Grid Resistance Research Articles

Design Optimization Analysis of Ground Grid in Extra High Voltage Substation using ETAP Software

The power system of Myanmar relies on the 500 kV substations. They provide the power needs of the entire power system while covering a huge region. Examining the substation's ground grid system thoroughly is necessary to safeguard the grid and maintain its functionality. The grounding system of the substation is thoroughly examined, incorporating practical data collection for detailed analysis. Special emphasis is placed on the application of the latest IEEE 81-2013 standards during the data collection phase. The analysis and modeling of the network are conducted using ETAP software version 19. Specifically, the Ground Grid System (GGS) module, available in the latest version of ETAP (version 19), is utilized for the study. The substation is planned for an extension, which includes the installation of a new power transformer. The addition of the new power transformer is anticipated to elevate the overall fault level of the substation. This increase in fault level is analyzed in a dedicated case study, and a potential solution is proposed. A new ground mesh is also designed for this area, serving as a benchmark for future substations in the region, ensuring that essential parameters are carefully considered. Additionally, a new ground mesh is designed for a 500 kV substation, as it is expected to become part of the national grid in the near future. This aligns with the ongoing feasibility study conducted by NCC in Myanmar for the establishment of the first 500 kV substation in the area. The impact of variations in ground grid resistance and key safety parameters, influenced by changes in ground grid mesh shape, depth, and size, is thoroughly explained using results derived from various scenarios.

Single‐Phase Ground Fault Current Mitigation in Distribution Network Considering the Influence of Grounding Grid Resistance

Single‐Phase Ground Fault Current Mitigation in Distribution Network Considering the Influence of Grounding Grid Resistance

Parallelizing the Computation of Grid Resistance to Measure the Strength of Skyline Tuples

Several indicators have been recently proposed for the measurement of various characteristics of the tuples of a dataset—particularly the so-called skyline tuples, i.e., those that are not dominated by other tuples. Numeric indicators are very important as they may, e.g., provide an additional criterion to be used to rank skyline tuples and focus on a subset thereof. We focus on an indicator of robustness that may be measured for any skyline tuple t: the grid resistance, i.e., how large-value perturbations can be tolerated for t to remain non-dominated (and thus in the skyline). The computation of this indicator typically involves one or more rounds of computation of the skyline itself or, at least, of dominance relationships. Building on recent advances in partitioning strategies allowing the parallel computation of skylines, we discuss how these strategies can be adapted to the computation of the indicator.

TOPCon Solar Cells With Al-Free Ag and Cu Metallization

This work presents an approach to lower the silver consumption of screen printed TOPCon (Tunnel Oxide Passivated Contact) solar cells by reducing and partially replacing the silver by low cost copper metallization paste. On the solar cells front side an adapted process sequence enables the use of a pure Ag paste, which compared to the industrially established AgAl paste offers a better conductivity and respectively requires less laydown to enable similarly low grid resistance. On the solar cells rear side the conductivity of the metal grid is accomplished by a copper paste which is realized within a print-on-print step on top of the Ag contact layer with minimized laydown. A reduction in Ag paste consumption by 40% to less than 9 mg/ Wp without sacrificing conversion efficiency seems achievable and can enable a significant cost reduction for TOPCon solar cells.

Transmission line earthing system; Advanced design diagram for safety compliance

An electrical high-voltage power system is essential to support everyday electrical demands. Due to the increase in electrical loads, a more rigid design is required to ensure system compliance with standards and policies. High-voltage safety is the number one priority when it comes to the design, installation, commissioning, and operation of the electrical power system network. Safety compliance is getting more complex due to the joining infrastructure between residential and high-voltage projects. Nowadays, high-voltage infrastructure, including substations and transmission lines, is constructed near residential properties. This neighboring setup increased the safety concerns of high voltage systems, especially under fault or system malfunction situations. Safety concerns are addressed during the design stage and verified during the commissioning stages.The paper discusses the minimum transmission line earthing system requirements. This document provides a clear and consistent approach to assess transmission line earthing system design. The work contents comply with current IEEE standards including rigid author research outcomes. The works reduce the complexity of the assessment and explain the critical role of different sectors within the transmission line network. The work introduces the boundaries when the fault current analysis should include the earth grid resistance. A case study is also included.

Study on ice resistance of Antarctic krill ship with trawl under floating ice sea conditions

IntroductionThis study focused on a Chinese Antarctic krill vessel utilising continuous pumping fishing technology. The resistance characteristics of Antarctic krill ships trawling in floating ice areas is of great significance for the navigation and fishing of krill ships in ice areas.MethodsFirstly, MATLAB programming using discrete elements combined with genetic algorithms was used to construct a normal distribution ice flow model. Secondly, a fluid-structure coupling interface is created through the contact between the fluid and the trawl grid, and the displacement and resistance of the trawl grid are evaluated on the shared interface. Finally, the effects of ice density and ship sailing speed on ice resistance were studied.Results and discussionThe results of the calculations results show that ice resistance is positively related to the concentration and speed of floating ice, moreover, there is a special speed point where ice resistance increases rapidly. As the speed increases, the proportion of trawl resistance to the total resistance continues to increase, while the proportion of ice resistance continues to decrease. This paper provides a reference for the navigation and fishing resistance assessment of Antarctic krill ships in floating ice areas.

A Series Impedance Reshaping Control Method Considering PLL Dynamics for Grid-Connected Inverters Under Weak Grid Conditions

Grid-connected inverters are the key part in renewable energy power generation systems. Usually, phase-locked loop (PLL) is adopted in grid-connected inverters to achieve synchronization. However, prior-art works have revealed that the negative resistance behavior in the low-frequency band caused by PLLs may lead to system instability under weak grids. In this paper, first, a comprehensive small-signal output impedance modeling of the LCL-filtered single-phase grid-connected inverter is derived for stability analysis, where the digital control delays and PLL dynamics have been taken into account. Then, a simple but effective virtual series based impedance reshaping method is proposed. With that, the inverter system can operate stably even under a very weak grid (e.g., short-circuit ratio (SCR) is as low as 1.2). Compared with the traditional grid impedance compensation by virtually increasing grid resistance or reducing the grid inductance, the proposed method does not require grid impedance estimation and is robust against system parameter variations. Thus, its feasibility is improved. Finally, experimental tests are carried out on a single-phase 5-kW prototype, validating the effectiveness of the proposed scheme.

Communication—Improving Corrosion Resistance of Lead-Alloy Positive Grid of Lead-Acid Battery by an Electrochemical Prepassivation Interphase

Lead-acid battery (LAB) has a huge world market in both energy storage and power supply. However, most LAB failures are caused by the serious corrosion of positive grids. To this, we propose an electrochemical prepassivation strategy to form a compact interphase on the lead-alloy grid surface composed of lead oxides and lead sulfate, exactly the same as lead paste. The results show that the corrosion resistance of pre-passivated lead alloy is improved due to the inhibition of vertical growth of corrosion layer, providing a feasible solution to prolong the service life of LAB.

Numerical study of mixing vane spacer grid effect on subchannel mixing in a 5 × 5 rod bundle

Numerical study of mixing vane spacer grid effect on subchannel mixing in a 5 × 5 rod bundle

A comparative numerical evaluation of linear anode arrangements for enhancing above ground storage tank cathodic protection via mesh grid and concentric ring designs

Cathodic protection as a complementary method is one of the most effective ways to prevent corrosion, along with coating and choosing the suitable material. There are different ways to protect the storage tank bottom. Due to the presence of the geo membrane layer and its effective and pivotal role, the use of mixed metal oxide (MMO) anodes is highly recommended. In the current study, the protection process of the above-ground storage tank bottom is simulated using MMO backfilled wire (concentric rings) and ribbon anodes (mesh grid system). In this regard, several parameters must be considered in reaching the protection criteria. The simulation results show that the effect of the limiting oxygen current density, soil resistivity and the anodic current have the greatest role. Anode depth and the spacing between the anodes are also critical factors if they have large values. Due to the importance of the number of conductor bars and feeding cables, two configurations have been presented for ribbon anodes. These configurations have a direct impact on grid resistance, rectifier size, and related costs. Finally, an economic comparison has been made regarding the use of sacrificial and MMO anodes in the form of ribbon next to wire anodes. The results show that, in the use of ribbon anodes, MMO anodes have better performance than magnesium and zinc sacrificial anodes, and the cost required for MMO linear anodes is far lower than the method of sacrificial ribbon anodes. In the present study, the cost of the MMO linear anode system is approximately 20% of zinc and magnesium sacrificial ribbon anode system cost.

TCI Tester: A Chip Tester for Inductive Coupling Wireless Through-Chip Interface

The building block computation system is constructed by stacking various chips three-dimensionally. The stacked chips incorporate the same TCI IP (Through Chip Interface Intellectual Property) but cannot provide identical characteristics, requiring adjustments in power supply and bias voltage. However, providing characteristics measurement hardware for all chips is difficult due to the limitation of chip area or pin numbers. To address this problem, we developed TCI Tester, a small chip to measure electric characteristics by stacking on TCI of every chip. By stacking two TCI Tester chips, it appears that the up-directional data transfer has a stricter condition than down directional one on power supply voltage and operational frequency. Also, the transfer performance is poorer than designed. Similar measurement results are obtained by stacking TCI Tester on other chips with TCI IP. To investigate the reason, we analyzed the power grid resistance of various chips with the TCI IP. Results also showed that the chips with higher resistance have a narrow operational condition and poorer performance. The results suggest that the power grid design is important for keeping the performance through the TCI channel.

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.

A Modified VSG Control Scheme With Virtual Resistance to Enhance Both Small-Signal Stability and Transient Synchronization Stability

The existing studies show that the virtual resistance scheme has positive effects on synchronous resonance (SR) suppression but negative effects on transient synchronization stability of virtual synchronous generator (VSG). To address this contradiction, this article proposes a modified VSG control scheme. The basic idea is that the virtual active power at virtual PCC, instead of real active power, is introduced as the power feedback into the control loop. Then, the effect of virtual resistance on transient stability can be equivalent to that of grid resistance, which improves transient stability. Besides, a proportion integral controller is added at the forward loop to control the real active power to track the power reference. Compared with the existing VSG control methods, the modified VSG control scheme can well solve the conflict caused by virtual resistance between small-signal stability and transient stability. The effectiveness and superiority of the proposed method are verified by CHIL experimental results.

Multilayer co-sintered Pt thin-film strain gauge for high-temperature applications

Multilayer co-sintered Pt thin-film strain gauge for high-temperature applications

Design and Optimization of A 4-bit Absolute-value Detector Using Half Adder and Comparator

In this paper, a design and optimization of a 4-bit absolute value detector is realized by using the CMOS technique, transmission gates, and the traditional comparator, which can compare the two positive input values all expressed in binary form. To optimize the overall performance of the absolute value detector, this paper chooses to minimize the number of transistors and simplifies the circuit through logical analysis. As for calculating the overall delay and energy consumption, critical path identification is also studied and analyzed in this paper. Based on the theory of path effort and path parasitic delay, the grid capacitance and resistance are introduced into the calculation of inverter ratios. To achieve various optimization objectives, this study also combines the grid size and power supply voltage scaling techniques to reduce the delay and energy of the circuit, and finally finds the minimum energy loss at a 1.5x delay. The overall delay and energy can be expressed by the multiple of the unit size inverter of that. As a compromise, a minimum delay of 1.5 times is selected to reduce energy consumption by 39.16 %.

Comparative Analysis of Equal and Unequal Grounding Grid Configurations by Compression Ratio and Least Square Curve Fitting Techniques

The primary aim of the power system grounding is to safeguard the person and satisfying the performance of the power system to maintain reliable operation. With equal conductor spacing grounding grid design, the distribution of the current in the grid is not uniform. Hence, unequal grid conductor span in which grid conductors are concentrated more at the periphery is safer to practice than equal spacing. This paper presents the comparative analysis of two novel techniques that create unequal spacing among the grid conductors: the least-square curve fitting technique and the compression ratio technique with equal grid configuration for both square and rectangular grids. Particle Swarm Optimization (PSO) is adopted for finding out one optimal feasible solution among many feasible solutions of equal grid configuration for both square and rectangular grids. Comparative analysis is also carried out between square and rectangular grids using the least square curve fitting technique as it results in only one unequal grid configuration. Simulation results are obtained by the MATLAB software developed. Percentage of improvement in ground potential rise, step voltage, touch voltage, and grid resistance with variation in compression ratios are plotted.

Impact of the contacting scheme on I-V measurements of metallization-free silicon heterojunction solar cells

I‑V measurements are sensitive to the number and positioning of current and voltage sensing contacts. For busbarless solar cells, measurement setups have been developed using current collection wires and separate voltage sense contacts. Placing the latter at a defined position enables a grid resistance neglecting measurement and thus I‑V characteristics independent from the contacting system. This technique has been developed for solar cells having a finger grid and good conductivity in the direction of the fingers. The optimal position of the sense contact in case of finger-free silicon heterojunction solar cells has not yet been studied. Here, the lateral charge carrier transport occurs in a transparent conductive oxide layer resulting in a higher lateral resistance. We perform finite difference method simulations of HJT solar cells without front metallization to investigate the impact of high lateral resistances on the I-V measurement of solar cells. We show the high sensitivity on the number of used wires for contacting as well as the position of the sense contact for the voltage measurement. Using the simulations, we are able to explain the high difference of up to 7.5% in fill factor measurements of metal free solar cells with varying TCO sheet resistances between two measurement systems using different contacting setups. We propose a method to compensate for the contacting system to achieve a grid-resistance neglecting measurement with both systems allowing a reduction of the FF difference to below 1.5%.

An optimal design for grounding grid configuration with unequal conductor spacing

An optimal design for grounding grid configuration with unequal conductor spacing

Experimental Study on the Blast Resistance Performance of FRP Grid & Mortar Reinforced Concrete Arch Structure.

In order to verify the feasibility of using FRP grid and mortar reinforcement technology to enhance the blast resistance of concrete arch structures, this paper designed and fabricated FRP grid and mortar reinforced concrete arch structures and conducted blast resistance tests in the field. A detailed design of anti-explosion scheme was carried out before the experiment. The tests were conducted to observe the structural cracking, concrete collapse, and reinforcement peeling of FRP grid and mortar reinforced concrete arch under the explosion. In order to compare the anti-explosion performance with the protective arch structures in other literature, the explosion of 2 kg TNT with a blast distance of 600 mm was selected. After the explosion, it was found that the blast resistance of the FRP grid and mortar reinforced concrete arch was significantly higher than that of the unreinforced arch, and the concrete arch reinforced with FRP grid and mortar has a better damage patterns and improved blast resistance performance than that of the FRP and steel plate reinforced arch. According to the research results, the FRP grid and mortar composite reinforcement technology can be used to enhance the blast resistance of arch structures in protection projects.

New Framework of RoCoF-FD for Wideband Stability Evaluation in Renewable Energy Generators With Virtual Impedance Control

This research proposes a new perspective for identification of wideband stability in virtual synchronous generator (VSG) with virtual impedance control strategy. At first, the drawback of magnitude-phase-motion-equation (MPME) of grid-forming VSG system is briefly discussed. Then, based on the derived MPME model, a RoCoF-FD framework, which includes two most important indices of frequency performance, e.g., rate of change of frequency (RoCoF) and frequency nadir/deviation (FN/FD), is established to illustrate the interaction between RoCoF and FD based on feedback effect. Moreover, the vector analysis can quantitatively sketch the dynamics of RoCoF impacted by the FD via the loop of feedback effect. In addition, the secure operation regions are defined for the VSG system. It is found that system has a higher risk of oscillation instability when ratio of grid resistance divided by grid inductance gets smaller. However, greater ratio will lessen grid strength/stiffness, which will trigger aperiodic loss of synchronization. To cope with such issues, an adjustable-parameter virtual impedance control strategy (APVICS), based on principle of energy conservation, is proposed to dampen oscillation as well as avoid loss of synchronization of the system, thereby enhance damping behaviors and grid stiffness. Finally, theoretical analysis is validated experimentally.