Ground Fault Location Research Articles

A new technique for determining the location of ground fault in the rotor of synchronous generators with various types of excitation system

Summary Ground fault in the rotor winding of generators can cause serious damage to the generators and consequently, to the power plant. This paper proposes a practical online technique to determine the ground fault location in the rotor winding of a synchronous generator. The proposed technique is based on the analysis of the measured voltage and input/output currents of the rotor winding. The main distinguishing feature of the proposed technique is that, contrary to the existing technique, it is applicable to various types of excitation system. The accuracy and applicability of the proposed technique is demonstrated through both computer simulations and experimental tests. The experimental tests have been carried out using a new device which works based on the proposed technique. The results show that the proposed technique can determine ground fault locations with a higher accuracy compared with the existing techniques. Copyright © 2016 John Wiley & Sons, Ltd.

Novel Rotor Ground-Fault Detection Algorithm for Synchronous Machines With Static Excitation Based on Third-Harmonic Voltage-Phasor Comparison

This paper presents a new algorithm for detecting ground faults in rotor windings. This location method is suitable for synchronous generators with static excitation, whose excitation field winding is fed by controlled rectifiers through an excitation transformer. This new algorithm is an improvement of an online ground-fault location method presented previously, in which the effect of the rotor capacitance has a high influence in the correct detection of the fault. The detection of the ground fault is performed by the supervision of the phase angle between two phasor voltages. The first one is the third-harmonic phasor voltage obtained from the measurement of the field voltage, which is used as a reference. The second one is the third-harmonic voltage phasor obtained by the measurement in a grounding resistance placed in the neutral of the excitation transformer. It allows not only detecting the ground fault along the field winding but also distinguishing the cases of ground fault in the rotor winding, from the cases of high influence of the rotor capacitance in healthy condition. This new algorithm has been tested with satisfactory results in a 106-MVA hydro generating unit.

A Research of Single Phase Grounding Fault Location Method Based on the Component of Zero Sequence Current in Distribution Network

A Research of Single Phase Grounding Fault Location Method Based on the Component of Zero Sequence Current in Distribution Network

Ground Fault Detection and Location for Ungrounded DC Traction Power Systems

A fault protection and location method for ungrounded dc traction power systems is presented in this paper. Many dc traction power systems have an ungrounded power circuit to increase the leakage path resistance. Although ungrounded systems can continue operating with a single ground contact, unlike solid- or low-resistance grounded systems, because of the very low fault current, a second ground fault in another pole will result in a line-to-line fault that could cause significant system damage. However, it is difficult to detect the first ground contact due to the low ground current and even harder to locate because it can be seen by many detectors in the network. The proposed scheme in this paper uses a probe unit to detect and locate the first single ground fault in ungrounded traction power systems. The probe unit applies probe voltage to detect the fault and, once the fault is detected, analyzes the response to dc or swept-frequency ac probe voltage to locate the fault. The proposed concepts have been verified with computer simulations and hardware experiments and demonstrated a successful performance.

Ground Fault Location Using the Low-Voltage-Side Recorded Data in Distribution Systems

Ground fault location and isolation are challenging in compensated distribution systems due to the fact that the fault current is too small to be measured. Considering that massive intelligent electronic devices and “smart meter” are installed in the distribution networks with the development of the “smart grid,” this paper proposes a fault location method using the low-voltage-side smart metering unit recorded data. The developed method uses the faulted negative-sequence voltage and locates the faulted sections by applying the relationship between fault distance and the clustered measurement groups. The method is tested using multibranched distribution systems, and results show that it is suitable for systems with both passive loads and distributed generations and not influenced by the system harmonic distortions, measurement noises, and loss of communication from one or even more of the metering units. The proposed method uses the wide-area measured data but does not require any synchronization. Accompanied with the low-cost contactors, the method can locate and isolate the fault sections without interrupting the healthy system operations, and this makes it feasible for industry application.

A Novel Ground Fault Identification Method for 2 × 5 kV Railway Power Supply Systems

The location of ground faults in railway electric lines in 2 × 5 kV railway power supply systems is a difficult task. In both 1 × 25 kV and transmission power systems it is common practice to use distance protection relays to clear ground faults and localize their positions. However, in the particular case of this 2 × 25 kV system, due to the widespread use of autotransformers, the relation between the distance and the impedance seen by the distance protection relays is not linear and therefore the location is not accurate enough. This paper presents a simple and economical method to identify the subsection between autotransformers and the conductor (catenary or feeder) where the ground fault is happening. This method is based on the comparison of the angle between the current and the voltage of the positive terminal in each autotransformer. Consequently, after the identification of the subsection and the conductor with the ground defect, only the subsection where the ground fault is present will be quickly removed from service, with the minimum effect on rail traffic. This method has been validated through computer simulations and laboratory tests with positive results.

On-line stator ground-fault location method for synchronous generators based on 100% stator low-frequency injection protection

Locating stator-winding ground faults accurately is a very difficult task, especially in high-impedance grounded generators. Through the conventional measurements of power plants, obtaining the precise location of these defects in on-line operating conditions is not possible, because the fault resistance is unknown. This paper presents a general algorithm for locating stator-winding ground faults in on-line operating conditions, based on the measurements provided by the 100% ground-fault low-frequency injection protection, and other available measurements. Some simplifications are applied to the general algorithm, and a simplified method is also presented for generators with especially low capacitance-to-ground, whose implementation in modern protective relays is more simple. The location through the general algorithm, and the simplified algorithms, has been validated by simulation and experimental tests, for several fault resistance values at different points of the stator winding. These algorithms assure an acceptable accuracy for a wide range of fault resistance values and locations, without the need of any additional equipment.

New Fault-Resistance Estimation Algorithm for Rotor-Winding Ground-Fault Online Location in Synchronous Machines With Static Excitation

This paper presents a new algorithm for estimating the ground-fault resistance value in rotor windings. This new algorithm is an improvement of an online ground-fault location method previously presented. This location method is suitable for synchronous generators with static excitation, whose excitation field winding is fed by controlled rectifiers through an excitation transformer. The estimation of the fault resistance is obtained through the comparison between the third-harmonic voltage measured in a grounding resistance placed in the neutral of the excitation transformer and the third-harmonic voltage calculated by the algorithm. This latter variable is obtained with the dc component of the output voltage of the controlled rectifier and the ac supply voltage of this converter. The fault resistance value is used in the novel technique of online ground-fault location, and it allows improving the accuracy of the location of the defect. This new algorithm, integrated in the complete location method, has been tested with satisfactory results in a 5-kVA laboratory synchronous generator and in a 106-MVA hydro-generating unit.

配電線でのセンサ開閉器を用いた地絡点に至る分岐点推定の検討

Ground fault location in distribution line is specified the restricted area by sequential fault detection system. Then, ground fault location is identified by detecting magnetic field originated discharge current from direct pulse device on electric pole. It needs much time to identify ground fault location due to involving works on electric pole. Recently, introducing switch with built-in sensor (ITSW) is considered on the purpose of efficient operation against amount of diffusion of Photovoltaic Power Generation Systems Source. For the purpose of introducing IT switch, ground fault location detecting method is studied by IT switch. As one of the means, it is studied the shortening of ground fault location detecting hours. For example, ground fault location is identified by the difference in arrival time of ground faults surge current from different measuring points, classification of characteristics from wave form in ground fault current, and so on. In this paper, we propose that it is estimated the brunch point from the high frequency component by measuring the wave form of ground fault current in transient state of both feeding direction and terminal point, and is verified by ATP simulation to check the validity of proposed method. In addition, we study the improvement of proposed method precision.

High-Resistance Grounded Power-System Equivalent Circuit Damage at the Line–Ground Fault Location—Part I

This paper provides the electrical equivalent circuits of high-resistance grounded (HRG) power systems other than the delta-wye-connected utility power supply transformer included in Part I of this paper. This paper also provides the HRG of a medium-voltage generator for connection to an industrial power system and to a utility power system, and this paper discusses a line-ground fault with fault resistance. Three-line diagrams of ungrounded power systems are also included to illustrate the HRG application and its effect on the ground fault current during the line-ground fault. The damage at the fault location is based on the assumption that the fault remains a line-ground fault until it is cleared by appropriate ground fault protection relays. The fault resistance and the fault current that have an effect on the damage at the fault location are included. This paper provides guidance to update the current edition of the IEEE STD. 142, with respect to HRG systems.

High-Resistance Grounded Power-System Equivalent Circuit Damage at the Line–Ground Fault Location—Part II

This paper provides the electrical equivalent circuits of high-resistance grounded (HRG) power systems other than the delta-wye-connected utility power supply transformer included in Part I of this paper. This paper also provides the HRG of a medium-voltage generator for connection to an industrial power system and to a utility power system, and this paper discusses a line-ground fault with fault resistance. Three-line diagrams of ungrounded power systems are also included to illustrate the HRG application and its effect on the ground fault current during the line-ground fault. The damage at the fault location is based on the assumption that the fault remains a line-ground fault until it is cleared by appropriate ground fault protection relays. The fault resistance and the fault current that have an effect on the damage at the fault location are included. This paper provides guidance to update the current edition of the IEEE STD. 142, with respect to HRG systems.

The Method Analysis of Overhead Transmission Line Single-Phase Grounding Fault Detection and Location

Small current grounding power system is widely used in overhead transmission line in medium voltage distribution network in China. Because of its long lines, branch, space truss structure is complex, low level of automation, It is easily influenced by outside force and the natural environment, and single-phase grounding failure rate is high. It is an important topic to quickly and accurately detect the location of the fault line, and improve the reliability of power supply and distribution system.This paper has carried on the induction and the comparison of various fault detection and location method of overhead transmission line which is currently used in single phase to ground, and analyzed their advantages and disadvantages,given the corresponding conclusions, provided the reference for finding out the reasonable single-phase earth fault location method or improvement.

The Study of Fault Location Method Based on FTU Feeder Automation Technology

With the development of power distribution automation system, feeder automation technology in the small current grounding system single-phase grounding fault location plays an important role. In the neutral arc suppression coil grounding system, because of the compensation effect of arc suppression coil, the system fault feature is not obvious. This paper puts forward a method of RL series branch parallel in arc suppression coil, when system single-phase grounding fault occurs, the series branch switch gets closed and acts on the neutral, that changes the compensation degree of arc suppression coil to zero sequence current in fault line, the change of zero sequence residual current being the biggest in the fault section from neutral to fault point. FTU is used to monitor the change in each fault line for fault regional location.

The Fault-Current-Based Protection Scheme and Location Algorithm for Stator Ground Fault of a Large Generator

This paper presents a stator ground protection scheme based on the fault current flowing in the breakdown channel. It trips only if the fault current exceeds the fault current tolerance capacity of the generator. Otherwise, it will just emit alarm signals. Thereby, the unnecessary trip-out of large generator can be avoided. The stability of the power system and the generator security can then be ensured. To achieve the scheme, methods of calculating the fault current in real time are proposed for three common generator neutral grounding methods based on the zero-sequence equivalent circuits. In addition, a ground fault location algorithm is presented which can automatically identify the faulted coil in a large generator with multicircuit stator winding. It greatly reduces the workload of repair. An implementation scheme is given on the basis of the subharmonic injection protection device. Simulation results show the validity of the protection scheme and the accuracy of the fault location algorithm.

Calculation of Interference Voltage on the Nearby Underground Metal Pipeline due to the Grounding Fault on Overhead Transmission Lines

Electromagnetic interference on the underground metal pipelines in parallel with the faulted power transmission lines includes two parts: inductive and resistive coupling. Based on the multiconductor transmission line model consisting of overhead power lines and underground pipeline, the tower grounding resistance is, respectively, modeled by the lumped-parameter processing and distributed-parameter equivalent method. Then, the formulas of voltages and currents along the transmission lines are derived combined with the constraints of voltages and currents at the transmission line's ends and the location of grounding fault. Regarding the earth-fault currents along the towers as the excitations, the method of moment is used to investigate the resistive coupling voltage on the nearby underground metal pipeline. Compared with the results of commercial software CDEGS employing the electromagnetic field analysis, the proposed method is proved to be correct and effective. The simulations also show that the results by the lumped-parameter processing method are more accurate than those by the distributed-parameter equivalent method during the tower grounding resistance modeling. Finally, the proposed method is applied to investigate the influence of parallelism length, separation distance, soil resistivity, tower grounding resistance, insulation coating resistivity, grounding fault location, and fault currents from the substations on the pipeline's coating stress voltage.

Transient Component-Based Distribution Network Single-Phase Ground Fault Location

The paper study the single-phase ground Fault Location. Which analysis neutral non-effectively grounded distribution network transient characteristics of single-phase. and verify the HHT method accuracy that through the actual system simulation of single-phase ground fault experiments .It proposed the fault localization criterion which is based on parameter identification. current single-phase ground fault detection and section targeting methods. The paper proposed the implementation which fault information is incomplete. It is help for theoretical study and power engineering..

Research on Earth Fault Location for Distribution Network Based on Zero Sequence Current Ratio

Due to the large amount of branches and high grounding resistance of distribution networks, the grounding fault location has not been solved effectively. The matrix based live location method is proposed for single-phase-to-earth fault section in ungrounded distribution networks with radial lines. The method is based on on-line distributed detectors installed in the main branch of the distribution network. The distributed detectors measure the zero sequence current value and send them to the monitor center via the GPRS. Then according to the topological structure of distribution network, the software in the monitor center analyzes zero sequence current value and the feeder length, and extracts the zero sequence current ratio, detects the earth fault based on signal singularity. Route matrix T and fault information matrix G are multiplied to locate the earth fault section. An artificial earth fault test confirmed that the system could accurately locate faults in distribution networks with radial lines.

A New Algorithm of Phase to Ground Fault Location for Electric Power Feeder

t is a great significance for power supply reliability and smart grid to locate feeder fault quickly and accurately for distribution network. A new ground fault traveling-wave signal time-frequency analysis method is proposed, which decomposes the aerial mode component and zero mode component of fault current based on EMD to get multi-stage stable intrinsic mode function (IMF). The first IMF contains high frequency components which can reflect the mutation of signal. Hilbert-Huang transformation is done for the first IMF to get the instantaneous frequency of signal. And then check the moment of traveling wave arrival by the instantaneous frequency in the figure of IMF time-frequency. The fault distance is computed based on the time difference between the moments of wave arrived of aerial mode component and zero mode components. Simulation shows that this method is able to accurately give the distance of fault without the influence of the random fault condition such as fault transition resistance and the moment of fault.

Identifying ground-fault locations: Using adjustable speed drives in high-resistance grounded systems

One of the more difficult problems to solve in industrial plants is how to identify and eliminate ground faults in a high-resistance ground (HRG) system. This is because ground-fault conditions in these systems do not draw enough current to reliably trigger fault current sensors in the drive. This article develops an approach to identify the ground-fault location in HRG systems using voltage sensing, rather than current sensing techniques, inside an adjustable speed drive (ASD). This approach consists of a simple analog circuit and digital signal processing technique to detect a fault condition, as well as to identify the fault location, be it on the load motor side, inside the ASD, or ac line side. The use of this ground-fault identification method is also extended and discussed for application to multiple drive lineups.

Short-Circuit and Ground Fault Analyses and Location in VSC-Based DC Network Cables

The application of high-power voltage-source converters (VSCs) to multiterminal dc networks is attracting research interest. The development of VSC-based dc networks is constrained by the lack of operational experience, the immaturity of appropriate protective devices, and the lack of appropriate fault analysis techniques. VSCs are vulnerable to dc-cable short-circuit and ground faults due to the high discharge current from the dc-link capacitance. However, faults occurring along the interconnecting dc cables are most likely to threaten system operation. In this paper, cable faults in VSC-based dc networks are analyzed in detail with the identification and definition of the most serious stages of the fault that need to be avoided. A fault location method is proposed because this is a prerequisite for an effective design of a fault protection scheme. It is demonstrated that it is relatively easy to evaluate the distance to a short-circuit fault using voltage reference comparison. For the more difficult challenge of locating ground faults, a method of estimating both the ground resistance and the distance to the fault is proposed by analyzing the initial stage of the fault transient. Analysis of the proposed method is provided and is based on simulation results, with a range of fault resistances, distances, and operational conditions considered.