Half-wavelength Line Research Articles

Constant absolute bandwidth third-order tunable bandpass filter with reconfigurable bandwidth using single λ/2 resonator

This paper presents a third-order bandpass filter with bandwidth tuning and constant bandwidth center frequency tuning. Based on the analysis of modal voltage waveforms of a varactor-terminated half-wavelength microstrip line, a varactor is loaded at the center to control even modes, four varactors are loaded between two symmetric specific positions to tune, only, odd modes and two varactors at the ends to tune both the even and odd modes. Using these varactors, the passband is formed by bringing the first even and second, third odd modes close to each other. To keep the bandwidth of the passband constant, these three modes are controlled separately. The S-matrix has been derived to analyze and the coupling matrix has been synthesized to design the filter for a specification. An example filter has been designed and fabricated whose band can be tuned from 1.0 to 1.45 GHz (36.73) with absolute bandwidth of 260 MHz and bandwidth is tunable from 130 to 490 MHz.

Fault classification and phase selector algorithm for half-wavelength transmission lines

This study presents a new phase selector algorithm and fault type classification for very long transmission lines, known as the half-wavelength lines (HWL). For this work, the Clarke components variation rate method applied to current magnitudes was used. The method was implemented in a real-time digital simulation hardware-in-the-loop (HIL) test environment. We applied different fault types at each 5% line length, obtaining Clarke component current phasors. The proposed algorithm is stable for the native behavior of the half-wavelength line, including the resonance zones and their mitigation procedures. In addition, the algorithm is immune to the fault insertion angle, fault resistance, and line loading level. Finally, the algorithm could be applied in commercial microprocessor-based relays or could be used as a post-fault analysis tool.

Steady-state voltage-control method considering large-scale wind-power transmission using half-wavelength transmission lines

Half-wavelength transmission can transmit large-scale renewable energy over very long distances. This paper proposes an improved steady-state voltage-control method for half-wavelength transmission systems considering large- scale wind-power transmission. First, the unique voltage characteristics of half-wavelength lines are deduced based on the distributed parameter model. In the secondary voltage-control level, reactive power-transmission limits of half-wavelength lines are introduced as another control objective except for tracing the pilot bus voltage reference. Considering the uncertainty and fluctuation of wind power, the overvoltage risk-assessment method of half-wavelength lines is presented to determine specific voltage-control strategies. Simulation results demonstrate that the proposed voltage-control method delivers superior tracking performance according to a voltage reference value and prevents the overvoltage risk of half- wavelength lines effectively in different wind-power penetrations.

Fault impedance analysis and non-conventional distance protection settings for half-wavelength transmission line applications

This paper presents an analysis of fault phase impedance and its dynamic response for half-wavelength (HWL) transmission lines. One important issue of this technology is fault protection as distance protection elements are based on impedance for conventional AC lines. HWL line has very long length, preventing the direct application of classical impedance method because the capacitance effect produces different impedance behavior. This paper analyzes and characterizes the phase impedance response, and proposes alternative distance protection settings focusing on solving the problem of line-to-line fault detection. It is proven that the algorithm covers 84% of the line length. However, faults in the central region have a high resistance characteristic and cannot be detected with the proposed method. The paper takes into account the influence of line transpositions that further affects the protection performance near central region. Transient analysis and software in the loop tests were performed with PSCAD/EMTDC.

Application of a robust faulted phase selector to high-resistance and weak-infeed fault conditions on a 1000-kV UHV transmission line

This work proposes the use of a novel faulted phase-selection phasor-based algorithm to solve the high-resistance and weak-infeed fault condition selection problem in existent long compensated transmission lines. The algorithm was originally developed for future half-wavelength lines (3000 km for 50 Hz system or 2500 km for 60 Hz), and was slightly modified and tested in a real 645 km 1000 kV Ultra High Voltage transmission system. The algorithm was implemented in a programmable protective relay and tested using a real-time simulator. A series of tests under extreme conditions (such as high impedance fault and very week infeed system together) were conducted to evaluate the performance and robustness of the proposed algorithm.

Differential Filtering Phase Shifter With Wide Common-Mode Suppression Bandwidth and High Frequency Selectivity

A differential filtering phase shifter is proposed utilizing two three-end folded coupled lines with three half-wavelength microstrip lines. Four differential-mode (DM) transmission zeros (TZs) can be obtained on both sides of the DM passband because of the cascaded two three-end folded coupled lines and one half-wavelength line. Thus, the frequency selectivity and out-of-band suppression can be enhanced. Wide CM suppression bandwidth can be obtained by the multiple common-mode (CM) TZs and the upper and lower half-wavelength lines. The phase shift bandwidth can cover the passband and the passband performance for different phase shifts can keep constant by controlling the parameters because all lines contribute to the control of phase shift deviation and 3-dB bandwidth. Compared with the reported differential filtering phase shifter, the proposed phase shifter obtains higher frequency selectivity and wider CM suppression. Complete theoretic odd- and even-mode analysis and design procedure are carried out. Two prototypes centered at 3.3 GHz are designed, which exhibit fractional bandwidth (FBW) for 45° ± 2.29° (90° ± 4°) of 42.7% (42.4%), the 3-dB FBW of 39.4% (39.4%) and the CM suppression FBW of 141% (145%).

Local-Measurement-Based High-Speed Protection for Half-Wavelength UHV Lines

The half-wavelength ultra-high-voltage transmission system is an alternative technique for bulk-power transmission over very long distances. However, the operations and fault-characteristics of such systems are extremely different from conventional ones. Therefore, there is an urgent need to propose a protection scheme that adapts to the characteristics of the half-wavelength line. Towards this end, a local-measurement-based approach is proposed. According to the frequency-dependent model of the half-wavelength line, this paper uses the wavelet transform to decompose the arrival of the aerial-modal surge into several frequency bands. To acquire better accuracy, a weighted average approach is employed to modify the surge arrival time in each frequency band. According to the surge arrival interval between the predefined low-frequency and high-frequency bands, all types of fault, except single-line-to-ground faults when the fault inception angle is at zero-crossings, can be identified in a very short time-window. Simulation results indicate that the proposed protection scheme has satisfactory performance against internal faults and is quite secure under external fault conditions. Using local measurement only, the reach of the proposed protection scheme is no less than 80% of the entire length of the line, and the resistive coverage is also sufficiently high for UHV transmission systems.

Multilayered additive-manufactured half-wavelength coupled line filters

This work presents the design, fabrication and measurements of third-order multilayered filters by additive manufacturing technology. The filters are fabricated using conventional half-wavelength line resonators and a low-cost 3d polylactic acid polymer additive manufacturing process, which allows rapid prototyping and fabrication of complex topologies. The designs, performed at a centre frequency of 2.0 GHz, aim to provide fast manufacturing and get enhanced performances when compared to conventional coupled line third order filters using microstrip technology on commercial substrates. The simulated and measured responses of the fabricated prototypes are in all cases in good agreement.

Applications of the Open-Stopband Suppression in Various Periodic Leaky-Wave Antennas With Tapered Half-Wavelength Line

This paper presents applications for the suppression of the open stopband (OSB) in various periodic leaky-wave antennas (P-LWAs) using a tapered half-wavelength line. With the adoption of a slightly tapered half-wavelength line for each unit cell, the OSB can be completely suppressed. The technique is very convenient for engineering application, without the calculation of the characteristic impedance of the line. It can be applied to various structures, including planar and nonplanar structures. The design rule is generalized. Three examples are illuminated to demonstrate the applications. The first example is a series-fed microstrip patch antenna. The second one is a coaxial cable leaky-wave antenna. The third demonstrated antenna is a new substrate integrated waveguide (SIW) P-LWA with trapezium slots. The SIW antenna owns the advantages of wide-angle scanning and high efficiency. A prototype of the SIW antenna is fabricated and measured, to validate the effectiveness of the technique.

Transient Analysis and Mitigation of Resonant Faults on Half-Wavelength Transmission Lines

This paper presents an analysis of resonant faults and their transient responses on half-wavelength lines. This type of transmission line has been studied for many years in countries that need alternatives for bulk power transmission over very long distances. An important issue for this technology is the occurrence of critical faults, which produce peculiar behavior in the main electrical entities and can jeopardize line insulation and compromise system stability. Here, the main factors influencing the severity of faults are analyzed: the type of fault and fault location. This paper shows that faults involving positive and negative sequences are the most critical when applied at specific regions and produce high voltage and power with a high rate of rise. The necessity for a mitigation method that removes this severe resonant fault condition until the operation of a protection system is discussed, and such a method is established. A method using two spark gaps with a new and improved location criterion is proposed, tested and evaluated, providing promising results for controlling voltage and power at terminal substations. Digital simulations are performed with PSCAD/EMTDC.

An improved secondary voltage control method for half-wavelength transmission system

The half-wavelength transmission has the potential application to transmit bulk power through very long distances. In this paper, an improved secondary voltage control method is proposed for half-wavelength transmission system without dependency on remote control signal communication. At first, quantitative relationships between terminal voltages of half-wavelength line and transmission power are deduced based on the distributed parameter model. Then, three main improvements are proposed in secondary voltage control level. Reactive power transmission restriction of half-wavelength line is introduced as another control objective except for pilot bus voltage regulation. Variable pilot bus voltage reference setting method is given according to the voltage/active power correlation considering load fluctuation. Specific voltage control activation conditions are deployed to avoid control direction error or voltage oscillations. After that, simulation results demonstrate that the proposed voltage control method can trace variable voltage reference accurately and flat voltage profiles along half-wavelength line effectively in different disturbance conditions.

Relevant factors for temporary overvoltages due to fault-resonance conditions on half-wavelength transmission lines

This article explains the phenomenon of severe temporary overvoltage (TOV) due to critical faults on a very long transmission line with half-wavelength properties. Such non-conventional AC lines are an alternative to bulk power transmission over very long distances and present excellent steady-state properties. However, half-wavelength lines can present fault cases with very different natures of the voltage response due to fault-resonance conditions. The present document introduces a further explanation of these fault-resonance conditions. First, this study analyses the resonance at the fundamental frequency and analytically determines the TOV considering the fault location, the type of fault, and a simple model of system components. Coherence of major phenomena is obtained with time-domain simulation. Then, a more detailed method for analysing overvoltages on half-wavelength lines under fault conditions is presented. Here, a sensitivity analysis is implemented using PSCAD/EMTDC with more accurate models of system components. Factors such as the type of fault, sequence circuit, fault location, short-circuit level, fault resistance, loading level, transformer saturation and ground resistivity are considered. Finally, the paper interprets the impact of those factors on fault-resonance conditions and TOV.

A four‐way broadband filtering power divider with improved matching network for X‐band application

AbstractThis study presents a novel design methodology of one‐to‐four filtering power divider (FPD) with a broadband response. It comprises three one‐to‐two power dividers (PDs) and a broadband bandpass filtering circuit in series. The impedance transformer of the one‐to‐two PD is designed into a dual‐T‐type symmetrical structure for improving the matching network and broadening the bandwidth, which includes a tapered transmission line, two cascaded microstrip lines with the same characteristic impedance, as well as a stepped‐impedance open stub. The bandpass filtering circuit is formed by three coupled quarter‐wavelength microstrip lines in parallel, where the intermediate subresonator is grounded via a hole instead of half wavelength line for pursuing a wider bandpass characteristic. The proposed FPD is fabricated and measured. The good performance is achieved with the return loss of >13.8 dB for input/output ports as well as minimum insertion loss of <0.21 dB (over the −6 dB splitting ratio) from 7.3 to 13 GHz.

A low phase noise oscillator based on substrate integrated coaxial line technology

In this article, a miniaturized resonator based on substrate integrated coaxial line technology (SICL) is presented. The SICL resonator consists of a hairpin half-wavelength open-ended coaxial line element and two symmetrical parallel coaxial feed lines. The gap between the feed lines and the hairpin element can be adjusted properly to obtain a steep phase change, which can result in a higher group delay peak and achieve a superior phase noise performance. Based on the proposed SICL resonator, an X-band oscillator has been designed and demonstrated by using low-cost printed circuit boards (PCBs). Great consistency between the measured and simulated results is verified. According to the measured results, the oscillation frequency of the SICL oscillator is 10.0625 GHz with −1.81 dBm RF output power, and the phase noise is −138.6 dBc/Hz@1 MHz. The statistic figure of merit (FOM) is −206.1 dBc/Hz@1 MHz.

A Transformer-Based 3-dB Differential Coupler

This paper presents a transformer-based 3-dB differential coupler, which features the suppression of both common-mode and cross-mode signals. Transformer is utilized rather than the quarter-/half-wavelength lines, and the circuit size can be significantly reduced. The bandwidth of the proposed differential coupler can be enhanced by increasing the coupling coefficient of the transformer. For the proof of concept, the proposed transformer-based 3-dB differential coupler is implemented on the substrate integrated suspended line (SISL) platform. Well agreed simulated and measured results verified the feasibility of the proposed differential coupler. From 0.4 to 0.6 GHz, the measured common-mode suppression is better than 10 dB with a maximum 30 dB, and the measured cross-mode suppression is better than 30 dB. Compared with the previous designs, the self-packaged SISL differential coupler has a much smaller size of $0.08 \lambda _{0} \times 0.08\lambda _{0}$ . The proposed design methodology has advantages of compact size, suppression of both common-mode and cross-mode signals, and controllable bandwidth.

Overvoltage Study on UHV AC Half Wave Length Transmission System

In China some resource bases in the west are located at a distance of about 2800~3000km from the load centers in the east. AC Half Wave Length transmission in UHV stage is an alternate for the long distance and large capacity power transmission. A study model of half wave length line transmission system was established. The power frequency overvoltage, switching overvoltage and grounding fault overvoltage were studied using EMTP. The study result shows that the highest overvoltage occurs during grounding faults. The amplitude and waveform of overvoltage during grounding fault are affected by fault type, fault location as well as the characteristic of the protection system. The use of metal oxide arresters to limit overvoltage is discussed. The parameters and configuration of metal oxide arresters is suggested.

Faulted Phase Selection for Half-Wavelength Power Transmission Lines

In this paper, a novel faulted phase selection algorithm is proposed to be used for distance protection applied to half-wavelength power transmission lines. These lines represent an alternating current solution for very-long point-to-point interconnections as an alternative to HVDC. However, no such lines are currently in operation, and if this type of line is to be constructed, it will require its own protection philosophy because of its peculiar characteristics. This paper shows that the fault selection algorithms used in conventional relays do not work properly when applied to half-wavelength lines. The algorithm proposed herein is initially studied in the steady state and ultimately implemented in a programmable protective relay that is tested using a real-time simulator.

Single‐phase auto‐reclosing mitigation procedure for half‐wavelength transmission line

In this study, the main results of a new mitigation method to single-phase auto-reclosing switching in half-wavelength transmission lines are presented. Initially, the behaviour of single-phase reclosing on conventional lines was evaluated, then, the results obtained for half-wavelength lines are presented. Finally, the proposed solution for the manoeuvre to be successfully executed is described. The study proposes a very advantageous solution for the application of the single-phase switching in half-wavelength lines.

Compact Differential Wideband Bandpass Filters Based on Half-Wavelength Lines

A compact differential wideband bandpass filter is proposed based on three half-wavelength transmission lines. The main advantages of small size and simple configuration are achieved. The improved design with two cascaded quarter-wavelength coupled lines can further improve the bandwidth of common-mode (CM) suppression and frequency selectivity. Two prototypes centered at 1.8 GHz with the size of $0.07\lambda _{g}^{2}(\lambda _{g}$ is the guided wavelength at the center frequency $f_{0}$ ) and $0.056\lambda _{g}^{2}$ are designed, fabricated, and measured. The measured results of Design I (Design II) exhibit the minimum insertion loss of 0.27 dB (0.6 dB), 3-dB fractional bandwidth of 57.8% (52%), and the bandwidth of 20-dB CM suppression of $0.67 f_{0}~(4.1 f_{0})$ .

Adaptive Simulation of Fault Trip Criterion in Stability Control Device for Half-Wavelength Line

Half-wavelength AC transmission (HWACT) is an ultra-long distance AC transmission technology, whose electrical distance is close to half-wavelength at the system power frequency. Due to the excellent transmission capacity, stability control device must be installed in HWACT system. But the characteristics of the voltage and current of half -wavelength transmission line under fault condition are different from the characteristics of the ordinary short line. Its distributed-parameter characteristics are notable. So it is necessary to study the adaptability of the fault trip criterion for traditional lines to the HWACT lines. Simulation of the transmission line under fault condition was conducted in this paper based on the Bergeron model and adaptive analysis of fault trip criterion in stability control device for half-wavelength line was given. The results show that the fault trip criterion for traditional lines can’t be well applied to half-wavelength line. New fault trip criterion needs to be proposed to keep the safe operation of half-wavelength transmission line.