Terminals Of Transmission Line Research Articles

Wavelet-based analysis and detection of traveling waves due to DC faults in LCC HVDC systems

This paper presents qualitative and quantitative analysis of the traveling waves induced by faults on direct current (DC) transmission lines of line-commutated converter high-voltage direct current (LCC HVDC) systems for detecting the wavefront arrival times using the boundary wavelet coefficients from real-time stationary wavelet transform (RT-SWT). The qualitative analysis takes into account the steady-state operation and the detection of the inception times of both first and second wavefronts at the converter stations. The behavior of the boundary wavelet coefficients in DC transmission lines is examined considering the effects of the main parameters that influence the detection of the traveling waves, such as mother wavelets, sampling frequency, DC transmission line terminations, electrical noises, as well as fault resistance and distance. An algorithm designed to run in real-time and able to minimize the factors that hamper the performance of traveling wave-based protection (TWP) methods is proposed to detect the first and second surge arrival times. Quantitative results are achieved based on the accuracy of one- and two-terminal fault location estimation methods, and indicate the proper operation of the presented algorithm.

DAC-Less and DSP-Free 112 Gb/s PAM-4 Transmitter Using Two Parallel Electroabsorption Modulators

Four-level pulse amplitude modulation (PAM-4) is widely regarded as the modulation format of choice for the next generation of 400 gigabit Ethernet short-reach optical transceiver. However, generating and receiving PAM-4 at line rates of 112 Gb/s has proven challenging, without relying on power-hungry tools as digital signal processing and digital-to-analog converters, as it requires linearity from the E/O-components in the link and/or predistortion techniques. Moving the binary to multilevel conversion to the optical domain would greatly relax these requirements. Electroabsorption-based transceivers would be ideally suited for this type of data center interconnects as they are capable of combining low-power and high bandwidth operation with a very compact layout, removing the need for large travelling wave structures and dedicated 50 Ω terminations. In this paper, we present a novel transmitter topology for generating PAM-4 using two binary-driven electroabsorption modulators in parallel. Using this approach, we achieve superior performance with respect to a single, but identical multilevel-driven EAM. Finally, we demonstrate the first silicon-based modulator capable of transmitting single-lane 112 Gb/s PAM-4 over 2 km of standard single-mode fiber without any electrical digital-to-analog converter, DSP, or long transmission line structures and terminations.

RETRACTED: Modern optimization algorithms for fault location estimation in power systems

Abstract This paper presents a fault location estimation approach in two terminal transmission lines using Teaching Learning Based Optimization (TLBO) technique, and Harmony Search (HS) technique. Also, previous methods were discussed such as Genetic Algorithm (GA), Artificial Bee Colony (ABC), Artificial neural networks (ANN) and Cause & effect (C&E) with discussing advantages and disadvantages of all methods. Initial data for proposed techniques are post-fault measured voltages and currents from both ends, along with line parameters as initial inputs as well. This paper deals with several types of faults, L-L-L, L-L-L-G, L-L-G and L-G. Simulation of the model was performed on SIMULINK by extracting initial inputs from SIMULINK to MATLAB, where the objective function specifies the fault location with a very high accuracy, precision and within a very short time. Future works are discussed showing the benefit behind using the Differential Learning TLBO (DLTLBO) was discussed as well.

Wavelet Based Protection Scheme for Multi Terminal Transmission System with PV and Wind Generation

A hybrid generation is a part of large power system in which number of sources usually attached to a power electronic converter and loads are clustered can operate independent of the main power system. The protection scheme is crucial against faults based on traditional over current protection since there are adequate problems due to fault currents in the mode of operation. This paper adopts a new approach for detection, discrimination of the faults for multi terminal transmission line protection in presence of hybrid generation. Transient current based protection scheme is developed with discrete wavelet transform. Fault indices of all phase currents at all terminals are obtained by analyzing the detail coefficients of current signals using bior 1.5 mother wavelet. This scheme is tested for different types of faults and is found effective for detection and discrimination of fault with various fault inception angle and fault impedance.

New ANN method for multi-terminal HVDC protection relaying

This paper proposes a comprehensive novel multi-terminal HVDC protection scheme based on artificial neural network (ANN) and high frequency components detected from fault current signals only. The method is shown to accurately detect, classify and locate overhead line faults. Unlike existing travelling wave based methods which must capture the initial wavefront and require high sampling rates, the new approach is more robust since it gives accurate fault detection and fault location over a range of windowed post-fault signals. Furthermore, the proposed method is fault resistance independent meaning even a very high fault impedance has no effect on accurate fault location. A three-terminal VSC-HVDC system is modelled in PSCAD/EMTDC, which is used for obtaining the fault current data for transmission line terminals. The method is verified by studying different cases with a range of fault resistances in various fault locations, and in addition, external faults. The results show that the proposed method gives fast (<5ms) and reliable (100%) fault detection and classification and accurate location (<1.16%) for DC line faults.

Wavelet‐alienation based transmission line protection scheme

This study presents a wavelet-alienation based algorithm for protection of two terminal transmission line. The proposed algorithm makes use of wavelet transform based approximate coefficients of three-phase voltage and current signals, obtained over a quarter cycle to detect, classify and locate various faults. Detection and classification of these faults are achieved with the help of alienation coefficients of current signals from both the terminals of the transmission line. The approximate coefficients of voltage and current signals, obtained over a quarter cycle, are fed to artificial neural network to locate the faults precisely. The proposed algorithm has been tested successfully for various types of faults with the variations in location, inception angle and fault impedance.

Modeling of VHF Current Conversion From Excited Antenna Mode to Differential Mode at Transmission Line Terminals

The current induced by an incident electric field can convert from the antenna mode to differential mode at unbalanced terminals of transmission lines (TLs), causing severe interference to a number of applications such as broadband power line communication, especially in the very high frequency (VHF) band. The previous work on modeling the current conversion is not applicable to VHF. We present a new model of the VHF current conversion which includes a general formula for the antenna mode characteristic impedance and two solutions to the formulated problem: 1) a numerical solution referred to as the antenna theory numerical (ATN) approach, which gives the exact value of the characteristic impedance; 2) an analytical solution referred to as the enhanced TL approximation (ETLA) approach, which gives the mean of the characteristic impedance. This is the first reported work to obtain the antenna mode characteristic impedance by the antenna theory. Furthermore, the ETLA approach outperforms the previous frequency-independent solution and requires a reduced complexity over the ATN approach. Our model is general as it converges to the previous model at lower frequencies. Simulation results also show the relationship between the antenna mode characteristic impedance and the power of the interference caused by the current conversion.

线路故障测距的人工智能算法研究

本文提出了一种基于智能算法的动态故障测距算法，用于带有多支路的输电线路故障测距。该算法通过测量输电线两侧的电流、电压值，得到相对应的判别指标，从而可预先识别出故障对应的区域；然后将非故障分支进行等效，得到合并后的电气量；再对故障处的分支应用基于遗传算法的双端测距法进行初步的测距，并利用神经网络算法对所得到的测距结果进行进一步的调整，提高了线路故障的测距精度。本文所提出的计算方法只需使用变电站故障后状态下所测得的电压和电流值，并继承了基于遗传算法的故障测距方法的优点，不受故障点位置与过渡电阻的影响，且减小了线路参数偏差对最后结果的影响。使用PSCAD对所提出的方法进行验证，结果表明所提出方法的正确性和高精度性。 Considering the transmission line with multi-branch, a dynamic fault location algorithm based on intelligent algorithm is presented in this paper. Based on the measured voltage and current at two terminals, a discrimination index is proposed by which the faulted section can be located first. After that the equivalent voltage and current at the branch node is obtained by the equivalent calculation of the healthy branches. It corrects the results of fault location method based on genetic algorithm by the way of neural network algorithm, with the ranging accuracy improved when there are faults at two terminals of transmission line. The proposed algorithm only demands the measured voltage and current on the two terminals, and inherits the advantages of fault location method based on genetic algorithm, which is independent of fault type, fault resistance at fault point, etc., the influence on ranging accuracy by line parameters deviation is greatly reduced. The proposed method is simulated by PSCAD, and the results verified the correctness and high precision of the algorithm.

Extreme Learning Machine Based Adaptive Distance Relaying Scheme for Static Synchronous Series Compensator Based Transmission Lines

This article presents an extreme learning machine based fast and accurate adaptive distance relaying scheme for transmission lines in the presence of a static synchronous series compensator. The ideal trip characteristics of the distance relay is greatly affected by pre-fault system conditions, ground fault resistance, and zero-sequence voltage. The proposed research develops an extreme learning machine based adaptive distance relaying scheme for two-terminal transmission networks with static synchronous series compensators when a single-line-to-ground fault situation is most likely to occur. The study includes an analytical approach, including a steady-state model of static synchronous series compensator with detailed simulation on MATLAB/Simulink (The MathWorks, Natick, Massachusetts, USA) and open real-time simulation software with MATLAB (OPAL-RT) platform (OPAL-RT Technologies, Montreal, Quebec, Canada). The proposed extreme learning machine based adaptive distance relaying scheme is extensively validated on the two terminal transmission lines with static synchronous series compensators, and the performance is compared with the existing radial basis feed-forward neural network based adaptive distance relaying scheme. The results on simulation and real-time platform show significant improvements in the performance indices, such as speed, selectivity, and reliability of the digital relay.

An extreme learning machine based fast and accurate adaptive distance relaying scheme

Abstract The ideal trip characteristics of the distance relay is greatly affected by pre-fault system conditions, ground fault resistance, shunt capacitance and mutual coupling of transmission network. This paper presents an extreme learning machine (ELM) based fast and accurate adaptive relaying scheme for stand-alone distance protection of transmission network. The proposed ELM based fast adaptive distance relaying scheme (FADRS) is extensively validated on the two terminal transmission lines with complex mutual coupling and shunt capacitance and, the performance is compared with the conventional artificial neural networks (ANNs) based adaptive distance relaying scheme (ADRS). The simulation results show significant improvement in the performance indices such as relay speed and selectivity. Further, the performance of proposed FADRS is tested for stressed condition such as power swing and found to be effective and reliable.

Regularization techniques for the high-frequency electromagnetic field coupling problem with terminated lines

The problem of the high-frequency electromagnetic field coupling with a terminated transmission line is formulated and discussed in detail. Existence and uniqueness of the solution of the integro-differential equation describing the model are shown, pointing out, on the contrary, the not continuous dependence on the data. The problem is solved with three regularization methods (Landweber, Tikhonov and Truncated Singular Value Decomposition algorithms), and a comparative analysis is presented taking as reference the numerical results obtained using the Numerical Electromagnetic Code (NEC-2).

An Equivalent Two-Port Model for a Transmission Line of Finite Length Accounting for High-Frequency Effects

The aim of this paper is the definition of an equivalent two-port model of a transmission line that is able to take into account high frequency radiation effects. Such a model is particularly useful when one has to represent the line into a more complex power system, modeled in a lumped way. To reach this goal, it is necessary to produce a reliable and computationally effective solution to the problem of the high-frequency electromagnetic field coupling with a terminated transmission line. From a mathematical standpoint, this problem can be presented by means of an integral equation whose solution can be achieved with regularization procedures for linear inverse problems. In order to obtain a computationally efficient result, the unknown current is first developed in a Fourier series and then the Landweber iterative algorithm is applied to identify the series coefficients. The proposed method is then tested taking as reference the numerical results obtained using the Numerical Electromagnetics Code (NEC-2), reaching a good agreement.

The Influence of Network Impedance on Conducted Disturbances Within the High-Voltage Traction Harness of Electric Vehicles

Currently, automotive traction systems are increasingly being revised from combustion engine drives to electric propulsion. The high power cables of electric vehicles are routed close to various communication, sensor, or control units. This circumstance results in a tightened challenge for the developing engineers, who need to ensure the electromagnetic compatibility of these miscellaneous and adjacent systems. A trial-and-error approach in the development process of electromagnetic interference filters can only be avoided if the influence of the network impedances within the high voltage traction harness on conducted RF disturbances is known. This contribution presents the current methodology of determining the conducted emissions of power inverters for electric driven cars. It highlights the differences between the traditional low-voltage cable wiring and novel high-voltage traction harnesses, and their impact on the network impedances. An adaption of the line impedance stabilization networks used recently to the characteristic impedance of the high-voltage cables applied shows the influence of termination mismatch on conducted emissions within the traction harness. High-voltage components employed in a car are usually supplied by a traction accumulator battery, which acts as transmission line termination. The influence of a battery's input impedances on disturbances within a component level EMC test setup is shown.

Research on a novel suppressing methodology for secondary arc extinction based on an impedance paralleled to line circuit breaker

A novel scheme is proposed for secondary arc extinction, preferably applicable to extra high voltage (EHV) and ultra high voltage (UHV) transmission lines. The topology and the operational principle of the scheme are elucidated in details. Mathematical expressions for topology parameters design and optimization under different conditions have been established based on equivalent circuit transform and are verified by simulations. Results suggest that the proposed methodology can largely reduce the forced component of the secondary arc current, one part of the complete response of a circuit under excitation. The recovery voltage is not affected by fault location, transmission power and the shunt inductors. The decay factor and oscillation frequency of the free components of the secondary arc current and the recovery voltage are also computed based on the equivalent impedance network and Laplace Transform. In addition to causing possible resonant overvoltage, the proposed theme may prolong the arcing time due to cancelling zero-crossing of the secondary arc current while shunt inductors are installed at the transmission line terminals. Simplified formula for calculating the critical compensation point are given as to be used as a reference for the re-optimization of the novel theme. The proposed methodology presents an alternative to suppress the secondary arcs for EHV and UHV transmission lines. Copyright © 2013 John Wiley & Sons, Ltd.

Time-Domain Generalized Telegrapher's Equations for the Electromagnetic Field Coupling to Finite Length Wires Above a Lossy Ground

In this paper, a time-domain variant of the generalized telegrapher's equations for transient electromagnetic field coupling to a finite-length wire above a lossy half-space is derived. The approach is fully based on the thin-wire antenna theory. The lossy ground effects are taken into account by means of the reflection coefficient approximation. The obtained equations are handled numerically via the Galerkin-Bubnov indirect boundary element method. Computational examples are presented for the case of a single-wire line excited by an electromagnetic pulse excitation source. The obtained results for the induced current along the line are compared with those obtained using 1) the method of moments solution of the electric field integral equation implemented in the numerical electromagnetics code (NEC-4), and 2) the transmission line (TL) theory. It is shown that the results obtained by the proposed method are in excellent agreement with those of NEC-4. It is also shown that the TL approximation yields in general results which are in reasonably good agreement with the full-wave results, especially for the early time response and even beyond the limits of the accuracy of the TL theory. The TL theory can, however, give accurate results only for times before the arrival of the first reflection from the TL terminations and it fails to reproduce accurately the dispersion effects occurring after the first reflection.

A fast and low noise charge sensitive preamplifier in 90 nm CMOS technology

A fast charge sensitive preamplifier was designed and built in a 90 nm CMOS technology. The work is part of the R&D effort towards the read out of pixel or small strip sensors in next generation HEP experiments. The preamplifier features outstanding noise performance given its wide bandwidth, with a ENC (equivalent noise charge) of about 350 electrons RMS with a detector of 1 pF capacitance. With proper filtering, the ENC drops to less than 200 electrons RMS. Power consumption is 5 mW for one channel, and the closed loop bandwith is about 180 MHz, for a risetime down to 2 ns in the fastest operation mode. Thanks to some freedom left to the user in setting the open loop gain, detectors with larger source capacitance can be read out without significant loss in bandwidth, being the rise time still 5.5 ns for a 5.6 pF detector. The output can drive a 50 Ω terminated transmission line.

CROSSTALK AND DISCONTINUITIES REDUCTION ON MULTI-MODULE MEMORY BUS BY PARTICLE SWARM OPTIMIZATION

Due to high-density routing under the CPU and DIMM areas, the original design of even and odd mode characteristic impedances changes. The occurrence of multi-drop problem between the CPU and memory chip causes over- and under-driven that reduce the eye opening. Furthermore, the difierent phase velocities of even- and odd-modes cause timing jitter at the receiver end. This paper proposes two steps to solve the complex issue of signal integrity for the multi-module memory bus. First, particle swarm optimization (PSO) is used to tune the characteristic impedance of the transmission line and on-die termination (ODT) values to improve transmission line impedance changes to obtain maximum power delivery. The fltness function of the algorithm is deflned by selecting the minimum re∞ection coe-cient at the driver side and maximum the transmission coe-cient at the receiver side to reduce the over- and under-driven Second, the timing jitter can be reduced by placing a capacitor to compensate for the velocity difierence caused by difierent propagation modes. Finally, signal integrity enhancements for the DDR3 are verifled by measuring S parameters in the frequency domain and postprocessed eye diagrams in the time domain.

Fault-Location System for Multiterminal Transmission Lines

This research presents the development and implementation in a computational routine of algorithms for fault location in multiterminal transmission lines. These algorithms are part of a fault-location system, which is capable of correctly identifying the fault point based on voltage and current phasor quantities, calculated by using measurements of voltage and current signals from intelligent electronic devices, located on the transmission-line terminals. The algorithms have access to the electrical parameters of the transmission lines and to information about the transformers loading and their connection type. This paper also presents the development of phase component models for the power system elements used by the fault-location algorithms.

Recording Front-End Systems Analysis

As data rates continue to increase, front-end design techniques and analysis must evolve in order to manage the transmission line effects and the parasitic effects of the transducer, electronics, and electrical interconnect. In addition, the complete write process contains linear and non-linear effects, which requires write signal wave-shaping for optimum performance. Data signal fidelity is maintained by proper termination at the read/write integrated circuit (IC), which is dependent on the read/write transducer's impedance range. For writing, transmission-line termination techniques along with the write-driver electronics are utilized to induce the required overshoot for transitions in the write current waveform. For reading, the key aspects of signal-to-noise ratio (SNR) and bandwidth are the parasitic components at the read transducer and the input at the read amplifier. The Noise Figure (NF) of the front-end system can be modeled to include the parasitic effects along with the transmission losses of the interconnect. Here, we expound on design techniques and component values for the front-end system.

Load response of terminated transmission lines exposed to external electromagnetic fields

Plane-wave excitation fields are by far the most commonly used in field-to-wire coupling computations. Nevertheless, such excitations are not always adequate for the immunity assessment of wire-type structures operating in the contemporary man-made environment. To reinforce this conjecture, this study examines two-wire transmission lines excited by common non-uniform fields. Numerical results for the induced load voltages show notable deviations from those obtained under the assumption of plane-wave incidence.