Substation Grounding System Research Articles

On-Site Electrochemical Detection of Corrosion in Substation Grounding System

On-Site Electrochemical Detection of Corrosion in Substation Grounding System

Experimental Study of Electromagnetic Interference from Concentrated Discharge Channels within the Soil to Adjacent Directly Buried Cables during Lightning Current Inflow to the Ground

Independent lightning rods are often installed in substation grounding systems for lightning protection. The concentrated discharge channel formed when a lightning current flows to the ground through a grounding electrode will cause electromagnetic interference to the directly buried secondary cable. And the three-dimensional structure of the discharge channel will affect the transient electromagnetic field distribution, thereby affecting the electromagnetic transients on cable shields. In order to explore the influence of soil discharge phenomena on the electromagnetic interference of the directly buried secondary cable, in this paper, we carried out experiments on cables in two different grounding modes, single-ended and double-ended grounding, and captured image of soil discharge channels. The results show that the cable grounding mode will affect the coupling mode that causes the shielding layer current. The relative spatial position of the soil discharge channel and the cable has a significant impact on the magnitude of the shielding layer current under both grounding modes. The water content and salt content of the soil also have different degrees of influence on the coupling current of the shielding layer in different grounding modes.

Design Of A Main Substation Grounding System Based On Variations In Area and Number Of Electrodes

The function of the grounding system is to limit the voltage between equipment and the ground and neutralize the voltage that arises at the ground surface due to fault currents flowing in the ground. An unsafe grounding system can disrupt system reliability and human safety in the substation area. This research aims to simulate the design of a substation grounding system with the influence of variations in location and number of electrodes installed in grids and rods in swampy soil conditions with different soil resistivity values. The impact of these parameters is on the resistance value, touch voltage, and step voltage at a weight of 70 kg by using the CYMGRD application as a medium to see the effectiveness and optimization of whether the substation grounding system with variations in the outside area and variations in the number of electrode rods meets the requirements without exceeding safe limits on systems or humans. This grounding system design is designed for two cases, namely case 1: the maximum touch voltage and maximum step voltage values exceed the permitted touch voltage and maximum step voltage, so conditions like this are included in the criteria for being unsafe and can endanger personnel in the field. Case 2: the touch voltage and step voltage values are smaller than the permitted touch voltage and step voltage values, so this design is included in safe conditions and meets the criteria for a good and safe grounding system.

Soil Resistivity Assessment and Correlation on Geotechnical Properties of Backfill Soils for Substation Grounding System in Thailand

Soil Resistivity Assessment and Correlation on Geotechnical Properties of Backfill Soils for Substation Grounding System in Thailand

Evaluation of Kenten Main Substation Grounding System Based on IEEE 80-2013

Grounding system in a Substation has an important role in human and equipment safety therefore the grounding system condition should always be under observation. Maintenance and evaluation regularly should be carried out in line with the possibility of fault current increasing that embark in the system and disturbances from lightning strokes. In this study, the grounding system at the Kenten substation was analysed by using an analytic calculation method and a numerical method software. The calculation was based on IEEE Std. 80-2013 (IEEE Guide for Safety in AC Substations Grounding). From the study, it was obtained that the grounding system of Kenten substation just fulfils the safety standard regulation.

Reduction of the step voltages of MV/LV substation grounding system based on shaping electric field

Reduction of the step voltages of MV/LV substation grounding system based on shaping electric field

Analysis of grounding system transient with consideration of soil ionization and mutual coupling effect

The grounding system of an electrical substation provides safety to both operator and equipment. The lightning current waveform has a major influence on the dynamic performance of ground electrodes. If lightning current is large enough, soil will be ionized, which will have a great effect on the transient performance of the grounding system. Many numerical models have been developed to evaluate the transient performance of grounding system, still it is a challenging task to analyze the impulse behavior of grounding system efficiently. In this paper, the transient behavior of grounding systems with consideration of nonlinear and dynamic effects of soil ionization is presented. Grounding systems such as vertical rod, horizontal conductor and grounding grid buried in the homogeneous soil are considered as case study. Proposed model is the combination of circuit theory approach and method of moment with consideration of frequency-dependent impedance and mutual coupling effect between the conductor segments. Self and mutual component of inductance and resistance are considered in the analysis. Initially, transient performance of grounding system is analyzed for single vertical rod, horizontal and square grounding electrodes, further it is extended for vertical rod (more than one), horizontal conductor and grounding grids with different configurations. The analysis of grounding system with the consideration of mutual coupling effect is compared with devoid of mutual coupling, and differences between them are evaluated. For validating the developed method, simulated results are compared with the results reported in the literature, and good agreements are found. Analysis shows that the grounding impulse impedance decreased with increasing the magnitude of injected current. Developed method will help to improve the modeling of simple as well as complex grounding system buried in homogeneous soil.

Numerical Investigation of the Use of Electrically Conductive Concrete-Encased Electrodes as Potential Replacement for Substation Grounding Systems

This paper presents a numerical investigation regarding the possibility of using electrically conductive concrete (ECON) combined with concrete-encased electrode (CEE) technology to develop new substation grounding systems (SGSs) called ECON-EE as a replacement for conventional copper or galvanized steel grounding grids. In the first step, the validation of the commercial FEM software used to perform grounding system analysis was performed in terms of the grid resistance (RG), ground potential rise (GPR), and step and touch voltages, using a symmetrical 70 m × 70 m conventional copper SGS. Next, several numerical simulations of an ECON-EE grounding system with the same dimensions as the conventional copper grid used for FEM software validation were performed. Thus, several parameters of the ECON-EE grounding system were studied, such as the geometry, dimensions, and resistivity of ECON and the diameter of the rebar. The numerical results obtained permit us to demonstrate that ECON-EE grounding systems can perform better than conventional SGSs equipped with vertical rods, particularly in the case of high ground resistivity. Moreover, it was demonstrated that the two main ECON-EE parameters affecting the grounding resistance and the touch and step voltages are the section area and the resistivity of the ECON. As discussed in detail in this paper, the proposed ECON-EE grounding system can offer several advantages compared to conventional SGSs in terms of efficiency and durability, as well as in terms of simplicity of conception and implementation.

Analysis Duration of Potential Difference Neutralizer for Substation Grounding System

The grounding system design of the 150 kV substation have resolve affect in lightning strike area. The purpose of this study is to determine the duration of the potential difference penetration that occurs due to direct or indirect lightning strikes. The parameter method grounding system uses a combination of R and L for the grid section and a combination of RLC for the rod section. Simulations due to direct lightning strikes in nearby areas greatly affect the spike in the amount of potential difference. The potential difference in the area closest to the lightning strike with a maximum surge of 57.42 V with a neutralization duration of 0.21 μs. At the furthest distance from a lightning strike, the maximum potential difference spike is only 3.14 V with a neutralization duration of 2 μs. The average duration of neutralization due to lightning strikes is 2 μs. In the simulation of a direct lightning strike striking electrical equipment, it causes a very high potential difference spike in lightning strike area of ​​992.96 V with a spike duration of 0.012 μs. The farthest area point at the location of the lightning strike has a spike of 31.07 V with a spike duration of 0.06 μs. The duration of neutralization at a potential difference below 1 V, has a duration of more than 2 μs depending on the distance from the location of lightning strike. The grounding system design is able to perform good performance with a fast potential difference neutralization duration in the event of a direct or indirect lightning strike. Lightning strikes that occur will not cause dangerous step and touch voltages for personnel in the 150 kV substation area.

Considerations in the design of electrical substations, including the effect of potential gradient on surrounding metallic structures

For designing and studying an electrical substation grounding system [GS], a simple remote substation is considered according to the safety procedures indicated in the IEEE 80 Standard. Buried metallic materials or nearby metallic structures permanently endanger human life when electrical faults occur. Scenarios related to the design of electrical substations that consider the transfer of electrical potentials that can occur between the GS and buried metallic materials in their vicinity are presented, the behavior of potential transfer is evaluated, values of transferred voltages are calculated, and the main variables that influence the transferred voltage levels are identified. The simulations are performed with the CYMGRD software specific for GS calculations. Its analysis generates real results in the potential transfer that must be considered by the GS design engineer, which enables to avoid designing isolated substations without taking into account existing elements that may affect the substation surroundings.

A Simplified Approach to Calculate the Earth Fault Current Division Factor Passing Through the Substation Grounding System

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.

Transient overvoltage analysis in the medium voltage substations based on full-wave modeling of two-layer grounding system

In this paper, a comprehensive investigation of substation grounding soil structure effects on switching/lightning transients is presented. The full-wave computational solution Method of Moments (MoM) is adopted to solve Maxwell’s equations. The significant advantage of this technique is its ability to deal effectively with substation grounding systems (SGSs) at high frequency. This evaluation is carried out considering two soil structures: (1) a uniform soil and (2) soil with a layered structure. The impacts of both soil structures on the peak transient overvoltage values are compared. To begin with, the harmonic impedance matrix (HIM) of the layered multi-terminal SGS is computed. Then, a vector fitting approach is employed to incorporate the accurate SGS behavior by relying on the obtained HIM into time domain simulations. Finally, the transient overvoltages and maximum ground potential rise (GPR) are computed. The chief contribution of this paper is the transient assessment of the two-layer multi-terminal soil structure of the large SGS taking into account the frequency dependence model of the electrical parameters of soil, which is not generally investigated and instead, treated simplistically. According to the results of the study, the lack of an exact grounding system models may lead to underestimations/overestimations of the GPR and the overvoltage values. The results demonstrate the need for the grounding modeling of SGS considering layered soil structure to be incorporated into power system transient analysis in a wide range of frequencies.

Assessment of the Grid Safety Values for Substation Grounding Grid Design Parameters in Vertical Two-Layer Soil Structure

Typically, the impact of the structure of vertically layered soil on the grounding behavior is not considered while designing a substation grounding system. Therefore, it will result in poor grounding designs due to computed inaccurate grid safety values. Besides, no comparative analysis of the grounding design parameters’ impact on the grounding grid systems’ behavior and protection level between vertical and horizontal two-layer soil structures is presently available. Computing and analyzing the grounding behavior of apparent soil resistivity installed in a vertical two-layer soil structure is more challenging than in a horizontal two-layer soil. There are many other parameters to consider, such as the distance ‘a’ between the test electrodes and the angle ‘β’ between the perpendicular line to the soil boundary and the location of the test electrodes. One of the important findings of the assessment shows that the influence of vertically layered soil on grid impedance, step, and touch voltages of a grounding system is insignificant compared to a homogeneous and horizontally layered soil structure. The current flow is affected by an entire grounding grid placed in a specified layer of soil with a specific resistivity for horizontally layered soil. In contrast, soil boundaries separate a grounding grid with various resistivities for vertically layered soil. The outcome of this work is crucial in helping the engineers to understand the behavior of grounding systems in diverse soil conditions and tropical climates.

Research on Protection Effects of Drainage Line on Secondary Cable in Substation

Ensuring the operation safety of secondary cable is an important part of substation grounding system design. In some cases with high soil resistivity and large grounding grid, the safety of secondary cable can not be guaranteed by optimizing the design of grounding grid. This paper compares the core-to-skin potential difference and the shielding layer current of secondary cable with or without drainage line. It is shown that the drainage lines, which are laid in parallel with the secondary cable, can significantly reduce the core-to-skin potential difference and shielding layer current of secondary cable during power frequency short-circuit and lightning stroke. When the radius of the drainage line reaches 5mm, core-to-skin potential difference and shielding layer current of secondary cable will be reduced to 1/3 of those when it is not laid.

Measurement and calculation method of substation grounding system parameters based on CDEGS

Indoor substations are often located in areas with intensive power consumption, and its grounding design has become a very important task. In this paper, the whole process of grounding design is studied from the grounding resistance measurement obtained in the early geological exploration to the final grounding resistance, touch voltage and step voltage verification to ensure the accuracy of the design. According to the design parameters of grounding performance, the simulation calculation based on CDEGS software is adopted and optimized, which improves the design accuracy. Taking a 110kV actual substation as an example, the simulation results are accurate and reliable, which shows that the research method of grounding design based on CDEGS software can effectively improve the design quality.

Limitation of cross country fault currents in MV distribution networks by current limiting reactors connected between cable screens and primary substation earth electrode

MV distribution networks with ungrounded or grounded neutral by compensating impedance are exposed to Cross-Country-Faults (CCFs). If CCFs occur in cable lines, fault current value can reach that of line-to-line fault current. This is because the large part of the fault current flows through cable screens and only a small amount through grounding systems of secondary and primary substations. Cable screens in the joints can reach very high local temperatures where screen and copper stocking connecting the sectioned screens are not pressed enough each other. In these small areas high electric contact resistances cause large joule losses, potentially leading to insulation burning. Successive temporary/switching over voltages can cause dielectric failure, i.e. faults to ground. A way to prevent the screen insulation thermal damage could be a drastic reduction of CCF currents, especially when they occur in different cable feeders of the MV network. The paper illustrates a countermeasure able to reduce CCF currents: the use of current limiting reactors (CLRs) connecting the cable screens to the earth electrode of the primary substation. The influence of the CLRs on the equivalent earth impedances of primary and secondary substations is investigated. The methodology is applied to an existing MV distribution network.

Experimental Investigation of Surge Propagation Characteristics on a Substation Grounding System

With the correct choice of the arrester by voltage class and compliance with the calculated protective distance without taking into account the propagation velocity of the current wave on the grounding grid, overvoltages exceeding discharge or residual voltage may occur on the protected equipment, in particular the transformer. Thus, when calculating the installation of the arrester that protects the substation from incoming lightning surges from a transmission lines, it is necessary to take into account the propagation of the current wave on the grounding grid. The propagation velocity of electromagnetic waves in a 150 kV substations grounding grid was measured. The measured wave propagation velocities are in the range of 50–100⋅106 m/s. Thus, the obtained velocity of wave propagation on the grounding grid used in service is several times less than the speed of light. The measured value correlates well with similar experiments conducted for buried conductors located in soils with similar parameters and the results of mathematical modeling for a grounding grid having similar dimensions and mesh size.

Optimization of substation grounding grid design for horizontal and vertical multilayer and uniform soil condition using Simulated Annealing method.

Grounding systems are critical in safeguarding people and equipment from power system failures. A grounding system’s principal goal is to offer the lowest impedance path for undesired fault current. Optimization of the grounding grid designs is important in satisfying the minimum cost of the grounding system and safeguarding those people who work in the surrounding area of the grounded installations. Currently, there is no systematic guidance or standard for grounding grid designs that include two-layer soil and its effects on grounding grid systems, particularly vertically layered soil. Furthermore, while numerous studies have been conducted on optimization, relatively limited study has been done on the problem of optimizing the grounding grid in two-layer soil, particularly in vertical soil structures. This paper presents the results of optimization for substation grounding systems using the Simulated Annealing (SA) algorithm in different soil conditions which conforms to the safety requirements of the grounding system. Practical features of grounding grids in various soil conditions discussed in this paper (uniform soil, two-layer horizontal soil, and two-layer vertical soil) are considered during problem formulation and solution algorithm. The proposed algorithm’s results show that the number of grid conductors in the X and Y directions (Nx and Ny), as well as vertical rods (Nr), can be optimized from initial numbers of 35% for uniform soil, 57% for horizontal two-layer soil for ρ1> ρ2, and 33% for horizontal two-layer soil for ρ1< ρ2, and 29% for vertical two-layer soil structure. In other words, the proposed technique would be able to utilize square and rectangle-shaped grounding grids with a number of grid conductors and vertical rods to be implemented in uniform, two-layer horizontal and vertical soil structure, depending on the resistivity of the soil layer.

Evaluation of the Planning of a 150 kV Jabon Substation Grounding System with Simulation Software CYMGRD

Salah satu sistem proteksi dalam sistem kelistrikan adalah Sistem Pentanahan. Sistem Pentanahan Gardu Induk berfungsi untuk membatasi tegangan antar peralatan, antara peralatan dengan tanah dan meratakan gradien tegangan yang timbul di permukaan tanah saat terjadi gangguan/arus lebih. Sistem pentanahan menggunakan elektroda yang ditanam ke tanah, kemudian dihubungkan dengan peralatan/sistem gardu induk. Dalam sistem pentanahan terdapat parameter yang harus terpenuhi agar personil dan peralatan aman saat terjadi gangguan. Sistem pembumian yang buruk mengakibatkan masalah kesinambungan layanan dan personil dilokasi dapat terkena bahaya sengatan listrik. Jurnal ini berisi tentang evaluasi perencanaan sistem pentanahan pada Gardu Induk 150 kV Jabon dengan menggunakan sistem Grid-Rod. Kombinasi antara jumlah Grid dan Rod yang kedalaman penanaman konduktornya sesuai nilai tahanan jenis tanah area Gardu Induk 150 kV Jabon. Pada perencanaan sistem pembumian Gardu Induk ini didapat hasil, tahanan jenis tanah sebesar 30,71 Ω.m, ukuran konduktor yang digunakan sebesar 150 mm2. Dengan panjang konduktor grid (LC) sebesar 1916 meter dan panjang konduktor rod (LR) sebesar 67,1 meter dan ketebalan gravel 0.20 meter, didapat tegangan sentuh (Em) sebesar 551,40 volt, tegangan langkah (Es) sebesar 449,21 volt dan tahanan pentanahan (Rg) sebesar 0,226 Ω, perencanaan ini disumlasikan menggunakan software CYMGRD dan kesimpulannya perencanaanya memenuhi persyaratan dan aman untuk diterapkan.

Effects of lightning impulse front time on substation grounding system performance

&lt;table width="593" border="1" cellspacing="0" cellpadding="0"&gt;&lt;tbody&gt;&lt;tr&gt;&lt;td valign="top" width="387"&gt;&lt;p&gt;The role of the grounding system in the safety of the power system and protection of personnel is obvious during an unexpected short circuit or lightning discharge at the substation. The aim of this work is to analyze the effects of several parameters: lightning impulse front time, soil resistivity and types of grid materials on the grounding system of the Substation. The ground potential rise (GPR), touch voltage and step voltage of a 50 m x 60 m grounding grid buried at a depth of 0.5 m were computed using CDEGS when injected by impulse with different front times. Results show that the shorter the front time of lightning impulse waveform, the higher the value of GPR, touch voltage and step voltage. Meanwhile, when the value of soil resistivity is increased, the value of GPR, touch voltage and step voltage is also increased. Lastly, different types of grid conductor materials give different values of GPR, touch voltage and step voltage. However, it can be said that the differences are too small to be of any significance.&lt;/p&gt;&lt;p&gt; &lt;/p&gt;&lt;/td&gt;&lt;/tr&gt;&lt;/tbody&gt;&lt;/table&gt;