D-dot Sensor Research Articles

Influence of the Temperature of the Deionized Water on the Sensitivity of D-Dot Sensor

Influence of the Temperature of the Deionized Water on the Sensitivity of D-Dot Sensor

Development of Combined Instrument Transformer for Gas-Insulated Switchgears

Accurate measurement of current and voltage information is essential to the safe reliable operation of railway substations. This paper dealt with a combined instrument transformer (CIT) built in a spacer for the purpose of miniaturization and eco-friendliness of a GIS, rated 72.5 kV and 2,000 A. A D-dot sensor and a Rogowski current sensor were applied to voltage and current measurement, respectively, to secure the insulation of the CIT in high-voltage and high-current conditions. As a result of an evaluation based on IEC 60044-7 and IEC 60044-8, the performance of the prototype CIT was found to sufficiently satisfy Class 0.5. When the CIT proposed in this paper was applied to a GIS of rated 72.5 kV, it was possible to reduce the size by 33% in length, 11% in height and 90% in weight per bay of the GIS compared to conventional iron-core transformers. In addition, since the amount of SF6 will be reduced by 15% in terms of volume, it is expected that this method can be used for the digitization, miniaturization and eco-friendliness of railway substations.

Characteristics of the D-Dot Sensor for Measurement of High Voltage Pulse of a Water-Insulated Transmission Line

The characteristics of the differential-output D-dot sensor, which is employed to diagnose the voltage pulse across the water-insulated component of the pulsed power accelerator, are investigated by theory, circuit simulation, and experiments. The leakage current from the D-dot sensor to the inner electrode of the measured component will degrade the low-frequency response property of the monitor. The lower level of the water medium resistivity the worse performance of the sensor’s low-frequency response property will be. The actual lower-limited response frequency of the D-dot sensor is not related to the sensor itself but is mainly determined by the resistivity of the water. These are not only deduced from theory but also approved by the experimental results. Circuit simulation results suggest that the D-dot sensor without consideration of the leakage current will over-evaluate the amplitude and rise time of the voltage pulse across the water-filled element. We have proposed a method to make compensation for such an effect by using a passive resistor–capacitor (RC) integrator instead of the numerical process suggested previously. It is approved both by circuit simulation and experimental results that the output of the D-dot sensor post-processed by the RC integrator could give accurate measurement results providing that the time constant of the RC integrator is identical to the characteristic time of the D-dot sensor.

Identification and Compensation for D-Dot Measurement System in Transient Electromagnetic Pulse Measurement.

The measurement of the transient pulsed electromagnetic (EM) field is essential for analyzing electromagnetic compatibility. Due to their good performance, D-dot sensors, combined with numerical integration computation for signal recovery, are commonly used to measure electromagnetic pulses (EMPs). However, the integration approach is occasionally flawed due to a non-ideal frequency response or noise, causing distortions in the reconstructed signal. In order to better understand the dynamic performance of the sensor, a nonlinear Hammerstein model is employed in the system identification for the sensor with the calibration data collected in the laboratory environment. When identifying the linear component based on the ultra-wideband characteristics of the measured transient pulse, a two-step identification approach with two different pulse excitation modes, low frequency and high frequency, is utilized to conduct the modeling across the entire frequency range. Based on the reliable identification and modeling of the D-dot sensor, a compensation system that corresponds to the nonlinear Hammerstein model has been developed for the practical signal recovery of the incident E-field. After compensation, the dynamic characteristics of the sensor are significantly improved, and the system compensation approach outperforms the integration method in signal recovery for the incident E-field.

Overshoot of D-dot sensor in measurement of electric field

This paper analyzes the cause of the overshot of the signal measured by D-dot sensor, and points out that the second-order RLC equivalent circuit model can explain the overshot Taking the asymptotic conical antenna as an example, the inductance L of the second-order model is obtained by using CST simulation and Pspice parameter scanning method. The first-order model and the second-order model are used to calculate the electric field waveform. Under the given conditions, the first-order model is used to obtain the electric field waveform, the waveform overshot is serious, the maximum overshoot reaches 27%, while the second-order model is used to improve the ringing phenomenon, And the maximum overshoot is reduced to 5%.The results show that the second-order model is more accurate than the first-order model and can improve the precision of electric field measurement using D-dot sensor.

Planar Near-Field Electric Field Sensor Array Applications Facilitated by Neural Networks

Electrical capacitance tomography is employed for various process tomography applications, typically with circular imaging regions (e.g., to estimate fluid levels in plastic pipes). Typical state-of-the-art implementations focus on circular or cylindrical sensor arrays. In contrast, this research explores using a planar 2D array of electric-field sensors to image volumes composed of various dielectric materials. The array is designed to be used with very-low-frequency electric fields, which are desirable due to their ability to differentiate between various non-conducting objects. D-dot sensors (i.e., charge induction sensors) are used as the electric-field sensing element. In this research, imaging regions of interest are modeled as a composition of (25 cm) <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> voxels of dielectric material with randomized relative permittivities. Neural networks are utilized as the inversion algorithm to map measured E-field distortions to the voxels’ relative permittivities. Three applications are explored in a simulated environment: 1) predicting relative permittivities of the entire (pseudo-3D) imaging region from one measurement of electric-field distortions (modeled in free space), 2) imaging regions arbitrarily large (in two dimensions) using the planar array as an imaging kernel, and 3) repeating application (1) in a model of a practical, real-world imaging scenario both with and without interfering material. Application (3) is performed with a real-world experimental setup using a room-sized “E-field Cage” meant to generate a uniform electric field. This work showcases a new electric-field imaging modality using a planar 2D D-dot sensor array paired with a DNN-based inversion algorithm.

SIMULATION AND MEASUREMENT OF EXTERNAL ELECTROMAGNETIC ENVIRONMENT OF TOKAMAK DEVICE.

Magnetic confinement nuclear fusion is an important way to realize controllable nuclear fusion. Due to the large current and complicated coil arrangement, there is a complicated electromagnetic environment around the fusion device. In this paper, the B-dot sensor is used to measure the magnetic field, the D-dot sensor is used to measure the electric field, the MAXWELL electromagnetic simulation software is used to simulate the electromagnetic field strength; the simulation and measurement of the spherical Tokamak SUNIST device and the measurement of MARX generator are carried out, then we give corresponding electromagnetic protection suggestions.

A deconvolution method for signal recovery of electromagnetic field sensors

The broadband pulsed electromagnetic (EM) field measurement is significant in the analysis of electromagnetic compatibility. As an efficient measurement method, the D-Dot sensor has good performance. However, the integration method sometimes shows flaws due to the non-ideal frequency response or noise. We propose a deconvolution method based on the Maximum A Posteriori method (MAP). In the practical signal recovery test, the method performs better than the integration method. The adaptability is also tested on four types of different signals. Furthermore, we discuss the influence of white Gaussian noise (WGN) and quantization noise. The relationship between the relative error and the signal-to-noise ratio (SNR) of WGN is given. When the SNR of WGN is greater than 30 dB, the relative error can be reduced under 10%. Besides, when the SNR of quantization noise is greater than 30 dB, the relative error can be reduced to under 30%.

D-Dot Sensor Response Improvement in the Evaluation of High-Power Microwave Pulses

This article investigates the issue of measuring high-power microwave (HPM) pulses. The high energy of these pulses poses a significant threat to many electronic systems, including those used to manage critical infrastructure. This work focuses on requirements for a potential portable measurement device and suggests the application of a method for this purpose, involving the use of a D-dot sensor and a rapid A/D converter. The applied converter enables recording the time waveform on the measuring chain output, also in the case of repetition and time duration of HPM signals. The authors also present a quantitative description of signal processing by the analogue section of the measurement chain solution presented herein and suggest algorithms for digital processing of the signals, the objective of which is to minimize low-frequency interference in the process of reconstructing the time waveform of an electric field using numerical integration.

A study on the calibration of an HPM meter based on a D-dot sensor and logarithmic RF power detector

A study on the calibration of an HPM meter based on a D-dot sensor and logarithmic RF power detector

A time-domain calibration method for transient EM field sensors

The traditional calibration methods are based on the frequency domain, which is not suitable for transient field sensors. As a substitute, a time-domain calibration method for transient field sensors is proposed in this article. Considering the characteristics of various devices, we select TEM cells and monocone TEM cells as the calibration devices for two aspects of sensors’ calibration. Corresponding to the frequency-domain calibration, the calibration is divided into amplitude sensitivity and rising edge calibration. The amplitude sensitivity represents the relationship between the amplitudes of recovered signal and excitation signal. And the rising edge calibration represents the ability of recovering a fast signal. We introduce the procedure of the two aspects of calibration in detail. And then an example of calibrating a D-Dot sensor is also presented. Due to only using pulse signals, the calibration method we proposed in this article is efficient and practical.

Hybrid Sensing of Internal and Surface Partial Discharges in Air-Insulated Medium Voltage Switchgear

Partial discharge (PD) measurements have proved their reliability for health monitoring of insulation systems in power system components including synchronous generators, power transformers, switchgear and cables etc. Online condition monitoring and pro-active detection of PD faults have been highly demanded over the last two decades. This paper provides results from a research project to develop advanced non-intrusive sensing technologies that are cost effective, reliable and efficient for early detection of PD faults in medium voltage (MV) and high voltage (HV) air-insulated switchgear. Three sensors (high frequency E-field (D-dot) sensor, Rogowski coil and loop antenna) have been developed and tested under various PD faults and their performance were evaluated in comparison with high frequency current transformer (HFCT) which is being used commercially for PD testing and measurement. Among these three sensors, it is shown that D-dot sensor and Rogowski coil are more dependable when it comes to the PD measurements due to their high signal to noise ratio and hence high accuracy. These sensors can be customized according to a specific application and can be connected together with one data acquisition device while developing an online condition monitoring system.

Simulation and Test of a Contactless Voltage Measurement Method for Overhead Lines Based on Reconstruction of Integral Node Parameters.

To improve the stability and adaptability of the voltage measurement based on the E-field (electric field) integral method, in this paper we introduce a new method for the contactless voltage measurement of the overhead lines. The method adopts the node parameter reconstruction technology, which is based on the Gauss–Chebyshev algorithm. In order to achieve high-quality E-field detection at the reconstructed node position, we designed a novel D-dot sensor with parallel distributed electrodes. A Maxwell simulation model of multi-level voltages of the overhead lines was carried out to determine a comprehensive criterion of the reconstruction factors. The simulation employed a three-phase overhead line experiment platform to calculate and measure the distribution and the changing trend of the E-field. The deviations of the voltage measurement were reduced at a significantly low level within 0.4%. The result of the simulation demonstrates that the method optimizes sensor distribution by reconstructing node parameters, which enables the system to have high accuracy and reliability on the contactless voltage measurement of the overhead lines.

Simulation, Design, and Test of a Dual-Differential D-Dot Overvoltage Sensor Based on the Field-Circuit Coupling Method.

Accurate measurement of overvoltage in power grids is of great significance to study the characteristics of overvoltage and design of insulation coordination. Based on the research of D-dot voltage sensor, we designed a Dual-Differential D-dot overvoltage sensor. In order to quantify the structural parameters of the sensor, improve the performance and measurement accuracy of the sensor. The Field-Circuit Coupling method was proposed to be used in the parameter design of D-dot overvoltage sensor. The joint simulation of space electromagnetic field model and equivalent circuit model of the Dual-Differential D-dot overvoltage sensor was established with the finite element simulation software Ansoft Maxwell and circuit simulation software Simplorer. Finally, the actual sensor was manufactured. A test platform was built to verify the steady-state and transient performance of the sensor. The results show that the Dual-Differential D-dot sensor has excellent steady-state and transient performance, the error of phase and amplitude are small, and the sensor can achieve the non-contact measurement of power transmission line. Simultaneously, the rationality of the Field-Circuit Coupling method was further verified.

Laboratory Calibration of D-dot Sensor Based on System Identification Method.

D-dot sensors can realize the non-contact measurement of transient electric fields, which is widely applied to electromagnetic pulse (EMP) measurements with characteristics of the wide frequency band, high linearity, and good stability. In order to achieve accurate calibration of D-dot sensors in the laboratory environment, this paper proposed a new calibration method based on system identification. Firstly, the D-dot sensor can be considered as a linear time-invariant (LTI) system under corner frequency, thus its frequency response can be characterized by the transfer function of a discrete output error (OE) model. Secondly, based on the partial linear regression of the transfer function curve, the sensitivity coefficient of the D-dot sensor is obtained. By increasing the influence weight of low-frequency components, this proposed method has better calibration performance when the waveform is distorted in the time domain, and can artificially adapt to the operating frequency range of the sensor at the same time.

Method and Experimental Study of Voltage Measurement Based on Electric Field Integral With Gauss–Legendre Algorithm

At present, the method of obtaining the voltage of transmission lines by using the inverse problem of the electric field is generally faced with the difficulties of solving data equations. Aiming at the above problems, the method that solves transmission wire voltage through spatial electric field integration based on D-dot sensor is proposed. In this paper, with the ground as the reference potential and the vertical line of the transmission line to the ground as the integral path, D-dot electric field sensor is applied to measure the instant electric field values of several nodes on the integral path and the transmission wire voltage is directly solved combined with Gauss–Legendre numerical integration algorithm. The Gauss–Legendre algorithm is verified by the electric field distribution data on the integration path obtained by simulation. Furthermore, the improvement of the Gauss–Legendre algorithm is realized through optimizing the integral interval so that the location of integral nodes is more reasonable. Finally, the measurement system based on LabVIEW is designed and the experiment platform of the analog transmission line is constructed. Experiment results show that the measurement method of transmission wire voltage through the improved Gauss–Legendre algorithm based on D-dot sensor owns high accuracy with an error of less than 1%.

Far-Field Wireless Power Transfer Using GRIN Lens Metamaterial at GHz Frequency

In this letter, the far-field wireless power transfer up to 6-m distance from the transmitting horn antenna (Tx) aperture using a new design gradient refractive index lens metamaterial (GRIN MM) is proposed for the first time, which increases the efficiency of power transfer. Double-sided-S-shaped GRIN MM unit cell dimensions are optimized for the operating frequency of 2.45 GHz. The D-dot sensor is placed at 6-m distance from the Tx aperture to measure the electric field without and with the proposed GRIN MM and hence the power density. The same amount of power is received experimentally without GRIN MM as obtained by the Friis transmission equation, thus validating the theoretical and experimental analysis. Experimentally, it is observed that due to the point directive beam obtained after passing through the GRIN MM array, 86% more power is received with it compared to without it, thus increasing the maximum theoretical power received.

Determining the effect of relative size of sensor on calibration accuracy of TEM cells

The time-domain calibration coefficient of a D-Dot sensor should be identical across various transverse electromagnetic (TEM) cells to comply with the IEEE Std 1309. However, in our previous calibration experiments, poor consistency was observed. The size of D-Dot sensors relative to TEM cells is considered the main reason for this poor consistency. Therefore, this study aims at determining the calibration coefficient of a D-Dot sensor. We calculate the theoretical coefficient as a reference. Practical calibration experiments involve the processing of TEM cells with three different sizes. To observe the response more clearly, corresponding models are constructed and numerical simulations are performed. The numerical simulations and experimental calibration are in good agreement. To determine the calibration accuracy, we quantify the accuracy using the relative error of the calibration coefficient. By comparing the coefficients obtained, it can be concluded that the perturbation error is about 15% when the relative size is over 1/3. Further, the relative size should be less than 1/5 to obtain a relative error below 10%.

Research on Transmission Line Voltage Measurement Method Based on Improved Gaussian Integral

Currently, there are two non-contact measurement methods of the transmission line voltage based on field sensor: one is calculation with the inverse problem of electric field for the solution, and the other is to solve by the numerical integration algorithm. In general, the first one is confronted with data equation solving problems and difficulties in accurate calibration as well as low precision, while the second one is troubled by the complexity of algorithm equation and unsatisfactory integration node. In view of the above problems, this paper improves on the basis of the Gaussian integral algorithm to seek better nodes, in order to reduce the difficulty of solving and improve the measurement accuracy of the integral algorithm. First, starting from the Gaussian integral algorithm and making research to improve the Gaussian integral algorithm theory. Then, the finite element simulation of three-phase transmission line through Maxwell software is built, and the space electric field distribution data is acquired to calculate an integral node as well as its corresponding weights. Finally, the three-phase transmission line voltage measurement test platform with D-dot sensor voltage measurement system is built to test verification. The text results show that the voltage measurement method based on the improved Gaussian Integral has characteristics of a simple solution, better integral node, and higher precision, and all the measured voltage errors are less than 0.45%.

Design, simulation and test of a double differential D-dot overvoltage sensor

A double differential D-dot overvoltage sensor is proposed based on the D-dot principle for the purpose of faster and more accurate measurement of overvoltage signals. The proposed sensor is a new D-dot sensor structure consisting of four electrodes.