Electric Field Signal Research Articles

Ground‐level DC electric field sensor for overhead HVDC/HVAC transmission lines in hybrid corridors

Measurement of electric fields is crucial for the evaluation of the electromagnetic environment in electric power transmission system. Due to limited transmission corridor resources, the hybrid transmission lines including high-voltage alternating current and high-voltage direct current (HVAC/HVDC) are more common nowadays. However, commonly used field-mill direct current electric field sensors (DC EFSs) can only be used beneath HVDC lines and the emergence of alternating current (AC) electric fields has adversely affected measurement results recorded by DC EFS. In this work, a DC EFS was designed that is capable of measuring ground-level DC electric fields generated by overhead HVAC/HVDC transmission lines in a hybrid corridor. A field-mill structure was used to modulate the DC and AC hybrid electric field and then a narrow band-pass filter was used to realise suppression of the AC electric field signal. Subsequently, the phase-sensitive detection method was used to realise amplitude demodulation and phase discrimination of the DC electric field. Sensor prototypes based on the foregoing method were experimentally tested in the China national high-voltage base. These DC EFSs could be mass-produced conveniently from current field-mill for hybrid corridors application.

Ag-modified carbon fiber as a stable sensor

Carbon Fiber (CF) electrode has a wide range of applications as an electric field sensor. However, its use is limited because of its poor stability. In this paper, the CF was pretreated by thermal oxidation (400 °C, 1 h) to remove surface impurities, resulting in 2.3% mass reduction, which means the increase of effective specific surface area. XRD and EDS confirmed the nano-silver coating was chemically modified on the surface of CF by electroplating. Charging current density differences and Tafel slope showed 6.19 mF cm−2 and 77 mV dec−1, respectively, which implied outstanding electrochemical performance. As a sensor, the Ag-modified CF electrode-pair has small potential difference drift of 29 μV/24 h and excellent response property to low frequency electric field signal, along with lower AC impedance (1.42 Ω@1 Hz) and electrochemical self-noise (1.38 nV/rt (Hz)@1 Hz). The novel Ag-modified CF electrodes provided a potential choice for the design of high-sensitivity marine electric field sensor.

Schumann resonance on Titan: A critical Re-assessment

Extremely Low Frequency (ELF) electric field signals recorded by the Huygens probe have previously been interpreted as indicating a Schumann Resonance (SR) in the ionosphere-ocean cavity. This interpretation required accommodation of a number of anomalous features with respect to the terrestrial SR, namely a lack of observed lightning discharges with instead an appeal to excitation by interaction with the Saturnian magnetosphere, a horizontal field orientation, and the presence of only a single spectral peak speculated to be the second eigenmode. We suggest here that the data are dominated by artifacts due to mechanical oscillations of the booms or other elements of the probe. Although such an explanation was previously dismissed, we show in new analyses that the ELF time series correlates closely with the history of other mechanical vibration on the probe. In particular, the growth of the ‘ELF’ signals after the release of the main parachute, when the most extensive probe motions also began, and the disappearance of the signals within a few seconds after probe impact, point to a mechanical origin. We additionally review the capability of possible future SR measurements to constrain the thickness of an ice crust on Titan. Even if the magnetospheric excitation does not happen (it may or may not have occurred during the Huygens descent, we only argue that it is not required to explain the data), sporadic lightning during methane rainstorms could yet occur and excite occasional SR activity. However, the interpretation of the SR to retrieve ice thickness is challenged by ambiguities without simultaneous knowledge of the lower ionospheric structure.

Application of Ensemble Empirical Mode Decomposition in Low-Frequency Lightning Electric Field Signal Analysis and Lightning Location

The application of empirical mode decomposition (EMD) in the analysis and processing of lightning electric field waveforms acquired by the low-frequency e-field detection array (LFEDA) in China has significantly improved the capabilities of the low-frequency/very-low-frequency (LF/VLF) time-of-arrival technique for studying the lightning discharge processes. However, the inherent mode mixing and the endpoint effect of EMD lead to certain problems, such as an inadequate noise reduction capability, the incorrect matching of multistation waveforms, and the inaccurate extraction of pulse information, which limit the further development of the LFEDA’s positioning ability. To solve these problems, the advanced ensemble EMD (EEMD) technique is introduced into the analysis of LF/VLF lightning measurements, and a double-sided bidirectional mirror (DBM) extension method is proposed to overcome the endpoint effect of EMD. EEMD can effectively suppress mode mixing, and the DBM extension method proposed in this article can effectively suppress the endpoint effect, thus greatly improving the accuracy of a simulated signal after a 25–500-kHz bandpass filter. The resulting DBM_EEMD algorithm can be used in the LFEDA system to process and analyze the detected electric field signals to improve the system’s lightning location capabilities, especially in terms of accurate extraction and location of weak signals from lightning discharges. In this article, a 3-D image of artificially triggered lightning obtained from an LF/VLF location system is reported for the first time, and methods for further improving the location capabilities of the LF/VLF lightning detection systems are discussed.

Terahertz Imaging and Characterization Protocol for Freshly Excised Breast Cancer Tumors.

This manuscript presents a protocol to handle, characterize, and image freshly excised human breast tumors using pulsed terahertz imaging and spectroscopy techniques. The protocol involves terahertz transmission mode at normal incidence and terahertz reflection mode at an oblique angle of 30°. The collected experimental data represent time domain pulses of the electric field. The terahertz electric field signal transmitted through a fixed point on the excised tissue is processed, through an analytical model, to extract the refractive index and absorption coefficient of the tissue. Utilizing a stepper motor scanner, the terahertz emitted pulse is reflected from each pixel on the tumor providing a planar image of different tissue regions. The image can be presented in time or frequency domain. Furthermore, the extracted data of the refractive index and absorption coefficient at each pixel are utilized to provide a tomographic terahertz image of the tumor. The protocol demonstrates clear differentiation between cancerous and healthy tissues. On the other hand, not adhering to the protocol can result in noisy or inaccurate images due to the presence of air bubbles and fluid remains on the tumor surface. The protocol provides a method for surgical margins assessment of breast tumors.

A Multivariable, Two-Dimensional Plot of Electromagnetic, Electric Field and Seismic Information for the Characterization of Earthquake Precursors

Removal of the electrical shielding from a type of Fourier transform seismometer overlays seismic information with Extremely Low Frequency-range (ELF) electromagnetic signals between about 0.3 Hz and 36 Hz (the ITU-designated range of ELF is 3 to 30 Hz). The observed signals originate in the electric power grid, shown clearly by the fact that they are sum and difference heterodyne products with the power grid’s higher harmonics of 60 Hz, typically the 36th and 37th, because the seismometer’s chosen frequency modulation (FM) carrier frequency is roughly 2200 Hz. It is especially interesting that on 2017-03-19, prior to 14:25:12 UTC, the instrument recorded an 11 minute sequence of 20.3 Hz ELF outbursts that culminated intimately with a 3.2 magnitude earthquake located a few miles west of Bardwell KY. These ~20.3 Hz ELF signals, very near the third Schumann resonance frequency, have been recorded numerous times. They are distinctive and fairly strong, ranging 15 to 30 db or more above the noise floor, but definitely not an every-day event; months can pass without them. So far most of these ELF signals do not have an intimately associated earthquake, with the event of 2017-03-19 being one of only two exceptions recorded thus far. That quake’s location was more than one hundred miles from the instrument, in the New Madrid Seismic Zone (NMSZ). The second case, a quake in Kansas, was about three times farther from the instrument, and its ELF signals were correspondingly weaker. Those other, unassociated electromagnetic events might come from quakes too weak to detect, but it should be noted that stronger, easily detected quakes also rarely exhibit any ELF/seismic “connectivity”. This paper describes an instrument that overlays ELF, electric field and seismic signals. The instrument’s two-dimensional (2D) output has a time axis (horizontal) resolution of ~3 seconds and an ELF frequency (vertical) resolution of ~0.3 Hz.

Electric Field Signal Recognition Method of DS Switching Operations Based on Wavelet Packet Analysis and PSO-HSVM

In order to monitor the state of Gas Insulated Substation (GIS), this paper established a fault simulation experimental platform for Disconnecting Switch (DS), and collected data through a 3D radiation electric field (E-field) measurement system. For extract the feature parameters, four-layer wavelet packet decomposition was performed on the data to obtain normalized energy, and the dimension of the eigenvector was reduced by principal component analysis (PCA) algorithm. Then, the model was trained with the hybrid kernel support vector machine (HSVM) algorithm, and the parameters was optimized with the particle swarm optimization(PSO) algorithm. The result shows that compared with the traditional SVM model, the method proposed in this paper improves the diagnosis accuracy of DS defect signals.

A new impedance matching approach for microstrip Rotman lens based on analyzing the standing wave pattern of an electric field

AbstractThis article proposes a new impedance matching method to provide an energy transformer between 50 Ω beam ports and the cavity of a Rotman lens. The model is derived from a quarter length transition line impedance transformer. The suggested matching technique is based on determining and analyzing standing wave patterns of electric field signals underneath feeding lines of the beam ports when they are excited with a designed frequency of 2.45 GHz. The proposed approach demonstrates the ability of the model to achieve an acceptable return loss compared to traditional taper line model matching methods, even though it increases the operating bandwidth frequency based on the measured results. Moreover, it solves the optimization iteration time consuming that is required to determine the tapering line length used in the conventional impedance matching techniques. The predicted results of the return loss are validated by measurements of the fabricated prototype microstrip lens printed on an FR‐4 substrate that is designed to work in the industrial, scientific, and medical (ISM) band in order to form five beams in the directions −26°, −13°, 0°, 13°, and 26°.

The influence of alternating current and direct current electric fields on the rheological behavior of electrorheological fluids with particles of the different crystalline structure

The rheological behavior of electrorheological fluids with dispersed fillers whose particles have different crystalline structures is investigated in direct and alternating electric fields. The dielectric characteristics of the materials were measured and the influence of the strength, frequency, and shape of the signal of electric field was investigated, and the influence of temperature on the shear stress in electrorheological fluids was estimated in direct current electric field.

Sub-Nyquist sampling method and its application in high-frequency electric-field measurement

A high-frequency signal sampling approach by combining with compressive sensing and random equivalent sampling technology is proposed. The proposed sampling method achieves ∼10 times faster equivalent sampling rate by utilizing three parallel sub-Nyquist low-rate analog-to-digital converters (TPSL-ADC). By the union of the optical electric-field sensor with wide dynamic range and the proposed TPSL-ADC sampling method, a complete high-frequency electric-field signal measurement system has been realized. The high-frequency electric-field signal with an equivalent sampling rate of 1 GS / s is captured by utilizing three parallel ADCs with sampling rates of ∼32.3, 31.3, and 30.3 MS / s, respectively. The effectiveness of the proposed electric-field sensing and detecting system has been experimentally demonstrated.

Essence of the Magnetism

In this paper, it is proposed that the magnetic field is an electric field that contracts in the direction of motion. This viewpoint is taken as the basic principle of analyzing the magnetic phenomena. The law of Lorentz force is proved by deduction, and any necessary correction is made. The law of electromagnetic induction is also proved by deduction, and the specific physical process of electromagnetic induction is clarified. The displacement current and Ampere circuit law is also proved by deduction. It is considered that the contraction of electric field in the direction of motion is the source of generation of magnetism, while the contraction of electric field in the direction of motion is fundamentally derived from the principle of constancy of light velocity. Since the magnetism has contributed the modern science and technology to the human beings, so it is convinced that the principle of constancy of light velocity is the most precious gift which the God has given to mankind. The motion with variable velocity of the electric field is also analyzed. It is pointed out that the generation of electric wave is essentially resulted from the distortion and contraction of the electric field caused by the propagation of the motion with variable velocity of the electron of the wave source at the velocity of light in its electric field. The electric field energy of the electric wave is propagated by the distortion of the electric field, while the magnetic field energy of the electric wave is propagated by the contraction of the electric field. The electric field energy is identically equal to the magnetic field energy. The electric field signal and the magnetic field signal are always in the same phase. The law of electromagnetic induction is derived from a distorted electric field. The common electromagnetic induction phenomenon is essentially a transmission and reception effect of electric waves. It is proved that the Ampere circuit law is derived from the displacement current, and that the displacement current is derived from the magnetic field, which is the electric field in motion. The propagation of electric wave is analyzed. It is pointed out that, if the propagation velocity of electric wave is greater than the velocity of light, the propagation effect of electric wave will be rapidly weakened. If the propagation velocity of electric wave is less than the velocity of light, the electromagnetic interference and radiation will be increased rapidly. Therefore, it is firmly believed that the actual velocity of light of about /s is the best propagation velocity of electric wave for mankind. It is considered that the actual velocity of light is another precious gift which the God has given to mankind.

Development and characterization of high-stability all-solid-state porous electrodes for marine electric field sensors

Marine electromagnetic (EM) methods can be used for marine geophysical exploration. We proposed an all-solid-state porous Ag/AgCl electrode with high stability and a long service life as a marine electric field sensor with the ability to withstand deep sea high pressures while improving the accuracy of electric field measurements for long-period marine EM method engineering projects. Compared with a plate electrode, the all-solid-state porous electrode has excellent polarization resistance in seawater. To avoid the short service life of the sensor used in marine EM method engineering, the all-solid-state porous Ag/AgCl electrodes were manufactured by a ball-milling and sintering process, and the electrochemical channel of the electrodes was observed under a scanning electron microscope. A sensor casing based on the porous electrodes used in the deep sea environment was designed. An experimental system for evaluation and characterization was designed to measure the polarization resistance, sensitivity, noise, self-potential and drift of the proposed electrodes, which are important properties and will affect the accuracy of marine electric field measurements. The results show that the source resistance of the electrode is 2.13 Ω/cm2, the electrode noise level is 1.57 nV/rt(Hz), the self-potential of the proposed electrode pair is less than 35 μV, and the potential drift is less than 10 μV/day. After more than 180 days of use, the electrodes showed outstanding stable drift potentials of below 15 μV/day. The proposed all-solid-state porous electrodes can ensure the measurement accuracy of marine electric field signals and promote the exploration of marine resources.

Inspection in overhead insulators through the analysis of the irradiated RF spectrum

Failures in high voltage insulators can cause significant injuries for the consumers, since these piece of equipment play a fundamental role for the transmission lines operation. Insulator inspection and diagnosis techniques are widely researched, varying mainly regarding to the data collection method, as example: ultrasound, thermal imaging, leakage current, corona, electric field and RF signals. In this article, the RF signals radiated by the insulators were used to classify them into three levels of pollution: “light”, “medium” and “heavy”. For this, we used the standard IEC 60815-1 as reference, which takes into account the ESDD and NSDD indices. The proposed classification method was based on the wavelet transform, for signal processing, and artificial neural network for the classification. The success rate was approximately 95% in the 1.2–1.4 GHz frequency range.

Discriminating cloud to ground lightning flashes based on wavelet analysis of electric field signals

Lightning discharges produce electromagnetic radiation in a wide frequency range, but its propagation in a certain frequency range are usually used by lightning detection networks. Investigation of lightning activities in time-frequency domain can be obtained by using the wavelet transform. This study proposes a new approach using the discrete wavelet transform (DWT) algorithm to classify the detected lightning strikes. The measuring station would capture lightning electric field in 500 ms time scale and then utilizes a wavelet based recognizer algorithm to duly differentiate the cloud to ground flash from other cloud activities. Wavelet transform allows the expansion of transient events into a small number of coefficients. A total of 200 lightning flashes were randomly selected among the captured lightning discharges in South of Malaysia in one year. Initially, the cloud to ground and other cloud activities were manually analysed and discriminated. Then, these lightning flashes were analysed using different mother wavelets such as Haar, symmlet, Coiflet, and Daubechies by means of MATLAB program. Haar mother wavelet gives the best result for CG decomposition analysis. A total of 24 decomposition layers were chosen and the energy level of each layer was calculated to obtain the correlation between energy fluctuation and type of signal. The investigations reveal that the CG discharges have higher energy in 17th to 20th layers compared to the rest. However, the opposite results were obtained for the case of other cloud activities. To increase the accuracy of the wavelet transform approach algorithm, another filter was added to the algorithm flowchart. The proposed CG discrimination algorithm successfully classified 92% of the randomly selected flashes.

Onboard software of Plasma Wave Experiment aboard Arase: instrument management and signal processing of Waveform Capture/Onboard Frequency Analyzer

We developed the onboard processing software for the Plasma Wave Experiment (PWE) onboard the Exploration of energization and Radiation in Geospace, Arase satellite. The PWE instrument has three receivers: Electric Field Detector, Waveform Capture/Onboard Frequency Analyzer (WFC/OFA), and the High-Frequency Analyzer. We designed a pseudo-parallel processing scheme with a time-sharing system and achieved simultaneous signal processing for each receiver. Since electric and magnetic field signals are processed by the different CPUs, we developed a synchronized observation system by using shared packets on the mission network. The OFA continuously measures the power spectra, spectral matrices, and complex spectra. The OFA obtains not only the entire ELF/VLF plasma waves’ activity but also the detailed properties (e.g., propagation direction and polarization) of the observed plasma waves. We performed simultaneous observation of electric and magnetic field data and successfully obtained clear wave properties of whistler-mode chorus waves using these data. In order to measure raw waveforms, we developed two modes for the WFC, ‘chorus burst mode’ (65,536 samples/s) and ‘EMIC burst mode’ (1024 samples/s), for the purpose of the measurement of the whistler-mode chorus waves (typically in a frequency range from several hundred Hz to several kHz) and the EMIC waves (typically in a frequency range from a few Hz to several hundred Hz), respectively. We successfully obtained the waveforms of electric and magnetic fields of whistler-mode chorus waves and ion cyclotron mode waves along the Arase’s orbit. We also designed the software-type wave–particle interaction analyzer mode. In this mode, we measure electric and magnetic field waveforms continuously and transfer them to the mission data recorder onboard the Arase satellite. We also installed an onboard signal calibration function (onboard SoftWare CALibration; SWCAL). We performed onboard electric circuit diagnostics and antenna impedance measurement of the wire-probe antennas along the orbit. We utilize the results obtained using the SWCAL function when we calibrate the spectra and waveforms obtained by the PWE.

Optical Mapping of RF Field Profiles in Resonant Microwave Circuits

We demonstrate a technique for mapping the electric field profiles in resonant microwave circuits. Optical pumping of microwave circuits fabricated on semiconductor substrates is shown to result in a modulation of the load power dependent on the local electric field of the microwave signal in the resonant circuit. By reading out the modulation in transmitted signal as a function of the position of the optical excitation, for a range of driving frequencies, we are able to produce 2D images related to the microwave electric fields in our circuits. Images are generated for a range of resonator designs and compared to numerical simulations. The presented technique is analytically modeled for insight to the relationship between electric field and modulation signal.

DWT-based methodology for detection of seismic precursors on electric field signals in Mexico

ABSTRACTThis paper presents an analysis of atmospheric electric field signals which were taken on an important seismic activity period from 2012 to 2015 to study its relationship with seismic events. For this purpose, several measurements were acquired every second by using a triaxial electric field monitoring system. Furthermore, the discrete wavelet transform (DWT) was applied to electric field signals with seismic events of magnitudes greater than Mw > 5.5, which occurred in Mexico with different focal mechanisms. The analysed epochs consist of 24 h of observations for a data-set corresponding to 55 different earthquakes (EQs). The time series were processed 12 h before and 12 h after each seismic event. The proposed methodology proves to be an efficient tool to detect signals with relations between electric field and seismic activity. The methodology presented herein shows important anomalies on different time instants according to the focal mechanism. Finally, a statistical post-processing algorithm was performed in order to quantify the data dispersion as a measure of seismic activity. It is found that the variance increases before, during, and after the seismic event about the coefficients D1 to D7 obtained using the DWT.

Effect of Curcumin Addition on the Adsorption and Transport of a Cationic Dye across DPPG-POPG Liposomes Probed by Second Harmonic Spectroscopy.

The effect of addition of curcumin on the adsorption and transport characteristics of a cationic dye, LDS+, across negatively charged bilayers composed of POPG and DPPG lipids were investigated by the interface selective second harmonic (SH) spectroscopic technique. Curcumin induced changes in the SH electric field signal of the LDS+ ions (E2ω (LDS+)) were observed to depend critically on the bilayer acyl chain saturation/unsaturation ratio (S/U). Following earlier works, the increase in the E2ω (LDS+) signal is attributed to the release of the Na+ counterions present in the head group region of the bilayer by curcumin and the decay of the E2ω (LDS+) signal is attributed to the bilayer intercalated state of curcumin. While the changes observed in the E2ω (LDS+) signal in the presence of POPG liposomes were consistent with our earlier study ( Varshney, G. K. et al. Langmuir , 2016 , 32 , 10415 - 10421 ), they were significantly different for DPPG liposomes, following curcumin addition. While the increase in the E2ω (LDS+) signal in the presence of POPG liposomes, is marginal (∼10-20%) and instantaneous (<1 s) followed by a rapid decay (completed within ∼100 s), in the presence of DPPG liposomes it was observed to increase slowly and at saturation shows a substantial increase (100-200%), following curcumin addition. When liposomes consisting of a mixture of POPG and DPPG lipids are used, curcumin induced kinetic characteristics of the E2ω (LDS+) signal showed a mixture of the individual kinetic characteristics observed for the unsaturated (POPG) and saturated (DPPG) liposomes. The observed kinetic trends of the E2ω (LDS+) signal following curcumin addition are explained on the basis of the relative strength of the Na+-POPG and Na+-DPPG interaction. Higher ordering of the lipid acyl chain region in DPPG liposome makes the Na+-DPPG interaction much stronger than the Na+-POPG interaction. Further, it is proposed that, in POPG-DPPG liposomes, individual domains of POPG and DPPG lipids exist at low temperature as suggested by the observed temperature dependent kinetic characteristics of the E2ω (LDS+) signal following curcumin addition. These domains are dependent on the S/U ratio and phase state of the bilayer. The gel phase was observed to be more conducive for individual domain formation. Results presented in this work not only support the notion that biological activity of curcumin is associated with its bilayer altering properties, but more interestingly it provides a qualitative insight about how bilayer phase separation can be achieved by modulating the hydrophobic interactions between the lipid acyl chains.

Fabrication of novel Ag/AgCl electrode pair on the template of carbon foam as marine electric field sensor and its electrochemical performances

A kind of novel Ag/AgCl electrode pair on the template of carbon foam is fabricated as electric field sensor for marine electric field test. The microstructure of AgCl layer and BET surface area are characterized and the electrochemical performances are tested, such as polarization resistance, stability of potential difference, signal response of electric field, and electrochemical self-noise. The results show the average diameter of AgCl grain is in the scale of 26 nm and the BET surface area of electrode is 1.40 m2/g. The polarization resistance is 21.17 Ω, meaning that the electrode has good anti-polarization property. The electrode pair has little potential difference drift (less than 0.02 mV/24 h) and excellent response property to low frequency electric field signal (1 mHz). Its electrochemical self-noise is about 1.60 $$ \mathrm{nV}/\sqrt{\mathrm{Hz}} $$ @ 1 Hz. All these results indicate that this electrode pair can offer a promising electric field sensor for marine oil-gas resources prospection.

Denoising of Lightning Electric Field Signals Based on EMD-Wavelet Method

In this paper, a new lightning electric field (LEF) signals denoising approach combined with empirical mode decomposition (EMD) and wavelet transform (WT) is proposed. Unlike the conventional EMD or WT denoising approaches, we use EMD to decompose the LEF signal firstly, the continuous mean square error(CMSE) criteria are used to determine a turning point in the original signal energy, then the Birge-Massart threshold wavelet denoising method is employed to denoise the high frequency component which contains lots of noise. Finally, the clean high frequency component and the remaining low frequency intrinsic mode function, and the residual of the EMD operation are employed to synthesize a cleaner LEF signal. The method is illustrated on real data, and the performance of the proposed method is evaluated in terms of several standard metrics. The results show that the proposed method is able to reduce noise from the noisy LEF signals more accurately and effectively in comparison to EMD filtering and Wavelet filtering methods.