Article

Computation Of Maximum Earth Current In Substation Switchyards

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Abstract

This paper presents recent developmental advances for the computation of maximum ground potential rise of grounding structures or alternatively maximum earth current in substation grounding systems. An advanced methodology for short circuit analysis is presented. The methodology is based on modeling of power system elements in direct phase quantities. Coupled with equivalency techniques, it provides an extremely efficient algorithm for performing numerous sequential short circuit analyses. An easy to use computer program has been developed under EPRI sponsorship. The computer algorithm uses the methodology to search for the fault condition which yields the maximum earth current in a substation grounding system. The methodology has been validated with actual system measurement on a Georgia Power Company Substation. Validation results are presented. Typical results as well as program utilization factors are discussed. The results demonstrate that the worst fault location is highly dependent on system parameters and cannot be predicted with simple rules.

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... Such situation normally appears in the case of large generating stations. It is then necessary to perform a ground fault analysis including the faults on outgoing transmission lines [3]- [5]. ...
... First, a continual effort is being made to make these methods more convenient for application [2], [5] since there is a great number of cases that should be solved. On the other hand, the accuracy of the methods is improved by including new factors of lower significance [3], Manuscript received July 20, 1998. The author is with JP "Elektroprivreda Srbije," Belgrade, Yugoslavia. ...
... Since relevant parameters of both lines are identical, all expressions have a relatively simple mathematical form. The problem of the determination of the fault current injected into the earth through the station ground grid and the external grounding circuits in the cases of a ground fault on an outgoing single line is considered in [3], [5], and [8]. It is shown that the largest (critical) value of this part of the fault current can appear at the end of a relatively short line, or, for long enough lines, on a certain critical distance from the generating station. ...
Article
Full-text available
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
... In the past three decades, a number of researchers have investigated several approaches to determine the earth fault current division and distribution which have been reported [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. A number of methods have made some different approximations and simplifications for evaluation of this issue such as considering identical spans of incoming/outgoing overhead lines, uniform tower footing resistances, an overhead ground wire connected to the earth at various towers through the tower footing resistance which is substituted by an infinite ladder network and etc. [2][3][4][5][6][7] and [12] while the other approaches have been reported as analytical methods [1] and [8][9][10][11][12][13][14][15][16][17][18]. ...
... In the past three decades, a number of researchers have investigated several approaches to determine the earth fault current division and distribution which have been reported [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. A number of methods have made some different approximations and simplifications for evaluation of this issue such as considering identical spans of incoming/outgoing overhead lines, uniform tower footing resistances, an overhead ground wire connected to the earth at various towers through the tower footing resistance which is substituted by an infinite ladder network and etc. [2][3][4][5][6][7] and [12] while the other approaches have been reported as analytical methods [1] and [8][9][10][11][12][13][14][15][16][17][18]. In addition, the problem of earth fault current division factor was discussed in [19][20][21][22] which does not provide an approach for this issue with considering the different length of spans, nonuniform tower footing resistance and adjacent the substation grounding system. ...
Article
Full-text available
The main aim of designing a safe grounding system is to provide a low impedance path to the flow of the earth fault currents without exceeding the operational constraints and equipment limits that will ensure electrical continuity. One of the most significant and well-known parameters to design a safe grounding system in power systems is the exact determination of the maximum earth fault current division factor. This paper presents a simplified and accurate method to calculate the earth fault current division factor in different states of the earth fault occurrence within and the vicinity of the substation under study. In the proposed method, a hybrid overhead-cable line, the impact of the frozen soil, mutual coupling between phase conductors and guard wires, grounding system resistance of adjacent substations, different tower footing resistances, the impact of the phase conductor impedance, and different spans in transmission lines can be considered. In addition, a closed-form formulation is also developed for the occurrence of the earth fault on the transmission line. Finally, details of the analysis results of this study have been compared with other methods in the literature. The validity and accuracy of the proposed approach also have been assayed and confirmed in details.
... When the fault occurs at any tower of an overhead transmission line in an effectively grounded power network, the fault current returns to the grounded neutral through the towers, ground return path and ground wires. The estimation of the ground fault current distribution is an important step to design a safe substation grounding grid and the associated line's grounding systems, and it had been undertaken by many researches and numerous analytical methods have been published [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Rudenberg [2] introduce an analytical method based on Kirchoff's theorems, in order to determine the ground fault current distribution in effectively grounded power network. ...
Article
Full-text available
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 parameters of overhead ground wires and power conductors, soil resistivity etc. In this paper, we comparatively analyze, using different models, the ground fault current distribution in a single circuit transmission line with one ground wire. A parametric comparative analysis was done in order to study the effects of the non-uniformity of the towers footing impedances, number of power lines spans, soil resistivity, grounding systems resistances of the terminal substations etc., on the ground fault current distribution. There are presented some useful qualitative and quantitative results obtained through a complex dedicated developed MATLAB 7.0 program.
... All of these substation grounding grids are represented with the circular grounding metal plates. Radii of these equivalent grounding metal plates are computed using equation (13). Equivalent metal plate self resistance of substation SS 35/10 kV is 1.25 , of substation SS 110/35 kV is 0.25 , and of substations SS 10/0.4 kV is 10 . ...
Article
Full-text available
This paper presents a hybrid numerical model for computation of the phase-to-ground fault current distribution between soil and neutral conductors of grounding system. Hybrid model is combination of electromagnetic model and transmission line model. In numerical realization, the finite element technique is used. Using electromagnetic model, conductive coupling between all buried non-insulated conductive parts of grounding system is taken into account. Using transmission line model, inductive coupling between phase conductors and ground wires of parallel overhead power lines is used. Similar transmission line approach is used for parallel power cable lines and cable line grounding wires. In computer programs developed for ground fault current distribution, the conductive coupling between all buried non-insulated conductive parts of grounding system can be taken into account or neglected. From the numerous numerical examples, it can be deduced that one can introduce a significant error by neglecting the conductive coupling. In presented numerical example, error caused by neglecting the conductive coupling between all buried non-insulated conductive parts of grounding system can be observed in rms values and phase angles of currents and potentials.
... Along with these conditions, different methods have been introduced to determine this factor. Some have made different approximations and simplifications [2][3][4][5][6], while others have been recorded as analytical methods [7][8][9][10][11]. In general, the ability of methods to consider the contribution of the following parameters in a simple way may be proposed as appropriate criteria for evaluating their performances: ...
Article
Full-text available
To design a safe substation grounding grid, it is necessary to compute the split factor for earth fault current and also current distribution in other possible paths. In this paper, a novel, simple and accurate method is developed for determination of this factor. In the proposed algorithm grounding grid impedance of adjacent substations, dissimilar tower footing resistances, different parallel circuits, more than one earth wires and different spans in transmission lines can be considered. In addition, the formulation for the earth faults through line towers is presented. Finally, the results are compared with the addressed cases that are comparable and show good agreement and accuracy.
... After the impedances Zs and Zm are determined according to [lo], we use the method presented here to perform calculations whose results are graphically shown in Fig.7. Applying a coinputer program based mostly on the procedure presented in [13], we obtain the results which are practically identical to those shown in Fig. 7. It can be explained by the fact that the method presented here is based only on the approximations identical to those which we are otherwise forced to adopt (because of the uncertainty of relevant data) at the design stage. ...
Article
Full-text available
The 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 uniform and different 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. 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 paper also derives simple and exact expressions for solving ladder circuits formed by the discretization of underground conductors which are in continuous contact with earth (e.g.: the sheaths of a cable, an interconnecting copper buried in the soil, a pipeline, etc.). The correct prediction of the expected ground fault current parts in soil and neutral conductors is of great importance in designing safe and economical substation grounding installations
Chapter
This chapter considers the special measures enabling a certain improvement of the reduction factor of high-voltage (HV) feeding lines by burying a copper conductor in the earth along these lines. Such measure could be the only solution in the case of HV substations situated deep within the urban area, where normally there are no available plots for laying sufficiently large grounding electrodes and where there are many relatively old buildings without foundation ground electrodes. The presented analytical expressions enable a relatively easy quantification of the effects achieved by the application of these measures. The final decision concerning the necessity of applying this measure should be made on the basis of the previously determined actual reduction factor of the feeding line, which takes into account the favorable influence of all surrounding metal installations. The methodology for determining the actual reduction factor of the feeding line is also described here and as necessary for obtaining the correct assessment concerning the achieved safety conditions should be used both before and after the application of this special measure.
Chapter
The analytical expressions presented in this chapter enable the determination of the ground-fault current distribution for a fault anywhere along a power line performed by one three-core cable or three single-core cables and at the end of the cable line with applied cross-bonding. Primarily, the correct estimation of ground-fault distribution is necessary in contemporary electric-power engineering practice for obtaining a correct evaluation of critical potential differences (step and touch voltages) appearing during a ground fault on the grounding system of a supplied substation. The second reason is the possibility to select cable(s) metal sheath that is in accordance with the real needs. This means that a selected cable sheath must be capable of withstanding thermal stresses caused by the ground-fault current fraction passing through it, but not to such extent to cause too high expenditure in cable production and too high values of harmful circulating currents appearing during normal operating conditions.
Chapter
Grounding is the fundamental measures to ensure the safe operation of power systems, including power apparatus and control/monitoring systems, and guarantee the personal safety. Grounding technology is an interdiscipline involving electrical engineering, high voltage technology, electric safety, electromagnetics, numerical analysis, and geological exploration Methodology and Technology for Power System Grounding: Covers all topics related to power system grounding Presents fundaments and theories of grounding systems Well balances technology and methodology related to grounding system design Helps to understand the grounding analysis softwares Highlights the advanced research works in the field of grounding systems Comprehensively introduces numerical analysis methods Discovers impulse ionization phenomenon of soil around the grounding conductors Touches on lightning impulse characteristics of grounding devices for towers and buildings As a comprehensive treatment of the topic, Methodology and Technology for Power System Grounding is ideal for engineers and researchers in power system, lightning protection, and grounding. The book will also better equip postgraduates, senior undergraduate students in electrical engineering.
Article
Due to the shunting action of the overhead ground wires of transmission lines or the neutral conductors connected to substation grounding, evaluating the ground wire division factors is a key step while designing the substation ground system or measuring the grounding resistance. In this paper, the principle and calculation models of the fault current division factor and the measuring current division factor are Wanalyzed. The distinctions and relations of the two division factors are discussed. A method to evaluate the fault current division factor based on the measuring current division factor is put forward. Both the fault current division factor and the measuring current division factor are measured in a 220-/110-kV substation. The simulation results are in good agreement with the measured ones.
Article
A field investigation of a ground grid using continuous 60Hz power source was carried out in a 115/12kV distribution substation. Field measurements included the grid potential rise (GPR), surface voltage gradients and distribution of the fault current. Four different fault locations were investigated to determine the worst fault and its location. By scaling up the measured data, safety-related grounding parameters corresponding to a full scale fault, are determined. Measured data is compared with computer calculated data. The field test presented in this paper can be a valuable tool for utilities to analyze ground grids for assessing safety and for verifying the design method by comparing the design parameters with the measured data.
Article
The fault current division factor describes the shunting ability of the ground wires of the transmission lines or that of the neutral conductors connected to a substation ground. As the power system capacity grows rapidly in China, more substations with higher voltage classes are constructed, and the grounding grid is becoming larger and larger in area. As a result, the potential difference within the grounding grid may become more obvious and, hence, its influence on the fault current division factor cannot be ignored. This paper proposes a multiport circuit model for grounding grids with multiple grounding points to take into account the potential difference. With the help of commercially available tools for power system simulation, the model can be easily used to calculate the fault current distribution and the fault current division factor. The main factors that affect the potential difference within the grounding grid as well as the fault current division factor are analyzed. As an application, the fault current division factor of a 1000-kV ultra-high voltage substation is further calculated.
Conference Paper
This paper presents a commentary, computational procedures for design of grounding systems using copper or Copperweld® ground conductors and comparison of these designs. The methodology is based on the IEEE Std 80. Safety and integrity of the grounding system can be achieved by proper selection of ground conductor sizes and installation procedures. The paper examines the technical performance of Copperweld® ground conductor systems and provides a number of example designs. It is concluded that the performance of ground systems designed with copper conductors or with comparable Copperweld® conductors is similar. The use of Copperweld® conductors, is a viable technical solution with the additional benefit of being a good deterrent against theft.
Article
Full-text available
To design a safe substation grounding grid, it is necessary to compute the split factor for earth fault current, and also current distribution in other possible paths. In this paper, a novel, simple and accurate method is developed for the determination of split factor. In the proposed algorithm grounding grid impedance of adjacent substations, nonsimilar tower footing resistances and parallel circuits, more than one earth wires and different spans in transmission lines can be considered. Finally, the results are compared with the others which show good agreement and accuracy.
Article
This paper deals with calculations of alternate components of states of power systems in arbitrarily chosen composite fault conditions. Canonical model is applied for these calculations. This model was already established for calculations of states of energized parts of faulted power systems. It is applied in this paper for calculations of the states of grounded parts as well. Thus, the model refers to arbitrarily small or large portions belonging to only one or both energized and grounded parts of power systems. By the canonical model application, standard procedures established for calculations of states in energized parts are extended for calculations of states of grounded parts of faulted power systems. This extension is provided by three basic generalizations: (1) the standard three-dimensional three-phase quantities are generalized as four-dimensional ones; (2) the standard three-dimensional symmetrical components transformation is generalized as four-dimensional one; (3) the application of the standard p.u. method is substituted by the generalized p.u. method. The model is verified in details by an example referring to a line to ground short-circuit occurred on an overhead line. It is also stated for solution of a composite fault which consists of the above mentioned fault associated with a line interruption.
Article
Full-text available
To determine a safe substation grounding grid in power systems, it is important to compute the split factor for earth fault current including the proximity influences among the grid and the earthing systems of the incoming/outgoing transmission lines' towers. In this paper, a novel, simple and accurate method is developed for computing this factor that can correctly take into account the proximity effects. The results are compared with those that have been published (for the cases that they are able to compute) which show good agreement and accuracy.
Article
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.
Conference Paper
A new modeling method for the analysis of conduit enclosed electric circuits is presented. The model permits the computation of the magnetic field around the circuit and the apparent impedance of the circuit as a function of the electric current. The nonuniform magnetic saturation of the steel conduit is accurately predicted. The conduit enclosed circuit model has been integrated into a network solver, which is capable of simulating power distribution systems with any number of embedded conduit enclosed circuits and other devices. This approach allows performance evaluation of conduit-enclosed circuits, taking into account the interactions with the overall electric power system. Several types of conduit materials can be simulated, including electrical metallic tubing (EMT), intermediate metal conduit (IMC), galvanized rigid conduit (GRC), aluminum conduit (ARC) as well as nonconductive conduit (for example PVC). The model has been validated with a series of laboratory tests
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The performance of steel EMT, IMC and rigid conduit enclosed power distribution systems with respect to safety is examined. A model of the integrated power system has been developed and validated with full-scale high current tests. The tests and model indicate the suitability of steel conduit as a ground conductor
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Full-text available
A method is proposed for the analysis of the distribution of the earth fault currents and earth electrode potentials in composite power systems. The approach suggested extends the application of the method of symmetrical components allowing exact representation of system elements including earth electrodes and bonds effects. Transmission lines and other system elements are modelled using compact multiport representation which is appropriate for a successive interactive calculation with low computer memory requirements
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Full-text available
When a substation is fed by a combined overhead-cable transmission line, a significant part of the ground fault current flows through cable sheaths and is discharged into the soil at the transition station where cables are connected to the overhead line. Such a phenomenon, known as ldquofault application transfer,rdquo may result in high ground potentials at the transition station which may cause shocks and equipment damage. The scope of this paper is to present new analytic formulas which can be used for the direct calculation of the fault current transferred at the transition station and its ground potential rise as well as the substation earth current. The proposed formulas allow evaluating the influence of the main factors to the fault application transfer phenomenon and can be employed, at the preliminary design stage, to easily assess the most appropriate safety conditions to avoid dangerous effects.
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This paper presents the results of a study conducted to assess the accuracy of a widely used computer algorithm for the analysis of grounding grids. The paper concludes with recommended practices for both horizontal and vertical grid conductor segmentation for the calculation of resistance and earth surface voltages for simple structures.
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Full-text available
When a ground fault occurs at a substation, the part of the fault current that flows between the grounding system and the surrounding earth is known as grid current. This current determines the magnitude of the dangerous voltages within and around the station. It may vary from a few percent to almost 100% of the earth fault current. It is necessary to make an accurate estimate of grid current for an economical and safe design of ground electrode. The available analytical methods for determining the grid current require complete system data, which is voluminous and often unavailable. In this paper a simple and accurate analytical method for determining the grid current is presented. The method requires limited data. A computer program based on the proposed method has been developed and tested
Article
Full-text available
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
Article
An advanced methodology and a computer model for analysis of practical grounding systems based on the method of moments are presented. The practical methodology is applicable to both simple and complex grounding systems. The grounding system may consist of cylindrical conductors as well as rectangular earth conductors or metallic surfaces buried in earth or located on the surface of the earth. The method consists of computing an equivalent circuit model of the earth embedded electrodes and conductive soil. Uniform or two-layer soil can he accommodated. The problem of computational efficiency is addressed. Several innovations have been introduced to minimize execution time, including adaptive segmentation of grounding structures and adaptive computation of self and mutual impedances. The procedure enables accurate computation of touch and step voltages, body currents, grounding system impedance, voltage profile, etc. The method and computer program have been validated with actual system measurements
Article
A method for modeling URD cables with explicit grounding representation is presented. The model accurately represents the skin effect in the cable conductor and shield, as well as in the soil and multiple grounds connected to the cable shield. The method is capable of representing insulated cables, semiconducting jackets, or bare concentric neutral cables. The accuracy of the model is validated by comparison with closed-form solutions of simple cable arrangements. The URD cable model has been integrated into EPRI's SMECC program, a program designed to analyze the ground potential rise of grounding structures. The overall model is also useful for analysis of effects due to loss of cable neutral. Typical results illustrate the effectiveness of URD cables in reducing ground potential rise and effects of loss of neutral
Article
Typical electric power systems may exhibit resonance conditions at relatively low frequencies. The resonant frequency depends on (1) the point of excitation, and (2) the power system parameters. It has been observed, experimentally, that the soil resistivity, grounding, and electric load play an important role in determining the resonance characteristics. This paper presents an analytic model which predicts the impact of soil resistivity, grounding, and electric load on power system resonance characteristics. A parametric study is reported which illustrates the significance of these parameters and provides a quantitative evaluation of their effects. The model is also compared with experimental data obtained at an actual 12 kV power distribution system.
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The performance of steel electric metallic tubing, intermediate metal conduit and rigid-conduit-enclosed power distribution systems with respect to safety is examined. A model of the integrated system has been developed and validated with full-scale high-current tests. The tests and model indicate the suitability of steel conduit as a ground conductor
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Full-text available
The zero sequence components of electrical quantities of overhead lines appearing at unsymmetrical ground faults are analysed, taking into account the mutual coupling among line phase circuits and earth wires as well as the conducting effects of line towers. The line model, developed using the Z-Transform, enables an accurate analysis of ground fault current distribution and magnitudes. As an illustration, the line model is applied for evaluation of various earthing system parameters of an EHV line connecting two substations. Analytical expressions for some of these parameters are also given.Die Nullkomponente der elektrischen Gren, die etwa bei unsymmetrischen Erdkurzschlssen auf Freileitungen vorkommen, werden unter Bercksichtigung der elektromagnetischen Kopplungen zwischen den Hauptleitern und den Erdseilen sowie der Maststrme analyisert. Das unter Verwendung der Z-Transformation entwickelte Leitungsmodell ermglicht eine genaue Bestimmung der Verteilung und der Gre der Erdkurzschlustrme. Als Beispiel wird es zur Berechnung verschiedener Erdungsparameter einer Hchstspannungsfreileitung angewandt, die zwei Umspannwerke verbindet. Analytische Formeln fr einige dieser Parameter werden angegeben.
Article
This User's Manual is provided as an adjunct to the final report on EPRI Research Project 1494-2. The manual is a self-contained document intended to provide detailed and complete instruction on the use of the computer programs developed by the research project. The manual includes user documentation on the two computer programs, entitled SGSYS and SMECC, developed on the contract. Brief program descriptions are followed by operational instructions, data formats, and output specifications. Preceding the program documentation is an introductory section which defines terms and outlines basic elements of grounding system analysis. Following this, a simple but detailed example is given which may be used as a guide in program utilization and also as a test case for individual program users. Following the user documentation is a completed practical example which shows data preparation for a specific substation and computer results obtained for that substation. The example also provides suggested procedures in approaching the problem of substation design using the methodologies developed by this project.
Article
When a phase-to-ground fault occurs on a grounded power network, the current returns to the generating sources through the soil and the neutral conductors. The magnitude of the fault current and its distribution in soil and neutral conductors are of prime importance to, design safe grounding installations, calculate accurately electromagnetic induction on neighbouring circuits and determine the optimum setting of the protective relays. This paper presents an analytical method to determine the magnitude and distribution of the ground fault current, duly taking into account all the overhead and underground network parameters as determined by field measurements. No approximations or simplifying assumptions are necessary. Despite this fact, the analytical method developed in this paper does not require excessive computer memory space, nor does it result in long computer time. Numerical examples are given in order to show the influence of the various parameters involved. More detailed numerical results are also described in a companion paper [1]. Copyright © 1980 by The Institute of Electrical and Electronics Engineers, Inc.
Article
It is often difficult, at the design stage, to assess the magnitude of fault current flowing in the grounding grid of a sub-station, while an assumption of the total ground fault current flowing in such a grid results in a considerable waste of expenditure. An analytical method to determine the ground fault current distribution in substation, towers and ground wire in case of a ground fault near the substation is presented, duly taking into account the effect of counterpoise and that of coupling between the phase conductor and the ground wire.
Article
A general methodology for the analysis of electrical grounding systems is presented. Earth is represented as a two layer semiinfinite region. An equivalent circuit model of the earth embedded electrodes and conductive soil is developed via numerical lution of Laplace equations. The equivalent circuit model, together with the electric power system network, represents a large scale network which is solved via the modified nodal analysis method. The procedure enables accurate analysis of complicated grounding systems and computation of touch, step and transfer voltages. Effects of tower footing resistance, counterpoised wires, types of system faults (phase to ground, line to line, etc.) can be analyzed. Practical grounding systems can be easily analyzed because model reduction techniques can be incorporated in the analysis method. The methodology is demonstrated with the study of a nontrivial grounding system analysis problem.
Article
Methods are presented to calculate rms symmetrical Station Ground Potential Rise (not including dc offsets), due to single or double line-to-ground faults. Faults may occur at station HV or LV buses or anywhere along transmission lines. Short and long lines are treated. Limitations of these methods are discussed. Methods were successfully implemented and tested.
Article
The zero-sequence current distribution among ground wires and the ground-return path of overhead transmission lines is subject to change in the vicinity of a ground fault and the feeding point. This paper introduces the concepts used in connection with the end-effect phenomena of transmission lines and describes the necessity for solving the end-effect current distribution. After dealing with the influential factors and basic assumptions, it describes a new calculation method which can be extended to develop generalized equations. The procedures to be followed in the case of ground faults supplied from either one or both sides are detailed. A summary of field tests is also included. The deviations between the measured and the computed values are found to be less than 15 percent. Several cases were studied to investigate the effect of factors, such as ground-wire material, tower-footing resistance, soil resistivity, and distance between feeding point and fault.
Article
Since ground fault currents in high-voltage systems are on the increase, the hazards associated with transmission tower voltages during ground faults have become of concern. An analytical method is presented to determine these voltages for long and short lines, arbitrary ground network terminations, and any combination of skywires and counterpoise conductors. The proportion in which the fault current is supplied by the line on both sides of the fault location is taken into account, and the effect of fault currents flowing in parallel external circuits is also considered. The touch and step potentials at the faulted tower are determined and an assessment is given of the hazard they may represent. In a numerical example, several measures aimed at reducing this hazard are compared.
Computer Based Grounding System Analysis
  • A P Meliopoulos
  • E B Joy
  • R P Webb
  • S Patel
A. P. Meliopoulos, E. B. Joy, R. P. Webb, and S. Patel, "Computer Based Grounding System Analysis," paper submitted for presentation at the 1983 IEEE-PES Winter Meeting, New York, NY, Feb. 1983.
Zone of Influence of Earth Potential Rise
  • K H Feist
K. H. Feist, "Zone of Influence of Earth Potential Rise", ELEC-TRA, No. 60, pp. 57-68, October 1978.
Groundfield Tests at Texas Valley 115/12 kV Substation of Georgia Power Company
  • S G Patel
S. G. Patel, "Groundfield Tests at Texas Valley 115/12 kV Substation of Georgia Power Company," Final Report for Electric Power Research Insti-tute on Project No. 1491-2, December 1981.
Current Division in Substation Grounding Systems
  • A P Meliopoulos
  • A Papalexopoulos
  • R P Webb
A. P. Meliopoulos, A. Papalexopoulos, and R. P. Webb, "Current Division in Substation Grounding Systems," Proceedings of the Protective Relay-ing Conference, Atlanta, GA, May 1982.
Maximum Earth Current Computations
  • A P Meliopoulos
  • R P Webb
A. P. Meliopoulos and R. P. Webb, "Maximum Earth Current Computations," Presented at the Workshop on High Voltage Power System Ground-ing, Georgia Institute of Technology, Atlanta, GA, May 12-14, 1982.
Substation Grounding Analysis Programs: User's Manual
  • E B Joy
  • A P Meliopoulos
  • R P Webb