Earth Fault Current Research Articles

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.

An Examination of Mutual Influences Between High-Voltage Shore-Connected Ships and Port Earthing Systems During Phase-to-Ground Faults

High-voltage shore connection (HVSC) is a technical solution to supply ships at berth in an economic way while reducing air pollution in city ports. When multiple megawatt-HVSC installations are to be exercised, electric power has to be delivered to the port from a primary high-voltage (HV) line at voltages higher than 100 kV. In this case, large earth fault currents can arise on the HV side, flowing through the port earthing system and the bonded ship hulls. Due to these faults, possible dangerous voltage gradients in sea water around the bonded ship hulls may occur. This phenomenon is pointed out and investigated in this paper to identify possible safety issues in some given scenarios.

Evaluation of induced AC voltages in underground metallic pipeline

PurposeThe purpose of this paper is to make a study of electromagnetic interference between electrical power lines and nearby underground metallic pipelines.Design/methodology/approachThe equivalent electrical circuit of the studied electromagnetic interference problem between electrical power lines and nearby metallic pipelines is created and solved using a loop currents technique based on a hybrid method. The used circuit solving technique was implemented in a software application developed by the authors.FindingsThe authors have identified the influence of phase sequence on induced voltage level in an underground pipeline for a double circuit electrical power line. Also the effect of different normal operation and phase to earth fault currents have been revealed.Practical implicationsThe study has been made through a research project with the Romanian gas transportation company, in order to find the proper protection techniques for underground metallic pipelines.Originality/valueThe paper reveals the influence of some electrical and geometrical parameters that have not been studied in detail previously.

Grounding Faulted Feeder Detection Based on Fuzzy Clustering Algorithms

Many power distribution systems have been operated with neutral ineffectively earthed, and earth fault current is no more than a few tens of amperes. Traditional earth fault detection methods based on zero sequence current has poor precision and sensitivity in this case. For improvement, a novel principle for feeder grounding fault protection based on fuzzy clustering algorithms is presented in this paper. First, the historical data are divided into two groups by fuzzy clustering algorithms. The space relative distance among detected pattern and two cluster centers is then calculated to discriminate the faulted feeder. It can detect high impedance grounding faults (HIGF). The scheme has been verified by EMTP simulation, and results show that the proposed scheme always trips all kinds of grounding faults with high sensitivity and robustness in neutral ineffectively earthed power systems (NIEPS).

Zero-sequence admittance used to protect distribution networks with low earth fault currents

The method for revealing single-phase earth faults based on controlling the admittance of the zero-sequence circuit is considered. The key theoretical statements are given. An improved measurement algorithm and protection actuation characteristics are proposed. The effectiveness of the proposed solutions is verified by the results of investigations aimed at analyzing the efficiency of the method based on the calculation model and real distribution network.

Computation of the split factor of earth fault currents by considering the proximity effects

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 earthin...

Mesh voltages at earthing grids buried in multi-layer soil

Expressions for the mesh voltages caused by earth fault currents leaking from earthing grids buried in uniform, two- and three-layer soils are proposed based upon the examination of a large set of grids and soil structures using the finite element approach. Simple empirical correction factors are developed to modify the mesh voltage formulae for uniform soil to take into account the multi-layer soil structure. A comparative analysis of available expressions for uniform and two-layer soils is performed in order to check their applicability in various cases.

Application of Apparent Impedance Method at Variable Specific Resistance of Phase Conductor

Application of Apparent Impedance Method at Variable Specific Resistance of Phase ConductorThe apparent impedance to single-phase earth fault place is obtained applying the classical algorithm of distance protection. Thanks to a complex character of this impedance, the expression for the algorithm decomposes into two equations, allowing two unknowns to be calculated: the reactance to a fault place and the fault resistance, provided the faulty phase voltage and current as well as ground current or zero sequence current are known. To do this, a special mathematical procedure called here the apparent impedance method is employed, which implies the use of specific line parameters. For high voltage two-terminal and radial lines of distribution networks the iterative procedure could be applied under the condition that the faulty phase voltage is measured in a distribution network with sufficient precision. Among other specific line parameters, the inconsistency of specific resistance of the phase conductor deserves special attention because of its unpredictable nature and wide range of deviations causing inadmissible errors in distribution networks. To cope with this shortcoming, the temperature of the phase conductor wire should be known at the moment of fault inception. Otherwise, the single-phase earth fault current should be increased to the level above the half the line load current.

Ground-Fault Feeder Detection With Fault-Current and Fault-Resistance Measurement in Mine Power Systems

Many mine power systems operate with a floating neutral or are high-resistance grounded, and earth fault current is no more than a few tens of amperes. Traditional earth-fault-detection methods based on zero-sequence current have poor sensitivity in this case. For improvement, a fault-detection scheme with fault-current and fault-resistance measurement is presented in this paper, which is capable of detecting high-impedance ground faults. The scheme has been verified by electromagnetic-transient-program simulation, and a fault-detection prototype has been developed and tested in the laboratory. Results show that the scheme has high sensitivity and robustness.

Protection Against Electric Shock Using Residual Current Devices in Circuits with Electronic Equipment

One of the means of protection in the case of fault in low voltage systems is automatic disconnection of supply. Automatic discon-nection of supply is required where a risk of harmful pathophysiological effects on humans can arise, resulting from dangerous touch voltage. In order to fulfil this requirement, residual current devices (RCDs) are used as protective devices. In circuits with electronic equipment various frequencies and distorted earth fault current can occur. The analysis indicates that earth fault current frequency other than the rated value often causes improper operation of RCDs. In some cases the protective device cannot trip at all and thus protection against electric shock is not effective. In circuits with electronic equipment transient and steady state leakage current can occur so it causes the RCDs unwanted tripping. This paper presents special problems of selection and operation of RCDs in circuits with electronic equipment, based on the laboratory and field investigations. Ill. 11, bibl. 6 (in English; summaries in English, Russian and Lithuanian).

A Practical Approach for Determining the Ground Resistance of Grounding Grids

This paper starts from the premise that ground resistance is independent of earth-fault current and presents a new method for calculating the ground resistance of grounding grids using the finite-element method. The results obtained using the method proposed are compared with results measured experimentally and results published by other authors. Once ground resistance and earth-fault current are known, grid potential and touch-and-step voltages can be calculated. The main advantage of the method proposed here is that it permits us to analyze symmetrical and nonsymmetrical grids of any shape in uniform soils. It provides a fast-resolution industrial application with acceptable results for calculating the ground resistance of grounding grids of any shape. The results obtained with the proposed method are used as the basis for formulating an easy-to-use equation for calculating the ground resistance of grounding grids in uniform soils.

Method for Calculating the Ground Resistance of Grounding Grids Using FEM

Taking as given that ground resistance is independent of earth fault current, this paper presents a new way of calculating ground resistance of grounding grids using the finite-element method (FEM). Ground resistance is calculated by means of three consecutive tests, with an acceptable number of elements, and fast resolution. The results of the proposed method are compared with those measured experimentally or determined by other authors. Once ground resistance and earth fault current are known, grid potential and touch-and-step voltages are calculated. The main advantage of the method proposed here is that it permits us to analyze symmetrical and nonsymmetrical grids of any shape in uniform, two-layer, and multilayer soils. The method developed in this paper constitutes a fast-resolution industrial application, with acceptable results, for calculating the ground resistance of grounding grids of any shape.

Compact models of nonuniform lines for earthing-system analysis

Simple compact models or overhead lines and metal sheathed/screened cables are suggested for the analysis of earth-fault currents and voltages. Models for lines and lines combined with cables are also developed. The models proposed make it possible to compose relatively simple expressions for calculating the earth-electrode voltages and currents of faulted substations, and for assessing the enhancements which can be achieved by using it nonuniform line or a combined line cable supply.

A practical approach for computation of grid current

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.

Phase co-ordinate approach to calculate earth-fault current and shock voltage

The paper summarises an alternative approach for the calculation of earth fault currents and shock voltages for low voltage systems up to 1000 V without using the conventional symmetrical components. As the shock voltage at each section of the installation has to be modelled during fault conditions, the system equations are formulated entirely in the phase co-ordinates including the representation of neutral and grounding conductors. Test results on two different earthing systems demonstrate the ability in modelling the untransposed cable parameters and the influence of the unbalanced load currents on the postfault voltages. More accurate results can thus be obtained as compared with other methods of calculation.

Quality of residual current‐operated circuit breakers

AbstractIn the last few decades, residual current‐operated circuit breakers, with (RCBO) or without integral overcurrent protection (RCCB, hereafter referred to indistinctly as “residual current devices” ‐ RCD), have assumed a fundamental importance for the electrical safety of low‐voltage systems. In accordance with IEC and CENELEC International Standards, they are a necessary protection against indirect contacts in TT systems, are recommended in TN and IT systems, and are able to prevent fires due to small earth‐fault currents. RCD with a rated residual operating current Idn ≤ 30 mA also constitute the only existing active protection against direct contacts and in the case of failure of the protective or earthing conductor. Hence, it is upon their reliability that, to a large extent, the safety of persons, of livestock and property depends in the use of low‐voltage electric power. This paper presents the results of a specific research conducted in Italy on approximately 21000 RCD installed in residential and nonresidential premises. The results of the research are analyzed in the dual intent of drawing, on a statistical basis. useful indications for improving the installation, manufacturing and testing requirements of RCD.

Prony's method: an efficient tool for the analysis of earth fault currents in Petersen-coil-protected networks

Prony's method is a technique for estimating the modal components present in a signal. Every modal component is defined by four parameters frequency, magnitude, phase, and damping. This method is used to analyse earth fault currents in Petersen-coil-protected 20 kV networks. The variations of Prony's parameters in terms of some of the power systems characteristics (distance between the busbar and the fault, fault resistance and capacitive current of the whole network) are presented. It is shown that some of the Prony's parameters relating to the fault current transient may be useful to determine what kind of fault occurred, and where it occurred.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Earth fault currents and potentials distribution in composite systems

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.

Experimental investigations of overvoltages in neutral isolated networks

For more than a decade, the Nikola Tesla Institute has worked intensively on experimental investigations of transient voltages and currents in neutral isolated networks, usually at 6 kV. The paper presents the results of investigations of overvoltages at the instant of appearance of an earth fault and during its interruption, the earth-fault currents and overvoltages during ferroresonance. Investigations were performed on cable station service networks in hydro- and thermal-power plants, industrial and similar installations in Yugoslavia. On the basis of these investigations, some measures are suggested for improving the reliability of operation of neutral isolated networks.

A Computerized Information System for the Medium and Low Voltage Networks

Within the Swedish State Power Board a computerized information system has been developed for the medium (20 and 10 kV) and low (400 V) voltage networks. The information system is based on modem data base technics, remote communication and terminals with visual display units (VDUs). Thus the local decision makers far out in the country can use the central computer installation in Stockholm directly, without depending on the help from other organization units. Calculations and other manipulations cure performed automatically by the computer and the results are presented on VDUs or on lists, produced by local printers. Among other things the system provides -load forecasting-load flow and voltage drop calculations with automatic control of capacities-calculation of short circuit and earth fault currents with aùtomatic control of the safety regulations-statistics and technical dataThe system stores the essential data describing the distribution networks. Stored data thus concern line sections, apparatuses and other components constituting the existing distribution plants. The purpose is to make the computer perform most of the routine work and supply the decision makers with basic data of such quality that further manipulation shall not be necessary. The user will initiate and control the system by use of only a few parameters.