Short-circuit Studies Research Articles

Study of double short circuits on earth in 10 kV power grids with isolated neutral and with high level penetration RES

Study of double short circuits on earth in 10 kV power grids with isolated neutral and with high level penetration RES

Study on the thermal runaway behavior and mechanism of 18650 lithium-ion battery induced by external short circuit

This study investigated the external short circuit (ESC) characteristics of 18650-type NCM lithium-ion batteries under different states of charge (SOC) and short-circuit currents. The research includes the macroscopic electro-thermal characteristics, microscopic morphology, structural damage, and internal damage evolution mechanism of short-circuited batteries. The tests provided an in-depth study of external short circuit (ESC) failure and thermal runaway (TR) behavioral characteristics. The results indicate that all the temperature changes of the short-circuit batteries were found to be in an upward and then downward trend. The surface temperature rise rate of batteries with low SOC were faster, and the maximum surface temperature rise of batteries with high SOC were higher. And with the increase of short-circuit current rate, the temperature rise gradually increased. In particular, thermal runaway occurred at 25C and the maximum temperature exceeds 500 °C. Different SOC batteries showed different degree of voltage fluctuation. The voltage curve of low SOC batteries showed “falling-rising-falling” trend with a brief platform. High SOC batteries formed a distinct voltage platform near 2.75 V. As the short-circuit current increased, the voltage platform shortened, followed by the rapid drop to zero. X-ray CT and SEM test results showed that the deformation of the battery jelly roll was mainly due to the separator shrinkage and tearing. Major changes occurred in the cathode and separator, including secondary particle rupture and irreversible pore blockage in the separator. The damage mechanism of ESC and its evolution are revealed. The results of this study can provide support for the research work on the thermal safety design of lithium batteries.

Novel estimation framework for short-circuit current contribution of type IV wind turbines at transient and steady-state of the faults

Given the increasing penetration of converter-interfaced resources in power systems, properly estimating the short-circuit current (SCC) contribution in large networks has become a growing challenge and necessity to ensure the security and stability of the systems and assets. This paper presents two novel methods to estimate the SCC contribution of type IV wind turbines at both the transient and steady-state stages of unbalanced and balanced faults: (1) a machine learning-based method trained with electromagnetic transient (EMT) simulations and capable of estimating some of the initial peak and transient current magnitudes; (2) an analytical approach to estimate the steady-state SCC based on the voltage and grid code dependency of the converter during the fault. The methods are coupled into a single framework and compared to field-validated EMT models of a real turbine. The results show that the majority of the estimated currents in the transient stages present errors below 5%. In steady-state, the errors are not greater than 1.21%. Given the complexity of the problem, these margins may be deemed acceptable for short-circuit studies.

Comparative Study of Short Circuits and Demagnetization in Delta, Star, and Hybrid Winding Connections for Surface-Mounted Permanent Magnet Machines

Comparative Study of Short Circuits and Demagnetization in Delta, Star, and Hybrid Winding Connections for Surface-Mounted Permanent Magnet Machines

Characteristics of symmetrical components for high impedance faults in distribution networks with photovoltaic inverters

This work models a photovoltaic (PV) inverter connected to an IEC microgrid system. The purpose of this study was to find the characteristics of symmetrical components before and after a high impedance single phase short-circuit fault. The IEC microgrid system is tailored to the distribution system in Indonesia, where the applied voltage is 20 kV. Only parameters related to the short-circuit study are included in the model. A second-order generalized integrator frequency-locked-loop is utilized to represent the 3-phase PV inverter. The inverter model, previously treated as an ideal current source, and positive sequence current are no longer employed, as they fail to depict the characteristics of symmetric components during a phase-to-ground short-circuit fault. The IEC microgrid system connected to the PV inverter is simulated using ATPDraw-electro magnetic transient program (EMTP). Simulation results reveal that the changes in the symmetric component values of current after a fault experience a very insignificant increase. Meanwhile, the positive sequence voltage values following the short-circuit fault exhibit a negligible decrease. In contrast, the negative sequence and zero sequence voltage components after the short-circuit fault undergo a significant increase.

Load flow, short circuit and motor starting studies in electrical power substations

Load flow, short circuit and motor starting studies in electrical power substations

Phasor and EMT models of grid-following and grid-forming converters for short-circuit simulations

Phasor models have been widely used in short-circuit simulations, in which system operators verify the behaviour of the grid over thousands of different contingencies. However, it is still unclear if phasor models can still be used in fault studies in modern or future power grids dominated by renewable generation with power electronics and converters. Therefore, this paper analyses the suitability of phasor models to simulate short-circuit transients in grids with grid-following (GFL) and grid-forming (GFM) voltage-source converters (VSC). Phasor models of GFL and GFM were developed and tested in two test systems, one with 50% of converters in the generation mix and another powered 100% by converters. Asymmetrical and symmetrical faults were applied at different points of the systems and key variables were used to compare the phasor models against EMT models during the transients. The results showed that, despite neglecting transients in the grid, phasor models could be used in a preliminary stage of short-circuit studies as it was capable of tracking the steady-state value of almost all variables analysed. In this case, detailed EMT simulations, although necessary, would be used only at more advanced stages of the studies.

Development and validation of a real-time testbed for renewable energy integration studies: South African grid code case study

Purpose Despite South Africa’s ailing electrical grid, substantial renewable energy (RE) integration is planned for the country. As grid-integrated RE affects all grids differently, this study aims to develop an adaptable grid code-guided renewable power plant (RPP) control real-time simulation testbed, tailored to South African grid code requirements to study grid-integrated RE’s behaviour concerning South Africa’s unique conditions. Design/methodology/approach The testbed is designed using MATLAB’s Simulink and live script environments, to create an adaptable model where grid, RPP and RPP guiding grid codes are tailorable. This model is integrated with OPAL-RT’s RT-LAB and brought to real-time simulation using OPAL-RT’s OP4510 simulator. Voltage, frequency and short-circuit event case studies are performed through which the testbed’s abilities and performance are assessed. Findings Case study results show the following. The testbed accurately represents grid code voltage and frequency requirements. RPP point of connection (POC) conditions are consistently recognized and tracked, according to which the testbed then operates simulated RPPs, validating its design. Short-circuit event simulations show the simulated wind farm supports POC conditions relative to short-circuit intensity by curtailing active power in favour of reactive power, in line with local grid code requirements. Originality/value To the best of the authors’ knowledge, this is the first design of an adaptable grid code-guided RPP control testbed, tailored to South African grid code requirements in line with which RPP behavioural and grid integration studies can be performed.

Study of Short Circuit and Inrush Current Impact on the Current-Limiting Reactor Operation in an Industrial Grid

Current-limiting reactors are widely used in industrial electrical grids to reduce the current amplitude in the equipment and stabilize the voltage on the busbar during short circuits. Their application is distinguished by high technical and economic efficiency. However, mechanical damage to the reactors has been observed within extensive industrial grids with many induction motors and internal synchronous generators. The article analyses a case study of the reactor damage in the true industrial grid during a short circuit. An analysis of the damaged reactor’s previous operation had shown that there was a weakening of the fastenings in the reactor design, caused by the repeated starting currents of the grid motors and generators. A study of grid transients during short circuits was carried out by Matlab/Simulink software. The simulation results showed that the reactor could be damaged by a critical peak current in an unfavourable combination of the grid configuration and the short circuit location. The results of the study prove that, for industrial networks containing powerful induction motors and internal synchronous generators, the standardized procedure for selecting current-limiting reactors should additionally consider such factors as the localization in the grid, the effect of equipment-starting currents and possible grid configurations.

Simplified Inverter-Based Generation Model for Protection and Short-Term Stability Studies in Electromagnetic Transient Resolution

The new dynamics of inverter-based generation (IBG) and the lack of accurate models jeopardize the safety of power systems. Additionally, most of the detailed models for electromagnetic transients (EMT) from manufacturers are black boxes. For this reason, the objective of this work was to propose a generic IBG model in EMT resolution suitable for short-circuit, protections, and short-term voltage stability studies. For this purpose, the model considered different functionalities, such as synchronization in case of unbalanced voltage sags, flexible negative sequence current injection, peak current limitation, dynamic reactive power control, and fault ride-through (FRT). This model allowed grid operators to meet the challenge of performing accurate simulations with high integration of renewable resources in their energy matrix. The model was also based on a voltage-controlled current source in the ATP/EMTP software. The short-circuit response was evaluated in a simulation scenario for different fault events presenting a reliable behavior due to the consideration of technical and regulatory requirements and constraints of IBGs. Finally, the proposed model has a fast initialization and is suitable for simulations with large time steps, making it valuable for EMT simulations in large grids.

Optimal adaptive protection of smart grids using high‐set relays and smart selection of relay tripping characteristics considering different network configurations and operation modes

Much attention has been paid to optimizing smart grids (SGs) and microgrids (MGs) protection schemes. The SGs’ operation in different operating modes (especially grid-connected and islanded conditions) and various system configurations (such as the outage of each of the distribution generations) adversely influence the protection system. The adaptive protection schemes using different setting groups are suitable and reliable solutions to achieve a fast protective system. However, the literature shows a research gap in developing optimized adaptive protection schemes, focusing on constraint reduction, besides the optimal selection of time-current characteristics for direction overcurrent relays (DOCRs) and high-set relays (HSRs). This research aims to fill such a research gap. The power system analyses, such as power flow and short circuit studies, are done in DIgSILENT, and the genetic algorithm (GA) is used to find the optimum solutions. Test results of the IEEE 38-bus distribution system illustrate the advantages of this study compared to existing ones. The comparative test results emphasize that 31.78% and 21.62% decrement in time of the protective scheme in different topologies for the distribution networks of the IEEE 38-bus and IEEE 14-bus test systems could be achievable by simultaneously optimizing relay characteristics and HSRs compared to existing approaches.

Short Circuit Modelling and Analysis of PV Inverters in Large Solar Farms

The short circuit behavior of solar farms are different from conventional generating stations. These generating resources arestatic in nature and have a rich power electronic interface with a grid, limiting these solar farms’ short circuit capabilities.The solar inverter voltage versus short circuit current characteristics is modeled to supply the fault current within inverterdesigned ratings. In this research paper, a large number of solar power investors are grouped to pool their power into thegrid. Short circuit studies are carried out for a 500 MW solar farm with string inverters rating of 3125 kW per IEC 60909.The protective relaying coordination is performed as per IEEE C37.90 and IEC 60255-1 relaying standard.

A Resilience-Oriented Methodology for Transformation of the Distribution Networks into MicroGrid

Transformation of the distribution network, integrated with Distributed Energy Resources (DER), into a MicroGrid (MG) is an attractive approach in improving the reliability and resilience of the network. In this paper, by introducing the important and necessary aspects of the MG formation problem, an effective methodology for transformation of a distribution network into the MG is proposed. In the presented methodology, optimal allocation of DERs within MG is obtained by optimization of power losses and voltage stabilization along feeders. Moreover, the short-circuit constraints are also taken into account simultaneously while allocating DERs. The reason for the latter is that the integration of DERs alters the amplitude and direction of the short circuit current, which can cause the overall fault current to exceed the designed fault-level capability of the circuit breakers. This issue may put CBs at risk of failure and degrading MG resilience. In this regard, resilience-oriented evaluation of the MG formation, from the perspective of considering short circuit level and coordination of OCRs, is also performed. Another advantage of short circuit studies is devising complete and economic overcurrent-based protection plan for MG in both operating modes (grid-connected and islanded). It should be pointed out that adopting an appropriate control routine is a key element in the MG formation. Hence, a control strategy, based on Energy Storage System (ESS) utilization, is suggested in this paper. This feature, which is another contribution of the paper, will guarantee seamless transition to island mode and stable operation of the MG. The proposed formulation of the MG formation is solved using a modified multi-objective PSO and the Pareto-optimal set is obtained. However, since the optimal solutions are nondominated to each other, a Fuzzy Satisfaction Method (FSM) is utilized to find the optimal solution among the Pareto-set. Utilization of the proposed methodology leads to the successful transformation of the distribution network into a MG, which not only considers the load flow constraints but also preserves the optimal coordination of the protective relays and resilience of the MG. In addition, seamless transition and stable operation of the MG in island mode is achieved.

Primary Human Nasal Epithelial Cells: Biobanking in the Context of Precision Medicine.

Human nasal epithelial (HNE) cells are easy to collect by simple, non-invasive nasal brushing. Patient-derived primary HNE cells can be amplified and differentiated into a pseudo-stratified epithelium in air-liquid interface conditions to quantify cyclic AMP-mediated Chloride (Cl-) transport as an index of Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) function. If critical steps such as quality of nasal brushing and cell density upon cryopreservation are performed efficiently, HNE cells can be successfully biobanked. Moreover, short-circuit current studies demonstrate that freeze-thawing does not significantly modify HNE cells' electrophysiological properties and response to CFTR modulators. In the culture conditions used in this study, when less than 2 x 106 cells are frozen per cryovial, the failure rate is very high. We recommend freezing at least 3 x 106 cells per cryovial. We show that dual therapies combining a CFTR corrector with a CFTR potentiator have a comparable correction efficacy for CFTR activity in F508del-homozygous HNE cells. Triple therapy VX-445 + VX-661 + VX-770 significantly increased correction of CFTR activity compared to dual therapy VX-809 + VX-770. The measure of CFTR activity in HNE cells is a promising pre-clinical biomarker useful to guide CFTR modulator therapy.

Functional role of histamine receptors in the renal cortical collecting duct cells.

Histamine is an important immunomodulator, as well as a regulator of allergic inflammation, gastric acid secretion, and neurotransmission. Although substantial histamine level has been reported in the kidney, renal pathological and physiological effects of this compound have not been clearly defined. The goal of this study was to provide insight into the role of histamine-related pathways in the kidney, with emphasis on the collecting duct (CD), a distal part of the nephron important for the regulation of blood pressure. We report that all four histamine receptors (HRs) as well as enzymes responsible for histamine metabolism and synthesis are expressed in cultured mouse mpkCCDcl4 cells, and histamine evokes a dose-dependent transient increase in intracellular Ca2+ in these cells. Furthermore, we observed a dose-dependent increase in cAMP in the CD cells in response to histamine. Short-circuit current studies aimed at measuring Na+ reabsorption via ENaC (epithelial Na+ channel) demonstrated inhibition of ENaC-mediated currents by histamine after a 4-h incubation, and single-channel patch-clamp analysis revealed similar ENaC open probability before and after acute histamine application. The long-term (4 h) effect on ENaC was corroborated in immunocytochemistry and qPCR, which showed a decrease in protein and gene expression for αENaC upon histamine treatment. In summary, our data highlight the functional importance of HRs in the CD cells and suggest potential implications of histamine in inflammation-related renal conditions. Further research is required to discern the molecular pathways downstream of HRs and assess the role of specific receptors in renal pathophysiology.

Teaching Short - Circuit Calculation with Off - Nominal Turns Ratio Transformers

Teaching short-circuit analysis is conducted primarily through case studies; however, there are not many validated short-circuit studies available on the subject, especially when considering off-nominal turns ratio transformers. In order to improve the teaching of short-circuit analysis, a three phase short-circuit study in an industrial system according to ANSI/IEEE standards by means of Zmatrix method is presented; two case studies are considered: the industrial system with nominal and offnominal turns ratio transformers, in both cases the step by step solution is given in an explicit manner and the analytical results are validated through software simulation.

Modelling of Electric Grid to Enhance Generated Power Evacuation

The study of evacuation of power from the power plants in Rivers State Nigeria, connecting to the 330kV transmission network of the Transmission Company of Nigeria (TCN). The Power World Simulator Educational version was used in the modelling and simulation of the electric power grid. The study of load flow analysis, short circuit, transient and N-1 contingency analysis and their effect on the 330 kV/132kV transmission bus connected to the existing power plants in Rivers State Nigeria namely; Rivers IPP (180MW), Afam III (265.6MW), Afam IV & V (351.00 MW) and Afam VI G. S (650.00 MW) was carried out. From the short circuit study, it is observed that when a bus is faulted with a 3-phase fault, the three-phase voltages of the system drastically become zero in all the phases. The other buses of the network experience an increase in voltage and all the buses fed have the same effect as the bus under fault, though the effect is felt more on the buses. However, with the introduction of substation splitting at Afam III and ongoing Afam IV substations, the short circuit level will be reduced by 15%; leading to improvement in the overall system stability.

An improved fault current calculation method and protection scheme of Doubly-fed Induction Generator

Existing research on Doubly fed Induction Generator (DFIG) short-circuit current studies are based on hypothesis the rotor current is zero when the Crowbar is input after the fault, which ignores the impact of rotor current attenuation process. It would bring the error to the calculation results. To solve this problem, on the basis of analyzing variation process of DFIG’s transient equivalent potential and the influence of rotor current attenuation process, the flux is calculated accurately. An accurate calculation equivalent model for DFIG short-circuit current is proposed. With the RTDS, an experiment platform with physical controller of converter is founded, the proposed model is validated. The effect of short circuit current to wind farms transmission line is studied, and an improved protection scheme is put forward.

Design of Electrical Setting Protection System Indarung VI Cement Plant (Case Study New Cement Plant Construction at PT Semen Padang)

Along with the rapid development of technology and the development of civilization, electrical energy is very important in all fields. This research will conduct a study on the electrical protection system design of PT Semen Padang's Indarung VI Cement Plant using the ETAP 12.6 software. PT Semen Padang's Indarung VI Cement Plant uses three transformers of 150 / 6.3 kV of 30/35 MVA (ONAN / ONAF) and each Main Substation has substations that will supply all the loads to be used. The power flow study shows that the addition of a capacitor bank and a tap changer setting will improve the power factor and voltage of the system, thereby reducing the power supply sent by PLN. The short circuit study shows that the largest short circuit current, which is 35 kA, can be protected by a circuit breaker with a breaking capacity of 40 kA. The protection system coordination study shows that the results of the overcurrent relay setting can protect the electrical system of Indarung VI Cement Plant selectively and safely.

Short circuit network equivalents of systems with inverter-based resources

Large transmission networks are often represented with short circuit network equivalents to share with neighboring utilities and distribution providers. The computation of network equivalents for short circuit studies is straightforward in systems predominantly based on conventional synchronous generators (SGs). However, the integration of renewable powered plants such as solar and wind parks (WPs) introduces inverter-based resources (IBRs) in the grid with different and nonlinear fault current characteristics. The increasing share of IBRs changes the way power systems respond during disturbances. The application of conventional approach to obtain network equivalents based on the computation of Thevenin equivalent at the point of interest to systems with high share of IBRs will result in misleading short circuit calculations. This paper is the first step in the identification of active nonlinear network equivalents for short circuit studies in systems with IBRs. A new concept of voltage dependent network equivalents (VDNEs) is proposed. Considering the increasing complexity of networks with several and different type of IBR installations, a measurement-based approach using simulated fault currents is proposed to obtain VDNEs. The short-circuit response of VDNEs are validated considering a network with WPs consisting of Type-IV/Full-Size Converter (FSC) wind turbine generators (WTGs).