Ground Fault Current Distribution Research Articles

Single‐phase to ground fault current distribution in transmission system based on the improved double‐side elimination method

In order to calculate the fault current distribution when a single‐phase to ground fault occurs in a transmission system with asymmetric parameters, this paper proposes an improvement on the traditional double‐side elimination method based on the phase component model. The improved double‐elimination method widens the range of the original method to the situation of multiple overhead ground wires and double power sources at both terminals. From the fault point, it divides the system into the left and right networks. Taking the left network as an example, the equations of all spans are formed. Then, the forward–backward recursive process of the theory is demonstrated. By optimizing the matrix calculation process, the calculation model for computers is formed, which can easily calculate the fault current on phase wires and overhead ground wires when a single‐phase to ground fault occurs. By comparing the results from this theory and the results from the EMTP simulation software, the correctness of the theory is established. Furthermore, in this paper we give a detailed discussion on the influence of tower grounding resistance and overhead ground wire operation mode on the fault current distribution. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

A Comparative Parametric Analysis of the Ground Fault Current Distribution on Overhead Transmission Lines

The ground fault current distribution in an effectively grounded power network is affected by various factors, such as: tower footing impedances, spans lengths, configuration and param ...

Impact of MV Ground Fault Current Distribution on Global Earthing Systems

Global earthing systems (GESs), created by the interconnection of local earthing systems, should guarantee the absence of dangerous touch voltages. One of the reasons for this safety characteristic of GESs is the fault current distribution between grounding electrodes and medium-voltage (MV) cable sheaths: Only a small portion of the fault current is injected into the ground by the ground grid of the faulty substation. In systems with isolated neutral or with resonant earthing, this effect may be sufficient to provide safety from electric shock. In this paper, a model describing the behavior of the MV distribution system with interconnected grounding electrodes during a ground fault is built. It is then used to analyze the impact of different factors on the fault current distribution. A sensitivity analysis is performed, varying the main parameters, and the results are used to draw some conclusions on the current distribution influence on GESs.

Self and mutual ground impedances of cylindrical metal plates buried in homogeneous earth

SUMMARYThis paper presents a numerical procedure for computation of self and mutual impedance of cylindrical metal plates buried in homogeneous earth. Procedure is based on an analytical expression for scalar potential distribution of an equipotential metal plate in homogeneous unbounded medium. The effect of the air–earth boundary condition is taken into account by the exact imaging method. The robustness and accuracy of the computation procedure is based on the combination of analytical integration and 1D and 2D Gaussian quadratures for solving integrals present in expressions for self and mutual ground impedances of metal plates. The attenuation and phase shift is taken into account approximately by introducing the attenuation‐phase shift factor. The numerical procedure developed for the computation of self and mutual ground impedances of cylindrical metal plates buried in homogeneous earth is efficient, numerically stable and generally applicable. Numerical model developed for the computation of self and mutual ground impedances of cylindrical metal plates buried in homogeneous earth represents a basis of a wider numerical model for computation of ground fault current distribution in which grounding grids are approximated by metal cylindrical plates. Copyright © 2014 John Wiley & Sons, Ltd.

GROUND FAULT CURRENT DISTRIBUTION WHEN A GROUND FAULT OCCURS IN HV SUBSTATIONS LOCATED IN AN URBAN AREA

The paper presents a method of determination of ground fault current distribution when HV (high voltage) substations are located in urban or suburban areas, or where many relevant data necessary for determination of this distribution are uncertain or completely unknown. The problem appears as a consequence of the fact that many of urban metal installations are situated under the surface of the ground and cannot be visually determined or verifled. On the basis of on-the-site measurements, the developed method enables compensating all deflciencies of the relevant data about metal installations involved with the ∞uctuating magnet fleld appearing around and along a feeding power line during an unbalanced fault. The presented analytical procedure is based on the fact that two measurable quantities, currents in one phase conductor and in one neutral line conductor, cumulatively involve the inductive efiects of all, known and unknown surrounding metal installations. Once, this quantity has been determined, the problem of determination of difierent parts of a ground fault current becomes solvable by using a relatively simple calculation procedure. The presented quantitative analysis indicates at the beneflts that can be obtained by taking into account the presence of surrounding metal installations.

Determination of actual reduction factor of HV and MV cable lines passing through urban and suburban areas

The paper presents the method for determination of ground fault current distribution in the cases when feeding cable lines are passing through urban and/or suburban areas, or when many relevant data are uncertain, or completely unknown. The problem appears as a consequence of the fact that many of surrounding urban installations are situated under the surface of the ground and cannot be visually determined or verified. On the basis of on site measurements, the developed method enables compensation of all deficiencies of the relevant data about metal installations involved with the fluctuating magnet field appearing along and around of a power line during an unbalanced fault. The presented analytical procedure is based on the fact that certain measurable quantities cumulatively involve the inductive effects of all, known and unknown surrounding metal installations. The performed quantitative analysis points on at the significance of taking into account the existence of surrounding metal installations.

Time-Harmonic Modelling of Two-Winding Transformers Using the Finite Element Technique

In this paper a model of a two-winding transformer based on the finite element technique is proposed. The model employs a T-equivalent circuit of the transformer. Local systems of equations are derived both for the case of a single-phase transformer and for the case of the three-phase transformer. Three most often used transformer connections are observed in the case of the three-phase transformer. These models of a two-winding single-phase or three-phase transformers will be used in an electromagnetic model for analysis of ground fault current distribution based on the finite element technique.

배전계통에서 1선 지락고장 시험에 의한 지락고장전류 분류에 관한 연구

Phase to ground faults are possibly one of the maximum number of faults in power distribution system. During a ground fault the maximum fault current and neutral to ground voltage will appear at the pole nearest to the fault. Distribution lines are consisted of three phase conductors, an overhead ground wire and a multigrounded neutral line. In this paper phase to neutral faults were staged at the specified concrete pole along the distribution line and measured the ground fault current distribution in the ground fault current, three poles nearest to the fault point, overhead ground wire and neutral line. A simplified equivalent circuit model for the distribution system under case study calculated by using MATLAB gives results very close to the ground fault current distribution yielded by field tests.

Evaluating ground fault current distribution on overhead transmission lines using an iterative nodal analysis

PurposeThe purpose of this paper is to present an original iterative nodal approach to calculate the fault current distribution on overhead lines.Design/methodology/approachBy changing the mutual couplings among different conductors into the equivalent voltage sources, node voltages are updated iteratively by using conventional nodal analysis with those additional sources until the convergence is achieved.FindingsThe proposed algorithm can handle the complicated topology of a power transmission line and has no difficulties in taking all physical couplings into account. The fault current distribution calculated by this method is in good agreement with those published in the literature. Although the proposed approach is iterative, the CPU time needed is still reasonable compared to the direct solution approach. The memory requirement is low because the coefficient matrix is highly sparse for the nodal analysis of each iteration loop.Originality/valueThe proposed approach can serve as an alternative in calculating the fault current because of its efficiency and ease of implementation.

22.9[kV] 다중접지 배전계통에서 고장전류의 접지저항 영향 분석

During a ground fault the maximum fault current and neutral to ground voltage will appear at the pole nearest to the fault. Distribution lines are consisted of three phase conductors, an overhead ground wire and a multi-grounded neutral line. In this paper phase to neutral faults were staged at the specified concrete pole along the distribution line and measured the ground fault current distribution in the ground fault current, three poles nearest to the fault point, overhead ground wire and neutral line. A effect by grounding resistance of poles of ground fault current in the 22.9[kV] multi-ground distribution system. by field tests.

About the Coupling Factor Influence on the Ground Fault Current Distribution on Overhead Transmission Lines

About the Coupling Factor Influence on the Ground Fault Current Distribution on Overhead Transmission Lines

Notice of Retraction: Influence of Metal Installations Surrounding the Feeding Cable Line on the Ground Fault Current Distribution in Supplied Substations

Retracted.

Analysis of ground fault current distribution along nonuniform multi-section lines

In case of a substation supplied by a combined overhead-cable line, most of the ground fault current flows through the cable sheaths and discharges into the soil surrounding the point of discontinuity, where cables are connected to the overhead line. In the paper a new method is presented for computing the ground fault current distribution in case of feeding line consisting of two or more different sections, i.e. part overhead and part underground cable. Besides the calculation of the earth current at the fault location, the leakage current at the transit/transition stations as well as at the overhead line towers can be evaluated, in order to ensure proper safety conditions. Based on the two-port theory, the method allows to take into account all the relevant conductively and inductively coupled parameters which take part to the fault current distribution. A computer program based on the proposed method has been developed and some application examples are reported.

Improved analytical expressions for the reduction factor of feeding lines consisting of three single‐core cables

AbstractThe paper presents an original analytical procedure giving analytical expressions for the determination of ground fault current distribution for a fault located anywhere along a feeding line consisting of three single‐core cables. The derived analytical expressions are mathematically rigorous and take into account all the relevant factors without introducing some larger approximations or idealizations of the real electrical circuit. Correct estimation of ground fault current distribution is necessary in contemporary power engineering practice due to at least two important reasons. One of them is the possibility to a correct estimation of dangerous potential differences, touch and step voltage, which may appear during a ground fault at grounding system of the supplied station. The second reason is the possibility to choose single‐core cables of the feeding cable lines with a metallic sheath cross‐section large enough to withstand thermal strains caused by fault currents. The final result of the use of the analytical expressions derived here is the possibility to determine safe and cost‐effective solutions regarding the grounding systems of the supplied stations and regarding the cross‐sections of the metallic sheaths of single‐core cables. The validation of the derived expressions is verified by experimental measurements. Copyright © 2007 John Wiley & Sons, Ltd.

Ground fault current distribution in stations supplied by a line composed of a cable and an overhead section

AbstractThis paper presents an analytical procedure which enables a quick and, at the design stage, correct evaluation of the ground fault current distribution, for a fault in a substation supplied by a line composed of two or more mutually different (overhead and underground) sections. The advantages of the method are based on the simplicity and accuracy of the formulae for solving uniform lumped parameter ladder circuits of any size and under any terminal conditions. Copyright © 2006 John Wiley & Sons, Ltd.

Ground fault distribution on overhead transmission lines

When a ground fault occurs on an overhead transmission line in a power network with grounded neutral, the fault current returns to the grounded neutral through the tower structures, ground return paths and ground wires. This paper presents an analytical method in order to evaluate the ground fault current distribution in an effectively grounded power network. The effect of soil resistivity, ground resistance of towers and power line configuration, on the magnitude of return currents, has been examined.

Determination of the reduction factor for feeding cable lines consisting of three single-core cables

The paper presents an original analytical procedure for the determination of the ground fault current distribution in the cases when a feeding line is composed of three single-core cables. The procedure takes into account the existence of all three cable sheaths as the return path for the ground-fault current. The reduction factor for these types of cables as given by the cable manufacturer takes into consideration only the existence of the metal sheath of a faulted single-core cable. As a consequence of that, the estimations of the safety conditions (step and touch voltages) on the grounding systems of the supplied stations are too severe. For the high-voltage cables, a certain, sufficiently low reduction factor achieved by an increase of the sheath cross-section can be demanded from the manufacturer. In both cases, too conservative values for the reduction factor lead to unnecessary expenditures. The quantitative analysis performed in this paper shows that the reduction factor for three single-core cables belonging to the same line is significantly lower in comparison to the situation when each of these cables is treated separately.

Grounding Effects of HV and MV Underground Cables Associated with Urban Distribution Substations

The paper derives a model for the evaluation of the performances of composite grounding systems of urban main distribution substations and associated cable networks. The effects of the cables upon the dangerous voltages, transferred potentials, and ground fault current distribution are encompassed, including the conductive and magnetic coupling among grounding system elements as well as the nonlinearity of cables sheaths impedances. An application example is presented and some experimental data.

A practical method for evaluation of ground fault current distribution on double circuit parallel lines

The paper presents an original analytical procedure for quick and, for practical purposes sufficiently accurate evaluation of the principal components of the ground fault current. The procedure is valid for faults at any of the towers of a double 3-phase circuit line with an arbitrary number of spans. The method is obtained by application of relatively simple and exact equations for uniform ladder circuits of any size (for any number of pis, from one to infinity) and for any terminal conditions. The method can be applied to solve several practical problems: the evaluation of the maximum substation grounding system fault current, the selection of a ground wire capable of withstanding the fault currents and the prediction of step and touch voltages near the transmission towers. In the case of a double circuit 3-phase line, the solution of these problems is additionally complicated by the mutual inductive coupling between the two parallel lines.

Practical method for evaluating ground fault current distribution in station, towers and ground wire

The paper presents an original analytical procedure which enables a quick and, for practical purposes sufficiently accurate evaluation of the significant parts of the ground fault current, for a fault at any of the towers of a transmission line of an arbitrary number of spans. The advantages of the method are the simplicity and accuracy of the formulae for solving uniform ladder circuits of any size (from one up to an infinite number of pis) and any terminal conditions. The formulae are obtained by applying the "general equations of the line represented by discrete parameters" on a specific electrical circuit formed by a transmission line ground wire during ground faults. The presented method is suitable for analyses aimed at evaluating the maximum substation grounding system fault current, at selecting the ground wire capable of withstanding the fault currents and at the prediction of step and touch voltages near transmission towers.