Short-circuit Position Research Articles

Comprehensive Investigation of Winding Mechanical Properties in Generators under RISC: Impact of Position, Degree, and Eccentricity

This paper provides an in‐depth study of the winding mechanical properties in generators under rotor interturn short circuit (RISC) cases. Unlike previous studies, this research investigates not only the influence of RISC degrees, but also the RISC positions and the eccentricity on the winding mechanical properties. The electromagnetic force (EF) formulas as well as the electromagnetic‐structure coupling model are first proposed to derive the mechanical winding response characteristics, such as the vibration, deformation, the strain, and the stress. Subsequently, both finite element analysis (FEA) and experimental investigations are conducted to validate the theoretical findings. The results reveal that RISC introduces additional harmonics to the EF. Furthermore, as the eccentricity/RISC degree or the distance between the short circuit position and the N‐pole increases, the end winding vibrations become more pronounced. When comparing single eccentricity and RISC faults to cases where both faults occur simultaneously, it is observed that the combined faults have a more detrimental impact on the end winding mechanical properties. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

Fault data generation of lithium ion batteries based on digital twin: A case for internal short circuit

Battery accidents are emerging for various kinds of applications, such as commercial electronics, electric scooters, electric vehicle and energy storage stations. Effective early warning algorithm is essential for mitigating the damage caused by battery failure. An early warning algorithm needs to be trained by failure data. However, building battery failure data (such as internal short circuit) by experiment consumes so much time and cost that it cannot match the development requirement of new product. This work demonstrates the validity of using digital twin technique to generate battery failure data to train the online early warning algorithm. The digital twin is formed by a highly reliable thermal-electrical coupled battery model. The influential factors, e.g., load current, short circuit position, equivalent short resistance and environment temperature, which determine the performance of the early warning algorithm were discussed. The warning threshold that may judge the fault warning rate and response speed of the algorithm was also analyzed. The digital twin helps us find that there is a temperature difference between the sensor location and the failure (short circuit) point. The temperature difference enlarges under the cases that the failure point is far from the measurement point, thereby hindering the timely detection and alarm for fault. The temperature gap can be as high as 261.2 °C under the extreme case of 0.1 Ω short circuit resistance. Therefore, the mismatch of the failure point and the measurement will give us the illusion that the failure occurs suddenly, or the so-called sudden death. The thermal runaway boundary for battery module varies with the ambient temperature and the short resistance, helping the determination of the threshold of the detection algorithm for thermal runaway. At last, a guidance on how to develop fault diagnosis algorithm with the help of digital twin to judgement of fault diagnosis threshold is summarized, with clear discussion of the accuracy, cost and efficiency of the method. The proposed method paves a way for the application of the digital twin on the fast development of battery management algorithms.

Three-Dimensional Modeling for the Internal Shorting Caused Thermal Runaway Process in 20Ah Lithium-Ion Battery

Better understanding of how internal short circuit causes thermal runaway will benefit the engineering for safer lithium-ion batteries. In this study, three-dimensional (3D) numerical simulations of a 20Ah lithium battery under internal shorting condition are performed. The effects of internal short circuit area, resistance, penetration depth, convective heat transfer coefficient and internal short circuit position, on the thermal runaway are investigated with the simulations in this work. This study demonstrates that the average cell temperature is only weakly affected by the internal short circuit area, penetration depth, and position. On the other hand, the internal short circuit resistance and the convective heat transfer coefficient have large impacts on the thermal runaway propagation in the lithium-ion battery. A high convective heat transfer coefficient can effectively suppress the thermal runaway propagation. However, such a high convective heat transfer coefficient is hard to achieve at the cell surface.

A Novel Universal Model Considering SAGE for MFD-Based Faulty Property Analysis Under RISC in Synchronous Generators

This article proposes a new rotor interturn short circuit (RISC) fault analysis model for the electromechanical property study in synchronous generators. The specific novelty of this model lies in two aspects: First, It considers that most generators exist static air-gap eccentricity (SAGE), so it analyzes the RISC fault under normal and SAGE, making the model more versatile, and second, it takes into account not only the short circuit degree, but also the short circuit position, consequently it is more universal. By feeding the number of short circuit turns (denotes the short circuit degree), the angle between the two slots, where the short circuit takes place (denotes the short circuit position) and the detailed parameters of the generator into the model, the developing tendency of the key magnetic flux density (MFD)-based parameters can be conveniently predicted. The advantages of the proposed model primarily lie in the universality and the calculation speed. It can quickly evaluate the generator operating conditions. The phase current and the electromagnetic torque are selected in this article as the representatives of the electrical parameter and the mechanical parameter, respectively. Two-dimensional finite element analysis and experimental studies validate the proposed model.

Research on inter-turn short circuit fault location of SF6 circuit breaker energy storage motor coil based on traveling wave reflection method

—The traveling wave reflection method is proposed to locate the inter-turn short circuit fault of the circuit breaker energy storage motor coil. The capacitance and inductance matrices of the energy storage motor coil are calculated by finite element simulation, and the wave impedance model of the coil is established based on ATP-EMTP. The low-voltage square wave pulse signal is injected at the winding head to detect the characteristic curve of reflected wave when inter-turn short circuit fault occurs. The variation law of generalized fractal dimension of reflection wave characteristic curve with short circuit position is analyzed. The short-circuit position is evaluated based on BP neural network, and the evaluation accuracy is 100 %, indicating that this method is feasible.

Short-circuit fault evaluation of SF6 circuit breaker energy storage motor coil based on high-frequency equivalent model

Abstract The capacitive inductance parameters of the energy storage motor windings were calculated by finite element method, and the high-frequency equivalent model of the winding was established based on ATP-EMTP. Square wave pulse voltage signal was applied to the input end of the model, and the response voltage curve at the end of the circuit model was measured. The wavelet packet-energy spectrum was calculated as the characteristic parameter of the response curve in different short-circuit positions, and the short-circuit position was evaluated by the random forest algorithm. The accuracy rate of short-circuit fault location in the test set was 75%, indicating that the method has certain feasibility.

Insulation failure evaluation of SF6 circuit breaker relay coil based on high-frequency equivalent model

Abstract In order to evaluate the insulation failure of SF6 circuit breaker relay coil, the finite element model of the relay coil was established, and the capacitance inductance matrix was calculated by simulation calculation, and the high-frequency equivalent circuit model of the coil was established. Inject low-voltage square wave pulse signal at the input end of the circuit, and the response curve is detected at the end of the circuit, and the characteristic curve is obtained by combining the response curve under the condition of inter-turn short circuit fault and no fault. The wavelet packet - energy spectrum analysis shows that the energy proportion of each frequency band of the characteristic curve changes when the short-circuit position between turns is different. Taking energy spectrum as input and combining with extreme learning machine to locate inter-turn short circuit fault, the simulation sample analysis shows that the correct rate of fault location is 93.3%.

Research on Fault Location of SF6 Circuit Breaker Relay Coil Based on Traveling-Wave Reflection Method

—The traveling wave-reflection method is proposed to locate the short circuit fault of the opening/closing coil of the circuit breaker, the capacitance and inductance matrix of the opening/closing coil are calculated by finite element simulation, and the wave impedance model of the coil is established based on ATP-EMTP. A low-voltage square wave pulse signal is injected into the head end of the winding to detect the characteristic curve of the reflected wave when an inter-turn short-circuit fault occurs. The generalized fractal dimension of reflection wave characteristic curve was calculated and its variation as the position of short circuit change was analysed. Compared with box dimension, the variation of information dimension and correlation dimension are more obvious, thus information dimension and correlation dimension are selected as inpus, and the evaluation model of inter-turn short circuit position is established based on probabilistic neural network.

Impact of the Field Winding Interturn Short-Circuit Position on Rotor Vibration Properties in Synchronous Generators

This paper investigates the effect of the field winding interturn short-circuit (FWISC) position on the rotor vibration properties in turbo generators. Different from the previous studies which focused on the influence of the short-circuit degree, this work pays much attention to the impact of the short-circuit position on the rotor unbalanced magnetic pull (UMP) properties and vibration characteristics. The theoretical UMP model is firstly deduced based on the analysis of the magnetic flux density (MFD) variation. Then, the finite element analysis (FEA) is performed to calculate the UMP data. Finally, the rotor vibrations are tested on a CS-5 prototype generator which has two poles and a rated capacity of 5 kVA. It is shown that the occurrence of FWISC will greatly increase the UMP as well as the rotor vibration. In addition to the short-circuit degree, the short-circuit position will also affect the UMP and vibration. The nearer the short-circuit position is to the big rotor teeth, the larger the UMP and vibration will be. The proposed study in this paper will be beneficial for the monitoring and diagnosis of FWISC faults.

DESIGN AND SIMULATION OF A 2.4 GHz MONOPOLE ANTENNA ARRAYS WITH PARASITIC ELEMENTS FOR WIRELESS COMMUNICATIONS

Purpose: This paper presents the design and analysis of a 2.4 GHz monopole antenna arrays with parasitic elements for Wireless communications using the Finite-Element Method. 
 Methodology: The antenna arrays are constituted of five quarter wave antenna monopoles of section ¶. The selected configuration is the side coupling on a plan of mass out of rectangular copper of form posed on a FR-4 substrate materiel with relative permittivity of 4.4 and the thickness of section ¶. Only the central monopole is fed and the others known as parasitic are in short-circuit position by an effect of mutual coupling. The so-called CST Microwave Studio simulation software is used to simulate the design antenna.
 Findings: It is shown that this array is directive with high gain.
 Recommendations: To integrate this antenna arrays into wireless telecommunication systems, future research must be based on reducing its weight and dimensions. The use of printed monopole elements based on metamaterials may be a possible path for this integration.

Impact of DG on short circuit current detected by protection

DG (distributed generation) access causes the change of current detected by the protection, and then affects the sensitivity of the original protection. In order to solve the problem, the influences of DG capacity, DG access location and short-circuit location on short circuit current are analysed in this paper. When the DG capacity and grid-connected position remain unchanged, the unit current method is used to solve the short-circuit current by solving the transfer impedance. The relationship between the change of short circuit position and the impact degree of DG is discussed in detail, and the calculation formula of extreme point is derived. When the DG capacity and short circuit location remain unchanged, the impact of DG grid-connected position on the upstream and downstream current is analysed. The characteristic curve of the impact of DG position change on protection current detection is given, and the impact of DG grid-connected position on protection sensitivity is explained clearly. The conclusion provides an important reference for the selection of DG grid-connected position and the calculation of relay protection in distribution network with DG.

Research on Five-Loop Simplified Scaling Model for Dry-Type Air-Core Reactors With Inter-Turn Short Circuit Fault

In order to simplify the research method of the spatial magnetic field distribution (SMFD) of dry air-core reactors (DARs) in the case of inter-turn short circuit fault, the concept of simplified scaling model was put forward, and the optimal simplified scaling model for different inter-turn short circuit fault was calculated by using the least square method. Firstly, in order to simplify the calculation, 7 typical directions describing the SMFD of DARs were determined based on the similarity degree of magnetic induction intensity in each direction. Then, the simplified scaling model parameters corresponding to different short circuit positions and degrees were studied, and the variation rule was described by using the method of fitting function. Finally, the original model and the simplified scaling model of the DARs in the case of inter-turn short circuit were established respectively in the laboratory. The results show that the optimal structure relative height obtained by experiment is 30% and 20% respectively, which is the closest to the parameters obtained by computer simulation, i.e.,28% and 20.3%.

Impact of Stator Interturn Short Circuit Position on End Winding Vibration in Synchronous Generators

This article presents a comprehensive analysis on the end winding vibration characteristics due to different stator inter-turn short circuit (SISC) positions in synchronous generators. Different from other studies, this article not only pays attention to the effect of SISC on the end winding electromagnetic forces, but also considers the impact of the short circuit position, which is related to the static air-gap eccentricity, on the end winding vibrations at the meantime. The whole work is based on the qualitatively theoretical analysis, the finite element analysis (FEA), and the experimental validation on a 6-pole synchronous generator. The study shows that SISC will considerably enlarge the electromagnetic force and intensify the radial vibration of the end winding, especially at 100 Hz, 200 Hz and 300 Hz. The closer the short circuit position is to the minimum air-gap point, the more severe the end winding vibration will be.

High-Gain Planar Array of Reactively Loaded Antennas for Limited Scan Range Applications

This paper proposes a novel high-gain antenna element that can be used in antenna arrays that only require a limited scan range. Each high-gain antenna element uses a linear sub-array of highly-coupled open-ended waveguides. The active central element of this sub-array is directly fed, while the remaining passive waveguides are reactively loaded. The loads are implemented by short-circuits positioned at various distances from the radiating aperture. The short-circuit positions control the radiation pattern properties and the scattering parameters of the array. The proposed sub-array antenna element is optimized in the presence of the adjacent elements and provides a high gain and a flat-top main lobe. The horizontal distance between the sub-array centers is large in terms of wavelengths, which leads to limited scanning capabilities in the E-plane. However, along the vertical axis, the element spacing is around 0.6 wavelength at the central frequency that is beneficial to achieve a wider scan range in the H-plane. We show that the sub-array radiation pattern sufficiently filters the grating lobes which appear in the array factor along the E-plane. To demonstrate the performance of the proposed array configuration, an array operating at 28.0 GHz is designed. The designed array supports scan angles up to ±7.5° along the E-plane and ±24.2° along the H-plane

Probabilistic transmission line fault diagnosis using autonomous neural models

Fault diagnosis is a critical task when a severe disturbance is caused by insulation failure on a transmission line. Fault diagnosis should be concluded as soon as possible to avoid further financial and social costs because of load interruptions. Intelligent systems have been successful in dealing with fault diagnosis. This paper proposes the application of autonomous neural networks for mapping the relationship between electrical signals at one terminal and fault information on transmission lines. The proposed autonomous neural networks allow automatic adaptation of the neural models responsible for fault detection, classification, and location. The proposed autonomous neural models can provide the uncertainty associated with the inference process. If a fault is likely, the detection model provides the inference probability of a false positive. Probabilities for each class are given in fault classification, while fault location provides an error margin around the estimated short-circuit position. Another contribution of the paper is the extraction of useful information from oscillography to feed the neural models. An efficient voltage and current representation is proposed. The tests consider realistic fault conditions for main transmission lines in the Brazilian power network. The methodology has proven to be robust also for dealing with multi-terminal and series-compensated lines.

Switchable Slant Polarization Filtering Antenna Using Two Inverted Resonator Structures for 5G Application

This study presents a novel design of two filtering antennas with a +45° and −45° slant polarization, using the co-design of a third-order filter and a rectangular patch antenna. Slant polarization is obtained by directing the surface current that flows to the radiator by applying two parallel inverted resonators in the transmission line. The resonators consist of two parallel strips with alternate open and short circuits at each end and the 45° and −45° polarization is determined from these short circuit positions. The rectangular patch antenna is fed using proximity coupling, and it is parallel to the resonators. The filtering antennas provide not only 45° slant polarization, a flat gain response but also a controllable bandwidth. Operating at 4.65 GHz for 5G application, the antennas have a controllable bandwidth range from 5.9% to 8.4% without affecting the polarization and center frequency. The gain responses are filter like and attain the maximum value of 6.82 and 6.69 dBi at 4.7 GHz. This design needs no extra component or rotation of the radiator and transmission line because the inverted resonators can switch the polarization to be +45° and −45°. The results of the 45° and −45° polarization filtering antenna simulation and experiments are consistent with each other.

Mechanism of the dynamic behaviors and failure analysis of lithium-ion batteries under crushing based on stress wave theory

Although quasi-static responses of lithium-ion batteries has been studied by many researchers recently, the dynamic behaviors and its underlying mechanism under crushing are still not fully understood. In this paper, the stress wave theory is employed to analyze the dynamic behaviors of 18,650 lithium-ion batteries for the first time. A numerical model of the battery cell is established and validated by experiments, which is then used to study the dynamic response under crushing within a wide scope of crushing velocity (up to 45 m/s). Many different responses are found that differ from quasi-static cases, including the early short circuit before drop in force, the “rise-drop-plateau-rise” force-displacement curve, the velocity-dependent crack positions and so on, all of which can be well characterized by stress wave. It is interesting that the failure displacement and the short-circuit position of the battery depends on the range of crushing velocity, which is resulted from different dynamic failure mechanism in each velocity range. Accordingly, a velocity-dependent failure criterion is obtained. The results show that a more specific strategy is needed in the safety design of battery modules under various crushing velocities.

A New Hybrid Model for Electromechanical Characteristic Analysis under SISC in Synchronous Generators

This paper proposes a novel hybrid model for analyzing the electromechanical characteristics under stator interturn short-circuit (SISC) fault in synchronous generators. The hybrid of the model lies in that it considers the static air-gap eccentricity and SISC at the same time. Different from other studies, the proposed model can manage not only the impact of the short-circuit degree, but also the influence of the short-circuit positions on the magnetic flux density (MFD), which is the basis to analyze electromechanical characteristics. The phase current and the electromagnetic torque (EMT) are selected in this paper as the representative of the electrical parameter and the mechanical parameter, respectively. Two-dimensional finite-element analysis and experimental studies confirm the validation of the proposed model. The model employs two primary factors, i.e., the short-circuit turn number nm and the position angle αsm , to reflect the short-circuit degree and the short-circuit position, respectively. By feeding these two factors as well as the detailed parameters of the generator into the model, the electromechanical feature data such as the phase current and EMT can be quickly assessed, and the developing tendency of the key MFD-based parameters can be conveniently predicted.

A New Detection Coil Capable of Performing Online Diagnosis of Excitation Winding Short-Circuits in Steam-Turbine Generators

Because excitation winding short-circuit faults that occur in steam-turbine generator will lead to heavy financial losses, accurately detecting excitation winding short-circuits (EWS) can help power generation operations. It can allow them to take timely actions and shorten downtime as well as cut the costs of troubleshooting. This paper introduces a method for detecting EWS faults online using a new detection coil. Here, a large-dimension detection coil is installed inside the generator to span over an iron-core segment in the stator. The even or fractional harmonics induced by the detection coil are used to determine whether an EWS fault has happened, and the short circuit position can also be determined. This method can reveal short-circuit faults that occur in one turn of the excitation winding, and with obviously higher sensitivity.

Simulation on Transient Characteristics of Inter-Turn Short Circuit Fault of Dry-type Air-Core Reactor Based on ANSYS Maxwell

Transient characteristic analysis of inter-turn short circuit fault has been done which is paramount for detecting the earlier fault of dry-type air-core reactor. Dynamic physical process of inter-turn short circuit is theoretically analyzed for dry-type air-core reactor from normal running condition to inter-turn short circuit fault condition. Using ANSYS Maxwell, transient field circuit coupling calculation model is set up and the transient characteristic of inter-turn short circuit fault is simulated, which is also verified by experiments. The study shows that the short circuit ring causes a sudden change of magnetic field at the position of short circuit which can be detected by the detecting coils installed on the package of reactor. Inter-turn short circuit fault can be detected in the earlier fault period by the method proposed in this paper.