Terminals Of Transmission Line Research Articles

Identifying and Modeling Resonance-Related Fluctuations on the Experimental Characteristic Impedance for PCB and On-Chip Transmission Lines

It is well known that the fluctuations in experimentally obtained characteristic impedance versus frequency curves are associated with resonances originated by standing waves bouncing back and forth between the transitions at the transmission line terminations. In fact, microwave engineers are aware of the difficulty to completely remove the parasitic effect of these transitions, which makes obtaining smooth and physically expected frequency-dependent curves for the characteristic impedance a tough task. Here, we point out for the first time that these curves exhibit additional fluctuations within the microwave range due to standing waves taking place within the transition itself. Experimental verification of this fact was carried out by extracting this fundamental parameter from measurements performed on on-chip and printed circuit board (PCB) lines using probe pad adapters and coaxial connectors. We demonstrate that the lumped circuit approach to represent the transitions lacks validity when the additional fluctuations due to the connectors become apparent, and we propose a new model including transmission line effects within the transition.

Comprehensive fault reporting for three-terminal transmission line using adaptive estimation of line parameters

In this study, the post-fault synchronized phasors acquired from the local phasor measurement units (PMUs) are used to provide comprehensive fault reporting in Three terminal transmission line system (TTTL). The reporting data incorporates the classification, section identification, and localization of the fault based on the post-fault measurements of positive, negative, and zero sequence quantities. For accurate reporting, a proposed algorithm computes transmission line parameters, on hourly basis, to account for fluctuations in characteristics caused by temperature influences arising from either the loading factor or the climatic vagaries. Upon fault occurrence, the algorithm firstly determines fault classification and faulty section. Thereafter, localization of symmetrical faults is achieved via the positive sequence quantities to solve the positive sequence fault loop equation while that of asymmetrical faults is obtained through the negative sequence quantities to solve the negative sequence fault loop equation. The fault localization speed of the reporting proposed algorithm is attributed to the fact that synchronized data are obtained after one and half cycles from the fault onset. PSCAD/EMTDC platform is dedicated for time-domain investigations, while the proposed algorithm is carried out in MATLAB. The proposed algorithm was tested against 1537 fault characteristics at different locations along the TTTL, including varying fault resistances, loading conditions, and network configurations, in addition to assessing its sensitivity to changes in the TTTL parameters. These tests confirmed the algorithm’s reliability to be used with confidence in a variety of scenarios as the only 13 tests were observed with an error of estimation greater than 1%.

Discussion on the Range Configuration Strategy of Tension Sensor of Icing Monitoring Terminals of High-Voltage Transmission Line

Online monitoring of transmission line icing is an important means of anti-icing in the power grid. The accuracy mainly depends on the accuracy of the terminal tension sensor, which is one of the main sources of monitoring errors from large range configuration of tension sensor. This paper analyzes the working principle and characteristics of tension sensors and the load calculation method of different types of insulator hanging points to determine the output error of over-range configuration tension sensors. It finally proposes a principle and a calculation method for tension sensors’ range configuration, which is verified to be reliable by experiments. The results can provide a basis for the selection of tension sensors for icing-monitoring terminals and reduce the error caused by temperature drift and zero drift of tension sensors.

Precision Design and Fabrication of Noise-free High-Frequency Amplifier Board for Enhanced Signal Processing

An optical signal processing system is widely used for long-distance signal transmission with high speed and low attenuation. It plays a fundamental role in optical communication systems that involves transmitting, receiving, amplifying, and manipulating optical signals which are high-frequency signals. This paper portrays the design of a high-frequency amplifier to amplify the low-amplitude high-frequency, electrical signal procured from the optical signal. A four-stage high frequency amplifier has been designed using an AD8009 high-frequency Op-amp for the highest frequency of 1GHz, and for the fastest rise time of 0.35 nanoseconds. This amplifier board incorporates the high-frequency PCB design rules related to the characteristic impedance, impedance matching, signal crosstalk, the propagation delay of the transmission lines, transmission techniques for the ground plane, and termination of transmission lines for the effective use of high-frequency signals. It has also counted on the issues of electromagnetic interference, power supply decoupling, noise, and high-speed operational amplifier. The proposed system resulted in suitable amplification of low amplitude high-frequency electrical signal, having no signal cross-talks, electromagnetic interference, signal ringing, signal reflections, and posed larger bandwidth. The improved quality of high frequency processed signals with good signal integrity and moderate circuit oscillations achieved by this system will benefit the optical communication system.

Estimation of the electrical parameters of overhead transmission lines using Kalman Filtering with particle swarm optimization

The parameter estimation for transmission systems is important to power flow analysis, planning the expansion of electric power systems, stability, dispatch and economic analysis. This type of task is developed through systems identification methods, being the least squares method and its variations the most common techniques to obtain the transmission line parameters. However, these techniques have some disadvantages, such as non-recursive parameter estimation or the availability of an ideally transposed line, in order to address a problem with symmetric matrices, which simplifies the estimation process. In this paper, a non-linear method (Extended Kalman Filter) is presented to obtain the states of the transmission line terminals jointly with the vectorized matrix of parameters; such approach is strongly affected by the initial conditions; these conditions are usually obtained manually, which requires a lot of time and effort. Therefore, an optimization method (Particle Swarm Optimization) is applied in order to improve the convergence of the EKF, which reduces the time for adjusting the hyper-parameters and improves the estimated results. The proposed method showed accurate results for non-transposed systems, and also in comparison with results obtained from the same EKF-based method without the proposed optimization technique.

A travelling wave based primary and backup protection for MMC-MTDC transmission system using morphological un-decimated wavelet scheme

The primary protection speed requirement for the HVDC grid is much faster as compared to the conventional HVAC grid. This research article proposes a travelling wave-based primary and backup protection scheme for the multi terminal HVDC transmission system using the morphological un-decimated wavelet decomposition signal processing technique. Depending on the polarity and arrival time information of the first incident travelling wave at both DC transmission line terminals, the fault is identified to be either in the internal zone, forward external zone, or backward external zone of the DC transmission line. Each DC transmission line is covered by its own internal zone as well as forward & backward external zone of its neighbouring line. The internal zone fault identification of the protection scheme sends the primary relay trip signals to associated hybrid DC circuit breakers. But if the primary protection relay fails, then the neighbouring DC substation protection system identifies the fault either in forward external or backward external zone. Then it sends a remote backup trip signal to the DC circuit breaker in the forward or backward external direction with a coordinated time delay.

The impact of DFIG control schemes on the negative-sequence based differential protection

Negative-sequence currents at the transmission line terminals are widely adopted in differential protection to achieve excellent sensitivity. The underlying principle is that the traditional power sources (synchronous generators) can be treated as inductive reactance in the negative-sequence network. However, for the transmission lines connected to Doubly-Fed Induction Generator (DFIG) based wind parks (WPs), the negative-sequence currents are controlled by fault-ride-through (FRT) solutions. This paper first analyzes the phasor characteristics between negative-sequence voltage and current of a DFIG-based WP under three typical FRT solutions, and then evaluates their impact on the dynamic performance of negative-sequence differential protection elements (87LQ). The analysis indicates that a certain FRT control strategy would make DFIG-based WP provide capacitive current into the negative-sequence network. This impacts the sensitivity and even results in maloperation as shown for the first time in this work. The analytical results are validated with detailed time domain models and simulations in Simulink.

Impact of Resistive SFCLs on Superimposed Quantities in Power System Faults

Superimposed quantities, also known as delta quantities, are the transient signatures of fault currents and voltages that can be utilized by protective relays to achieve fast fault detection for electric power grid applications. With the installation of superconducting fault current limiters (SFCLs) on power transmission lines, the profiles of superimposed quantities in power system faults are affected due to the altered impedance properties at transmission line terminals, which may further affect protective relay performance. In this article, we investigate the impact of a resistive SFCL on superimposed quantity profiles. The equivalent circuit of a resistive SFCL connected to an electric power transmission system is first illustrated based on which the simulation model is established in an electromagnetic transients program. Various types of power transmission line faults are simulated. The superimposed current and voltage quantities at transmission line terminals are obtained. The simulation results demonstrate that the acquired superimposed quantities are significantly affected by the SFCL. Possible consequences to protection functions are discussed.

Fault Location in Overhead Transmission Lines Based on Magnetic Signatures and on the Extended Kalman Filter

This paper proposes a non-contact method for fault location in transmission lines, which is based on magnetic fields produced by current signals measured using magnetoresistive sensors installed only at transmission line terminals, under the phase conductors of the first transmission tower at both terminals or at the substations portals. The proposed method uses the Extended Kalman filter to process these measurements and is based on a travelling wave approach in order to perform the fault localization. This paper also describes the implementation and testing of the method, firstly introducing its overview, followed by an analysis of the magnetic fields produced by the current signals, as well as considerations on their measurement; secondly, detailing the Extended Kalman filter and the travelling wave approach; and, finally, presenting the results of the method with regards to simulations built using EMTP/ATP to evaluate its robustness under different conditions varying the fault resistance, fault inception angle, phases involved and fault location. The results indicate that the proposed method is robust and accurate.

Signal Transmission Capability Improvement of a Telemetry Drill String Using the Reflected Signal at the Transmission Line Termination

A telemetry drill string system consists of a string of wired drill pipes, and high-frequency signals pass the adjacent drill pipes through inductive couplers. Such a system is used to upload downhole information at high data transmission rates for measurements while drilling (MWD). Since the signal energy attenuates greatly in the system, many repeaters must be provided to ensure signal transmission. A reduction in the signal transmission in a telemetry drill string can extend the relay distance and improve the reliability of the transmission system. In this study, the transmission characteristic of the rod of the wired drill pipe is studied using transmission line theory, and the transmission characteristic of the inductive coupler is studied using high-frequency circuit theory. Using impedance matching between the transmission line of the rod and the inductive coupler, external impedance compensation elements, including a capacitor and a resistor, are recommended, and the electromagnetic parameters of the wired drill pipe are determined. Based on the determined electromagnetic parameters, certain changes in the external impedance compensation capacitance and resistance can lead to impedance mismatch between the transmission line and the inductive coupler. This will generate a reflected signal at the transmission line, and the vector superposes with the transmitted signal. The terminal reflection coefficient of the transmission line is controlled by increasing the compensation resistance value to enhance the signal amplitude, which can compensate the transmission loss when passing through the inductive coupler to a certain extent. Thus, the signal transmission capability of the telemetry drill string can be improved, allowing for long-distance signal transmission or drastically extending the relay distance, while maintaining a certain channel bandwidth.

A Novel $k$-Means Clustering and Weighted $k$-NN-Regression-Based Fast Transmission Line Protection

This article presents a k-means clustering and weighted k-nearest neighbor (k-NN) regression-based algorithm for the protection of transmission line. Three-phase current signals of both the terminals are synchronized and sampled with a sampling frequency of 3.84 kHz. Cumulative differential sum (CDS) is computed by subtracting the samples of current cycle from the previous cycle at both the terminals of transmission line. k-means clustering is applied on CDS to compute two centroids using moving window of width, equal to one cycle. Difference between the absolute values of centroids is computed at both the terminals and represented by the centroid difference (CD). The CD of both the terminals is added to compute the fault index. The computed fault index is used to detect and classify the types of faults. The location of the fault is estimated by the weighted k-NN regression method. Various case studies are performed to validate the robustness of the algorithm for different fault parameters such as fault impedance and fault location. The effect of noise is also considered to check the accuracy of the proposed algorithm in the noisy environment.

Radiated Susceptibility Analysis of Single-wire Transmission Lines by Means of Modified Stochastic Reduced-order Modeling

This work investigates the statistical radiatedsusceptibility of an electrically-short transmission line (TL)consisting of a single wire over a ground plane. The angularparameters of the impinging plane wave and the height ofthe wire over the ground plane are modelled as randomvariables with Gaussian/Uniform distributions. Thestatistical properties of the current in the TL terminations(i.e., mean value, standard deviation, and cumulativedistribution function) are derived through a properlydefined numerical methodology consisting in a modifiedversion of the conventional Stochastic Reduced-OrderModel (SROM) approach. The proposed methodologyconsists in a straightforward approximation of the inputcontinuous random variables with small-size discreterandom variables. In contrast with conventional SROM, nonumerical pre-processing is needed. The modified SROMproposed in this paper demonstrates high efficiency whencompared with classical Monte Carlo approach. Theproposed technique can be applied to the statistical analysisof much more complex systems whose input/outputrelationship requires a huge computational burden and forwhich the conventional Monte Carlo approach is notsuitable

Coaxial‐fed high‐gain triple‐band zeroth‐order circularly polarized antenna using pseudo‐open termination and asymmetric unit cells

A coaxial-fed tri-band zeroth-order resonance (ZOR) circularly polarized antenna with higher gains for all the excited ZORs is designed and analyzed in this paper. Epsilon negative transmission line (ENG TL) and pseudo-open termination (P-OT) unit cells with different series capacitances (CS and CS1) resonate shunt ZOR (fsh) and two series ZORs (fse and fse1), respectively. Asymmetric unit cell concept is applied to ENG-TL and P-OT unit cells to create vertical and horizontal components, and the 90° phase shift is provided by the ZOR, resulting in circular polarization (CP). Left-hand CP (LHCP) is achieved by creating two 90° right bends to the extended stubs in ENG TL and P-OT unit cells. Higher gains for all the excited ZORs are achieved by shifting the shorting pins of ENG TL and P-OT unit cells far away from the center position. After fabrication, the measured resonances occur at 4.64 GHz (fsh), 4.04 GHz (fse), and 3.86 GHz (fse1) with fractional bandwidths of 1.62%, 1.73%, and 1.6%, respectively. The measured LHCP peak gains are 4.05 dBic (fsh), 3.85 dBic (fse), and 3.94 dBic (fse1). The average axial ratio obtained is less than 3-dB in the 10-dB fractional bandwidth of the proposed antenna.

Synchrophasor Based Novel Fault Location Algorithm for Three- Terminal Transmission Line

A fault detection and location algorithm on three-terminal transmission line is proposed. Vast literature on fault location shows that to simplify the analysis, line charging currents are often ignored. To improve the accuracy of fault location, synchronized current and voltage measurements from three ends of the three-terminal line are utilized to detect and locate distance to fault while considering the line charging currents. The method first detects the zone at which the fault has occurred and then locates it from the respective line ends. Since three-terminal lines provide solutions for connecting existing system to the grid, facilitating bulk transfer of power, thus the fault detection and location on the same is important to maintain reliability and security of the system. Performance of the proposed algorithm is tested for various fault types, fault locations, fault resistances and fault inception angles. The 200-kV system is simulated in ATP/EMTP; however, the algorithm is developed in MATLAB. The extensive simulation studies demonstrate accuracy of the proposed scheme.

PMU–Based fault location method for Three–terminal transmission lines with outage of one line branch

This paper proposes a fault location method for three-terminal double-circuit untransposed transmission lines with outage of one line branch utilizing the synchronized voltage and current measurements obtained from both ends of in-service line branches. The proposed method is applicable for short, medium, and long transmission lines as it is based on a distributed line model parameters considering the mutual couplings between all phases. Initially, the faulted phases are identified and the fault location for in-service line branches is determined adopting previously proposed two-terminal fault location technique. In addition, a fault location method is introduced for out-service line branch. This method is based on the resistive nature of the fault impedance. The three calculated fault distances corresponding to each line branch are compared with each other to determine the faulted line branch and the fault location. Simulation studies implemented using DIgSILENT Power Factory software and MATLAB environment show that the proposed method has acceptable performance for different fault resistances, types, and inception angles.

Analytical method for electromagnetic coupling to a penetrated transmission line in cascaded multiple enclosures with hybrid apertures

An efficient analytical model has been developed for predicting the electromagnetic (EM) field coupling to a lossless transmission line (TL) penetrating through cascaded multiple rectangular enclosure with hybrid apertures (apertures with and without conductive sheets coexist) excited by an external plane wave of oblique incidence. First, The EM field in the enclosure through apertures covered by conductive sheets is derived using the dyadic Green’s function and the transfer impedance of the sheet. Then, the EM field in the enclosure through apertures without sheets is derived based on the Bethe’s small holes theory and the mirror procedure. Finally, the electric current induced at the TL terminals is obtained combining the equivalent lumped-pi circuit model of the TL and the Agrawal’s model. The analytical model has been successfully verified by the finite-difference time-domain (FDTD) method over the frequency range of 0.1 ~ 3 GHz, which consumes less time than numerical methods.

A Traveling Wave-Based Fault Location Method Using Unsynchronized Current Measurements

This paper presents a traveling-wave-based fault location method for two terminal transmission lines using unsynchronized current measurements from intelligent electronic devices (IEDs) recorded at both ends. In the formulation, the method considers practical implementation issues such as IED hardware and software processing delays, and data synchronization error. In this method, two possible fault location solutions are determined using the first two traveling wave arrival time recorded at both terminals. Then, the correct fault location is identified between the two based on the faulted half-section information. Identification of faulted half-section is accomplished by comparing the rise time of the first traveling wave recorded at both terminals of the line. The proposed method does not require GPS synchronization and field experiments to calibrate the various asymmetrical delays and synchronization error. The method is tested on a 220 kV transmission line using data simulated in EMTDC/PSCAD tool with frequency-dependent phase models. The proposed method can locate faults using unsynchronized data with various asymmetrical delays, whereas classical methods work properly only for synchronized data with symmetrical delays. The performance of the proposed method is evaluated for different fault scenarios. The proposed method demonstrated high accuracy, noise immunity, robustness against fault inception angles, and high impedance faults. Test results are compared with classical two-terminal methods for a transmission line.

A New Two-Port Network Model-Based Pilot Protection for AC Transmission Lines

Conventional pilot protections used for EHV/UHV ac transmission lines require data synchronization between the two terminals of transmission line, and their performances are affected by the line capacitive charging current and load conditions. To tackle these problems, this paper proposes a new pilot protection scheme based on two-port network model of ac transmission lines. The new protection scheme calculates the two-port network parameters from the online measurements via the sequence components method, and then compares the solved parameters with their setting values to distinguish the internal and external faults. It does not require the data synchronization between two terminals of the transmission line. Moreover, its performance is not affected by the line capacitive charging current and load conditions. The applicability of the proposed scheme for series compensated lines is also analyzed. Effectiveness and accuracy of the proposed protection scheme have been verified by simulation tests.

Matrix Power Amplifier With Open-Circuit Composite Right-/Left-Handed Transmission Line

A distributed matrix power amplifier with open-circuit (O.C) composite right-/left-handed (CRLH) transmission line (TL) is proposed. The matrix structure along with the zero phase-shift CRLH TL and the O.C termination of TLs have led to the design of reduced size, high-gain matrix amplifier with improved power performances. A new small size planar CRLH unit cell is presented. The maximum gain of 21.5 dB at the center frequency is obtained. The measured 1-dB gain compression (P1-dB) is 26 dBm, and the maximum power added efficiency is 29%. Better gain and P1-dB are achieved compared to the previously published narrowband distributed amplifiers. The amplifier has good linearity according to the measured input intercept point (18 dBm) and the output intercept point (39 dBm).

Compact Frequency Reconfigurable Antennas Based on Composite Right/Left-Handed Transmission Line

The compact reconfigurable antennas based on composite right/left-handed (CRLH) transmission line are proposed and analyzed in this paper. The proposed antenna is fed by the asymmetric coplanar strip (ACPS) and consists of coupling radiation patch as well as a PIN diode. The differences of the antennas with meander line and without meander line are discussed. By utilizing a PIN diode as the CRLH transmission line termination, the termination states can be controlled, and the resonance of the antenna can thus be tuned between the two zeroth-order resonant frequencies. By switching the diode, the antenna with meander line is able to operate in single-band of 2.08-2.54 GHz and dual-bands of 1.65-1.84 GHz and 5.35-6.40 GHz, while the antenna without meander line is able to operation between two single-bands of 1.84-2.28 GHz and 4.6-6.0 GHz. All these operation bands cover the UMTS (1750 MHz-1780 MHz), ISM (2.4 GHz), WIMAX (2.5-2.69 GHz) and WLAN (2.4-2.484 GHz/5.725-5.825 GHz) applications. The radiation performance was simulated by High Frequency Structure Simulator, and the measurements were taken in an anechoic chamber to verify the simulation results. Good agreements are observed between the simulated and measured results. Moreover, the radiation patterns of the proposed antennas remain stable at different reconfigurable bands.