Transmission Line Configuration Research Articles

Quantitative effect of dust on photovoltaic supply of transmission line monitoring device and configuration correction

Aiming at the problems that the photovoltaic power supplies of transmission lines monitoring devices are liable to be discontinuous and damaged, it is found that the power loss caused by surface dust deposition cannot be ignored. Improper configuration via empirical formula may result in power shortage and long-term undercharging of the battery, finally shorten the equipment's life. What is more, artificial and field experiments were carried out to find the qualitative impact, and the attenuation coefficient related to dust deposition may ensure a more appropriate configuration. This research provides a reference for power supply design and helps to save the replacement.

Power System Design for a Large, Dynamic Natural Gas Field: Improving the Field Production Profile

In this article, we detail the upgrading of a large natural GAS field to improve the field production profile of the nonassociated gas recovery rate of the existing wells. Several gas compression plants (GCPs) with nearly 20 large, high-voltage (HV) motors will be optimally located based on thermohydraulic modeling results. This requires a power system network that provides a reliable and stable power supply to critical operations, delivering over 3 billion standard cubic feet per day of compressed gas. These GCPs are located in remote areas with severe Middle East weather conditions. The technical challenges for designing and ensuring power delivery to these locations without sacrificing quality, reliability, and safety are reviewed. Analyzing the design, planning, installation options, construction techniques, safety requirements, and logistical methods used in the design are discussed. It also addresses the interface with the utility, HV transmission line configuration, selection of substation equipment, and motorstarting methods to distribute power from the bulk supply point (BSP) to the GCPs.

Selectivity-Enhancement Technique for Stepped-Impedance-Resonator Dual-Passband Filters

A class of stepped-impedance resonator (SIR) dual-band bandpass filter (BPF) with selectivity-enhancement cells is reported. These dual-band filtering cells, which are composed of two open-ended transmission-line segments interconnected at the input, are added at one node of the input and output coupled-line stages. Thus, with regard to the SIR dual-band BPF without cells, they increase the order of each passband by two and simultaneously generate transmission zeros (TZs) at both sides of the two transmission bands. The operating principles of the proposed dual-band BPF are detailed at the coupling–routing-diagram level and design guidelines for its transmission-line configuration are provided. Moreover, for experimental-validation purposes, a 1.57-GHz/2.38-GHz dual-band BPF microstrip prototype with symmetrical absolute bandwidths is manufactured and characterized.

A Millimeter-Wave Miniature Branch-Line Coupler in 22-nm CMOS Technology

A 60-GHz innovative quadrature branch-line coupler is proposed in this letter. The device was implemented in a 22-nm CMOS process, from global foundries. The proposed design merges two miniaturization techniques. On the one hand, slow-wave microstrip (SW-MS) lines based on bed of nails are demonstrated in CMOS technology for the first time. On the other hand, the two quarter-wavelength MS line sections required for the branch-line coupler implementation are realized using the SW-MS transmission line configurations with different form factors. As a result, the achieved miniaturization versus electrical performance is very good as compared to the state-of-the-art. Design insights addressing the coupler dimensions and losses are discussed. The experimental assessment shows an adequate frequency response with amplitude and phase imbalance of 0.8 dB and 1.8° at 60 GHz, respectively. The measured insertion loss is 2.35 dB at 60 GHz and the return loss is better than 15 dB at any port (from 54 to 66 GHz). The isolation is better than 15 dB (from 51 to 68 GHz). The overall size of the coupler is 0.3 mm $\times $ 0.22 mm, which is equivalent to $0.06 \cdot \lambda _{0} \times 0.044 \cdot {\lambda }_{0}$ , at 60 GHz.

Accuracy enhancement of the JMarti model by using real poles through vector fitting

The JMarti model is used worldwide for electromagnetic transient simulations of transmission lines. This paper proposes increasing the accuracy of the model by using only real poles through vector fitting. The JMarti model uses a rational approximation process that ends in models that include only real poles and zeros. By using vector fitting to synthesize the functions of the JMarti model, one can have complex and real poles. In this work, a process in which complex poles are replaced by real ones, based on the non-dominance of complex poles for smooth functions, is implemented. The improvement in the accuracy is demonstrated through the ATP-EMTP (alternative transient program) program by modeling two cases: a single-phase transmission line configuration and an asymmetrical overhead line configuration. Additionally, the solutions of the test cases with the numerical Laplace transform are taken as references. The results show that, through the proposed methodology, not only an increase in accuracy possible but also the proposed methodology also can be used to improve the computational efficiency of the JMarti model. The presented methodology can easily be applied to any application in which the frequency response data present a smooth behavior. Finally, the presented methodology can be easily applied in an iterative way.

Study on characteristics of slow‐front overvoltage of ±1100 kV UHVDC transmission lines

The ±1100 kV Zhundong–Wannan ultra high-voltage direct current (UHVDC) transmission project is under construction in China, which has the highest operating voltage in the world. The length of the UHVDC overhead transmission line is greater than 3000 km. The electromagnetic transient process caused by grounding faults might have significantly impact on the overvoltage level of DC transmission line, which is crucial for the external insulation configuration of the overhead transmission line. This paper presents a detailed electromagnetic transient simulation model for the UHVDC transmission system using an open-loop extinction angle control principle. The simulation results demonstrate that the single pole grounding fault into a bipolar system causes the most serious damage. The maximum overvoltage is 1.628 p.u. and the 2% statistic overvoltage is 1.635 p.u., while the reference value is 1122 kV. The influence of DC filters for line overvoltage is also analysed here. Furthermore, results show that adding a no gap line arrester at the midpoint of transmission line can suppress line overvoltage, while the maximum overvoltage reduces by 0.138 p.u. The results obtained provides a reference for the optimisation of the external insulation configuration.

Tower Air‐gaps discharge characteristics and insulation coordination for UHV AC double‐circuit line

In order to give out inverse V-type insulator tower air-gaps configuration of double-circuit UHV AC power transmission line, different distance air-gaps from high-voltage electrode to tower frame discharge tests of inverse V-string are carried out. Discharge characteristics curves of power frequency voltage, 1000 μs long wave-front switching impulse voltage, and lightning impulse of UHV AC double-circuit tower are obtained. Results show that the 50% discharge voltage gradient of bottom phase air-gaps is higher than middle phase. 1000 μs wave-front switching impulse 50% discharge voltage gradient of bottom phase air-gaps is 4.6% higher than the middle phase. Based on the test results and the characters of operating voltage and overvoltage of UHV AC power transmission system, the UHV AC double-circuit tower inverse V-type insulator air-gaps configuration is proposed. The air-gap configurations of power frequency voltage and switching overvoltage are 2.9 and 6.5 m, and the lightning protection air-gaps are 6.7 and 7.2 m, in mountains and plains.

Hyperwideband Microwave Crossover Using Bridged Suspended Substrate Line Configuration

A planar microwave crossover is presented. The structure uses a suspended substrate transmission line configuration to cross two independent RF channels. In the central crossed region, one channel is bridged by a conductor on the upper side of the substrate, while the second channel is bridged on the lower side. Two conductive stubs, realized as screws in the fabricated prototype, are placed on both sides of the crossed region to adjust the capacitance in this section and improve the impedance match of each channel. Measurements show that the overall bandwidth of the crossover with less than 0.5-dB insertion loss is from dc to 12 GHz (200% fractional bandwidth). Over this band, the measured return loss and isolation between the two channels are more than 15 and 17 dB, respectively.

Evaluation of Length, Dependent Earth Return Transmission-Line Parameters for Overhead Conductors in the Quasistatic Range

In this paper, a novel application of the matrix pencil method (MPM) is used to evaluate the length-dependent earth return parameters of overhead transmission lines in the quasistatic frequency range. The MPM is used to approximate the reflection coefficient by a series of complex exponentials, which allows the length-dependent transmission-line parameters to be evaluated in closed form. This methodology improves the accuracy of the length-dependent formulation when compared with the single image approximation used in previous publications, and can be applied to both parallel and angled overhead conductor configurations. Where large differences in results exist between the two methods, numerical integration confirms the accuracy of the MPM method. The proposed method can accurately evaluate the earth return parameters for conductors of arbitrary length and separations. This enables the proposed method to be applied to transmission-line configurations of all lengths, even in instances where the application of the per-unit method is not valid. This makes the length-dependent methodology ideal for generating transmission-line models from routing coordinates.

Fault Analysis and Traveling-Wave-Based Protection Scheme for Double-Circuit LCC-HVDC Transmission Lines With Shared Towers

Double-circuit transmission lines, with bipolar transmission lines of two different line-commutated-converter-based high-voltage direct-current (HVDC) systems constructed on the same towers, are a new technology emerging in China to increase the power transmission capacity. Double-circuit HVDC transmission lines sharing the same towers will lead to an electromagnetic coupling effect between the two circuits. According to the geometry configuration of same-tower double-circuit transmission lines in HVDC transmission projects, double-circuit transmission lines are unbalanced without transposition. Therefore, the coupling effects on the healthy circuit cannot be completely eliminated. These coupling components will affect the sensitivity of conventional traveling-wave-based protection criteria. This work first develops a fault analysis for double-circuit HVDC transmission lines with various internal fault conditions, and then, the linear combinations of four independent modal components based only on each single circuit are obtained and investigated. Finally, an integrated traveling-wave-based protection scheme for double-circuit HVDC transmission lines is presented. Numerous simulation results verify that the proposed protection scheme can operate correctly in double-circuit HVDC transmission lines even for a fault with high resistance up to the maximum of 300 Ω.

A 6–18-GHz GaAs Multifunction Chip With 8-bit True Time Delay and 7-bit Amplitude Control

This paper presents a monolithic microwave integrated circuit multifunction chip implemented using a 0.25- $\mu \text{m}$ gallium arsenide pseudomorphic high-electron-mobility transistor process for use in a phased array jammer transmitter. This chip, which operates in the frequency range of 6–18 GHz, provides several functions including 8-bit true time delay (TTD), 7-bit attenuation, wideband amplification, and digital serial-to-parallel conversion for 15-bit control. The TTD and attenuation coverage are 255 ps with a step of 1 ps and 31.75 dB with a step of 0.25 dB, respectively. The TTD employing an artificial transmission line configuration demonstrates a root-mean-square delay error of less than 1.7 ps in the operating frequency range. The chip has a compact size of $4\,\,\hbox {mm} \times 5$ mm and exhibits a typical gain of 12 dB and an output P1dB of 16.5 dBm over a frequency range of 6–18 GHz.

Low frequency electric field radiation level around high-voltage transmission lines and impact of increased voltage values on the corona onset voltage gradient

In this article the summary of measurement and calculation values of low frequency electric field radiation around the high-voltage transmission lines and impact of the increased voltage values on the AC corona onset voltage gradient are presented. The measurements of the low frequency electric field radiation level were performed under the 400 kV transmission lines of horizontal configuration with standard and compact dimensions. In all cases analyzed in this article, the measurements are performed in the middle of the span, because at this point the conductors are closest to the ground. The analysis in this article has been initiated by the increased voltage values of long duration that have been registered in nodes of the 400 kV network in Bosnia and Herzegovina and the neighbouring countries during the last years. The calculation of the low frequency electric field radiation of the different configuration of the high-voltage transmission lines will be useful for determining the non-ionization radiation exposure levels of the general public in the future as well as to determine their impact on the AC corona onset voltage gradient.

New Higher Order Method of Moments for Accurate Inductance Extraction in Transmission Lines of Complex Cross Sections

A new higher order (HO) method of moments is proposed for high accuracy extraction of the resistance and inductance matrices in the multiconductor transmission lines (MTLs) of complex cross sections. The computational framework is based on the numerical solution of a surface–volume–surface electric field integral equation of magnetostatics. In order to achieve an exponentially efficient reduction in the error of the solution, HO geometrical representation of the conductor cross sections is accompanied with the discretization of the unknown field quantities on the conductor boundaries and cross sections with 1-D and 2-D HO polynomial basis functions, respectively. The methodology allows for extraction of the network parameters in broad ranges of frequencies for which resistive and inductive contributions to the impedance matrix vary within a wide dynamic range. Comparison of numerically computed currents to the currents obtained analytically for canonical transmission line configurations is performed. Solutions of the extraction problem for MTLs with complex cross sections are compared against the finite-element method solutions to demonstrate the efficiency of the proposed methodology.

On the Generation Functions of DC Corona Performance

Definitions of generation functions of corona loss (CL), radio interference (RI), and audible noise (AN) traditionally used in the evaluation of ac corona performance were found to not be applicable to dc corona. Based on the results of CL calculations in cage and monopolar dc transmission-line configurations, proposals are made for a new definition of CL generation function that includes geometric parameters of the respective conductor configurations. Using published experimental data obtained for the same conductor bundle in two cages with different geometric parameters, it is shown that the same definition can be used for monopolar dc corona generated RI and AN. Calculations also show that the new definition applies to the case of CL from bipolar dc transmission-line configurations. Finally, the possibility and limitations of using cage tests for predicting the CL, RI, and AN performance of bipolar dc transmission lines are examined.

Effect of the Time-Varying Soil Resistivity on the Performance of the Protective Devices under the Electromagnetic Fields from Lightning

Background/Objectives: Transients in the overhead power lines due to lightning events can be caused by both direct and indirect strokes. Both direct and indirect events can cause severe issues in the power system. Methods/Statistical Analysis: The frequency of the indirect lightning return strokes is more when we consider the lightning studies on the overhead lines considering the height of the present distribution and transmission lines. Lightning-induced voltages on the overhead transmission lines have been computed using the finite-difference time-domain method. A source of lightning surge wave on power transmission lines is modelled as a double exponential wave using Modified Transmission Line with Exponential current decay (MTLE) model. Computation of overvoltage caused by lightning waves is calculated for single conductor lines with and without considering the soil reflections taking into account the dynamic characteristics of soil under lightning conditions. Findings: Computations are carried out for the various configurations of multi-conductor transmission lines. The effectiveness of the protective devices such as shield wires is also studied here. The surge arrester modelling is carried out and the design parameters for these protective devices are finalised after optimization. MATLAB and PSCAD software are used for simulation. Triangular configuration gave a better response to lightning than the horizontal and vertical configuration. Applications/Improvements: A 3D approach on the problem with use of COMSOL will give a better insight on the field pattern.

Description and stability analysis of nonlinear transmission line type metamaterials using nonlinear dynamics theory

Nonlinear metamaterials offer a potential technology to realize applications at microwave, terahertz, and optical frequencies. However, due to the strong and controlled nonlinearity, the wave interactions can be quite complex. In the current article, a framework based on nonlinear dynamics theory is developed to describe such complex interactions. This is demonstrated for the case of a harmonically pumped nonlinear left handed transmission line through the use of bifurcation theory, stability analysis, and linearization about the limit cycle to calculate the autonomously generated frequencies and their spatial distributions. Higher order parametric interactions, which can be mediated by the strong nonlinearity, are automatically included in the model. It is demonstrated that autonomous components can be visualized in both the phase and the set of solution spaces. The framework is general in terms of the transmission line configuration, the nature and strength of the nonlinearity, and the number of stages. It also provides accurate results when the autonomous frequencies are in the vicinity of the Bragg frequency.

Detection of secondary arc extinction for adaptive single phase auto‐reclosing based on local voltage behaviour

This study presents a non-communication based algorithm for detection of secondary arc extinction for adaptive single phase auto-reclosing of transmission lines. The algorithm is based on the behaviour pattern of the faulted phase voltage magnitude (VM) measured at the near end of the line. A prediction function is used to calculate the present VM few milliseconds in advance of its actual measurement. The difference between the actual and calculated values of the faulted phase VM is used as a criterion for detection of secondary arc extinction. A new method is proposed to analyse the arc extinction criterion which does not need a predefined threshold level. The algorithm uses low sampling frequency and is simple and fast. The algorithm can be applied on all transmission line configurations (transposed or untransposed) with different levels of reactive power compensation. The algorithm has been validated using the electromagnetic transient program software tool for simulation studies under many operational and fault cases. The presented test results for 465 cases verify the algorithm performance, which is not affected by the pre-fault line loading, the circuit breaker opening angle, arc type and fault location.

AC flashover performance of various types of insulators under fan-shaped non-uniform pollution

Previous simulation and observations showed that, the air flow field at windward and leeward side of insulator string will probably be different if the wind velocity is over a certain value, and thus causing the imparity of contamination degree at the two sides. In this paper, fan-shaped non-uniform polluting method was used to artificially simulate the different pollution severity at windward and leeward side of insulator string. Then, the effects of fan-shaped non-uniform pollution on ac flashover performance of 5 types of insulators were discussed. Test results indicate that, SDD, the ratio SDD of windward to leeward side (W/L), the occupation ratio of leeward side (k), will affect the ac flashover performance of insulator string. U 50 and SDD still can be expressed by the negative power function. A reduction in W/L from 1/1 to 1/15 would give a decrease about 23% in a value, which causes U 50 reducing about 25%, but n value changes little. The correction method proposed by EPRI is also applicable for fan-shaped non-uniform pollution, but has difference. A larger creepage distance of insulator does not mean that the creepage distance utilization rate is higher. Due to the influence of fan-shaped non-uniform pollution, the existing insulation configuration of transmission lines in heavily polluted areas may not satisfy the required insulation margin. The results have certain reference significance for the design and selection of transmission line external insulation.

Impact of HVDC line on the convergence property of AC/DC power flow calculation

This paper explores the impact of HVDC line on the convergence property of AC/DC power flow calculation. Firstly, the model of AC/DC power flow computation is constructed, including unified method and alternate iterative method. Then, an improved Levenberg–Marquardt (LM) method with line search technique is developed to solve the nonlinear equations of AC/DC power flow. To test the convergence property of the proposed method, LM method with trust region technique and Newton method are also employed. The researches on the impact of heavy DC transmission power and multiple HVDC lines on the convergence property of AC/DC power flow calculation are made on a modified IEEE 118-bus AC/DC hybrid test system. Simulation results show that the developed method under the model of alternate iterative method is superior to other methods under different models in convergence property. For the influence of heavy DC transmission power on the convergence property, it is improved by the new parameter configuration of DC transmission line firstly and adding proper new shunt capacitor on the weak nodes secondly; for the influence of multiple DC transmission lines on the convergence property, it can also be improved by the change of control mode firstly and adding new shunt capacitor secondly, which are based on the least square solution obtained by proposed method under the model of alternate iterative method.

Miniature Microwave Notch Filters and Comparators Based on Transmission Lines Loaded with Stepped Impedance Resonators (SIRs).

In this paper, different configurations of transmission lines loaded with stepped impedance resonators (SIRs) are reviewed. This includes microstrip lines loaded with pairs of SIRs, and coplanar waveguides (CPW) loaded with multi-section SIRs. Due to the high electric coupling between the line and the resonant elements, the structures are electrically small, i.e., dimensions are small as compared to the wavelength at the fundamental resonance. The circuit models describing these structures are discussed and validated, and the potential applications as notch filters and comparators are highlighted.