Design Of Grounding System Research Articles

Electrical Discharge and Its Impact on Drivetrains of Wind Turbines

Defects in drivetrains of wind turbines are typically very costly due to the difficulty in accessing the defective components for repair and maintenance. Electrical discharge has been identified as one of the key root causes to defects in wind drivetrains. Improving the reliability of key wind turbine components has been attracting a great research interest since the launch of the first wind turbine. In this paper, a study to understand the electrical discharge and its impact on wind drivetrains is presented. The root cause of electrical discharge in wind turbines is discussed. A field test is carried out on 1.5-MW doubly fed induction generator wind turbines in practical environments. Suggestions are provided on the design of the wind turbine grounding and protection system to improve turbine reliability and reduce defect rates due to electrical discharge.

국제 표준(IEC)에 의한 접지 설계 및 이에 대한 안전성 분석·평가

In this paper, we evaluate safety of grounding system which is designed according to IEC standards. Safety assessment of construction site and grounding system of building is needed before construction for the safety of human in building. Until now, in case of domestic field, design of grounding system is proceeded based on methods which are proposed in IEEE Std. 80. In other words, it is not in the situation that grounding system is designed based on IEC standards. Therefore, we propose a method which designs grounding system and evaluates safety of it according to IEC standards. We measure ground resistance of construction site using measuring equipment of ground resistance. Using this value, soil structure and ground resistivity are obtained through program analysis. CDEGS program of SES company is used for simulation analysis.

An Investigation on the Frequency Dependence of Soil Electrical Parameters

This paper presents the results of an investigation into the frequency-dependent electrical parameters for different types of soil as a function of moisture content. The frequency dependence of soil electrical parameters is very important in the design of grounding systems. In fact, the performance of grounding systems is greatly dependent upon various factors such as soil type, particle size, water content, temperature, frequency, and the like. The resistivity and relative permittivity for four different soils were measured and analyzed in the frequency range of 1kHz ? 1MHz. Soil resistivity declined as moisture content and frequency increased. In particular, the frequency dependence of soil resistivity was significant as the moisture content was low. In contrast, the relative permittivity of soil dramatically declined at the frequency of 10kHz or below as the moisture content increased, showing the opposite pattern in terms of variation patterns, compared to resistivity.

INVESTIGATION AND CALCULATION OF VALLEYS OF OUTGOING FROM SUBSTATION GROUNDING CONDUCTORS FOR SHORT-CIRCUIT IN SINGLE-PHASE SHORT OF ELECTRICAL GRID

Introduction. Earthing device electrical substation in modern conditions must meet both the requirements of electrical safety of people and animals, as well as electromagnetic compatibility requirements established her electrical equipment. These requirements are intended to address issues of protection against surges and interference caused by lightning impulse currents and switching. Aim. To investigate the distribution of single-phase short-circuit current in the substation grounding devices. Task. On the basis of the proposed design scheme of substitution substation grounding device, consisting of a substation earthing system and «cable-supported» an algorithm for calculating the resistance of the grounding device substation and distribution of single-phase short-circuit current on the circuit elements. Method. Mathematical modeling and calculation engine. Results. On the basis of calculations and studies analyzed the current distribution of single-phase short-circuit between the substation earthing system and earthing «rope-reliance». Studies carried out for the actual range of variation of the circuit parameters, showed that the earthing resistance substation substantially affects the current distribution in the one-phase short circuit fault. For example, using the graph shows that with increasing resistance grounding system of "rope-supported" the proportion of single-phase short-circuit current flowing from the substation earthing increases, while the proportion of single-phase short-circuit current flowing from the grounding device supports decreases and vice versa. In addition, when rationing grounding systems at substations for the touch voltage is necessary to analyze all the possible modes of operation of the network, which is substationed. Conclusion. The results obtained are recommended to take into account in the design of grounding systems at substations.

Effects of Ground Grid Configuration of Two Neighbouring Distribution Substations on Ground Potential Rise in MEA’s Power System

This paper presents construction planning procedures for a new small (temporary) or permanent distribution substation to replace an existing distribution substation that is served as a small or permanent substation to supply the load of the existing distribution substation while it has not yet been removed. In the meantime when the ground grids of the two substations are electrically disconnected, the auxiliary grounding system of the existing distribution substation can create steep ground potential rise between the ground grids of the two substations and hence introduces a risk for those who are working nearby. It is therefore important to incorporate safety criteria described in terms of step and touch voltage into electrical designs without any potential electrical hazards. Modeling and simulation is carried out on the Current Distribution Electromagnetic interference Grounding and Soil structure (CDEGS) program. A sequential transition process from the existing distribution substation to a new distribution substation is suggested to comply with the IEEE standard 80-2000. The results in this paper could be served a guideline in grounding system design of distribution substation and modification of grounding standards in MEA’s power distribution system.

Analysis of some Safety Assessment Standard on Grounding Systems

There are different safety assessment standards of grounding systems in different countries. Some of standards are widely adopted in the world, such as IEEE-80-2000, IEC-471-1, EA-TS41-24 and BS7354. In order to choose reasonable safety assessment standard in the design of grounding system of substation, these four standards are compared using a practical case. It showed that BS7354 is more conservative than IEEE-80-2000 and EA-TS41-24, and the definitions of allowable current are different between IEEE-80-2000 and IEC-471-1.

The influence of seasonal soil moisture on the behavior of soil resistivity and power distribution grounding systems

This paper discusses the influence of the moisture content on the seasonal behavior of both soil resistivity and ground resistance typical of power distribution grounding systems. Although field surveys indicate a wide variation in the moisture content only for the topmost soil layer, laboratory tests show that the resistivities of several types of soil are greatly affected. As a consequence, the ground resistance of systems with small dimensions may vary significantly and compromise the lightning performance of protection systems. The strong correlation, identified from measurements in this work, between soil moisture and, thus, soil resistivity, and monthly rainfall allows extrapolating resistivity measurements for the most critical conditions providing data that can be used to improve the design and performance of grounding systems.

수분함유량에 따른 토양의 전기적 파라미터의 주파수의존성

The electrical parameters of soils are highly dependent on the various factors such as types of soil, chemical compositions, moisture content, temperature, frequency, and so on. The analysis of soil parameters is of fundamental importance in design of grounding systems. In this paper, we present the experimental results of frequency-dependent impedance, resistivity, permittivity of soils as functions of types of soil and moisture content. The impedance and resistivity of soils are decreased as the moisture content and the frequency increase. In particular, the variation of the soil resistivity with the frequency is pronounced in the conditions of high resistivity and low moisture content. On the contrary, the permittivity of soils are sharply decreased with increasing the frequency below 10㎑ and the frequency-dependent permittivity of soils are highly changed in the conditions of high moisture and low resistivity.

Approximate Formulas for Terminal Voltages on the Grounding Conductor

This paper proposes approximate formulas to estimate voltages on a horizontal grounding conductor. The formulas are derived in the time domain using Bewley's lattice diagram method based on transmission and reflection coefficients. The expression of the approximate formulas is simple, and the formulas are useful for engineers to carry out grounding system design for lightning protection. This paper concerns a voltage source with step waveform. A formula for an arbitrary voltage waveform can be calculated by using Duhamel's integral. Surge characteristics of voltages and an effective length of a grounding conductor are discussed using the proposed formulas. It is easy to understand experimental and simulation results of a grounding system using the approximate formulas.

Modern Industrial Plant Electrical Grounding System Design and Installation

With the development of economy and society, there are more and more modern industrial workshop, electricity is the main energy of a modern industrial workshop. Ensure the safety of the power of the industrial building is a key consideration in the design of industrial distribution, and an important content of the healthy development of the industry. There are many problems in the current electrical system, these problems are associated with grounding system with large and small, so in the electrical system, grounding system installation process to ensure that the electrical use one of the main means of security. Modern workshop electrical grounding system is analyzed and the construction of all kinds of earthing measures should be taken.

Impact study of short-circuit calculation methods on the design of a wind farm's grounding system

Safe operation of a wind farm (W/F), under fault conditions, requires a grounding study to ensure protection against developed voltages (step and touch). A key stage in the design of a wind farm's grounding system is to determine the maximum ground fault current. The aim of this work is to examine how different short-circuit calculation (SCC) procedures affect the calculation of developed voltages (step and touch) at a wind farm and therefore the provided level of safety. For this purpose, the response of the interconnected grounding system of an actual wind farm is calculated, under fault conditions, using three alternative SCC methods and the results obtained concerning violation or not of safety criteria are presented.

An Optimal Design of Substation Grounding Grid Considering Economic Aspects Using Particle Swarm Optimization

Design of a safety grounding system is an important part of substation design in power systems. An appropriate designed grounding system ensures the adequate safety for people and protects the installation. Also, due to increasing the electrical equipment price and cost of land, the implementation of grounding system is faced with restrictions. Therefore, the design of optimal substation grounding grid considering the practical limits such as economic aspects is one of the important problem in system designing. This study presents to design an optimal grounding grid considering the economic aspects of designing. In this study, the number and diameters of conductors and rods which can carry the fault current, space between conductors for having the safety factors, the depth of burring the grounding system and investment cost are considered as parameters which affected on total cost of grounding system. Also to conducting the simulation to finding the best parameters of grounding grid to be optimum in all aspects, the Particle Swarm Optimization (PSO) algorithm is employed. Finally, the PSO is applied to a typical grounding system in two different scenarios and the results are compared to each other.

Designing Safe and Reliable Grounding in AC Substations With Poor Soil Resistivity: An Interpretation of IEEE Std. 80

IEEE Std. 80 “IEEE Guide for Safety in AC Substation Grounding” is most commonly used in the design of substation ground grids and is the basis for today's commercially available software. This paper discusses alternate design approach for substation grounding in areas that have high soil resistivity. It discusses various methods for designing a substation grounding system without changing the characteristics of the soil with additives or adding ground wells to establish a low resistance to remote earth. An interpretation of the equations and a better understanding of the IEEE Std. 80 allows the engineer to provide a cost effective, safe and reliable grounding system design when poor soil conditions exist.

탄소접지극이 병설된 접지그리드의 접지임피던스의 해석

This paper deals with the frequency-dependent ground impedance of ground grids combined with the carbon ground electrodes. Ground grids are generally valid for multipurpose grounding systems as well as lightning protection systems. The carbon ground electrodes may be supplementarily used to reduce the high frequency ground impedance and to improve the transient response to surge currents.BR The frequency-dependent ground impedances of ground grids combined with or without the carbon ground electrodes were measured and their simulations with due regard to frequency-dependent soil resistivity were implemented by using EMTP program and Matlab modeling. As a consequence, the ground impedance of ground grids combined with the carbon ground electrodes is significantly reduced when the test current is injected at the terminal of the carbon ground electrode. The measured and simulated data for the test ground grids fairly agree with each other. It was found that the proposed method of simulating the frequency-dependent ground impedance is distinguished. The simulation techniques of predicting accurately the ground impedances without actual measurements can be used in the design of grounding systems based on ground grids and the carbon ground electrodes.

Technique for Grounding System Design in Distribution Substation

Technique for Grounding System Design in Distribution Substation

Novel approach of estimating grounding pit optimum dimensions in high resistivity soils

Good grounding arrangement is very important for safe and reliable operation of a power system and to ensure safety of the power apparatus as well as the operating personnel. In most of the inland arid desert areas, the soil resistivity is significantly high and it is difficult to get low earth resistance with conventional methods. Therefore, an economical and efficient grounding system design of the earthing pit is necessary which can be achieved by using a low resistivity material (LRM). When such material is used, it is important to optimize the pit design. The grounding resistance for different configurations were calculated and based on the results, an optimized pit configuration is discussed. The intent of this paper is to present a simple general computational technique for finding the optimum economical size of grounding pit when filled with LRM. It was found that the use of too high volume of LRM does not reduce the earthing resistance in a corresponding manner. The suggested method can be readily used by engineers to obtain a good earthing pit configuration for efficient grounding of the power system components in high resistivity soils.

Frequency-dependent grounding impedance of the counterpoise based on the dispersed currents

When surges and electromagnetic pulses from lightning or power conversion devices are considered, it is desirable to evaluate grounding system performance as grounding impedance. In the case of large-sized grounding electrodes or long counterpoises, the grounding impedance is increased with increasing the frequency of injected current. The grounding impedance is increased by the inductance of grounding electrodes. This paper presents the measured results of frequency-dependent grounding impedance and impedance phase as a function of the length of counterpoises. In order to analyze the frequency-dependent grounding impedance of the counterpoises, the frequency-dependent current dissipation rates were measured and simulated by the distributed parameter circuit model reflecting the frequency-dependent relative resistivity and permittivity of soil. As a result, the ground current dissipation rate is proportional to the soil resistivity near the counterpoises in a low frequency. On the other hand, the ground current dissipation near the injection point is increased as the frequency of injected current increases. Since the high frequency ground current cannot reach the far end of long counterpoise, the grounding impedance of long counterpoise approaches that of the short one in the high frequency. The results obtained from this work could be applied in design of grounding systems.

Development of IEEE Complaint Software ‘Economical Substation Grounding System Designer’ Using MATLAB GUI Development Environment

Substations as a whole being an important part of the complete power system, grounding system of substations plays a vital role in overall performance of reliable power system. Grounding system of any substation deserves considerable care and attention at design stage, primarily to ensure electrical safety of persons working within or near substations. Looking to such great significance of grounding system design procedure, software which analyzes performance of ground grids of various shapes as per method described in IEEE standard 80 2000 has been developed using MATLAB. Proposed software is able to calculate various performance parameters of grounding system for given input data related to grid geometry, soil and system conditions for all the basic shapes of grounding grid in uniform and two layered soils. Additionally this software can also suggest optimal i.e. most appropriate, safe and costeffective design of the grounding system under given conditions and safety constraints. This software is deployed as windows standalone application using MATLAB run time compiler. Hence it can run on systems where MATLAB is not installed. In order to test the performance of the software, simple design problems have been solved and the results given by it are compared with those obtained form ETAP – GGS module and after verifying its technical performance it is found to be quite reliable tool in the field of grounding system design.

Grounding System Analysis and Design Considerations for Large Hydroelectric Power Plant

Grounding system analysis and design considerations for large hydroelectric power plant are analyzed and discussed in this paper. The main work that has been carried out includes: constructing adequate soil structures and analyzing the effects of the finite heterogeneous soil structure, the modeled river length and the water reservoir levels; conducting accurate fault current distribution calculations and studying the influence of circulating current on the touch and step voltages. The paper discusses the design of the grounding system and its safety performance while considering the impact of the circulating current and inductive coupling from cables and long parallel conductors inside the plant. Two practical examples have been provided in this paper. Furthermore, the paper demonstrates the effectiveness of using heterogeneous finite soil volumes to analyze large hydroelectric power stations and confirms that accurate grounding software packages are required to account for large circulating currents within the ground conductors and strong inductive coupling that exists between metallic elements within the substation. The results and discussions presented here can be used as a reference for engineers to analyze extensive grounding systems and to design appropriate grounding systems for large hydroelectric power plant.

매설지선의 접지임피던스의 주파수의존성에 대한 모사기법

A counterpoise is commonly employed in grounding systems installing near the ground surface of low resistivity soils and radial-type counterpoises are used in the limited space. Recently some studies on the evaluation of ground impedance of paralleling ground electrodes have carried out, but the data for providing the frequency-dependent ground impedances considering potential interferences are not yet sufficient. In order to provide the information about the design of grounding systems for surge protection, the simulations of the frequency-dependent ground impedance of various shaped counterpoises are carried out by using the distributed parameter circuit model including the effect of potential interferences. This paper presents the theoretical simulations and actual experiments of the frequency-dependent ground impedance of paralleling and 3 or 4-arms star counterpoises. The accuracy of the simulation methodology is examined by the comparison with the measured results, and the results show a good agreement between the simulation and the experiment.