Electromagnetic Disturbances Research Articles

Decision Algorithm Based on the Modified Bellman Equation to Deal With EMI-Induced Errors in Hamming-Based Communications

This article presents a decision-making algorithm based on a modified version of the Bellman equation to deal with electromagnetic interference errors in a communication channel inside a harsh electromagnetic reverberant environment. The Bellman equation is a fundamental concept in decision-making problems such as Markov decision processes. Such processes model decision making in situations where the outcomes are partly random and partly controlled by an agent (decision maker). Recent studies have implemented Markov decision processes as a tool for risk assessment in areas such as robotics or aviation. However, so far, no research has been reported that uses the Bellman equation or Markov decision processes to deal with risks related to electromagnetic disturbances. In our study, a wired communication channel that uses non-return-to-zero-level data encoding and Hamming code for error detection and correction is disturbed. First, the packet error rate (PER) is calculated and compared with and without the proposed algorithm for different electromagnetic disturbance frequencies and bit rates. The gain is compared at different PERs when the algorithm's parameters (called rewards) are optimized and when these are set as random. Finally, the influence of the rewards and the maximum number of resends on the algorithm's performance is also studied.

Characteristic identification of seismogenic electromagnetic anomalies based on station electromagnetic impedance

The main components of seismo-electromagnetic research are the deep underground electromagnetic seismogenic environment, electromagnetic field changes at different stages of the seismogenic process, and the physical mechanism and change rules of electromagnetic properties of the earth’s interior. Traditional electric and magnetic methods mainly analyze the single field change of the geoelectric field, geomagnetic field, or resistivity at frequencies less than 1 Hz. These do not include the extremely low-frequency band that is sensitive to seismic events, so it is difficult to obtain the characteristics of time-spatial variations and propagation characteristics precursors. In comparison, magnetotelluric stations observe magnetotelluric fields containing seismogenic-induced electromagnetic disturbances, and the observation frequency band is wide. In this paper, the three-dimensional numerical simulation method is used to calculate the magnetotelluric apparent resistivity anomaly generated by resistivity changes in the seismogenic zone, and the forward algorithm of arbitrarily orientated dipole source in layered earth is used to simulate the response of low-frequency pre-earthquake electromagnetic radiation. The magnetotelluric response including seismogenic resistivity anomaly and pre-earthquake electromagnetic radiation is obtained using the field component composition method. The frequency characteristics and spatial distribution characteristics of apparent resistivity anomalies are systematically analyzed, and the results are of important significance for the observation, data processing, and identification and analysis of seismic electromagnetic anomalies in different seismogenic processes.

Application of electromagnetic disturbance technology in predicting ventriculoperitoneal shunt dependency after aneurysm-associated subarachnoid hemorrhage.

The aim of this study was to evaluate the predictive power of electromagnetic disturbance technology in patients with hydrocephalus after subarachnoid hemorrhage. This prospective, observational cohort study was conducted at The First Affiliated Hospital of Zhengzhou University and Nanfang Hospital. A total of 155 patients with subarachnoid hemorrhage (SAH) were enrolled in this study. Disturbance coefficients were recorded using a continuous sinusoidal signal in real time after SAH. The patients were divided into two groups: hydrocephalus group (patients who underwent shunt insertion within a month after SAH) and non-hydrocephalus group (patients without need for a ventriculoperitoneal shunt). We used SPSS to draw a ROC Curve to assess the ability of disturbance coefficients to predict the probability of hydrocephalus. Hydrocephalus occurred in 37 patients after SAH. The average disturbance coefficient of patients with hydrocephalus decreased by 25.14±9.78, and the disturbance coefficient of patients with no hydrocephalus decreased by 6.58±10.10 (one aspect of the present invention is a system of non-invasively monitoring hydrocephalus, cerebral edema, and intracranial bleeding comprising of a source emitting electromagnetic waves to brain tissue, a detector detecting said wave that propagates through said tissue, a signal conditioning unit amplifying and filtering said wave, a quadrature detector estimating magnitude and phases of said wave, and a parameter estimator calculating the complex wave number, relative attenuation coefficient (RAC), relative phase shift (RPS), wave speed change (WSC), and travel-time difference (TTD) of said brain, and assessing status of hydrocephalus and cerebral edema). The difference was statistically significant (t=9.825, P<0.001). The decrease in disturbance coefficient can be used to predict the occurrence of hydrocephalus, and if the disturbance coefficient decreases by more than 15.5 (sensitivity, 92.37%; specificity, 86.49%), it can be used to indicate the occurrence of hydrocephalus. The disturbance coefficient can predict the occurrence of hydrocephalus. The greater decline of the disturbance coefficient, the greater probability of occurrence of intracranial hydrocephalus. Hydrocephalus can be early detected. However, the CT scan is necessary to confirm the occurrence of hydrocephalus. Early diagnosis and early treatment may improve the prognosis of patients with hydrocephalus after subarachnoid hemorrhage.

Analysis of statistical method and variation characteristic parameters of very fast transient electromagnetic interference

The very fast transient overvoltage/overcurrent (VFTO/VFTC) signals generated during disconnectors switching operation may result in a significant threat to the reliability of power grids. While there are several commercial types of disconnectors, there is still a lack of understanding of the electromagnetic interference characteristics that is generated during the very fast transient process of the disconnectors. Based on the transient voltage and current data of disconnector capacitive small current test, this paper extracts the characteristics of the corresponding macropulse and monopulse waveforms. Also, the paper presents a comprehensive statistical analysis of the transient waveform characteristic data through probability density function fitting and Kolmogorov–Smirnov (K–S) test of the sample cumulative empirical distribution. The statistical results show that the probability density distribution of the switching operation macropulse waveform follows generalized extreme value and inverse gaussian distribution. The maximum peak values of VFTO and VFTC monopulse are found to be 50 kV and 370 A with a respective rise time at the range of nano- and micro-seconds.​ The frequency bands of VFTO and VFTC macro waveforms are basically distributed within 16 MHz. Results of this paper can pave the way into a more scientific basis for the design of disconnectors considering the strong electromagnetic disturbance and the formulation of system level electromagnetic compatibility standard tests, ensure the safe and stable operation of the power grid.

Cable Coupling Characteristics of Wireless Network Convergence Nodes by Transient Electromagnetic Fields in Intelligent Substations

Switching operations in intelligent substations generate a wide range of extremely strong and asymmetric transient spatial electromagnetic fields, and this complex transient electromagnetic field can have a coupling effect with the wireless network sink node equipment cables. We conducted a study on the networking method of wireless network equipment in smart substations and analyzed the types of sink node cables used. In the GIS room of the 110 kV GIS smart substation, the transient spatial electromagnetic field generated by switching operation and the transient induced current of the sink node cable under different operating conditions were tested and obtained, and the time domain and frequency domain comparative analysis was performed. A near-field coupling model of the asymmetric and non-uniform cable transient spatial electric field at the sink node is established, and the validity of the model is verified by comparing and analyzing the measurement and simulation results. The results of the study can provide a reference for transient electromagnetic disturbances in 110 kV GIS intelligent substations and contribute to improving the reliability of wireless network equipment operation.

Frequency Extraction of Global Constant Frequency Electromagnetic Disturbances from Electric Field VLF Data on CSES

The electromagnetic data observed with the CSES (China Seismo-Electromagnetic Satellite, also known as Zhangheng-1 satellite) contain numerous spatial disturbances. These disturbances exhibit various shapes on the spectrogram, and constant frequency electromagnetic disturbances (CFEDs), such as artificially transmitted very-low-frequency (VLF) radio waves, power line harmonics, and interference from the satellite platform itself, appear as horizontal lines. To exploit this feature, we proposed an algorithm based on computer vision technology that automatically recognizes these lines on the spectrogram and extracts the frequencies from the CFEDs. First, the VLF waveform data collected with the CSES electric field detector (EFD) are converted into a time–frequency spectrogram using short-time Fourier Transform (STFT). Next, the CFED automatic recognition algorithm is used to identify horizontal lines on the spectrogram. The third step is to determine the line frequency range based on the proportional relationship between the frequency domain of the satellite’s VLF and the height of the time–frequency spectrogram. Finally, we used the CSES power spectrogram to confirm the presence of CFEDs in the line frequency range and extract their true frequencies. We statistically analyzed 1034 orbit time–frequency spectrograms and power spectrograms from 8 periods (5 days per period) and identified approximately 200 CFEDs. Among them, two CFEDs with strong signals persisted throughout an entire orbit. This study establishes a foundation for detecting anomalies due to artificial sources, particularly in the study of short-term strong earthquake prediction. Additionally, it contributes to research on other aspects of spatial electromagnetic interference and the suppression and cleaning of electromagnetic waves.

Assessment and analysis of the global ionosphere maps over China based on CMONOC GNSS data

The global ionosphere map (GIM) total electron content (TEC) data are extensively employed to statistically study the seismic ionospheric disturbance characteristics. Due to the limitation of spatial coverage of ground-based GNSS receivers, in many regions, the GIM TEC results are obtained by interpolation or extrapolation, and therefore the actual accuracy is different. In this paper, based on the CMONOC GNSS data, a high-precision regional ionospheric map (RIM) model over China is established, and the assessment and analysis of the post-processed IGS GIM over China are conducted. Statistical results show that the average RMS of IGS GIM over China is less than 2 TECu. The comparison of the TEC values calculated by the GIM with the RIM shows that the two models give similar results. The Bias and STD of the difference over most of China is less than 2 TECu except in some low latitude areas. Meanwhile, the correlation between GIM and RIM is better in the daytime than at night, and it is not affected by space electromagnetic disturbance. The assessment results of accuracy in this paper are only applicable to the China region, and the accuracy of other regions needs to be further assessed.

Experimental Study on Response of Non- and Externally-Gapped Metal-Oxide Arresters Excited by Nanosecond-Level Transient Electromagnetic Disturbances

Metal-oxide arresters (MOA), including the non-gapped MOAs (NG-MOA) and externally-gapped MOAs (EG-MOA), are the main equipment applied to protect the power system against conducted transient electromagnetic disturbances (TED). However, MOAs exhibit quite different electrical characteristics under microsecond-level and nanosecond-level transients. In order to figure out the response of MOAs under nanosecond-level TED, experimental platforms are built which contain a pulse generator with the amplitude of pulse current adjustable from 0 kA to 5 kA and the rise time of 20 ns. Then the dynamic hysteresis loops, the static V-I characteristics, the response time delay and the full response process of five types of 10-kV MOAs are investigated. From the dynamic hysteresis loops of NG-MOAs, the impedance conversion process can be seen clearly and can be explained by the grain-boundary theory. But EG-MOAs has not this conversion process due to the air-gap. And the experimental results demonstrate that there is no noticeable nanosecond-level conduction delay on NG-MOAs whereas the electric field non-uniformity of the air-gap has a significant influence on the time delay of the EG-MOAs. The response time delay of EG-MOAs changes ranging from tens of nanoseconds to hundreds of nanoseconds. This feature makes EG-MOAs more likely to raise insulation risks under nanosecond-level TED compared with NG-MOAs.

Statistical Study on the Time Characteristics of the Transient EMD Excitation Current from the Pantograph–Catenary Arcing Discharge

Electromagnetic disturbances (EMDs) resulting from arcing discharge between the pantograph and catenary pose a serious threat to the electromagnetic safety of electrified trains. The time characteristic of EMD excitation current has a significant impact on the generation mechanism and characteristics of electromagnetic emission from pantograph–catenary discharge, but there have been few studies on the topic. In this paper, a large sample of time-domain waveform parameters were collected through laboratory measurements considering the high randomness nature of the arcing discharge. The reference distributions of the waveform parameters were selected using the Kolmogorov–Smirnov test, and the probability density function parameters that vary with applied voltages and discharge gap spacings were examined. Then, a stochastic model for the derivation of the discharge current waveform was proposed based on statistical results using a modified double exponential function whose parameters can be derived from physical properties. Waveforms of the excitation currents representing different EMD severities were generated by adjusting the quantiles of the fitting distributions. The validity of the stochastic model was demonstrated by comparing the measured and simulated waveforms for both single pulses and pulse trains. The proposed method and generated waveforms can help recreate the electromagnetic environment of pantograph–catenary arcing.

Transient Response of Polar‐Cusp Ionosphere to an Interplanetary Shock

AbstractInterplanetary (IP) shock‐driven sudden compression of the Earth's magnetosphere produces electromagnetic disturbances in the polar ionosphere. Several studies have examined the effects of IP shock on magnetosphere‐ionosphere coupling systems using all‐sky cameras and radars. In this study, we examine responses and drivers of the polar ionosphere following an IP shock compression on 16 June 2012. We observe the vertical drift and concurrent horizontal motion of the plasma. Observations from digisonde located at Antarctic Zhongshan station (ZHO) showed an ionospheric thick E region ionization and associated vertical downward plasma motion at F region. In addition, horizontal ionospheric convection reversals were observed on the Super Dual Auroral Radar Network ZHO and McMurdo radar observations. Findings suggest that the transient convective reversal breaks the original shear equilibrium, it is expected that the IP shock‐induced electric field triggers an enhanced velocity shear mapping to the E region. The horizontal motion of the plasma was attributed to only the dusk‐to‐dawn electric field that existed during the preliminary phase of sudden impulse. We also found that ionospheric convection reversals were driven by a downward field‐aligned current. The results of these observations reveal, for the first time, the immediate and direct cusp ionosphere response to the IP shock, which is critical for understanding the global response of the magnetosphere following an abrupt change in Interplanetory Magnetic Field (IMF) and solar wind conditions.

(Adversarial) Electromagnetic Disturbance in the Industry

Faults occur naturally and are responsible for reliability concerns. Faults are also an interesting tool for attackers to extract sensitive information from secure chips. In particular, non-invasive fault attacks have received a fair amount of attention. One easy way to perturb a chip without altering it is the so-called Electromagnetic Fault Injection (EMFI). Such attack has been studied in great depth, and nowadays, it is part and parcel of the state-of-the-art. Indeed, new capabilities have emerged where EM experimental benches are used to cryptanalyze chips. The progress of this “field” is fast, in terms of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">reproducibility</i> , <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">accuracy</i> , and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">number of use-cases</i> . However, there is too little awareness about such advances. In this paper, we aim to expose the true harmfulness of EMFI (including reproducibility) to enable reasonable security quotations. We also analyze protections (at hardware/firmware/system levels) in light of their efficiency. We characterize the specificity of EM fault injection compared to other injection means (laser, glitch, probing).

Influence of Temperature on the EFT Immunity of Multistage Integrated Oscillators

The reliable operation of an integrated circuit (IC) can be affected by transient electromagnetic disturbances and temperature variations. In this paper, the performance of three oscillator circuits, namely 3- and 5-stage current-starved voltage controlled oscillators and a 3-stage ring oscillator, is compared with respect to electrical fast transients (EFT) under the influence of thermal stress. The main objective is to compare and assess, by means of measurements, the EFT immunities of integrated oscillators with the same electrostatic discharge (ESD) protections but different circuit topologies. The failure modes caused by EFT are proposed based on the considered failure criterion. Moreover, the importance of the IC package on the immunity levels of each oscillator is investigated. The output frequency response of each oscillator to the combined EFT and temperature stresses is analyzed without the external parasitics. The results show that the 5-stage CSVCO is most resilient towards temperature variations, whereas it is the least immune to the combined effect of EFT and temperature. Moreover, a distinct behavior in each tested oscillator's frequency is observed for the in-phase EFT injections due to the topology of the circuit. Relevant MOSFET characteristics such as on-state drain-to-source resistance, power dissipation, effective mobility and threshold voltage are further analyzed under the influence of thermal stress and EFT. The root cause of higher EFT susceptibility of the 5-stage CSVCO is found to be the considerable variation of the on-state resistance due to the combined reduction of effective mobility and absolute threshold voltage levels of the MOSFETs.

Vulnerability Assessment of Equipment Excited by Transient Electromagnetic Disturbances Based on Distribution-Free QMU Method

Based on the framework of quantification of margins and uncertainties (QMU) method, a distribution-free QMU method is proposed for the vulnerability evaluation of electrical and electronic equipment excited by transient electromagnetic disturbances. The proposed method can provide a comprehensive evaluation of the equipment considering the stress and the strength with uncertainties. The stress is represented by the induced responses on the equipment conductors, the strength is quantified by the occurrence probability of failure obtained from the experiment. The quantile-based QMU metric can take account of the inherent probability characteristics of stress and strength, as well as the aleatory uncertainties caused by sampling variability. The quantiles and their tolerance bounds are estimated by a nonparametric estimation method based on order statistics, which is a data-driven method without being constrained by the type of probability distribution. A case study of an electronic equipment in the power plant is carried out to illustrate the evaluation procedures of the proposed method.

Automatic Recognition of Constant-Frequency Electromagnetic Disturbances Observed by the Electric Field Detector on Board the CSES

Since the CSES (China Seismo-Electromagnetic Satellite) has been in orbit, it has detected a large number of constant-frequency electromagnetic disturbances (CFEDs), which are horizontal lines on the spectrum. In this paper, we present an algorithm for automatic recognition of CFEDs based on computer vision technology. The relevant results are of great significance for analysis of perturbation events and mining of the transformation laws of global space events. First, a grayscale spectrogram is obtained; then, a horizontal convolution kernel is used to enhance the horizontal edge features of the grayscale graph, and finally, black-and-white binarization is performed to complete data preprocessing. The preprocessed data are then fed into an unsupervised cluster model for training and recognition to realize automatic recognition of CFEDs. Experimental results show that the CFED recognition algorithm proposed in this paper is effective, with a recognition accuracy of more than 98%.

EMD based statistical analysis of nighttime pre-earthquake ULF electric field disturbances observed by CSES

To explore the correlation between earthquakes and spatial ultra-low frequency electric field disturbances and to study the phenomenon of seismic ionospheric disturbances, this study uses 3 years of electric field ULF band data from 2019 to 2021 observed by the electric field detector carried by the CSES to identify anomalous disturbances using the anomaly automatic detection algorithm based on empirical mode decomposition for the 2,329 seismic events of magnitude not less than 5.0 and the electric field ULF disturbances in this period are analyzed by Superposed Epoch Analysis, and the statistical results are compared and analyzed in depth by earthquake location and different magnitudes in terms of both spatial and temporal scales and spatial distribution. The results show that: 1) There is a correlation between earthquakes of magnitude not less than 5.0 and ultra-low frequency disturbances in the electric field. The abnormal disturbance mainly occurred 11 days before the earthquake, 2 days before the earthquake to the day of the earthquake, and the location of the earthquake is within 200 km from the epicenter. 2) Sea earthquakes can observe more pre-seismic anomalous electromagnetic disturbances than land earthquakes. 3) In terms of earthquake magnitude, the larger the magnitude, the earlier the pre-earthquake anomalous disturbances appear and the wider the range of anomalies. This study provides an effective way to explain seismic ionospheric phenomena, and also provides a reference for the application of electromagnetic monitoring satellites in earthquake prediction and early warning as well as disaster prevention and mitigation.

Development of the EM Field in a Shielding Enclosure with Aperture after Interference Caused by a Subnanosecond High-Power Parallelly Polarized EM Plane Wave Pulse

Due to the increase in the threat of attacks with high-power electromagnetic (EM) pulses, there is great interest in metallic enclosures with high shielding effectiveness (SE). Necessary technological apertures in these enclosures reduce their effectiveness. Understanding the penetration and internal propagation of the high-power EM pulses into an apertured enclosure is fundamental to assessing the EM SE of the enclosure. In the present paper, results of the numerical simulations of development of the EM field in a shielding enclosure with aperture after the interference of a subnanosecond high-power EM plane wave pulse of the parallel polarization (having the duration of 0.3558 ns and the amplitudes of the electric and magnetic fields of 106 V/m and 2.6 × 103 A/m, respectively) are presented. The results obtained include 3D and 2D images , vector maps of the EM field developed inside the enclosure, and time-varying distributions of the electric charges formed on the inner walls of the enclosure. They revealed the mechanism of formation of the EM field inside the enclosure caused by the subnanosecond high-power parallelly polarized EM pulse. The EM field formed in the enclosure with aperture has the form of the electric and magnetic field interference structures. They are a superposition of the incident EM pulse field, which entered the enclosure through the aperture in the way described by the geometrical (ray) optics, the electric field generated by the electric charges formed on the aperture edges and inner sides of the walls of the enclosure, and the magnetic field generated by the surface current formed on the aperture edges and on the inner walls of the enclosure. The amplitudes of the electric and magnetic fields of the strongest EM interference structures decrease non-monotonically to about 0.7 × 105 V/m and 200 A/m at t = 5 ns. We found that the points in the enclosure are subjected to the disturbance of a long series of subnanosecond EM pulses, which we have called internal EM pulses. The amplitudes of these internal pulses are lower than those of the incident EM pulse. Nevertheless, they can pose a severe EM hazard inside the enclosure due to their large number (about 900 internal pulses in 30 ns). This means a fundamental change in the character of the EM disturbance caused by the subnanosecond pulse when the enclosure with aperture is used as a shield.

Measurement and Analysis of Electrical Behaviors of Offline Discharge Between High-Speed Contact Wire and Pantograph of Locomotive

With the increase in the speed of locomotives, the offline discharge between the pantograph and catenary (PAC) occurs occasionally, which generates the electromagnetic disturbance. The main purpose of this article is to study the electrical behaviors of the offline discharge between the contact wire (CW) with a high current and the pantograph under their relatively high-speed motion, including the characteristics of the discharge voltage, current, and electromagnetic disturbance. By analyzing the experimental data measured by advanced high-power PAC equipment, two discharge forms were found macroscopically. Under different supply currents and speeds, the time and frequency domain characteristics of the discharge voltage, current, and surrounding electric field (EF) were obtained. The main factors causing electromagnetic disturbance were discussed. Then, from the perspective of the migration-diffusion motion of the particle, the main reasons for the pulsation of the discharge current during the PAC offline were explained. Depending on the frequency distribution of the measured results, a 3-D model was built for the research on the PAC offline electromagnetic disturbance. Also, the variation laws of the electromagnetic field in the near and far-field were got. The research results of this article provide the references for the electromagnetic protection of the railway wireless equipment.

Test and Analysis on Electromagnetic Disturbance of Digital Unit of Primary–Secondary Integrated 10kV Circuit Breaker

Test and Analysis on Electromagnetic Disturbance of Digital Unit of Primary–Secondary Integrated 10kV Circuit Breaker

Electromagnetic compatibility analysis of thermal energy recovery power system driven by new energy vehicles

In order to ensure the stability of battery management power system, improve the reliability of on-board electronic products, and ensure the stability of thermal energy recovery power system, the author proposes an electromagnetic compatibility optimization scheme based on wiring harness, power module, and PCB noise, taking the battery management system of vehicle electronic components as an example, the role of electromagnetic compatibility on products is described, the hardware circuit is analyzed and designed by electromagnetic compatibility design theory to ensure the reliability of vehicle components. The electromagnetic stability of the power battery is guaranteed through the electromagnetic compatibility optimization analysis of the battery management system, so as to achieve more stable battery management. The experimental results show that each module of the battery management system works stably, and the disturbance degree test shows that the resonant noise of the battery management system disappears, and there is no obvious narrowband electromagnetic disturbance, and the overall value is below the limit of 20 dB. In conclusion the electomagnetic compatibility optimization scheme can effectively ensure the stability of the battery management power system, and indirectly ensure the stability of the heat recovery power system.

Development and Experimental Research of VFTO Measuring Sensor

Very fast transient overvoltage (VFTO) generated by an operating disconnector is one of the main reasons for electromagnetic disturbance in gas-insulated switchgear (GIS) substations. Generally, the amplitude of VFTO can be used as one of the references for the insulation design of GIS primary electric power equipment, so it is necessary to obtain its accurate amplitude. In this study, a new VFTO measuring sensor is developed and its measurement performance is demonstrated through hundreds of operations by a disconnector in a 220 kV GIS test circuit. The validation shows that the low cut-off frequency of the new VFTO measuring sensor has been greatly expanded to 0.01 mHz, which is improved by about 50% compared with the old sensor. The measurement accuracy of amplitude of VFTO micro-pulse improves greatly by about 80% compared with the old one. Thus, the new VFTO measuring sensor can fully meet the measurement needs of trapped charge voltage, power frequency voltage, and high-frequency transient voltage in VFTO waveform. It can be used to provide more accurate data support for insulation design of GIS primary power electric equipment in extra-high voltage (EHV) and ultra-high voltage (UHV) GIS substations.