Calculation Of Impedance Research Articles

Small-argument analytical expressions for the calculation of the ground-return impedance and admittance of underground cables

Small-argument analytical expressions for the calculation of the ground-return impedance and admittance of underground cables

A personalized bikeability-based cycling route recommendation method with machine learning

Urban built environment quality along the travel route is positively correlated with active mobility. However, most previous personalized route recommendation research for cycling emphasizes non-visual attributes, ignoring the significance of visual attributes such as the built environment. Therefore, to take the built environment into consideration in the cycling route planning, we propose the personalized bikeability-based cycling route recommendation (PBCRR) method. The method consists of three steps: (1) deep neural networks are utilized to achieve statistics on built environment attributes and features of bikeability; (2) the weights road impedance calculation function is used to calculate route recommendation indicators according to minimum impedance sum of road segments; and (3) the recommended cycling route is found and shown to the user based on the calculated indicators. The results indicate that our PBCRR presents a high level of effectiveness and differences, and achieves better results than the current route recommendation algorithm in guiding cyclists towards routes with a better built environment.

Parametric study of equivalent homogeneous earth method for overhead lines above a multi-layer earth

This paper presents a systematic investigation of equivalent homogeneous earth method (EHEM) for calculation of earth-return impedance of overhead conductors above a multi-layer earth. The recently developed EHEM is based on the concept of equivalent propagation constant of earth. The characteristics of equivalent propagation constant of earth and integrand convergences of EHEM are further studied. The parametric studies of accuracy on earth-return impedance between exact formula (EF) and EHEM are also presented in this paper.

Distance Protection for Lines Connecting Converter Interfaced Renewable Power Plants: Adaptive to Grid-end Structural Changes

Typical fault current characteristics of converter interfaced renewable power plants have significant impact on the reliability of traditional line distance protection. Large degrees of system non-homogeneity introduce substantial error in the apparent impedance calculation. In this paper, an adaptive distance relaying method for lines connected to converter-interfaced renewable power plants is proposed. A range of fault current phase angles is identified using the local and remote equivalent source impedances, which are calculated using only local measurements. Corresponding to the lower and upper bound of the identified range of fault current phase angle, two apparent impedances are calculated based on priority to dependability and security of protection operation. The trip decision is made based on the weighted sum of the first and second apparent impedances. Tuning of the dependability and security weightage factors based on the calculated remote grid-end source impedance, ensures adaptability and reliability of operation, even after structural changes in the grid. The proposed method is verified using IEEE 39 bus system and validated using field data. Comparative assessment with practically proven distance and modified distance protection method for lines connected with renewables is also provided.

Local impedance drop guided versus lesion size index guided pulmonary vein isolation: long-term outcomes and chronic reconnections

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Insufficient lesion depth and discontinuity of lesion lines are reasons for reconnections after point-by-point radiofrequent pulmonary vein isolation (PVI). Different technologies have shown to be useful for prediction of effective lesions. Measurement of the magnitude of local tissue impedance drop (LID) and calculation of lesion size index (LSI) based on monitoring of contact force are examples for corresponding technologies. Purpose To compare the long-term outcomes of LID guided with LSI guided PVI. Methods In this retrospective study we compared two groups of patients who underwent point-by-point radiofrequency PVI for treatment of atrial fibrillation. In the LID-guided group (n=35) energy was delivered using an ablation catheter with local impedance monitoring. Ablation was terminated when LID reached a plateau (Fig. A). In the LSI-guided group (n=31) lesions were created using an ablation catheter with contact force monitoring until the target LSI was reached in each point (LSI=5 for anterior and LSI=4 for posterior segments, respectively, Fig B). The inter-lesion distance of <6 mm with power of 40 W for anterior and 30W for posterior segments was used in both groups. A gap-map and touch-up ablation was performed along the index ablation line if the first pass PVI did not occur, or in the case of an acute reconnection after 20 min of waiting time. In the long-term follow-up, a holter ECG was scheduled 3, 6 and 12 months after the initial ablation as well as symptom-driven visits with ECG registration. In case of symptomatic arrhythmia recurrence, a second procedure was performed including validation of PVI, mapping of reconnection site and RePVI, if necessary. Results All pulmonary veins were successfully isolated by encirclement of ipsilateral veins during initial procedure. During the 11.5±2.9 months follow-up, 12 out of 35 (34.3%) patients from LID-guided group and 5 out of 31 (16.1%) patients from LSI-guided group experienced arrhythmia recurrence. Kaplan-Meier survival analysis showed statistically significant higher probability of the arrhythmia recurrence in patients treated with LID-guided approach (log-rank=4.37, p=0.037, Fig C). Redo procedure was performed for 10 (28.6%) patients in LID-guided group and 3 (9.7%) patients in LSI-guided group and chronic pulmonary vein reconnections were detected in 7 out of 10 (70%) and 2 out of 3 (67%) patients, respectively (Fig D). Conclusions Despite initial successful isolation of all pulmonary veins, LID-guided ablation resulted in significantly higher probability of arrhythmia recurrence during the long-term follow-up as well as higher rate of chronic PV reconnections (although not statistically significant) as compared to LSI-guided ablation. This reflects the nature of contact force guided ablation anticipating the quality of catheter-tissue interface before each application, which is not possible with an impedance only guided approach.

Local impedance drop guided versus lesion size index guided pulmonary vein isolation: acute success and reconnections

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Insufficient lesion depth and discontinuity of lesion lines are reasons for reconnections after point-by-point radiofrequency pulmonary vein isolation (PVI). Different technologies have shown to be useful for prediction of effective lesions. Measurement of the magnitude of local tissue impedance drop (LID) and calculation of lesion size index (LSI) based on monitoring of contact force are examples for corresponding technologies. Purpose To compare the acute efficacy of LID guided with LSI guided PVI. Methods In this retrospective study we compared two groups of patients who underwent point-by-point radiofrequency PVI for treatment of atrial fibrillation. In the LID-guided group (n=35) energy was delivered using IntellaNav MiFi (Boston Scientific, MA, USA) ablation catheter. Ablation was terminated when LID reached a plateau (Figure A). In the LSI-guided group (n=31) lesions were created using Tacticath (Abbott, MA, USA) ablation catheter until the target LSI was reached in each point (LSI=5 for anterior and LSI=4 for posterior segments respectively, Figure B). The inter-lesion distance of <6 mm with power of 40 W for anterior and 30W for posterior segments was used in both groups. A gap-map and touch-up ablation was performed along the index ablation line if the first pass PVI did not occur, or in the case of an acute reconnection after 20 min of waiting time. In the post hoc analysis initial levels and drop of local and system impedance, average contact force and LSI were included in models predicting PV gaps. Results All PVs were successfully isolated by encirclement of ipsilateral veins with significantly longer median ablation time 30(IQR:27-35) min in LID-guided group as compared to LSI-guided group:25 (IQR:21-31) min (p=0.035). First-pass PVI was achieved in 97 out of 132(73%) circles (LID-guided:43 out of 70 [61%] circles vs LSI-guided:54 out of 62 [87%] circles, p=0.002). Acute reconnections occurred in 14 out of 132 (11%) circles (LID-guided:9 out of 70 [13%] circles vs LSI-guided: 5 out of 62 [8%] circles, p=0.54, Figure C). Overall, significantly more patients had PV gaps when LID-guided ablation was used as compared to LSI-guided (26 out of 35[74%] vs 13 out of 31[42%] respectively, p=0.016). In the post hoc analysis a LID<9.7Ω was the only predictive parameter for PV gap (sensitivity=96.4%, specificity=67%). Conclusions LSI-guided ablation resulted in successful PVI with significantly shorter ablation time and fewer PV gaps as compared to LID-guided. This reflects the nature of contact force guided ablation anticipating the quality of catheter-tissue interface before each application, which is not possible with an impedance-only guided approach.

Impedance-Based Online Estimation of Nodal Inertia and Primary Frequency Regulation Capability

Accurate estimation of inertia and primary frequency regulation (PFR) capability is important to ensure frequency stability in low-inertia power systems. This paper investigates how the inertia and PFR capability of a power source node can be evaluated using a non-invasive online estimation method from the impedance perspective. Based on small perturbation injection, a novel approximate relationship between the impedance and corresponding frequency response transfer function (FR(s)) is deduced. The features of the FR(s)&#x2019;s magnitude response curve, i.e., resonance frequency and DC gain, are then used to develop an overall implementation framework for nodal inertia and PFR capability estimation in real time. This method provides new insights with respect to obtain the synchronous and non-synchronous converter interfaced generator&#x0027;s inertia constant and PFR capability for grid operators via impedance calculation and measurements. Case studies on a modified 9-bus system and NETS-NYPS 68-bus system demonstrate the effectiveness of the proposed impedance-based estimation approach.<fn id="fn4" fn-type="other"> This work was supported in part by the National Natural Science Foundation of China (52077066), in part by the Hunan Provincial Natural Science Foundation for Excellent Young Scholars (2020JJ3011), and in part by the Huxiang Young Talents Science and Technology Innovation Program (2020RC3015). (<i>Corresponding author: Yunfeng Wen</i>) W. Zhang and Y. Wen are with the College of Electrical and Information Engineering, Hunan University, Changsha 410082, China (e-mail: ; ). C. Y. Chung is with the Department of Electrical Engineering, The Hong Kong Polytechnic University, Hong Kong 999077, China (e-mail: C.Y.). </fn>

Transverse impedance studies of 2D azimuthally symmetric devices of finite length

The accurate calculation of the beam coupling impedance for particle accelerators is necessary to carefully assess the machine stability against impedance-driven collective effects. A first order evaluation of the beam coupling impedance is often done by means of analytical formulas and/or 2D numerical codes. The infinite length approximation is often used to simplify the calculation of the beam coupling impedance of accelerator elements. This is expected to be a reasonable assumption for devices whose length is greater than the transverse dimension but may be a less accurate approximation for segmented devices. In this work, we present the application of the mode matching method to the calculation of the transverse dipolar impedance of a cylindrical cavity loaded with a toroidal insert. By choosing different insert electromagnetic properties (permittivity, permeability, and conductivity) and dimensions, the model can represent a beam pipe, a thin insert, a lossy cavity, or a collimator for which the effect of the finite length is investigated. The method is successfully benchmarked against available analytical formulas, field-matching codes, and 3D commercial solvers. The proposed model allows for performing wide parametric scans and reaching accurate results, therefore becoming an essential tool for the impedance evaluation of accelerator devices.

A Fast Fuel Cell EIS Measurement Method Based on Square Wave Excitation and Modified Wavelets

Electrochemical impedance spectroscopy (EIS) is an effective technique for real-time fault detection of vehicle-mounted proton exchange membrane fuel cell (PEMFC). In this study, a method to enable fast online measurements of the EIS for PEMFC is presented based on square excitation and modified Morlet wavelet transform (WT), which is validated experimentally. The Morlet wavelet function has been optimized to be more suitable for WT applications in impedance calculations. With this improvement, WT is able to cover the analysis frequency range of 1 Hz to 4 kHz by using very short time-domain data, precisely at the moment of a square-wave signal jump. This results in a significant reduction in computational cost and allows efficient impedance calculations. The calculated impedance based on the modified Morlet WT has a maximum calculation error of 2.57%, as confirmed by comparing the theoretical impedance at different frequency points. Compared to the general fast Fourier transform (FFT) EIS calculation method, the proposed method demonstrates significant advantages in terms of both calculation accuracy and test implementation.

Research on Short-Circuit Impedance Analysis Method of Auto-transformer for Side Column Voltage Regulation

In order to realize the accurate analysis of the impedance of transformers with complex connection relations, this paper derives the impedance calculation method of low-voltage excitation side column linear voltage regulating autotransformer by using the power method. The transformer network with different taps is analyzed, and the calculation formulas of transformer HV-MV impedance, HV-LV impedance and MV-LV impedance are derived. The analysis is simplified to the solution of concentric column coil impedance and magnetic potential of each coil. By comparing the calculated data of actual products with the measured data, the calculation deviation of this method is controlled within 2.03%; By using the finite element method, the impedance of the transformer with the measures to control the magnetic shielding is analyzed and calculated. By comparing the impedance of the transformer with different measures, it can be confirmed that the magnetic leakage measures have an impact on the impedance of the transformer.

Short-circuit Impedance Calculation of 25 MVA Autotransformer with Tertiary Winding using FEM

In this article, the percentage of short-circuit impedance is calculated using the finite element method for a single-phase power autotransformer with tertiary winding. The autotransformer specifications are: 25 MVA, 230 kV, 60 Hz, three-legged core type. A detailed 3D model where mixed formulations in terms of scalar and vector potential and circuit coupling is used. This type of study is essential to design the autotransformer and guarantee the impedance value, and so the safety and operability of electrical power systems. To calculate the percentage of short-circuit impedance the voltage relationship between the short-circuit voltage and the nominal voltage is used. In addition, the magnetic energy storage technique is presented as another alternative to calculate this parameter. The results are validated with the data from the laboratory tests obtaining differences of less than 5%.

Computation of the Characteristic Parameters of Coaxial Waveguides Used in Precision Sensors.

This paper presents a fast and computationally stable analytical algorithm used to perform the characteristic impedance of cylindrical multilayer waveguides used in high-precision sensors and apparatuses. Most of the algorithms used for the calculation of the characteristic impedance of those waveguides are based on approximations. Their application is limited to waveguides with a certain (usually small) number of layers. There may be insufficient layers, especially when coaxial waveguides are part of a precise measurement device. This article presents a numerically stable analytical algorithm using modified scaled Bessel functions to perform the characteristic impedance and the components of cylindrical coaxial multilayer waveguides. The results achieved by the extracted algorithm were compared to the results obtained by simulation using finite element method (FEM) software and the current method, whose main drawback is the fictive sublayers, which significantly increase the computation time. The excellent agreement between the results confirmed the precision of the algorithm and the time required for the calculation was reduced several times.

Eddy Current Testing of Conductive Coatings Using a Pot-Core Sensor.

Conductors consisting of thin layers are commonly used in many industries as protective, insulating or thermal barrier coatings (TBC). Nondestructive testing of these types of structures allows one to determine their dimensions and technical condition, while also detecting defects, which significantly reduces the risk of failures and accidents. This work presents an eddy current system for testing thin layers and coatings, which has never been presented before. It consists of an analytical model and a pot-core sensor. The analytical model was derived through the employment of the truncated region eigenfunction expansion (TREE) method. The final formulas for the sensor impedance have been presented in a closed form and implemented in Matlab. The results of the calculations of the pot-core sensor impedance for thin layers with a thickness above 0.1 mm were compared with the measurement results. The calculations made for the TBC were verified with a numerical model created using the finite element method (FEM) in Comsol Multiphysics. In all the cases, the error in determining changes in the components of the pot-core sensor impedance was less than 4%. At the same time, it was shown that the sensitivity of the applied pot-core sensor in the case of thin-layer testing is much higher than the sensitivity of the air-core sensor and the I-core sensor.

Three-dimensional time-domain particle-in-cell calculations of impedances and centroid deflections in a linear-accelerator cell

In linear induction accelerators, high-brightness electron beams are accelerated by voltages applied at gaps at discrete locations along the accelerator. At high currents, the beam itself induces wakefields in the accelerating gaps which can then feedback and distort the beam. The coupling of the gap-cavity modes and the beam can be characterized by frequency-dependent quantities known as the parallel and perpendicular gap impedances. Assessing the effects of instabilities resulting from these interactions requires accurate knowledge of these quantities. In this paper, we describe how a 3D finite-difference time-domain particle-in-cell code can be used to calculate both parallel and perpendicular gap impedances. We also demonstrate good agreement between full particle-in-cell simulations and results from a beam transport code making use of gap impedances to model beam centroid deflections. In practice, ferrite materials are often used in accelerating gaps to dampen cavity modes and reduce the severity of the resulting instabilities. We describe an implicit recursive convolution algorithm used to model the linear response of dispersive ferrite materials.

Portable RDFT-Based EIS System Design With a Low-Complexity Impedance Calculation

This paper presents a novel low-complexity impedance calculation based on a compact recursive discrete Fourier transform (RDFT) for electrical impedance spectroscopy (EIS) system design. Compared to a traditional fast Fourier transform, an arbitrary-length RDFT is not limited by the power-of-two transform length. By choosing a suitable integer ratio of the desired frequency/frequency resolution, the spectrum leakage can be significantly reduced by 4-Hz resolution per bin, which enables a lower magnitude relative error (MRE) and a phase absolute error (PAE) in impedance calculations. Here, the practical measurement results show that the maximum MRE and PAE are below 0.1% and 0.5°, respectively, making this approach superior to previously reported ones. Compared with the state-of-the-art Goertzel filter-based EIS system, the proposed method provides more frequency bins (+43.75%) within the same frequency band, and the operations in terms of square root, division, and arctangent are drastically reduced by 50%, 33%, and 50%, respectively. In addition, the proposed system only costs $474 USD and can serve as a suitable solution for various EIS applications in the future.

Influence of a lossy ground on the lightning performance of overhead transmission lines

• Accurate lossy ground representation impacts lightning overvoltages simulation. • Carson's classic formulation may lead to inaccuracies for high-resistivity soils. • Accurate lossy ground representation in simulations leads to higher TLs outage rate. • An increase up to 15% in TL outages was found when ground is accurately represented. This paper investigates the impact of incorporating both displacement currents and frequency-dependent soil parameters in the calculation of the ground-return impedance for the determination of the backflashover rate of 138 kV and 230 kV overhead transmission lines due to direct lightning strikes. This is done by considering the Sunde's formulation for calculating the ground-return impedance, which is incorporated in a time-domain simulator using an alternative implementation of Marti's transmission line model. The obtained results show that the peak of the lightning overvoltages computed considering Sunde's formula, along with frequency-dependent soil parameters, leads to higher amplitudes in comparison with those simulated using the classical Carson's formula, which neglects the frequency dependence of soil parameters and assumes conductive currents in the soil much larger than displacement currents. This effect is more pronounced in high-resistivity soils and leads to an increase in the line backflashover rate within 4-6%, 7-12% and 9-15% for 1000 Ωm, 5000 Ωm and 10000 Ωm soils, respectively, considering 138 kV and 230 kV lines, and assuming a typical median first stroke lightning current. Analyses performed with slow and fast first stroke currents confirm the trend of increase of the backflashover rate with the consideration of Sunde's formula.

Метод обобщенного импеданса для расчета отражения и прохождения волны через многослойную структуру. Часть 1. Последовательный пересчет импедансов и амплитуд

The algorithm for calculation of reflection and passage of single-dimension wave through multi-layer structure which is presented as the successive one to other uniform slides is proposed. On the basis solution of single-dimension wave equation for each slide as the parameter of slide it is established the wave number. It is proposed the conception of generalized impedance for single-dimension wave which consist of propagating wave velocity relation to the frequency of the same wave. It is proposed the conception of zero-impedance of uniform region of structure which is equal to inverse value of wave number in this region. The generalized impedance is presented in the product of zero-impedance to fraction which numerator is the sum of two special solutions of wave equation for this region and denominator is the difference of the same solutions. For the calculation of reflection and passage coefficients of wave by energy for the whole structure it is found two mechanisms successive calculation along the slides of structure – successive calculation of impedances and successive calculation of amplitudes. For the mechanism successive calculation of impedances it is proposed the conceptions of entrance and exit impedances of each separately slides. It is proposed the recurrence formula which allow to found the entrance impedance of preceding medium through the entrance impedance of following medium for anyone two neighbouring regions of structure. It is established the using of this formula proposed to found the entrance impedance in initial slide of structure from the entrance impedance in last slide of structure. In this case the successive calculation of impedances is made from the end of structure to its outset. For the mechanism of successive calculation of amplitudes it is found the system consisted of two recurrence formulas which allows to found the amplitudes of straight and backward directions in preceding medium through the amplitudes the same waves in following medium. It is proposed the scheme of step-by-step successive calculation which allows from the amplitude of initial falling wave found the amplitude of reflected and passage waves relative to structure as a whole. It is mentioned the possibility and proposed the formulas which allows to found the reflection and passage coefficients on energies for the structure as a whole. It is discussed the comparative characteristics of method successive calculation of impedances and successive calculation of amplitudes.

Investigation of RF heating for the multipole injection kicker installed at SOLEIL

During the commissioning of the new Multipole Injection Kicker (MIK) pulsed magnet at SOLEIL synchrotron, an anomalously high heating of the MIK chamber and flanges was found. To better manage the heat load, fans directed toward the MIK were added to improve the air-cooling flow. This allowed the nominal current to be reached in all operation modes while keeping reasonable temperatures on the MIK. Post-installation investigations subsequently showed that the initial estimate of the maximal heat load was in agreement with the measured temperature in several operation modes both with and without the additional fans. In this article, we present the complete study, starting from the impedance calculation to thermal simulations, and comparison with the measured data with beam.

Investigation of an M-Sequence based impedance spectrum acquisition method for lithium-ion batteries from the engineering application perspective

Electrochemical impedance spectroscopy (EIS) is frequently reported to be used in mechanism analysis, state estimation, and fault diagnosis of lithium-ion batteries. For a long time, EIS has been measured in the laboratory using carefully designed equipment, which has the problem of long measurement time and is not convenient for field applications. How to obtain broadband electrochemical impedance spectroscopy quickly and accurately has become a key issue. Being different from the traditional impedance measurement method based on sinusoidal frequency sweep, in this paper, we obtain the EIS by using Fast Fourier Transform (FFT) for maximum length sequence (M-Sequence) excitation current and corresponding response voltage. M-sequence excitation can be generated by fast responding charging and discharging equipment, etc., with higher flexibility. To guide the engineering application, for the first time, the effect of M-Sequence parameters and sampling frequency on the impedance calculation results are investigated through experiments. A series of experimental results show that when given the frequency range to be measured, the parameters of M-Sequence and the sampling frequency can be determined to calculate the EIS quickly and accurately.

A Review of Pile Foundations in Viscoelastic Medium: Dynamic Analysis and Wave Propagation Modeling

The dynamic viscoelastic theory of soil–pile interaction dominates the initial impedance calculation during the pile dynamic design and analysis. Further, it provides a firm theoretical ground for the wave propagation simulation, which could be the basis of seismic analysis and some geotechnical testing approaches. This review traces the development history and key findings of viscoelastic soil–pile interaction theory and expounds on the advantages and limitations of various theoretical advances in terms of dynamic design and wave propagation modeling. The review consists of three sub-divisions, which are the longitudinal, horizontal, and torsional viscoelastic soil-pile theories. The development and implement of multi-phase soil constitutive equations, multi-dimensional soil–pile interaction modeling methods, pile–soil–pile mutual interactions in pile groups, and the fluid–structure interaction problems in offshore piles are especially remarked and concluded. Finally, the shortcomings and deficiencies of the present development are pointed out with a view to addressing them in the future.