Lightning Impulse Discharge Behaviour in Tap-Water Gap

The objective of this paper is to present an approach for isolating the harmonic contents in both voltage and current waveforms of the montage feeder of Gharb Talkha substation (60/11 KV). A novel technique using Discrete Wavelet transform (DWT) for the analysis of the waveforms harmonics content At the beginning the substation is simulated using Simulink toolbox in Matlab program with and without the presence of capacitor bunk. The obtained voltage and current waveforms are compared to the actual data. The proposed model is used to study the effect of replacing the capacitor bank with single tuned parallel passive filter. The resulting current and voltage waveforms are analyzed using the proposed DWT technique. The analysis showed that the Total Harmonic Distortion (THD) of both voltage and current waveforms is improved as well as the power factor.

Pantograph arcing with AC supply generates transients, cause asymmetries and distortion in supply voltage and current waveforms and can damage the pantograph and the overhead contact line. The asymmetry generates a net dc component and harmonics, which propagate within the traction power and signalling system and causes electromagnetic interference. Unlike DC-fed systems (Part I), the arcing in ac supply is complex because of the zero crossing of currents and voltages. In this paper, we discuss the mechanisms of sliding contact and arcing between pantograph-contact wire using the experimental setup described in Part I. Influences of various parameters and test conditions on arcing phenomenon and their signature patterns on the supply voltage and current waveforms are presented. It is shown how the arcing mechanism and corresponding asymmetry in the voltage and current waveforms are governed by line speed, current, supply voltage, inductive load, and pantograph material. The asymmetry in the current waveform is mainly due to the difference in the duration of successive zero-current regions and uneven distortion of the waveshapes. This, in turn, creates the asymmetry in the voltage waveform. The findings presented in this paper could be beneficial for coming up with appropriate mitigation techniques from the electromagnetic interference due to pantograph arcing in AC traction systems.

An experimental investigation of a TRAPATT diode with its oscillator circuit is presented. The measurements of current and voltage waveforms were made with a sampling oscilloscope (3 dB bandwidth, 14 GHz)and an improved capacitive voltage-divider probe. Design information is given for this type of probe which can have an almost unlimited bandwidth. Voltage and current waveforms across the semiconductor chip are presented for a diode that oscillated at 1 GHz with an efficiency of 49%. It is shown that the mode of operation and the waveforms are explained well by a simple theoretical model that has been developed.

In this chapter, we shall discuss techniques used to fit faulted current and voltage waveforms, each to a sinusoidal waveform containing a fundamental component, a decaying/constant direct current (DC) component and/or harmonics.These techniques use the least squares (LSQ) method to minimise the fitting error, and all have the common goal of extracting the fundamental components of voltage and current waveforms, to calculate the impedance to the fault or the comparison of current-based signals in digital differential protection.

Voltage source inverter (VSI) had been used in dc traction power substation to deliver the trains braking energy back to the utility grid. To mitigate low order harmonics components, pulse-width-modulation (PWM) technique is commonly used in VSI controlled. As a result, the ac voltage and current waveforms may contain high frequency ripples. This paper proposes to mitigate the high frequency harmonics using LCL-filter with series <em>R</em>-damper. This filter offers good attenuation on harmonics with smaller size compare to other passive filter topologies. Theoretical analysis and simulation verification are conducted in designing the proposed filter. System level simulation had also been carried out. Sinusoidal grid current and voltage waveforms are recorded (THD<2%). This paper also includes damping losses analysis in conjunction with resonance peak suppression in designing the <em>R</em>-damper.

This paper introduces the power quality analysis of unidirectional and bidirectional ac voltages controllers. An AC voltage regulator coupled between the power supply and the load is a device having major components of two thyristors connected in inverse parallel manner and the power flow is controlled by varying the firing angle of thyristors. For each configuration, the experimental setup is implemented on Feedback Power Electronics Trainer and simulation is done using MATLAB/Simulink. The simulated and experimental waveforms of current and voltage in case of resistive and inductive loads are obtained by taking different firing angles and are correlated, which demonstrate the effectiveness of model and its configurations. Due to switching operations of power electronic converters, they contain nonlinearities and generate harmonics which not only disturb the performance of converters but also the quality of input power system is badly affected. The power quality factor is observed by Fluke Power Quality Analyzer that can monetize the cost of energy waste due to poor quality. In this research, the performance evaluation of controller with industrial inductive loads under different delaying angle is investigated and detailed comparative analysis is done by experimental readings and simulation results. Total Harmonic Distortion (THD) analysis for different waveforms of voltage and current, its calculation and comparison for change in loads have been presented in this paper.

The present methods used to calibrate an active power or energy meter device under test (DUT) under nonsinusoidal conditions are based on a limited number of current and voltage waveforms and do not exercise the dynamic range of the DUT. After reviewing a method recently developed at the National Physical Laboratory (NPL) to exercise the dynamic range of a DUT under sinusoidal and nonsinusoidal conditions for specified current and voltage waveforms, the paper reports on the performance of the DUT under nonsinusoidal conditions measured using the NPL method. Experimental results: 1) verify theoretical predictions that the active power fractional full-scale (FS) error depends on both the phase-angle group between the current and voltage waveforms and the phase angle between the harmonics and the fundamental of both the current and voltage waveforms and 2) show that the active power fractional FS error for sinewave excitation can be larger than that for nonsinusoidal conditions

The discharge characteristics of CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> nanosecond pulsed dielectric barrier discharge (DBD) under Mars atmospheric condition has been studied by using nanosecond pulsed source. A vacuum system, together with DBD chamber, is designed to achieve low pressure environment. Also, a one-dimensional fluid model of the CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> DBD is established for simulation research. Different energization parameters were used, including voltage magnitude, voltage rising rate, repetition frequency and plateau region duration. The relationships between discharge voltage and current waveforms and energization parameters have been analyzed. Experimental results were compared with simulated ones in order to figure out the mechanism and characteristics of CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> discharge under Mars atmospheric condition. Results showed that the discharge current magnitude is proportional to the voltage rising rate while it is reversely proportional to repetition frequency. The current magnitude is irrelevant to plateau region duration under Mars atmospheric condition. However, the current magnitude, on the falling edge of voltage, is proportional to the plateau region duration under Earth atmospheric condition. This is due to the difference in the mobility of charge carriers under different conditions.

An analytical method to study the discharge-radiation dynamics (DRD) in alternating current plasma display panels was developed. The input parameters for this DRD analysis were experimentally determined panel voltage and current wave forms. Discharge voltage, current, and power wave forms in the discharge volume of a cell were first obtained from the measured panel voltage and current wave forms using known geometrical configurations and electric circuit calculations. Intrinsic discharge parameters, such as electron temperature and density, were then determined to satisfy these discharge wave forms under the assumption of a hydrodynamic approach. A one-dimensional discharge structure with two regions (cathode fall and positive column) and several other assumptions which are plausible from the discharge physics point of view were also adopted. These assumptions took account of known cross sections and energies of electron-impact excitation and ionization of discharge gas atoms, and a secondary electron emission coefficient of the dielectric surface at the cathode side induced by ion bombardment. Radiation intensities from the discharge were calculated using the determined intrinsic discharge parameters, and the results were compared with those measured for the respective panel conditions used in the calculations, yielding a fair agreement. The luminous efficiency, defined as the radiation intensity divided by the discharge power, was also determined using the intrinsic discharge parameters. Discussion on the luminous efficiency change for different panel operating conditions revealed that the efficiency improvement at a lower voltage was attributable to a lower electron temperature for this condition.

Steady-state operation of a load commutated inverter (LCI) fed synchronous motor drive is analysed by means of a digital computer based solution of the synchronous machine equations. The solution permits calculation of current, voltage, and torque waveforms and includes the effects of finite DC link inductance, saliency of the rotor and all machine resistances. The continuity constraints for steady-state operation are exploited to enable the proper initial conditions to be calculated directly, without the need for iteration. Operating points are described by the firing angle yo, and the overlap angle μ, and are computed for an assumed DC supply voltage of 1.0 per unit. The linearity of the state equations allows the normalised solutions to be scaled to obtain any desired value of torque, DC link current etc. Sample calculations are provided, showing the influence of the DC link inductance on the torque, DC link current and voltage waveforms. These are then compared with experimentally measured data taken from a 3 kVA LCI fed synchronous motor drive, and a good level of agreement is achieved.

The operating power frequency fluctuates around its nominal value under normal conditions based on the dynamic balance between load demand and generation levels. This frequency variation creates a challenge in computing and analyzing voltage and current root-mean-square values over time, since sliding windows may not cover an integer number of cycles of the sampled voltage and/or current data. The overall objective of this paper is to present an adaptive resampling technique for the voltage and current waveforms, such that each sliding window used for computation of power quality parameters always cover an exact integer number of cycles. This technique is illustrated for a capacitor de-energizing operation, which is detected through a step change in the rms voltage profile. Once this de-energizing operation has been detected, the voltage waveform is resampled and the rms voltage profile with a high time resolution is obtained through a fast and recursive approach. Finally, the exact capacitor de-energizing instant is estimated. The proposed approach is shown to be simple, yet robust and accurate.

The atmospheric pressure glow discharge has a good industrial application prospect, but it is difficult to obtain a stable and diffusive atmospheric pressure glow discharge, especially in the large ambient air gap. In this paper, with a transverse magnetic field applied in the pin-to-ring electrode gap, a stable and diffusive atmospheric pressure glow discharge in ambient air was obtained. The influence of different factors such as the output-voltage amplitude of the power supply, the intensity of the external magnetic field, and the different sizes of ring-cathode were studied from the discharge voltage and current waveforms and the discharge morphology. The results show that a more diffusive and bigger-volume glow discharge can be obtained by increasing the amplitude of the output voltage or the intensity of the external magnetic field, and the more uniform and effective glow discharge can be obtained when choosing the smaller pin-to-ring inter-electrode gap.

A time-dependent hybrid plasma model composed of a zero-dimensional global model and a two-dimensional fluid model is proposed for simulation of plasma chemistry and transportation of plasma during Cr thin film deposition by deep oscillation magnetron sputtering (DOMS). The global model deals with plasma reactions in the ionization region near the target with discharge voltage and current waveforms as inputs. The temporal plasma characteristics calculated by the global model are utilized as a boundary condition for the two-dimensional fluid model to simulate high-density plasma transportation in the diffusion region through the entire macropulse period. The full momentum equation taking inertia force into consideration is applied for ion momentum conservation in the fluid model instead of using the drift-diffusion approximation, which ensures validity of the simulation for low-pressure plasmas. The deposition flux as well as the kinetic and potential energy fluxes transferred to the growing films are calculated by the hybrid model. Microstructure evolution of the DOMS deposited Cr thin films from zone I to zone T is attributed to the growing kinetic and potential energies as the charging voltage increases according to the structure zone diagram. The deposition rate loss in DOMS is explained by the back attraction effect, sputtering yield effect, and densification of the films.

Spark discharge under flow conditions in different gas media is compared. The gases include nitrogen, pure methane, and methane–air mixtures with different volume ratios. The self-illuminated spark plasma photos, and the discharge current and voltage waveforms are recorded.

Here, we compare the ionization region model (IRM) against experimental measurements of particle densities and electron temperature in a high power impulse magnetron sputtering discharge with a tungsten target. The semi-empirical model provides volume-averaged temporal variations of the various species densities as well as the electron energy for a particular cathode target material, when given the measured discharge current and voltage waveforms. The model results are compared to the temporal evolution of the electron density and the electron temperature determined by Thomson scattering measurements and the temporal evolution of the relative neutral and ion densities determined by optical emission spectrometry. While the model underestimates the electron density and overestimates the electron temperature, the temporal trends of the species densities and the electron temperature are well captured by the IRM.