Part Of Transmission Line Research Articles

Effects of Segmented Shield Wires on Signal Attenuation of Power-Line Carrier Channels on Overhead Transmission Lines—Part I: Modeling Method

Shield wire segmentation has been used for quite some time as an effective method for reducing transmission-line power losses, with most segmented shield wire applications on extra high-voltage lines utilizing phase-to-phase power-line carrier (PLC) coupling. As transmission system efficiency becomes more of a priority, some utilities may consider applying segmented shield wires to lower voltage lines, such as 115-kV and 230-kV lines, which most often utilize single-phase-to-ground PLC coupling. Thus, knowledge of the effects of segmented shield wires on PLC signal attenuation for various coupling methods would be useful to relay engineers. The purpose of this paper is to present a generalized method to model transmission lines for signal attenuation calculation at PLC frequencies, with special consideration given to shield wire connections. Terminating impedance and phase wire transposition are considered as well. The modeling method presented is validated with field measurements. In a companion paper, signal attenuation results considering the effects of various parameters are analyzed.

Development of Lightning-Resistant Overhead Ground Wire for Large-size Transmission Lines

The overhead ground wire of AC 150mm2 is applied for the large-size transmission lines. According to inspections of transmission lines, melted component wires of AC 150mm2 have been found in some parts of 500kV transmission lines and it is obvious that the damages have been caused by lightning. Hence, the authors have developed lightning-resistant overhead ground wires as well as being evaluated lightning-resistant performance of the conventional AC 150mm2. In the paper, firstly, it is reported on the lightning performance of the conventional AC 150mm2 resulting from a DC arc test which is considered the polarity of currents and injected current waveforms for summer and winter lightning. As a result, the least amount of electric charges which can melt the components of the conventional wire was 180C. Then, the paper outlines the improvement of lightning performance of the overhead ground wire. Some kinds of developed ground wires as a trial piece have been proposed and tested, and here presented the characteristics of two typical developed wires among them. One is coated with conductive ceramic on the outer components and the another is enlarged a diameter of outer components. Both types of the wires show the excellent lightning performance from the DC arc test, comparing with the conventional ground wire of AC 150mm2.

Design of Dualband Class-F PAs for Cellular and WLAN Applications

In this paper, highly efficient class-F power amplifiers(PAs) with harmonic-controlling transmission lines(TLs) were built for cellular and WLAN applications at 840 MHz and 2.4 GHz each. Also, based on these single-band PAs, a dualband class-F PA was designed after a careful investigation into the harmonics of the two frequencies. The harmonic-controlling TL was designed for the class-F operation at dualband by switching the length of the shunt <TEX>$\lambda$</TEX>/4 TL part, while the series <TEX>$\lambda$</TEX>/4 TL is optimized for both frequencies. To verify the performance, two class-F PAs optimized at each frequency and a dualband class-F PA at the corresponding frequencies were built with the secondand the third-harmonic control circuits at each frequencies. As a result, the PA#1 at 840 MHz has a peak drain efficiency of 81.2 % with an output power of 24.4 dBm, while the PA#2 at 2.35 GHz shows a drain efficiency of 94.5 % with an output of 22.8 dBm. Finally, the dualband class-F PA#3 showed 60.5 % and 50.9 % drain efficiencies at 840 MHz and 2.4 GHz, with powers of 23.8 dBm and 19.62 dBm, respectively.

The Role Played by Current Phase Shift on Magnetic Field Established by AC Double-Circuit Overhead Transmission Lines—Part I: Static Analysis

AC double-circuit overhead transmission lines may exhibit large phase-shift angles between current phasor terns of the two circuits. Here, a static analysis (relevant to single time instants or constant load conditions) of the role played by such a phase shift on the magnetic field established by these lines is performed, showing that the phase-shift angle interacts with the phase conductor arrangement, resulting in a wide variety of field profiles at a given line section. The analysis, carried out for two tower topologies and several couples of rms current values, reveals interesting general features of field profiles that depend only on the phase-shift angle. This proves that neglecting, or even misunderstanding, current phase-shift effects for ac double-circuit overhead transmission lines can lead to severe errors in field calculation that may have negative consequences on human exposure estimates, both at the design stage of new lines and at the rearrangement stage of existing lines.

The Role Played by Current Phase Shift on Magnetic Field Established by Double-Circuit Overhead Transmission Lines—Part II: Dynamic Analysis

The Role Played by Current Phase Shift on Magnetic Field Established by Double-Circuit Overhead Transmission Lines—Part II: Dynamic Analysis

Discussion of New Track Circuit Signalling System of Shinkansen

Shinkansen signalling system uses track circuits to detect Shinkansen trains. The basic logic of train signalling is that one train should not be introduced to the section where another train exists. So that the train detection information is very important and treated as absolute information. Track circuit uses rail as a part of electrical transmission line, and detects train by the short circuit which is composed by train axle and the both side rails, so it is very stable and reliable. Furthermore track circuit is used to transmit speed signal information to the train cab via the induction coil on the train. Shinkansen is 25000V A. C. electrified line that there are many harmonic waves in the power supply circuit and obstruct the track circuit current. To avoid this obstruction, Shinkansen track circuit adopts synchronized SSB, Single Side Band, system. This system is very excellent system without a fatal accident during 33 years since Shinkansen had begun its operation in 1964. Nevertheless the electromagnetic environment has been changing with the introduction of the high power rolling stocks with the standstill system like PWM, Pulse Width Modulation, converter, inverter, and so on. As the result of it, non-synchronized noise has increased. Moreover there are several problems in the synchronized SSB system now, for example, information number shortage and so on. So that new type signalling systems are being proposed. To evaluate new system, electromagnetic noise endurance character is necessary. In this paper, precise analysis of the Shinkansen track circuit electromagnetic environment is discussed, and electromagnetic noise endurance character of new type systems are evaluated. Moreover the character research of each system is carried out.

Development of 500-kV XLPE cables and accessories for long distance underground transmission line-Part I: insulation design of cables

This paper discusses the results of a basic study for the development of 500 kV XLPE power cables. The authors have established that the factors that decide the performance of today's XLPE cables are impurities in the insulator and protrusions on the semiconductive layer, and that the insulation performance of XLPE power cables is determined by the size of these defects. In model tests of XLPE power cables, the minimum insulation breakdown stress of cables was determined, to set the design values for 500 kV XLPE cable. As a result, it was found that it is possible to design cables having an insulation thickness of 25 mm.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Design of log-periodic two-stacked circular loop antenna

By taking into consideration the high gain characteristics of a circular twin-loop antenna and by distributing this antenna in a log-periodic arrangement, an antenna with a wide bandwidth was proposed. Equivalent circuits for the loop part and its transmission line part were established to perform a numerical analysis. After examining its properties, data to design such an antenna were obtained. In particular, the reason why this antenna had a high gain and wide bandwidth through its current distribution was clarified. Based on the design data of this paper, an antenna was constructed and its performance was measured. As a result, its half-power bandwidth was about 80 deg for the E-plane and 45 deg for the H-plane with a sharp directivity. Over a wide bandwidth of about 360 MHz for the 3-dB bandwidth, VSWR was less than about 2.2 and the directivity gain was more than about 10 dB. From these data, the validity of the present design method was confirmed. Thus, at present, the proposed antenna is a wideband antenna with a structure that has the highest gain.

Development and Field-Data Evaluation of Single-Eng Fault Locator for Two-Thermal HVDV Transmission Lines Part I: Data Collection System and Field Data

A prototype data collection system was developed in order to acquire field data as a part of the development of HVDC fault location techniques. The system was installed at the Celilo Converter Station of the Pacific HVDC Intertie, owned by the U. S. Department of Energy-Bonneville Power Administration in May, 1983. It monitors two line voltages, one neutral voltage, and two line currents. It also has an event detection function to trigger saving data onto a diskette. In this paper (Part I) the data collection system hardware is described, and several field data are plotted and analyzed. Development of an HVDC fault location algorithm and its evaluation using field data are given in the second paper, Part II.

Development and Field-Data Evaluation of Single-End Fault Locator for Two-Terminal HVDC Transmission Lines Part 2: Algorithm and Evaluation

Development and Field-Data Evaluation of Single-End Fault Locator for Two-Terminal HVDC Transmission Lines Part 2: Algorithm and Evaluation

Probabilistic Design of Transmission Lines Part II: Design Criteria Corresponding to a Target Reliability

This is the second of a series of two papers dealing with transmission line design criteria corresponding to a target reliability. In this part various design criteria are derived on the basis of calculations made in part I.

Probabilistic Design of Transmission Lines Part I: Probability Calculations and Structural Reliability

This is the first of a series of two papers dealing with design criteria for transmission lines based on probabilistic concepts. This part covers calculations of the probability of failure of a line when both load and resistance are random variables. For the first time the influence of two important parameters have been studied: the use factor of towers and the effect of a load event that acts simultaneously on N towers.

Appendix-Summary of Reference (1) Ground Switch Interrupting Duty and Total Ground Current Imposed by Induction from Parallel Transmission Lines Part I-Theoretical Analysis

Appendix-Summary of Reference (1) Ground Switch Interrupting Duty and Total Ground Current Imposed by Induction from Parallel Transmission Lines Part I-Theoretical Analysis

Pressure Dynamics in Wells During Gas Kicks: Part 2 - Component Models and Results

Summary This is the second part of a theoretical study of the dynamic pressure and flow behavior of an onshore well containing a gas kick controlled by the driller's method. The main results from this study show that (1) casing pressure profiles under assumed constant bottomhole pressure can be very sensitive to both pump stroke variations and standpipe pressure pump stroke variations and standpipe pressure variations, (2) the pressure time delay from casing choke to standpipe is extremely variable, (3) pressure changes rapidly as the gas begins to exit the choke, and (4) the effects of a sudden adjustment at the choke can be magnified at bottomhole, with the largest magnification occurring after the gas begins to exit the choke. Introduction In this paper, the proposed well model described in Part 1 is developed employing the transmission line Part 1 is developed employing the transmission line solution techniques of Part 1. The final model is operated as a real-time, manually controlled simulator, whose outputs are compared with actual test well data.In Part 1, the development of the digital and analog solution techniques were based on the flow of a Newtonian fluid in a line of constant cross section and length. Thus, to use either of these techniques to represent the drillpipe and annular lines, it is necessary to account for the facts that the drilling mud is actually non-Newtonian and that the annular liquid lines are of time-varying lengths and annular cross section. In addition, to represent the two-phase fluid line, the fact that the fluid within this region is a gas/mud mixture with the gas rising at a velocity relative to the mud must be taken into account. Accordingly, the necessary modification to the basic solution techniques to model these effects and suitable models for the mud pump, casing choke, and drill bit are discussed. Drillpipe Transmission Line To account for the change in inner diameter between drillpipe and collars, it is necessary to model the drillpipe as two coupled fluid-line sections. However, in the specific test well installation that is modeled, there are no collar sections in the drillstring. Thus, it can be assumed that the drillstring is a single constant-length section of constant circular cross- sectional area.Within the range of drillpipe velocities encountered in practice, the most commonly used drilling muds frequently are modeled as non- Newtonian Bingham plastics. Accordingly, to use the solution techniques of Part 1 to predict pressure and flow propagation in the drillpipe, it is necessary to make suitable modifications to reflect the non- Newtonian nature of the drilling mud. It can be shown that the steady-state frictional pressure drop per unit length dp/dz for the flow of a Bingham per unit length dp/dz for the flow of a Bingham plastic in a smooth circular pipe is given by plastic in a smooth circular pipe is given by(1) where p = fluid density, D = pipe diameter, U = mean fluid velocity, andf = Fanning friction factor. Unlike the Newtonian case, however, the Fanning friction factor in Eq. 1 for a Bingham plastic is a function of the Bingham Reynolds number N ReB 1 and the Headstrom number NHe . JPT P. 1367

A New Thermal Rating Approach: The Real Thermal Rating System for Strategic Overhead Conductor Transmission Lines Part V Monthly and Annual Accumulative Frequency Distributions of Hourly Real-Time Thermal Rating and their Comparison with Conventional Rating-Risk Curves

A new method is introduced which tests the risk of any conventional ampacity rating derived from fixed value weather parameters. This method indicates that the risk of some commonly used ampacity ratings may be as high as fifteen percent, whereas in the past, normal probability methods applied to the wind velocity and ambient temperature data have shown the risk to be only .02 percent. This conflict is due to not recognizing the probability of wind direction and its associated magnitude. It is also shown that the real time capacity may reach 298 percent of the normal rating, while the minimum capacity is 72 percent of normal. Finally, it is found that the real time conductor temperature for fifty percent of the time is only 47 percent of the conductor temperature used to establish the normal rating, while the load is approximately 45 percent greater than the normal rating for fifty percent of the time.

A New Thermal Rating Approach: The Real Time Thermal Rating System for Strategic Overhead Conductor Transmission Lines Part IV Daily Comparisons of Real-Time and Conventional Thermal Rating and Establishment of Typical Annual Weather Models

For the first time, comparisons are given between the real- time thermal capacity and conventional ratings derived from fixed value weather parameters. If conventional normal ampacity ratings, established from these conservative weather parameters, are applied to system peak day weather conditions, it is shown that the conductor temperature, depending on transmission line azimuth, can be much greater than the allowable limit and line to ground clearances could be reduced. This is primarily due to the absence of wind direction being considered as a relevant parameter in the determination of the conventional rating.

A New Thermal Rating Approach: The Real Time Thermal Rating System for Strategic Overhead Conductor Transmission Lines Part III Steady State Thermal Rating Program Continued-Solar Radiation Considerations

For the first time, equations and computer programs are developed to show how the solar radiation received by an overhead transmission line is dependent on the conductor sag or slope. In the past, the overhead line has been assumed to lie in a horizontal plane with respect to the earth for the entire span length. Mathematical relationships for determining the sun's position in terms of solar azimuth and solar altitude, as a function of latitude, declination and hour angle are formulated and a polar plot is constructed to show the apparent path of the sun during the day for each month. Two different methods are presented to determine the angle of incidence between the sun's ray and the normal to any sloped cylindrical surface oriented at any azimuth angle. Plots are provided to indicate the variation in the angle of incidence and the direct component of solar radiation absorbed as a function of solar time for four general transmission line azimuths and five slopes at one latitude and declination. In addition, plots are drawn for the total solar radiation received by a conductor on a typical clear day as a function of both the span length and any sag or slope for both minimum and maximum diffuse radiation conditions for four general transmission line azimuths at one latitude and declination. It is shown that the conductor slope can have as much of an effect on the total radiation as does the solar adsorption constant.

Extension of Surface-Wave Transducer Models to Nonsynchronous Frequencies

Absfracf-A useful equivalent circuit model is developed for surface-wave transducers which relates directly to the physics of surface waves and does not rely on the equivalent bulk-wave behavior implied by other circuit models. The surface potential is selected as the cross-variable of the transmission-line part of the model, and the through-variable is defined by means of the characteristic admittance and the power flux. With this model, the response of an alternate phase array is extended to frequencies other than the synchronous frequencies. Furthermore, with the aid of reciprocity, the admittance matrix of an elementary transmissionline section is obtained along with the corresponding equivalent circuit. The versatility of this approach is demonstrated through application of the model to the excitation and detection of surface waves by a twenty-element array. for surfxce-wave transducers. Each of these models is in essencf' an adapt'ation of Rlason's [8, 91 equivalent circuit model for bulk-wa8ve transducers. In developing his model, Mason considered the one-dimensional particlc motion of calast8ic bulk waves. These waves were induced either by series-field excitation or crossed-field cxcitnton. The pnrtick motion associatcd with surf:m waves is not quite as simple hccausc surfacc waves cannot hr described properly by ont4irncnsional particle motion. With surface ~a),~es, particle motion occurs in two- or three-dimensional elliptical trajectories. In addit,ion, t,hcre are complicated clectromc~chanical interactions with thr snrface clectrodcs. Because of t'hc complexity of the equations of particle motion for surface waves [IO, 111, no equivalent circuit, models haw yet been dewloped c,omplctely from first principlcs. Adaptation of the llason modcl to surface waves is justified ~~~orc by analogy than actual analysis, although certa,in parts of the equivalent circuit, such as t8hc intcrclcctrodc~ capacitance, have a rigorow theoretical basis [la]. In dcvrloping an equivalent circuit, researchers are fac:ed wit'h t,wo major problems: off-synchronous behavior must, bo accounted for while at, thc same timc a simplc, yet useful, thrw-port model must be ohtaincd. H. Skeic [l31 approached the problem employing perturbat,ion tmhniqurs; off-syxchrollous results were cstimatcd. The normal mode theory of Auld and Kino [I41 supports SL bssfully developed useful equivalent-circuit models

Generalized Derivation of Fields, and Impedance Correction Factors of Lossy Transmission Lines Part II. Lossy Conductors Above Lossy Ground

A step by step solution of fields in the air and resistive soil for a single-conductor line is presented. Expression for the total line series impedance is derived. Fourier transform technique is applied to provide solution in a generalized integral form. Numerical method is suggested and a suitable computer programming is appended. The single-conductor line solution is extended to multiconductor system above earth with arbitrary dielectric constant and permeability. Various methods developed by other authors are reviewed.

Generalized Derivation of Fields, and Impedance Correction Factors of Lossy Transmission Lines Part I. Lossy conductors Above Lossless Ground

A step by step solution of fields in the air and resistive soil for a single-conductor line is presented. Expression for the total line series impedance is derived. Fourier transform technique is applied to provide solution in a generalized integral form. Numerical method is suggested and a suitable computer programming is appended. The single-conductor line solution is extended to multiconductor system above earth with arbitrary dielectric constant and permeability. Various methods developed by other authors are reviewed.