Isotropic Broadband E-Field Probe

To address the lack of backup protection scheme of current flexible DC transmission lines and the failure of protection scheme under the low signal-to-noise ratio. In this paper, a similarity measure based on the combination of wavelet threshold denoising and improved edit distance algorithm is proposed. According to the characteristic of large difference between noise signal and fault signal wavelet coefficients, the fault traveling wavelet signal is pre-processed with noise reduction by wavelet denoising method. When external fault occurs, the DC transmission line satisfies the invariance of traveling waveform characteristics, and the similarity of traveling waveform on both sides of the line is high. And the similarity is lower for internal faults. According to this characteristic, an improved edit distance algorithm is proposed to realize the calculation of the similarity of the traveling waveforms of faults on both sides of the line and establish the criterion for identifying faults internal and external of the flexible DC transmission line. Through simulation, it is verified that the algorithm can accurately identify internal and external faults, and has stronger resistance to noise interference and transition resistance compared with EDR algorithm.

We report a comparative study on microwave control lines for a transmon qubit using (i) flexible stripline transmission lines and (ii) semi-rigid coaxial cables. During each experiment, we performed repeated measurements of the energy relaxation and coherence times of a transmon qubit using one of the wiring configurations. Each measurement run spanned 70–250 h of the measurement time, and four separate cooldowns were performed so that each configuration could be tested twice. From these datasets, we observe that changing the microwave control lines from coaxial cables to flexible stripline transmission lines does not have a measurable effect on coherence compared to thermal cycling the system or random coherence fluctuations. Our results open up the possibility of large-scale integration of qubit control lines with integrated component with planar layouts on flexible substrate.

With the development of flexible DC transmission and the shortage of transmission corridors, flexible DC transmission lines may be erected on the same tower or span vertically with traditional AC lines, greatly increasing the possibility of cross-line fault between flexible DC lines and AC lines. This paper focuses on this issue. Based on the equivalent circuit, the short-circuit current at the initial stage of this cross-line fault is analyzed first. Then, based typical ±500kV flexible DC system and Extremely High Voltage (EHV) AC system in China, the simulation model is established in Power Systems Computer Aided Design (PSCAD). The fault transient characteristics of cross-line fault is analyzed, and the significant interaction effect of AC and DC systems is verified. On this basis, the response of DC traveling wave protection to this cross-line fault is tested. Simulation results show that the values and gradients of fault traveling wave decrease under cross-line fault, and the reliability of traveling wave protection decreases.

Faults occurring on the DC side of the line are very harmful to the MMC-MTDC system, and with the popularization of flexible DC transmission technology based on overhead lines, how to discriminate the type of fault is the difficulty of MTDC DC line protection. This paper gives a fault kind identification approach based totally on the Pearson correlation coefficient, which discriminates the fault kind with the aid of calculating the Pearson correlation coefficient of the line voltage at each pole after the fault.

Traveling wave (TW) protection is crucial for ensuring the safety and stability of flexible DC transmission lines. Thereinto, shortening the sampling step is the key to improve the sensitivity of the derivative-based TW protection. However, higher sampling frequency is difficult to engineer and the protection performance will be constrained in case of the high resistance faults. To address this issue, a non-unit adaptive TW protection based on the supplement of voltage data has been proposed. Firstly, the voltage data is realized to complement utilizing the Lagrange's median theorem at the line boundary, which improves the sampling frequency. Then, it has been observed that the fault current variation is negatively correlated with transition resistance. Specially, the proposed protection takes this fully into account by incorporating the adaptive threshold that covers differences among various fault locations. Therefore, the proposed protection can effectively distinguish internal faults with high sensitivity. Finally, a two-terminal ±500kV MMC-HVDC (modular multilevel converter-high voltage direct current) system is built using PSCAD/EMTDC. The simulation results demonstrate that the line faults can be fast and correctly identified, even with 300 Ω fault impedance, in various fault scenarios.

The traditional flexible HVDC system protection scheme based on boundary conditions uses current-limiting reactors to extract fault features. When the size of the reactor is limited by the actual engineering, there is a problem that the protection is difficult to identify the fault. This paper takes the flexible HVDC transmission line as the research object. Considering the limited value of the current limiting reactor, a virtual impedance link is added to the control system to limit the fault current. Combined with the transient voltages of virtual impedance and current limiting reactor, a protection scheme is jointly constructed to identify the fault. The fault feature quantity composed of the traditional protection electrical quantity and the control quantity can improve the sensitivity and reliability of the protection, and effectively carry out fault identification.

It is difficult to accurately calibrate the traveling wave head and calculate the wave velocity by using the single-ended traveling wave location method. In this paper, a dynamic first traveling wave energy that varies with the fault distance by deeply analyzing the attenuation characteristics of the line transmission function on each first traveling wave frequency component. The maximum first traveling wave energy, namely the main frequency component, monotonically decays with the increase of fault distance, showing a one-to-one mapping relationship with the fault distance. On this basis, this paper proposes a single-ended fault location method for flexible HVDC transmission lines using the linear interpolation. The positioning results are calculated using the linear interpolation method on the distance-initial traveling wave main frequency component curve. The simulation results show that the proposed positioning method eliminates the dependence of traditional single-ended traveling wave positioning methods on the wave head calibration and the wave velocity calculation. The absolute positioning error is less than 0.6km, and the positioning result is not affected by transition resistance.

High Voltage (HV) equipment such as power switches, current or voltage transformers, and flexible HV transmission lines insulated by pressurized SF6 (or SF6/N2 mixtures) offer component compactness, high reliability and low maintenance demands compared to all conventionally insulating components (i.e. air, organic solid insulants, and mineral oils). Though SF6 insulation for HV applications was initially proposed during late '60s, it was spread worldwide rapidly due to offered significant economic advantages, and now SF6 GIS substations dominate the share in electrical networks in densely populated districts. However, it was in mid '90s when the first ecological concerns were brought about the SF6 gas use. These mainly stream out by either of the following facts: (i) SF6 is a strong green-house gas with a global warming potential of almost 25,000 greater than that of CO2 and its molecules exhibit an exceptionally high lifetime in earth atmosphere estimated to vary between 750 and 2500 years, and (ii) when electrically stressed (independent of temperature i.e. either high-power arcs developing at 20,000K during the switching actions, or corona discharges developing at 300K due to high electric field effects) toxic byproducts may be formed, some having high cyto-toxicities i.e. S2F10, oxyfluorides, H2S and HF.

This work proposes an approach for manufacturing of high precision ungrounded coplanar waveguides as high speed interconnections for flexible and wearable sensors as well as IoT systems. Characterization of these printed transmission lines up to a frequency of 24GHz reveals an insertion loss of up to 8dB/cm and therefore provides practical advice towards realizable line lengths. Although exhibiting approximately 4 times the attenuation as compared to conventionally manufactured flexible PCB transmission lines, the proposed approach allows for selectively realizing highly precise structures where necessary. Moreover, it is applicable on three-dimensional substrates, such as 3D-MIDs and therefore addresses various future applications.

An all optical communication is fast and reliable for next generation information carrying systems. For successful operation of fast data over flexible transmission line is only possible by all optical multiplexer and can serve for network. A 60 Gbps all optical multiplexer using cheap components has been realized and also tested on different speeds of input data streams. For integral and flexible multiplexer, optical semiconductor-based MZI switch taken into consideration. MZI-SOA is used to generate two logical gates outputs such as (AND)(XOR) gate. Multiplexer working is based on SOA nonlinearity properties and optical coupler. XOR logic gate contingent on cross-phase modulation in amplifier and logic AND for four-wave mixing is obtained from cross port and bar port respectively. Simulation is performed and multiplexer is tested for different launched power in tree architecture. System performance indicates that it can work for high speed (60 Gbps) and different data entities.

In this paper we describe the application of a personal digital assistant (PDA) or pocket PC as an effective communication device to telemonitor levels of asthma triggering gases collected from a remote location under test to a workstation which has a personal computer (PC) running on Windows XP® as the operating system. The Bluetooth® features of the PDA are explored to transmit data collected by a Direct™ Sense Tox toxic gas monitor equipped with five toxic gas probes and one temperature sensor in real time, thereby making this telemonitoring system an innovative instrument in monitoring levels of asthma triggering gases in the El Paso-border metropolitan region, a region in which asthma is highly prevalent especially in children. At the workstation or fixed location these readings are displayed using a custom made, user friendly graphical user interface (GUI) developed using software tools like action scripting with Macromedia® Flash™. The growing advancement in technology and ever diminishing sizes of handheld devices encouraged us to opt for this configuration. Moreover, the PDA and toxic gas monitor were also chosen for their light weight, portability, flexibility, low cost and data collection and transmission capabilities.

Now-a-days renewable energy sources are playing a vital role in global energy systems. Wind energy conversion method is cheaper compared to other conversions such as solar and tidal etc. There are many power quality issues in wind farms such as voltage sag, swell and harmonics arise due to grid, nonlinear load and three phase faults. These voltage fluctuations can be eliminated with the help of advanced reactive power compensation devices such as SVC (Static Var Compensator), STATCOM (Static Synchronous Compensator) and DVR (Dynamic Voltage Restorer). To reduce such power quality issues, it is essential to design, model and analyse the FACTS (Flexible AC Transmission line) device. In this project, STATCOM is used as a compensating device. STATCOM is a static synchronous generator operated as a parallel connection static reactive compensator. It is capable of generating or absorbing real and reactive power. Also, the compensator performance is analysed with the help of Proportional Resonant (PR) controller device. The STATCOM is connected parallel with the transmission line. When fault occurs, it will inject or absorb the reactive power to the line through the transformer according to the voltage requirement. The whole system is simulated through MATLAB/SIMULINK application. The simulation gives the effective influence of STATCOM on the improvement of voltage profile as well as reduction of Harmonics in grid connected Wind Energy Conversion System.

With an increase of non-linear load in today’s electrical power systems, the rate of power quality drops and the voltage source and frequency deteriorate if not properly compensated with an appropriate device. Filters are most common techniques that employed to overcome this problem and improving power quality. In this paper an improved optimization technique of filter applies to the power system is based on a particle swarm optimization with using artificial neural network technique applied to the unified power flow quality conditioner (PSO-ANN UPQC). Design particle swarm optimization and artificial neural network together result in a very high performance of flexible AC transmission lines (FACTs) controller and it implements to the system to compensate all types of power quality disturbances. This technique is very powerful for minimization of total harmonic distortion of source voltages and currents as a limit permitted by IEEE-519. The work creates a power system model in MATLAB/Simulink program to investigate our proposed optimization technique for improving control circuit of filters. The work also has measured all power quality disturbances of the electrical arc furnace of steel factory and suggests this technique of filter to improve the power quality.

Flexible direct current transmission system (FDCT) exhibits broad application prospects in new electricity system due to its technical advantages of active/reactive decoupling control and low demand for reactive power compensation. The DC power flow controller (DCPFC) significantly enhances the power flow controllability of meshed DC grids by emulating resistance or voltage regulation of transmission lines. However, conventional DCPFC proportional integral (PI) control struggles to effectively suppress transient resonance issues within DC grids when the damping capability of voltage source converter (VSC) station control systems is insufficient. This paper proposes a coordinated methodology integrating modular small signal modeling and linear quadratic regulator (LQR) damping control, which achieves precise analysis of transient oscillations by incorporating the complete VSC small signal model system into the system under investigation. Firstly, a comprehensive VSC based high voltage direct current transmission system (VSC-HVDC) small signal model encompassing VSC phase locked loop (PLL) dynamics and DCPFC dynamics is established. Secondly, based on the closed-loop transfer functions of VSC-HVDC, the resonance characteristics of DC grid are analytically evaluated. Furthermore, traditional supplementary power damping control and LQR damping control strategies are designed, enabling transient oscillation suppression as well as a comparative verification of control effectiveness. Finally, all theoretical analyses are validated through time-frequency domain simulations in MATLAB/Simulink.

Tinnitus is considered an auditory phantom percept. Recently, transcranial direct current stimulation (tDCS) has been proposed as a new approach for tinnitus treatment including, as potential targets of interest, either the temporal and temporoparietal cortex or prefrontal areas. This study investigates and compares the spatial distribution of the magnitude of the electric field and the current density in the brain tissues during tDCS of different brain targets. A numerical method was applied on a realistic human head model to calculate these field distributions in different brain structures, such as the cortex, white matter, cerebellum, hippocampus, medulla oblongata, pons, midbrain, thalamus, and hypothalamus. Moreover, the same distributions were evaluated along the auditory pathways. Results of this study show that tDCS of the left temporoparietal cortex resulted in a widespread diffuse distribution of the magnitude of the electric fields (and also of the current density) on an area of the cortex larger than the target brain region. On the contrary, tDCS of the dorsolateral prefrontal cortex resulted in a stimulation mainly concentrated on the target itself. Differences in the magnitude distribution were also found on the structures along the auditory pathways. A sensitivity analysis was also performed, varying the electrode position and the human head models. Accurate estimation of the field distribution during tDCS in different regions of the head could be valuable to better determine and predict efficacy of tDCS for tinnitus suppression.