Mitigation of Transients in Capacitor Coupled Substations Using Traditional RLC Filter Techniques

This article presents an extensive examination and modeling of Capacitor Coupled Substations (CCS), noting some of their inherent constraints. The underlying implementation of a CCS is to supply electricity directly from high-voltage (HV) transmission lines to low-voltage (LV) consumers through coupling capacitors and is said to be cost-effective as compared to conventional distribution networks. However, the functionality of such substations is susceptible to various transient phenomena, including ferroresonance and overvoltage occurrences. To address these challenges, the study uses simulations to evaluate the effectiveness of conventional resistor-inductor-capacitor (RLC) filter in mitigating hazardous overvoltage resulting from transients. The proposed methodology entails using standard RLC filter to suppress transients and its associated overvoltage risks. Through a series of MATLAB/Simulink simulations, the research emphasizes the practical effectiveness of this technique. The study examines the impact of transients under varied operational scenarios, including no-load switching conditions, temporary short-circuits, and load on/off events. The primary aim of the article is to assess the viability of using an established technology to manage system instabilities upon the energization of a CCS under no-load circumstances or in case of a short-circuit fault occurring on the primary side of the CCS distribution transformer. The findings underscore the effectiveness of conventional RLC filters in suppressing transients induced by the CCS no-load switching.

Temperature dependence of single-event transients in SiGe heterojunction bipolar transistors for cryogenic applications

We experimentally demonstrate that the dominant mechanism of single-event transients in silicon-germanium heterojunction bipolar transistors(SiGe HBTs)can change with decreasing temperature from+20℃to-180℃.This is accomplished by using a new well-designed cryogenic experimental system suitable for a pulsed-laser platform.Firstly,when the temperature drops from+20℃to-140℃,the increased carrier mobility drives a slight increase in transient amplitude.However,as the temperature decreases further below-140℃,the carrier freeze-out brings about an inflection point,which means the transient amplitude will decrease at cryogenic temperatures.To better understand this result,we analytically calculate the ionization rates of various dopants at different temperatures based on Altermatt's new incomplete ionization model.The parasitic resistivities with temperature on the charge-collection pathway are extracted by a two-dimensional(2D)TCAD process simulation.In addition,we investigate the impact of temperature on the novel electron-injection process from emitter to base under different bias conditions.The increase of the emitter-base junction's barrier height at low temperatures could suppress this electron-injection phenomenon.We have also optimized the built-in voltage equations of a high current compact model(HICUM)by introducing the impact of incomplete ionization.The present results and methods could provide a new reference for effective evaluation of single-event effects in bipolar transistors and circuits at cryogenic temperatures,and could provide a new evidence of the potential of SiGe technology in applications in extreme cryogenic environments.

Numerical Explanation of Slow Transients in an AlGaN/GaN HEMT

A series of slow drain current recovery transients at different gate biases after a short-term stress are observed in an AIGaN/GaN HEMT. As the variation of the time constants of the transients is small, the working trap is determined to be electronic. A numerical simulation verifies this conclusion and reproduces the measured transients. The electron traps at different spatial positions in the device-on the ungated surface of the AIGaN layer,in the AIGaN barrier, and in the GaN layer are considered;corresponding behaviors in the stress and the transients are discussed;and for the simulated transients, agreement with and deviation from the measured transients are explained. Based on this discussion, we suggest that the measured transients are caused by the combined effects of a deep surface trap and a bulk trap in the GaN layer.

Single Event Transients of Operational Amplifier and Optocoupler

The single event transient effects of the operational amplifier LM124J and the optocoupler HCPL 5231 are investigated by a pulsed laser test facility. The relation of transient pulse shape to pulsed laser equivalent LET is tested,the sensitive areas of the SET effects are identified in voltage follower application mode of LM124J, and the mechanism is initially analyzed. The transient amplitude and duration of HCPL5231 at various equivalent LET are examined,and the SET cross-section is measured. The results of our test and heavy ion experimental data coincide closely,indicating that a pulsed laser test facility is a valid tool for single event effect evaluation.

Influence of enlarged section parameters on pressure transients of high-speed train passing through a tunnel

The influence of enlarged section parameters on pressure transients of high-speed train passing through a tunnel was investigated by numerical simulation.The calculation results obtained by the structured and unstructured grid and the experimental results of smooth wall tunnel were verified.Numerical simulation studies were conducted on three tunnel enlarged section parameters,the enlarged section distribution along circumferential direction,the enlarged section area and the enlarged section distribution along tunnel length direction.The calculation results show that the influence of the different enlarged section distributions along tunnel circumferential direction on pressure transients in the tunnel is basically consistent.There is an optimal enlarged section area for the minimum value of the pressure variation amplitude and the average pressure variation in the tunnel.The law of the pressure variation amplitude and the average pressure variation of the enlarged section distribution along tunnel length direction are obtained.

Laser-Induced Single Event Transients in Local Oxidation of Silicon and Deep Trench Isolation Silicon-Germanium Heterojunction Bipolar Transistors

We present a study on the single event transient （SET） induced by a pulsed laser in different silicon-germanium （SiGe） heterojunction bipolar transistors （HBTs） with the structure of local oxidation of silicon （LOCOS） and deep trench isolation （DTI）. The experimental results are discussed in detail and it is demonstrated that a SiGe HBT with the structure of LOCOS is more sensitive than the DTI SiGe HBT in the SET. Because of the limitation of the DTI structure, the charge collection of diffusion in the DTI SiGe HBT is less than that of the LOCOS SiGe HBT. The SET sensitive area of the LOCOS SiGe HBT is located in the eollector-substrate （C/S） junction, while the sensitive area of the DTI SiGe HBT is located near to the collector electrodes.

Operation of the jet feedback mechanism (JFM) in intermediate luminosity optical transients (ILOTs)

We follow the premise that most intermediate luminosity optical transients （ILOTs） are powered by rapid mass accretion onto a main sequence star, and study the effects of jets launched by an accretion disk. The disk is formed due to large specific angular momentum of the accreted mass. The two opposite jets might expel some of the mass from the reservoir of gas that feeds the disk, and therefore reduce and shorten the mass accretion process. We argue that by this process ILOTs limit their luminosity and might even shut themselves off in this negative jet feedback mechanism （JFM）. The group of ILOTs is a new member of a large family of astrophysical objects whose activity is regulated by the operation of the JFM.

Heavy Ion and Laser Microbeam Induced Current Transients in SiGe Heterojunction Bipolar Transistor

Silicon-germanium （SiGe） hereto-junction bipolar transistor current transients induced by pulse laser and heavy iron are measured using a real-time digital oscilloscope. These transients induced by pulse laser and heavy iron exhibit the same waveform and charge collection time except for the amplitude of peak current. Different laser energies and voltage biases under heavy ion irradiation also have impact on current transient, whereas the waveform remains unchanged. The position-correlated current transients suggest that the nature of the current transient is controlled by the behavior of the C/S junction.

THE THEORY OF CURRENT TRANSIENTS AT TUBULAR ELECTRODES IN A FLOWING FLUID

A theoretical equation is developed which describes the response of the current transients to a constant potential at tubular electrodes for a reversible electrode reaction in the flowing fluid.

The Analysis of the Differences between Electromechanical Transients Simulation and Electromagnetic Transients Simulation

The paper firstly interprets the differences between electromechanical transients program BPA and electromagnetic transients program EMTDC in the field of principle, model and algorithm. Then the authors carry out the simulation based on single-machine infinite-bus system and draw some conclusions. The time consumption of the simulation using EMTDC is much longer than the simulation using BPA under the same length of time. The results of BPA are close to those of EMTDC under steady conditions. The fundamental frequency component of the EMTDC results seems closer to the BPA results than its original value, but they still away from completely consistent. In this simulation of single-machine infinite-bus system, the transient stability results of BPA and EMTDC are close, but the results of BPA are apt to be more conservative. All the conclusions above have a certain reference value to both hybrid simulation and comprehensive analysis method in the study of the AC/DC digital simulation of large power grid.

Could bright γ-ray burst optical transients have been recorded historically?

The brightest optical flash from a γ-ray burst （GRB） was, briefly, a naked- eye object. Several other GRBs have produced optical transients only slightly fainter. We argue that, based upon the recently accumulated data from hundreds of GRB transients, many such optical events should have been visible to the unaided eye in the course of human history. The most likely repositories of such observations are histor- ical records from the Orient, and we have located and discuss a number of candidates. We also consider the value of such observations, should any very likely ones be uncovered, to modern astrophysics.

Hyper Gravity-Induced Transients in <i>Phycomyces</i>as Measured by Single Beam Spectrophotometer on the Sounding Rocket TEXUS 50

In the first paper of two referring to the TEXUS 50 campaign using micro dual wavelength spectrometers (MDWS) we kinetically determined the threshold1 for GIACs (gravity-induced absorption changes) in Phycomyces to be lower than 25 × 10&minus;3 g (http://file.scirp.org/pdf/JMP_2015082810060783.pdf). In this second paper, we attended measurement of GIAC-spectra. Unexpectedly, during the upwards movement, i.e. the hypergravity phase up to top acceleration values reaching 11.6 g at 35.4 s after liftoff we observed transient GIAC-spectra ranging from 380 to 750 nm. In addition, during the whole acceleration phase of 68.2 s, another component near 700 nm develops which remains stable during the whole “free fall trajectory parabola” for 381.3 s. The subsequent reentry of the rocket leads to extraordinary deceleration values up 37.8 g, completely destroying Phycomyces sporangiophores excluding their spectral measurement. During the microgravity phase and by centrifuge operation we were unable to detect any GIAC-spectra (in contrast to kinetic MDWS-measurements, first paper).

Energization of a Half-Wavelength Transmission Line-Pre-Operational Transients Studies

In the present paper the main results of the pre-operational studies related to the energization maneuver of a Half-Wavelength Transmission Line (AC-Link), are presented. The simulations were performed in PSCAD with actual Brazilian system data. Specifically the following studies were performed: electromagnetic transient studies of energization maneuver considering no fault and the occurrence of fault along the trunk;dynamic analysis of generator units that will energize the AC-Link;TRV on the circuit-breaker that will energize the trunk. The main conclusion is that the AC-Link energization experiment can be implemented without jeopardizing or causing time-life reduction of the equipment involved in the experiment, which comprises the generator unit that will energize the trunk, the step-up transformer, the arresters that will be kept during the experiments, as well as the circuit-breaker that will energize and then trip the AC-Link.

Numerical Analysis for Transients in External Source Driven Reactors

The main purpose of this paper is to perform a numerical analysis of the Neutron Spatial Kinetic Equations, subject to transients of the External Neutron Source, by applying the Implicit Euler Method as well as the Runge-Kutta Method in order to check which methods are best applicable in transients caused by External Neutron Source. For this purpose, a one-dimensional ADS reactor with a constant external source was simulated based on the geometry of ANL-BSS-6 reactor for benchmark effects.

An Experimental Study of the Flowrate Transients in Slug Flow

An investigation of the characteristics of flowrate transientswithin slug flow was conducted in a large- scale outdoor testingfacility. The test section consisted of a 378 m long, 7.62 cmdiameter stainless steel pipe. Air and water were used as the testfluids. The response to a change of flowrate of either phase or twophases Was measured using a series of pressure transducers anddifferential pressure transducers. An increase or decrease In gasflowrate caused a pressure overshoot above the value at new steadystate or led to a pressure undershoot To form a temporary stratifiedflow.

CHAOTIC TRANSIENTS IN A CURVED FLUID CONVEYING TUBE

The chaotic transients of a curved fluid conveying tube subjected to a nonlinear foundation are investigated. The assumption of the inextensibility of the tube is applied to derive the nonlinear differential equation of motion via the Newtonian approach, with the differential quadrature method used to discretize the curved tube model in the spatial domain. And the nonlinear dynamic motion equation is obtained. The numerical analysis shows that, the final steady states are sensitive to the initial system conditions in a large parameter region of the fluid speed. This phenomenon of chaotic transients is infrequent for fluid conveying tubes.

Effect of capacitance on ZnO-Bi_2O_3-Yb_2O_3 based varistor for nanosecond transients

The microstructure and electrical properties of ZnO-Bi2O3-Yb2O3 based varistor ceramics were investigated with various temperature effects from 900°C to 1050°C.From the results,it was observed that the increase of sintering temperature offers a reduced capacitive effect from 0.460 nF to 0.321 nF.Furthermore,the grain sizes of varistors were varied from 6.8μm to 9.8μm.The consequence of such smaller grain sizes provided a better voltage gradient of about 895 V/mm for the disc sintered at 900°C and fallen drastically to 410 V/mm for the sample sintered at 1050°C.In addition,there was an increase of non-linearity index to a maximum value of 36.0 and reduced leakage current of 0.026 mA/cm2.However,the density of the varistor decreased with an increase of temperature from 5.41 g/cm3 to 5.24 g/cm3.With this base,the influence of varistor capacitance and high voltage gradient were scrutinized and it led an improved transition speed of the varistor assembly from non-conduction to conduction mode during intruding nanosecond transients.

DOUBLE METHOD OF CHARACTERISTICS TO ANALYZE HYDRAULIC-THERMAL TRANSIENTS OF PIPELINE FLOW

The hydraulic and thermal transients in pipeline flow were studied. The method of characteristics for hydraulic transient analysis of batch transport of pipeline flow had been improved. The thermal transient equation, in which the term with v 3 was involved, had been inferred, while the corresponding method of characteristics was constructed. The double method of characteristics, which can be used to study the coherent hydraulic-thermal transients of batch transport of pipeline flow, was developed.

The temperature dependence of single-event transients in 90-nm CMOS dual-well and triple-well NMOSFETs

This paper investigates the temperature dependence of single-event transients（SETs） in 90-nm complementary metat-oxide semiconductor（CMOS） dual-well and triple-well negative metal-oxide semiconductor field-effect transistors（NMOSFETs）.Technology computer-aided design（TCAD） three-dimensional（3D） simulations show that the drain current pulse duration increases from 85 ps to 245 ps for triple-well but only increases from 65 ps to 98 ps for dual-well when the temperature increases from-55℃ to 125℃,which is closely correlated with the NMOSFET sources.This reveals that the pulse width increases with temperature in dual-well due to the weakening of the anti-amplification bipolar effect while increases with temperature in triple-well due to the enhancement of the bipolar amplification.

Attenuation analysis of hydraulic transients with laminar-turbulent flow alternations

An improved compound mathematical model is established to simulate the attenuation of hydraulic transients with laminar-turbulent alternations,which usually occur when the pipeline flow velocity fluctuates near the critical velocity.The laminar friction resistance and the turbulent friction resistance are considered respectively in this model by applying different resistance schemes to the characteristics method of fluid transient analysis.The hydraulic transients of the valve closing process are simulated using the model.A more reasonable attenuation of hydraulic transients is obtained.The accurate attenuation is more distinct than that obtained from the traditional mathematical model.The research shows that the hydraulic transient is a type of energy waves,and its attenuation is caused by the friction resistance.The laminar friction resistance is more important than the turbulent friction resistance if the flow velocity is smaller than the critical velocity.Otherwise the turbulent friction resistance is more important.The laminar friction resistance is important in the attenuation of hydraulic transients for the closing process.Thus,it is significant to consider the different resistances separately to obtain more accurate attenuation of hydraulic transients.