Capacitance Of Transmission Line Research Articles

Stability analysis of virtual synchronous generator control in a high-voltage DC transmission system using impedance-based method

Numerous distributed generators (DGs), which often include renewable energy sources, are connected to modern power grids through grid-connected inverters. Conventional linear model approximation methods may not be sufficient to accurately analyze the dynamic response of DGs due to the harmonics and nonlinear distortions generated by power-electronic devices. Therefore, an impedance-based stability analysis method has been adopted and applied in high-voltage direct current (HVDC) power transmission systems as a practical data-driven alternative to the linear model approximation method. However, the presence of multiple AC/DC converters and the non-negligible ground capacitance of DC transmission lines increases the difficulty of analyzing the entire HVDC system. Previous studies have mostly focused on the stability of either the generator-side system or the load-side AC system. In this study, impedance-based analyses were performed on the generator-side AC system, DC transmission line, and load-side AC system to evaluate the entire HVDC system when the generator-side AC system was weak. Additionally, an advanced inverter control method called the virtual synchronous generator (VSG) control method, which can result in grid stabilizing effects, was introduced to the load-side AC system. The analysis results demonstrate that the VSG control significantly enhances the stability of HVDC transmission systems as compared with the conventional power control methods.

A 57-GHz CMOS Reflection Amplifier in 90-nm CMOS

A reflection amplifier is designed using 90-nm bulk CMOS technology for applications in the 60-GHz frequency band. Different from the conventional configurations, a proposed capacitive transmission line at the transistor source port results in negative input resistance and return gain. The return gain is further enhanced by adding an inductor at the drain port. The fabricated die occupies 0.38 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and consumes low dc power of 4.4 mW. The measured data show a peak gain of 8.4 dB at 57 GHz.

Optimal Parameter Estimation of Transmission Line Using Chaotic Initialized Time-Varying PSO Algorithm

Transmission line is a vital part of the power system that connects two major points, the generation, and the distribution. For an efficient design, stable control, and steady operation of the power system, adequate knowledge of the transmission line parameters resistance, inductance, capacitance, and conductance is of great importance. These parameters are essential for transmission network expansion planning in which a new parallel line is needed to be installed due to increased load demand or the overhead line is replaced with an underground cable. This paper presents a method to optimally estimate the parameters using the input-output quantities i.e., voltages, currents, and power factor of the transmission line. The equivalent π-network model is used and the terminal data i.e., sending-end and receiving-end quantities are assumed as available measured data. The parameter estimation problem is converted to an optimization problem by formulating an error-minimizing objective function. An improved particle swarm optimization (PSO) in terms of time-varying control parameters and chaos-based initialization is used to optimally estimate the line parameters. Two cases are considered for parameter estimation, the first case is when the line conductance is neglected and in the second case, the conductance is considered into account. The results obtained by the improved algorithm are compared with the standard version of the algorithm, firefly algorithm and artificial bee colony algorithm for 30 number of trials. It is concluded that the improved algorithm is tremendously sufficient in estimating the line parameters in both cases validated by low error values and statistical analysis, comparatively.

Effect of the transmission line on the ion temperature measured by the retarding field analyzer

Due to the presence of capacitance in the transmission line, the current collected by the retarding field analyzer (RFA) becomes asymmetrical (i.e., hysteresis) during voltage scanning, and it further affects the measurement of the ion temperature (Ti). In this article, we first analyze the hysteresis of the RFA’s I–V characteristics measured in the edge plasma of the J-TEXT tokamak, and we found that the ion temperature fitted from the falling side of the collector current is about 14% higher than that fitted from the rising side. An analytic model is built and verified by experimental results. Based on the model, the influence of the capacitance of transmission lines and the frequency of the scanning voltage on the hysteresis is investigated. It is found that the hysteresis becomes more remarkable with increasing capacitance or scanning frequency. Besides, the impact of the capacitance and the scanning frequency on the Ti measurement is also studied, which indicates that Ti is overestimated due to the hysteresis. The temperature error is linearly dependent on the capacitance and the scanning frequency. Furthermore, the analytical results are expected to be used in the prediction of scanning frequency for RFA applications.

Understanding the Impedance of CNOs-Graphene hybrid electrode through both experimental and simulated electrochemical impedance spectrum

Using a combination of experimental measurements and molecular dynamic (MD) simulations, we study the impedance of hybrid electrode composed of graphene and carbon nanometer onions (CNOs). On the experiment’s side, electrochemical measurements are conducted on the electrodde sample prepared from growing CNOs onto the graphitic plane. The general trend of impedance’s variations with frequencies is identified at different temperatures and ion concentration. Parameter fitting of equivalent circuit is accomplished with the assistance from machine learning technique using neural network. On the simulation’s side, electrode geometries including concave slit-pore and convex CNO-pore surfaces are modeled to investigate ion movements. Based on trajectories of ion dynamics, the physical origin of corresponding equivalent circuit component such as constant phase element is revealed. Regarding the geometry of electrode surface, the divide between planar and nonplanar part is observed in terms of charging level and charging time constant. Between the slit-pore and CNO-pore geometries, the differences in impedance spectrum is quantitatively characterized by solving the topology of and parameter of transmission line model of the equivalent circuit. In the branch of transmission line model, the resistance and capacitance are both larger for the space closer to the pore bottom or further from pore mouth.

Wideband (10–67 GHz) Dielectric Properties of Biosourced Cellulose Ester Flexible Films

In this article, the dielectric properties of a biosourced polymer are investigated. To that end, coplanar transmission lines were fabricated on a 600- $\mu \text{m}$ thick cellulose palmitate substrate by using a photolithographic process and a transfer technique. The ${S}$ -parameters of the transmission lines were measured in a broad microwave frequency band spanning from 10 to 67 GHz in order to determine the propagation constant. From these data, the complex dielectric permittivity was extracted by using two analytical methods (RLCG method, based on resistance, inductance, capacitance and conductance of transmission lines and conformal mapping method) and a numerical one [finite element method (FEM)]. The three methods allow distinguishing the dielectric losses from the total measured losses of the transmission lines. Finally, the dielectric constant and the loss tangent of this biopolymer were compared to the data of common and commercially available substrates: polyimide and polyethylene naphthalate.

Surface charge accumulation and pre‐flashover characteristics induced by metal particles on the insulator surfaces of 1100 kV GILs under AC voltage

With the increase in the voltage and capacitance of gas-insulated transmission lines (GILs), the insulation failure of GIL has attracted more and more attention. Further understanding of the partial discharge (PD) and flashover characteristics of metal particles on the insulator surface, as well as the flashover mechanism, is necessary to reduce the failure rate and improve the reliability of the equipment. In this study, an ultra-high voltage (UHV) AC insulator PD test and measurement system based on the cross-reference pulse current (PC) and ultra-high frequency (UHF) methods were established. The PD development and flashover characteristics of 5 mm-long metal particles at different positions on the surface of a UHV AC insulator, as well as the surface charge accumulation, were studied. The results show that the discharge of millimetre-scale metal particles on the insulator surface under PD test conditions is relatively low (generally lower than 2PC), and it is difficult to be detected by the conventional PC and UHF methods due to their insufficient sensitivity. Moreover, it is found that the weak PDs of the millimetre-scale metal particles will result in a charge accumulation on the insulator surface under AC voltage, which eventually will lead to the insulator flashover. The PDs of the UHV AC insulator before flashover are generally small, which will make it difficult for online monitoring systems to give an effective alarm before flashover.

Effective algorithm for fault discrimination and estimation of fault location in transmission lines

Sensitivity, selectivity, speed of operation and reliability of the conventional current differential protection schemes are affected and limited by the distributed shunt capacitance of high-voltage long transmission lines. In this study, a new pilot protection algorithm has been proposed based on the computation of change in shunt line admittance ‘Y’ during dynamic conditions using synchronised data. Therefore, it does not require a separate compensating technique to nullify the effect of line charging current in the fault detection. This scheme can quickly discriminate the internal faults and also detects the faulty phase. Also, it has an advantage of estimation of an accurate fault location. The performance of the proposed algorithm is evaluated on 400 kV, 50 Hz two-bus system as well as IEEE-39 bus 345 kV system using EMTDC/PSCAD and MATLAB simulation tools. The simulation results confirm the proposed algorithm can effectively discriminate the faults, independent of fault location, fault resistance, type of fault, series compensation lines and source impedance. Finally, a hardware experiment using National Instruments (NI) based LabVIEW platform is carried out to check the practical feasibility of the proposed algorithm.

HVDC System Commutation Failure Transient Judgement Method

In order to forecast the commutation failure of HVDC system, this paper analyzes the specific reasons for the rise of the direct current in the case of the receiving end failure of HVDC system and makes a quantitative analysis, It is found that the capacitance of direct transmission line discharging is the main factor of the increasing of the direct current during the initial stage, On the basis of two new physical quantities which are the variation rate of direct current and the variation rate of voltage of inverter AC bus, a new method using the variation rate is obtained to judge the process of commutation failed or not. Then in the PSCAD/EMTDC platform, the theoretical analysis results was verified, and they are close to the results of the simulation, The method mentioned in this paper can forecast the commutation failure, and it is beneficial to take measures in the near future.

Novel protection scheme for high‐voltage direct‐current transmission lines based on one‐terminal transient AC voltage

This paper considers the distributed capacitance of transmission lines to research the protection of high-voltage direct-current (HVDC) transmission line. According to the superposition theorem, the post-fault superimposed network of HVDC system is used to analyse the characteristic of the root mean square (RMS) of specific frequency voltage (SFV) during the transient period of internal and external faults. At the parallel resonant frequency of DC filter, for internal faults, the fluctuation of the RMS of transient AC voltage is larger than that of external faults. Based on the fluctuation characteristic of single-terminal transient AC voltage, a novel protection scheme for HVDC transmission lines is proposed. Various simulation results show that the proposed protection is immune to fault resistance and performs well under different fault types.

Energy current and computing.

In his seminal Electrical papers, Oliver Heaviside stated ‘We reverse this …' referring to the relationship between energy current and state changes in electrical networks. We explore implications of Heaviside's view upon the state changes in electronic circuits, effectively constituting computational processes. Our vision about energy-modulated computing that can be applicable for electronic systems with energy harvesting is introduced. Examples of analysis of computational circuits as loads on power sources are presented. We also draw inspiration from Heaviside's way of using and advancing mathematical methods from the needs of natural physical phenomena. A vivid example of Heavisidian approach to the use of mathematics is in employing series where they emerge out of the spatio-temporal view upon energy flows. Using series expressions, and types of natural discretization in space and time, we explain the processes of discharging a capacitive transmission line, first, through a constant resistor and, second, through a voltage controlled digital circuit. We show that event-based models, such as Petri nets with an explicit notion of causality inherent in them, can be instrumental in creating bridges between electromagnetics and computing.This article is part of the theme issue ‘Celebrating 125 years of Oliver Heaviside's ‘Electromagnetic Theory’’.

Advanced teaching method for balanced operations of overhead transmission lines based on simulations and experiment

An advanced teaching method for the analysis of balanced operations of overhead transmission lines has been described in this paper. The proposed educational method combines theoretical, simulation and experimental approaches with the purpose of a higher-level knowledge achievement. Several exercises have been defined and implemented in the teaching process. Some characteristic overhead transmission line steady state regimes, such as Ferranti effect, natural load flow and capacitive overhead transmission line behaviour, have been analysed. The special analysis has been carried out in order to determine the basic characteristics of the switching transients. Software package MATLAB/Simulink has been used for the estimation of system parameters and for the simulation analysis. Different overhead transmission line models have been compared and useful modelling guidelines have been recommended. Experimental calculations have been performed by using a physically scaled system consisting of multiple Pi sections representing 100 km length 400 kV overhead transmission line. The proposed method has been tested within High Voltage Engineering undergraduate course and useful application feedback from students has been obtained.

The delta-models of reactive elements and low-pass filters

Frequency limitations of lumped and distributed reactive elements traditional models are considered. Based on equivalent ciruit of infinitely short transmission line section inductance and capacitance models with properties correspond to delta-function are received. These models called delta-models are without frequency restrictions. In the delta-model graphic designation delta-function length is directly proportional to inductance or capacitance value. Unlike to ordinary graphic designations delta-models allow to represent scheme reactivities values ratios. Traditional models and delta-models reactive elements frequency characteristics are compared. It is found that because of frequency limitations traditional planar microstrip quasi-lumped reactive elements characteristics have substantial errors. Considerable reduction of errors is ensured by microstrip quasi-lumped reactive elements on the basis of three-dimensional inhomogeneities. Based on reactive elements delta-models Butterworth and Chebyshev low-pass filters delta-models are presented. Low-pass filter delta-model "prompt" possibility of filter selectivity increasing. Frequency characteristics of Chebyshev low-pass filter designed on traditional planar microstrip quasi-lumped reactive elements and three-dimensional inhomogeneities are given.

Modeling of Metal-Fill Parasitic Capacitance and Application to On-Chip Slow-Wave Structures

Modern integrated circuit manufacturing processes generally require the insertion of a large amount of metal fill in layout regions of low metal density to reduce manufacturing defects. We present a general, process-independent, and scalable modeling technique for the computation of distributed capacitance of on-chip transmission lines in the presence of metal fill. The technique reduces the complex 3-D problem to a set of 2-D problems and solves using an effective length and an effective dielectric constant approach. We obtain speedups of about 12 fold for solving the set of 2-D reduced problems compared with a 3-D problem. We verify the accuracy of the technique by comparison with electromagnetic simulations in three process technologies and measurements in a 0.18-μm BiCMOS process. The maximum error in self-capacitance and mutual capacitance is <;6% and <;10%, respectively, over a wide range of processes and physical parameters. The rootmean-square error between measured and modeled capacitance is 9.5%. To further demonstrate the effectiveness of our modeling method, we apply it to various transmission-line structures in the presence of floating conductors.

Anti-Interference Measurement Methods of the Coupled Transmission-Line Capacitance Parameters Based on the Harmonic Components

The traditional measurement methods of capacitance parameters of coupled transmission lines bring large measurement errors under a strong electromagnetic-interference environment. To solve this problem, new anti-interference measurement methods based on harmonic components are proposed. First, the voltages and currents at the head end and the tail end of the transmission line are sampled synchronously based on global positioning system (GPS) technology, then they acquire the third harmonic components from the measured data with an interpolation fast Fourier transform algorithm, and substitute them to the calculation formulae, so that the power frequency interference signals are filtered as noise and the capacitance parameters can be accurately measured. The wiring diagram of line parameter measurement and the hardware structure of the measuring system based on GPS are given. The simulation results with PSCAD and an example of measuring two 200-kV coupled transmission lines are given. The comparison of measurement results between the proposed methods and the traditional methods is also shown.

Comparison of Power Loss Due to Corona Phenomena Model with Peek's Formula in High Voltage 115 kV and 230 kV System

This paper studied the power loss due to corona phenomenon with Gary's model and Peek's formula using Matlab program for the power loss simulation in 115 kV and 230 kV system that the corona loss varies with transmission conductor radius and spacing. The corona phenomenon effects on leakage capacitance and inductance of transmission line. The leakage current would increase in the condition of the corona incepted. The power loss due to corona has an inverse variation with radius and spacing of conductor. The Gary‘s model is not suitable for 115 kV. Due to the operating point of power system, the model losses had the value 7.5% with difference from the formula for 115kV system and 14.5% for 230 kV system.

철도고배 전송선로 분로리액터 설치에 대한 모델링

I In power transmission systems, voltage changes continuously as reactive power is whether over supply or shortage. Reactive power produces in generators and consumes in transmission lines, and loads. Voltages at end points of transmission lines rise which is called Ferranti effect. Excessive voltage rising can reduce transmission equipment life, the voltage rising is usually permitted within the limit of 10%~30% excess. Shunt reactors are installed in transmission lines to put a curb on voltage rising. In this paper, we tried to do modelling for shunt reactor configuration types which are no grounding, grounded and grouded neutral reactor. Simulation are carried out for reactor magnitude for compensating transmission line capacitance.

Large‐scale photovoltaic plant harmonic transmission model and analysis on resonance characteristics

Harmonics generated from large-scale grid-connected photovoltaic plant (GCPV) has the characteristics of high frequency and wide frequency range. So the adverse impact of distributed parameter of high-voltage cables becomes more significant. Based on an actual GCPV, harmonic output particularities were discussed according to its operating mechanism. Step-up transformer, reactive power compensation device, distributed capacitance of transmission line and the loads were considered, the passive multiport network model was established, and the transmission mechanism of harmonics in this network was analysed by the definition of resonance amplification factors. Double resonance curves of harmonic current were discovered, that is, the transmission line of different distance may amplify a harmonic current twice. The simulation and data measurement in the field were carried out based on a large-scale GCPV in Qinghai province. The proposed scheme was verified by the comparison of simulation data and measurements.

Study on Wide-area Integrated Impedance Protection WIIP Algorithm

Wide-area integrated impedance protection (WIIP) algorithm based on wide-area measurement system is proposed for the purpose of improving the reliability and sensibility of fault component identification of wide-area protection. Two commonly used methods nowadays in wide-area protection are the current differential protection (CDP) and the directional pilot protection (DPP). The CDP, though responsive to all types of system faults, is subject to the distributed capacitance and earth resistance of transmission line; the DPP, which is easy to implement and does not need much traffic, is subject to system oscillations, conversion failure, and two phases operation. Integrating the advantages of these two algorithms, WIIP is obtained by evaluating in virtue of the ratio of the average voltages to the sum of all incoming and outgoing currents at each protected objects. The advantages of WIIP are verified by the fault analysis of two-terminal system and multi-terminal system. The research results show that WIIP presented in this paper is more preferable than CDP in the aspect of the sensitivity and DPP in the aspect of the dependability. The simulation effects can be obtained by using WIIP method applied in the case of abnormal operations of relay protections, circuit breakers, measurement error scenarios and substation DC failure. Keywords: Centralized system architecture, fault component identification, integrated impedance, wide-area protection.

Modeling of Blumlein Circuit and Calculation of Resistance and Inductance of Laser Plasma

Laser plasma discharge circuit can be simulated by Pspice through practical measuring result. We find that the circuit model of laser plasma should be simulated by a inductance in series with a resistor, furthermore in parallel with a capacitor. The value of the capacitor affect the oscillation frequency of the laser output voltage. The smaller the value of the equivalent capacitor, the less the rise time of the pulse voltage of the laser chamber. Also the rise time of the pulsed voltage of laser can be less when the stray inductance and transmission line capacitance are reduced. It is also found the time –invariant inductance is dependent on the total charge in the discharge area, the time-invariant inductance is dependent on the electric field in the laser chamber.