}}}$ -norm minimization. Because the number of nonzero values in the estimated current vector often exceeds the number of fault points, we analyze the nonzero values by Fuzzy-c mean to estimate four possible faults. Furthermore, the nonzero values are processed by a new machine learning method based on the k-nearest neighborhood technique to estimate a single fault location. The performance of our algorithms is validated by their implementation on a real distribution network with noisy and noise-free measurement.

A Sparse-Data-Driven Approach for Fault Location in Transmission Networks

This paper proposes an efficient wide-area fault location method to find single- and double-fault locations in transmission networks. Unlike earlier conventional fault location methods, we only require capturing the phasors in a limited number of buses by phasor measurement units (PMUs). The measured voltage phasors and impedance matrix of the system yield an underdetermined system of equations that can be solved by sparse representation recovery methods. The solution gives a sparse fault current vector whose nonzero elements assign the probable faulty zones. For areas with no faults, current phasors measured by PMUs are sufficiently accurate to calculate the adjacent bus voltages. The new calculated voltages and the measured data are used to estimate the faulted lines accurately. The substitution theorem and least-squares method are used to calculate the differences between pre- and during-fault voltages, and currents in both ends of the faulted lines. Transmission line equations developed based on distributed line parameters are then used to pinpoint the fault location along each faulted line. We demonstrate the satisfactory performance of our noniterative methodology and its low computational load using simulations of the IEEE 39-bus test system with noisy measurements, multiple combinations of all fault types, and different resistances.

System unbalance and fault impedance effect on faulted distribution networks

This paper presents a numerical study of the system unbalance and the fault impedance effect on faulted power system analysis. Two short circuit techniques, the symmetrical components and phase components algorithms are implemented and analyzed based on numerical simulations of the IEEE 13 bus test feeder. Test cases include voltage unbalance effect and fault impedance effect on during-fault voltages and currents. The results show that the during-fault voltages and currents are greatly affected by both voltage unbalance and fault impedance.

Improved Fault Location on Distribution Feeders Based on Matching During-Fault Voltage Sags

A fault location algorithm for distribution feeders based on matching during-fault voltage sags is presented. The basic principle of the algorithm is based on the fact that when a fault occurs on the feeder, voltage sags propagate presenting different characteristics for each feeder node. Knowing the voltage sag characteristics, it is possible to locate the faulty node or the faulty area of the feeder. This voltage-based approach ensures the efficiency and robustness of the algorithm, which provides suitable and accurate results. An overhead, three-phase, three-wire, 13.8 kV, 134-node, real-life feeder model is used to evaluate the algorithm. Test results show that the algorithm is quite suitable due to not only the faulted point being located, but also a faulted area being identified providing important information to direct the maintenance crew seeking to repair any fault inflicted damage.