Single Transmission Line Research Articles

Admittance Correction Effects of a Single Overhead Line

The admittance correction terms for ground effects of a single conductor overhead transmission line are computed and discussed. Propagation constants are evaluated and compared with those by other methods. They show how accurate the analyses with the admittance correction are. Step responses and attenuation constants of a single conductor are also shown in order to observe the behavior of the admittance correction term. According to the results, admittance correction should be taken into consideration in analyses of surges, power line carrier, and other characteristics of transmission lines over very lossy ground

An algorithm for digital impedance calculation using a single pi section transmission line model [Discussion with author reply

The full paper by W.J. Smolinski appears in IEEE Transactions on Power Apparatus and Systems, Vol. 98, No.5, Sept./Oct. 1979, pp. 1546-1551. The discussion and closure were inadvertently omitted and are given herein.

Development of z-transform electromagnetic transient analysis methods for multinode power networks

The paper continues and extends the recent development of z-transform electromagnetic transient analysis in power systems as reported in a companion paper. Whereas the original development was based on the configuration of a single transmission line and a simplified equivalent-source model, the present paper extends this to the more general case of multinode-power-transmission networks. In those terms, the formulation developed in the present paper provides for distributed-parameter transmission-line models with series-path nonlinear frequency dependence, together with lumped-parameter circuit elements of linear and nonlinear forms, in any arbitrary combination and interconnection. This general electromagnetic transient analysis formulation is complemented by means of representing any circuit-breaker switching sequence and any short-circuit fault constraint. An assessment of the inherent accuracy and stability of the multinode z-transform solution scheme derived is made from comparisons with solutions from formal frequency-domain analysis.

Dynamic Stability Improvvement at Monticello Station-Analytical Study and Field Tests

Turbine-generator Units #1 and #2 at the Texas Utilities Monticello Station were found to be dynamically unstable when operating near full load and connected to the power system by a single transmission line. Power system stabilizers (PSS) were applied to the excitation systems to provide stable operation under these conditions. Suitable settings for the PSS were predetermined analytically by frequency response and root locus analysis of a single machine-infinite bus configuration. A 3rd order generator model is shown to be adequate for this type of analysis. Dynamic performance measured in field tests is in close agreement with calculated performance.

An Efficient State Variable Transmission Line Model

Lumped models of distributed systems (power transmission lines) are considered. It is shown that models derived by a finite Fourier cosine transform are quite efficient, when compared to conventional pi and tee section models, in that the number of state variables is minimized. This paper is an introduction to the use of distributed system "modes of response" in developing these lumped models for single and multiconductor transmission lines including ground conduction and skin effect.

Computer-aided analysis of pulse signal propagation in digital systems

Pulse distortion and cross-talk arising at the propagation of pulse signals in digital systems are investigated by making use of simples models of a single transmission line and of a coupled pair. The transient analysis of simple interconnected line can be achieved by means of the computer programme TASIL, not only for cascades of transmission linos but also for more general structures in the form of a directed tree. The same programme with only a small modification (TACIL) can be used even when coupling is permitted between pairs of transmission lines. A multiple coupling can be considered by introducing the effective coupling coefficients. Two illustrative examples are given to show the potential applications of both programmes.

Velocity effect of a lightning charge wave moving along a single wire transmission line

A wave equation solution for a moving charge on a simple one-wire, lossless transmission line is presented using Laplace transforms. The effect of lightning charge velocity on line potential as the charge moves along the transmission line is shown mathematically to be discontinuous should the wave velocity become the speed of light.

Analog Data Processing Circuits for Thomson Scattering Diagnostic Systems

Simple analog data processing circuits are described which transmit serially over a single transmission line the integrated outputs of a multichannel Thomson scattering diagnostic system. The small, battery powered circuits may be mounted in the photomultiplier tube housing for maximum noise rejection.

Voltage pulse compression by transmission lines

The compression of voltage pulses by a cascade of transmission lines is investigated, and a simple derivation is given for the case in which the characteristic impedances of the individual lines are independent of the compression factor. The possibility of using a single nonuniform transmission line (NUTL) for voltage compression is examined, and it is shown that a distortionless compression is not attainable by a practical NUTL. Lumped parameter approximations of the NUTL are suggested.

Laplace analysis and computer simulation of transient current in power transmission lines

A systematic Laplace method is presented for the determination of transient-current propagation in a single transmission line. Earth distortion and skin effects are considered in the analysis. The method permits a quick and accurate evaluation of these currents without using numerical-integration techniques. From the theoretical study, an efficient method of digital simulation is also derived for a simpler current evaluation in computers. Both analytical and simulation expressions are in terms of line and earth parameters, which enables an easy computation of transient current propagation in different transmission lines to be carried out. Results are in good agreement with those obtained by other investigations. Part 1 of the paper deals with a basic single line which would represent either an a.c. or a d.c. scheme. Part 2 of the paper deals with polyphase systems with lossy earth returns (see p. 137).

Transmission Line Transformation Between Arbitrary Impedances Using the Smith Chart (Letters)

A graphical method for transforming between two complex impedances using a single transmission line matching section is described. The Smith chart is used in a mode where the chart normalizing impedance is arbitrary.

Subscriber Line Equipment for an Elastic Carrier Switching System

This is the third of three papers [l], [2] dealing with an elastic carrier-concentrator system. The functioning of the subscriber line equipment is described herein. The system serves 256 telephone subscriber lines by digital concentration switching and transmission of multiplexed message channels over a single T1 transmission line. The concentration switching function is nonblocking. Message channels are the individual communication links between terminals and are created on demand at the request of active subscriber lines. They are not merely inactive without service requests; they do not exist unless service is requested. The created message channels serve for their normal communication function and, in addition, carry for each line the ancillary functions of dialing, ringing, and pay-station coin disposal. Message channels are coded by delta modulation, which permits flexible digital concentration and provides a smooth tradeoff of channel quality versus the instantaneous traffic load. Each of two complementary subscriber line interface units, one per line at each end, provides the delta-modulation encoding and decoding functions for the analog voice-band signal input and output and, by overriding the delta codec, provides the desired signaling functions of dialing, ringing, etc. The line interface units provide the major equipment interface between the subscriber line and the digital T1 line. An integral test facility permits remote loop-back of any selected subscriber line unit via a test channel to the office terminals and at the same time connects the subscriber loop to an auxiliary programmed test facility which may transmit pertinent loop-test results to the office terminal.

Experimental Oxidant Production Rates for EHV Transmission Lines and Theoretical Estimates of Ozone Concentrations Near Operating Lines

This paper presents wind-tunnel measurements of ozone and NOx production rates for single and bundle transmission line conductors in dry and wet corona. Ozone production rates reported in the literature for transmission line and fine wire corona, together with the authors' results are summarized as a function of the maximum surface gradient factor. Numerical calculations estimating the ozone levels near actual 775-kV test transmission lines at the Apple Grove 750-kV Project are presented. It is concluded that pollutant concentrations generated by conductor corona on present EHV transmission lines are too low to be deleterious to the environment.

Exact Solutions to Some Deterministic and Random Transmission Line Problems

A special class of transmission lines is considered, in which the modes decompose into two noninteracting sets. Both a single transmission line with constant characteristic impedance and variable propagation factor, and two transmission lines with equal propagation factors and variable coupling, in which the forward modes do not interact with the backward modes, are investigated. Exact expressions are obtained for the reflection and transmission coefficients when a section of such a transmission system connects two semi-infinite transmission systems consisting of constant impedance and admittance lines. These results hold for arbitrarily varying propagation factors and coupling; and while they are of independent interest in the case of deterministic variations, we make an application of them here in the case of stochastic variations. Exact results are obtained for the ensemble averages of the transmission coefficient and transmitted power, and their variances, for the inserted section of single line, when the variable propagation factor is a random function involving either a Gaussian process or the random telegraph process. Asymptotic results are also obtained in the general case of weak fluctuations and long inserted sections. Analogous results may be obtained for the inserted section of two lines when they are randomly coupled, and the results are given in the case of matched lines, for which no reflections occur. Finally, some of the time domain statistics for lossless lines are considered, and expressions are derived for the ensemble averages of the transmitted pulse, due to pulses incident on the inserted section.

Data telemetry with adaptive sampling

In telemetry systems of greatly differing bandwidths, the sampling of several channels of information can be made more efficient if, instead of sequential sampling, the individual sampling rate of each channel is made a function of its information content. Several procedures for comparing such data are considered in this article, and a design for a multichannel telemetry system is proposed in which a single transmission line is used

Corona Loss Characteristics of Single Conductor and Bundle Conductor Transmission Lines

Corona Loss Characteristics of Single Conductor and Bundle Conductor Transmission Lines

Coupled Nonuniform Transmission Line and Its Applications

Theory and applications of coupled nonuniform transmission lines are described. Matrix representations of a general coupled nonuniform transmission line are presented, by means of which the behavior of any coupled nonuniform transmission line maybe completely described. Among a wide variety of applications of coupled nonuniform transmission lines, two typical networks, one the coupled nonuniform transmission-line folded all-pass network and the other the coupled nonuniform transmission-line directional coupler, are treated in detail. Equivalent circuit representatious of these two networks are presented, which enable the designer to synthesize them in a greatly simplified manner by making use of the theories now available for more conventional single nonuniform transmission lines. In addition, the properties of these two networks using coupled exponential line are investigated. Design procedure is also given for asymmetrical coupled exponential-line directional couplers having excellent characteristics.

Time-domain analysis of multiple parallel transmission lines by means of equivalent circuits

Thévénin's equivalent circuit for a single transmission line is well known. The letter presents an application of Thévénin's equivalent circuit for multiple parallel transmission lines to the time-domain analysis of wave propagation over such lines. For purposes of illustration, a system of two coupled transmission lines is treated.

Cross Coupling in High Speed Digital Systems

It is now well understood that the design of the signal distribution systems of high speed digital machines is as important as the design of the circuits themselves. The integrated circuit technology of today is pressing back the frontiers of speed and simultaneously providing more circuitry per unit area. A signal distribution system with suitable electrical characteristics for these high speed circuits and which is physically compatible with the circuit size is sorely needed. A candidate for such an application is the multilayer board. This paper considers the problem of cross coupling from line to line in multilayer when the excitation function is a fast rise time voltage pulse. Curves and equations are given which enable the design of a system with a given system characteristic impedance and a specified cross-coupling ratio. Experimentally obtained wave shapes from single ground plane transmission lines are given, and a practical numerical example is worked.

Influence of governors on power-system transient stability

The paper describes an investigation into the contribution that a conventional velocity governor controlling the input power to a synchronous generator makes to the transient stability of a typical power-system configuration. It seeks to ascertain the corresponding transient-stability effect using an alternative operating signal, derived from rotor acceleration, for the control of input power. A governor actuated from a compound of velocity and acceleration signals is described, and its effect on transient stability is compared. The effects on this stability of varying some of the parameters of the system, the machine and the governor are described. The paper concludes with a brief study of the effect of various governors on the transient stability of a synchronous generator connected to a large system by a single faulted transmission line that is fitted with autoreclosing circuit breakers.