Neutral Resistance Research Articles

Synthesis of a waterborne epoxy curing agent based on polyether triols and its application in 2K waterborne epoxy coatings

AbstractPolyether polyols can improve the performance of waterborne epoxy curing agent. In this paper, intermediates were synthesized from polyether triols with epoxy resin E‐51 and introduced into the epoxy curing agent by reacting with TETA. This paper focuses on the process of synthesizing the intermediates. The 2K waterborne epoxy coating film prepared with polyether triols‐modified waterborne epoxy curing agent exhibits desirable corrosion protection capacity and neutral salt spray resistance up to 600 h. In addition, the 2K waterborne epoxy coating film prepared using the modified waterborne epoxy curing agent with polyether triols displayed improved surface appearance, mechanical properties, and water resistance.

Analysis of Calculation of Artificial Neutral Point Resistance for Open-circuit Testing

This article focuses on the artificial neutral point device with ZN connection (ZN type connection refers to the way that the primary winding adopts a zigzag connection and the neutral point is led out). In the process of breaking test, the arc energy is an important criterion. For three-phase four-wire transformers, the test loop can be built by connecting the N-pole with a pure resistance. However, for three-phase transformers, the loop needs to be built through the artificial neutral point. By analyzing the calculation and actual test data, the calculation method for the artificial neutral point resistance used in the experiment is clarified. It is confirmed that the resistance of the artificial neutral point will not change with the change of input voltage, making the calculation of expected fault current more accurate in daily use.

Fabrication and electrochemical properties of bonded NdFeB magnetic rings coated with double layer epoxy resin coating

On bonded NdFeB magnetic rings (B/NdFeB), a double-layer epoxy resin (DL-EP) coating was created using rolling spraying and cathode electrophoretic deposition techniques. The corrosion behaviors of the B/NdFeB and coated samples were examined using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), high pressure accelerated aging test (PCT), and neutral salt spray resistance test (NSS). The DL-EP coating significantly improved the corrosion resistance of B/NdFeB, as evidenced by the comparison of corrosion current density (Jcorr), PCT time, and NSS time.

Very Small Power Plant Transformer without and with Installation of Neutral Ground Resistance on Relay Operation

Very Small Power Plant Transformer without and with Installation of Neutral Ground Resistance on Relay Operation

Lubrication, wear resistance and corrosion protection on aluminum alloy toward multifunctional coatings with nano-CeO2 inhibition effect

The coupling effect of wear and corrosion aggravates the damage and failure of key moving parts of high-end equipment, leading to a significant reduction in their service life. In present work, a functional integrated composite coating with exceptional corrosion resistance and tribological properties was developed by utilizing the responsive corrosion inhibition of nano‑cerium oxide (nano-CeO2) and the low surface energy and low shear characteristics of polytetrafluoroethylene (PTFE). The tribological behaviors and corrosion protection performance of coatings on aluminum alloy 2024 were evaluated and the corrosion inhibition mechanism was further discussed. The results revealed that Ce3+ on the surface of nano-CeO2 reacts with OH− generated by the REDOX reaction of the cathode to produce a uniform and stable passivation film, which can effectively improve the corrosion resistance of the metal matrix. Notably, the most obvious passivation effect is presented when the 2 % addition of nano-CeO2 as the larger low-frequency impedance modulus of 4.49 × 1010 Ω·cm2 and higher phase angle of 88°. The introduction of PTFE not only changes the coating from hydrophilic to hydrophobic, but also further improves the shielding properties of the coating. The low-frequency impedance modulus of the coating further increases by an order of magnitude to 2.38 × 1011 Ω·cm2, and its neutral salt spray resistance exceeds 210 days. Besides, the friction coefficient is reduced by 77.43 % and the wear resistance improved by 6.8 times compared with phenolic epoxy coating. Due to the enhancement and corrosion inhibition effect of nano-CeO2, the lower friction coefficient (0.044) and good wear resistance are further presented under the corrosive medium condition of 3.5 % NaCl solution.

Щит заземления нейтрали электроэнергетической системы 10,5 кВ ледокола «Арктика»

Object and purpose of research. This paper discusses neutral grounding switchboard of electric power system aboard Arktika icebreaker and estimates fault current for given neutral resistance. Materials and methods. The paper relies on the technical specifications of neutral grounding switchboard and follows common methods of electric engineering. Main results. Fault current estimates for neutral grounding switchboard of TPS-36-2M2 synchronous turbogenset. Design of the switchboard. Conclusion. Electric power system aboard Arktika icebreaker has neutral resistance rating of 600 Ohm, which corresponds to High-Resistance Grounding class. Neutral grounding switchboard discussed in this paper has been in operation since 2020.

Analisis Sistem Pentanahan Gedung Pascasarjana Menggunakan Metoda Tiga Titik di Universitas Lancang Kuning

The grounding system is a way to channel the electric current that occurs due to a lightning strike on an object in the building there is an electrical system used for electrical and electronic equipment. The grounding system is used to secure buildings from fire hazards due to lightning strikes, secure electrical and electronic equipment and humans connected by wires or conducting cables to electrodes that are installed in the ground. The research method analyzes data from the data obtained to obtain large values of grounding resistance, short fault current, healthy phase increase and touch voltage and step voltage in the Unilak Postgraduate building. The purpose of this study is to analyze the value of the resistance of the grounding system, analyze the short-circuit fault current that occurs in the grounding system, analyze the phase voltage increase, and analyze the touch voltage and step voltage in the Lancang Kuning University Postgraduate building. By using the three-point research method, the calculation results on the grounding of the Postgraduate Building are 28 ohms, the neutral point resistance value is 0.00465 ohms, the touch voltage is 149.5 volts, the step voltage is 208 volts, the short circuit fault current calculation is 1, 15 amperes, while the healthy phase voltage increase is 308 volts.

A Faulty Line Selection Method for Flexible Grounding System Based on Transient Fault Data

In view of the problem of high-impedance grounding faults (HIFs) in flexible grounding systems (FGS), a faulty line selection method based on transient waveform slope is proposed in this paper. The change of zero sequence (ZS) current of faulty line and non-faulty line (before and after the neutral point parallel small resistance are put in) are analyzed. After the parallel small resistance is put into operation, the waveform slope curve of the transient zero sequence current of each line is obtained, and the modified Hausdorff distance (MHD) algorithm is used to obtain the transient slope matrix. The faulty line is identified by comparing the sizes of each row of elements in the matrix. Simulation verifies the effectiveness of the proposed faulty line selection method.

A New Model for Correcting and Improving the Sequence Networks Method of Single-Phase Earth Fault to Accommodate All Resistance Grounding Systems

The method of sequence networks is still well-known and widely utilized for analyzing and computing unsymmetrical faults in power system networks today, particularly in solid grounding systems where it was initially introduced for short circuit analysis. When it comes to single-phase earth fault that is a dominant majority type of fault in power distribution grids, different neutral grounding methods with varied impedances result in distinct fault characteristics, to continue utilizing sequence networks could cause inaccurate calculations by the reason of neutral voltage during earth fault does not remain as close to zero as it’s pinned in solid grounding system. As neutral resistance increases gradually, the impact of line-to-ground capacitance becomes more pronounced and can no longer be ignored. In this case, applying sequence networks could lead to calculated results that are far from the actual situations in grids. This paper discovers and proves an obscurely hidden defect of the sequence network, while proposing a new and novel modeling to derive comprehensive equations of fault calculations for all types of resistant grounding systems, including solid grounding, low resistance grounding, high resistance grounding, and ungrounded systems.

Performance of Neutral Grounding Resistance and Solid Grounding on 60 MVA Power Transformer

This research will look at the protection system on a 60 MVA power transformer and compare two grounding systems, namely grounding with Neutral Grounding Resistance (NGR) and Grounding Solid (GS). The performance of the two systems will be seen, which is the most effective and efficient. Soil resistance is directly related to water content and temperature; thus, it can be assumed that the resistance of a grounding system will change according to climate change. To obtain a stable grounding resistance, the grounding electrode is installed at the optimal depth to achieve a constant level of water content. The study began by collecting data and then comparing grounding using NGR with GS and measuring the resistance values ​​of NGR and GS on a 60 MVA Power Transformer. The results of this comparison will obtain data on the NGR and GS resistance values ​​on the 60 MVA power transformer, then analyze and compare these values ​​which will provide a conclusion which of the two systems has the best value for grounding.

Fungicide Resistance and Host Influence on Population Structure in Botrytis spp. from Specialty Crops in California.

Botrytis is an important genus of plant pathogens causing pre- and postharvest disease on diverse crops worldwide. This study evaluated Botrytis isolates collected from strawberry, blueberry, and table grape berries in California. Isolates were evaluated for resistance to eight different fungicides, and 60 amplicon markers were sequenced (neutral, species identification, and fungicide resistance associated) distributed across 15 of the 18 B. cinerea chromosomes. Fungicide resistance was common among the populations, with resistance to pyraclostrobin and boscalid being most frequent. Isolates from blueberry had resistance to the least number of fungicides, whereas isolates from strawberry had resistance to the highest number. Host and fungicide resistance-specific population structure explained 12 and 7 to 26%, respectively, of the population variability observed. Fungicide resistance was the major driver for population structure, with select fungicides explaining up to 26% and multiple fungicide resistance explaining 17% of the variability observed. Shared and unique significant single-nucleotide polymorphisms (SNPs) associated with host and fungicide (fluopyram, thiabendazole, pyraclostrobin, and fenhexamid) resistance-associated population structures were identified. Although overlap between host and fungicide resistance SNPs were detected, unique SNPs suggest that both host and fungicide resistance play an important role in Botrytis population structure.

Development of Waterborne Heavy-Duty Anticorrosive Coatings with Modified Nanoscale Titania

The steel structures of coastal engineering in the moist tropics and subtropics are always under a C5/CX level corrosion environment with high temperature, high humidity, and high salt fog. Anticorrosive waterborne coatings with high weatherability and reliability are urgently to be developed. In this work, one kind of waterborne heavy-duty anticorrosive coatings, with the advantages of excellent corrosion resistance, self-repairing ability, self-cleaning ability, and high film compactness, was successfully achieved through modifying the side chains on the surface morphologies of the spherical nanoscale titania. The micromorphology and structure of the coating were characterized by a scanning electron microscope (SEM), transmission electron microscope (TEM), and atomic force microscope (AFM). The anticorrosion characteristics and forming mechanism of the modified nanoscale titania coating were analyzed. The salt spray tests showed that the neutral salt spray resistance time of the modified nanoscale titania coating was 1440 h. Its durability reached the H level and met the design requirements for 15 years of anticorrosion lifetime. The modified nanoscale titania coatings had been large-scale commercially applied at some typical steel structures under an extreme harsh corrosion environment in one coastal thermal power plant. The results showed that no rusting, peeling, or crack phenomena were observed after 3 years of service under different harsh coastal corrosion conditions.

Pilot Protection Based on Zero-Sequence Current Resistance-Capacitance Component for Large-Scale Inverter-Interfaced Power Stations

At present, zero-sequence current protection is generally used as the main protection for single-phase ground faults in resistance-grounded inverter power stations. However, limited by the principle, it is difficult for current protection to take into account selectivity and rapid action when the neutral point resistance is large, so there is protection mismatch with the inverter-type power supply for low voltage ride through leads to the risk of large-scale disconnection of non-fault lines. Aiming at the above problems, firstly, a fault analysis model of the inverter power station considering the capacitance to ground is established to study the distribution characteristics of resistive and capacitive zero-sequence currents in the collection system, when single-phase ground short circuit occurs on different types of lines. Then, based on the characteristic difference between the resistance and capacitance components of the zero-sequence current flowing through the two ends of the tie line in case of internal and external faults, a zero-sequence pilot protection algorithm is formed. Compared with the traditional zero-sequence current differential protection, the proposed protection algorithm only transmits logic information without synchronous sampling, and has significant economy. Finally, the feasibility and effectiveness of the proposed protection algorithm are verified by an engineering simulation example.

Preparation and Properties of Three-dimensional Graphene-based Multifunctional Thermal Control Coating

According to the requirements of spacecraft light alloy materials for thermal control, anti-static and corrosion protection, based on the synthesized three-dimensional graphene functional filler, a multifunctional thermal control coating with high emissivity, anti-static and anti-corrosion properties was prepared on magnesium alloy materials. By testing the coating properties, the hemispherical emissivity was 0.91,volume resistivity was 104Ωm and neutral salt spray corrosion resistance was more than 800 hours.

Preparation and Properties of Three-dimensional Graphene-based Multifunctional Thermal Control Coating

According to the requirements of spacecraft light alloy materials for thermal control, anti-static and corrosion protection, based on the synthesized three-dimensional graphene functional filler, a multifunctional thermal control coating with high emissivity, anti-static and anti-corrosion properties was prepared on magnesium alloy materials. By testing the coating properties, the hemispherical emissivity was 0.91,volume resistivity was 104Ωm and neutral salt spray corrosion resistance was more than 800 hours.

Performance of Restricted Fault and Bias Differential Protection Against Earth Fault on a Transformer

In this paper, the effectiveness of restricted earth fault and bias differential protection against earth fault on of transformer winding is presented. Earth fault is one of the failures that occurs on a power transformer winding. Its magnitude depends on how the neutral is connected and the location of fault. For a transformer which is connected to Neutral Earth Resistance (NER), as the fault moves towards its neutral, the magnitude of fault current decreases and the detection of fault diminishes, thus limiting percentage of winding that can be protected. To overcome this problem, restricted earth fault is employed. This paper will show that based on its principles, restricted earth fault protection is more sensitive and provide better coverage for the star winding against earth fault especially resistance earthed.

PENGARUH BESARAN HAMBATAN PEMBUMIAN TITIK NETRAL TERHADAP THD DI GEDUNG KAMPUS

The quality of electric power is influenced by harmonic factors that occur due to animbalance in the load on the power system. This load imbalance results in a current at theneutral point. This amount of current can cause equipment damage and loss of electrical power.Therefore, an earthing system is needed to parse the current flowing at the neutral point and asa safety for the electric power system in a building. The objective of this research was to specifythe impact of the grounding resistance value of the neutral point on the current THD on theMDP installed during peak load conditions at the Electrical Engineering Campus of UdayanaUniversity in Jimbaran. This research method uses simulation with Simulink Matlab software todetermine the effect of neutral point grounding resistance on current THD in areas withcalcareous soils. The simulation outputs indicate that the value of the earth resistance affectsthe THDi value in the electrical system. The simulation outcomes represent that when the earthresistance value is 5 , the THD of the R, S, and T phase currents is feasible at 17.55%, 19.42%, and 8.86%. Then when the resistance value is lowered by 0.5, the THD of the R, S, T phasecurrents is feasible 17.20%, 17.35%, and 8.79%. This shows that more slight the earthresistance number, the smaller the current THD value.

Effect of Titanium Addition on the Neutral Corrosion Resistance of Welding Overlay

Effect of Titanium Addition on the Neutral Corrosion Resistance of Welding Overlay

M-N interaction curves for rectangular concrete-filled steel tube columns subjected to uniaxial bending moments

abstract: In this paper, a computational code was developed to obtain M-N interaction curves for rectangular concrete-filled steel tube columns considering the strain compatibility in the cross-section. Considering the composite section subjected to uniaxial bending moments, expressions were developed to determine normal force, moment resistance, neutral axis depth and components resistance of cross-section. Such expressions were implemented in a computational tool developed to the authors and that allows to obtain the M-N pairs of strength. The steel and concrete ultimate strains were defined with the aid of the Brazilian standard for reinforced concrete structures ABNT NBR 6118. The obtained results were compared to simplified curves defined according to the theoretical models of ABNT NBR 8800, ABNT NBR 16239, EN 1994-1-1 and literature data. The proposed model showed good agreement with literature results and had good precision to estimate the ultimate moment values. To further understand the resistance of composite columns under uniaxial bending moments, parametric study was performed to evaluate the influence of the compressive strength of concrete, yielding strength of steel and steel area ratio on M-N interaction curves. The results indicate that the yielding strength of steel and the steel area ratio were the variables that most influenced the values of composite columns resistance (normal force and bending moment).

Method of Locating Ground Fault in Low Resistance Grounding Distribution Network by Grounding Wire Current

Three-core cables are increasingly used in urban distribution networks. The shielding layer, armor layer of the three-core cable and the earthing electrode constitute the earth-electrode network. When a ground fault occurs, a regular ground wire current distribution is formed in the network. This paper analyzes the distribution law of ground current, and according to the distribution law, puts forward a kind of grounding fault location method of neutral point small resistance grounding grid, and finally designs and implements the grounding fault location system.