Transmission Line Phase Research Articles

An Improved Design for Ka-Band Phase Shifter Using Distributed MEMS Transmission Line Structure

The paper presents a model which describes the stage circuit of Distributed MEMS Transmission Line (DMTL) phase shifter at Ka band and an approach for DMTL design utilizing the saw-shaped coplanar waveguide(CPW). The result of circuit simulation and full wave analysis prove that the model is in good agreement with theoretical analysis. The model can effectively simplify the design complexity after optimization. Simulation results show that the S11 and S21 can achieve -20 dB and -2.5 dB, respectively, and the phase shift arrives at −180 ◦ at Ka band. Comparing with literature data, it has been predicted that S11 improves about 8 dB and the phase shift can increase about 100 ◦ in the same condition.

Current Status of Petri Nets Theory in Power Systems

For the last two decades increasing attention has been given to Petri net's applications for the representation and analysis of large, complex, distributed, stochastic and discrete-event systems like flexible manufacturing, industrial control systems, communication protocol, distributed-software systems, distributed-database system, multiprocessor memory systems, data flow computing systems, fault-tolerant systems, and computer industries. Since power system is a large geographically wide distributed system, in the recent past, application of Petri net's theory in power systems have also been reported. This article presents literature survey of recent papers published in the area of power systems using Petri nets. Basics of Petri net's theory and its different forms applicable to power systems are also discussed. A method of detecting type of faults on three phase transmission line by using Petri net theory is discussed in details. Different examples based on Petri nets shows that such methodology is more efficient than the traditional approaches especially when the complexity of the problem increases.

Phase Position and Phase Relocation for the Feasibility of Electromagnetic Field Mitigation

Numerical optimization using recurrent Finite Difference Method (FDM) simulation is a promising direction in selecting power transmission line safe design. This article investigates the feasibility of electromagnetic field reduction by optimization of phase relationship in three-phase systems. Various transmission line phase positions are presented, which feature minimum electromagnetic effect on surface level. Different transmission line structure designs have been investigated in order to select the maximum phaser cancellation in three-phase systems. A deeper insight to the effects of changing the phase relocation has been presented, giving more understanding to the electromagnetic field reduction within the existing right-of-way. The primary objective of this ongoing project is to create rigorous methodology and software capable of solving electromagnetic field in three-phase systems, as well as solving various optimization problems in the field of electromagnetic field reduction for analysis and design of different phase locations. Examples of existing power lines and projects show practical applications.

Varactor-loaded transmission-line phase shifter at C -band using lumped elements

The design of varactor-loaded transmission-line phase shifters using lumped elements is discussed in this paper. A monolithic-microwave integrated-circuit (MMIC) phase shifter is fabricated to verify the proposed topology. Only one control voltage is required for phase control. Within a continuously adjustable phase-control range of 360/spl deg/ and a frequency range from 5 to 6 GHz, a low transmission loss of 4 dB/spl plusmn/1.7 dB is measured. The phase shifter is realized with a commercial 0.6-/spl mu/m GaAs MESFET process and requires a chip area of only 0.8 mm/sup 2/. To the knowledge of the authors, the best results reported to date are reached for a continuously adjustable passive phase shifter with comparable circuit size. The presented circuit is well suited to wireless adaptive antenna transceivers, operating in accordance with the 802.11a, high-performance radio local-area-network and high-speed wireless-access-network type-a standard.

Teaching transmission lines: a project of measurement and simulation

A junior-year project for a course in electromagnetic waves is described, including the theory, hardware, and basic measurements. The essence of the project is to simulate transmission-line properties based upon theory developed in the classroom and to measure those properties in the laboratory for comparison. The equipment chosen is readily available and inexpensive, but is used here to illustrate concepts usually requiring an expensive vector network analyzer. The transmission-line properties of insertion loss, input impedance, and crosstalk are measured as a function of frequency on Category 5 cable. The transmission-line phase shift, propagation velocity, attenuation, characteristic impedance, impedance under various transmission-line configurations, and crosstalk are modeled and measured. Measured and theoretical results are in good agreement, reinforcing the strength of the underlying theory for the student. Evaluation of the project over a three-year period with more than 120 students is very positive in terms of developing confidence in and understanding of this abstract material.

Impact of six phase transmission line faults on turbine-generator shaft torsional torques

This paper explores the impact of six-phase transmission line faults and their subsequent fault clearing and reclosing on the torsional torques induced in turbine-generator shafts. In this context, investigations have been conducted on a large turbine-generator unit connected to a sample power system. The paper presents also a comparison between the torsional stresses induced in the turbine-generator shafts during these events with their corresponding disturbances of a three-phase transmission system. The results of these investigations are presented in the form of typical time responses as well as parametric studies. The EMTP is used for the simulation studies. The studies conclude that six-phase transmission line faults generally induce torsional torques in the turbine-generator shaft whose magnitudes are relatively higher than those induced due to transmission line faults in a three-phase system. This conclusion is true for both sustained faults and faults followed by clearing and high-speed reclosing operations.

Design method for antenna arrays employing ferrite printed transmission line phase shifters

Ferromagnetic substrates are attractive for microstrip antenna array applications. An alternative method for using ferrites for beam steering with microstrip arrays is demonstrated. In addition, a method is presented to determine the optimum applied bias field values for maximising the array's beam steering angular span. The method relies on a knowledge of the propagation constant (/spl beta//sub eff/) behaviour within the ferrite substrate, and the finite element-boundary integral (FE-BI) method is employed for extracting /spl beta//sub eff/. Experimental and numerical data are included for validating the evaluation of /spl beta//sub eff/. To account for finite magnet dimensions, a static analysis is conducted to account for field spatial variations associated with the bias field. These spatial variations must be taken into account to properly model the ferrite propagation constant behaviour. Results are shown for this alternative array configuration, which achieves scan angles as large as 18/spl deg/.

Optimization of distributed MEMS transmission-line phase shifters-U-band and W-band designs

The design and optimization of distributed micromechanical system (MEMS) transmission-line phase shifters at both U- and W-band is presented in this paper. The phase shifters are fabricated on 500 /spl mu/m quartz with a center conductor thickness of 8000 /spl Aring/ of gold. The U-band design results in 70/spl deg//dB at 40 GHz and 90/spl deg//dB at 60 GHz with a 17% change in the MEMS bridge capacitance. The W-band design results in 70/spl deg//dB from 75 to 110 GHz with a 15% change in the MEMS bridge capacitance. The W-band phase-shifter performance is limited by the series resistance of the MEMS bridge, which is estimated to be 0.15 /spl Omega/. Calculations demonstrate that the performance of the distributed MEMS phase shifter can be greatly increased if the change in the MEMS bridge capacitance can be increased to 30% or 50%. To our knowledge, these results present the best published performance at 60 and 75-110 GHz of any nonwaveguide-based phase shifter.

Evaluation of the performance of line protection schemes on the NYSEG six phase transmission system

This paper describes the performance of different line protection schemes during testing and operation which were used to protect the first commercially operated six phase transmission line in the world-the New York State Electric and Gas 93 kV (phase to phase and phase to ground) line from Goudey station to Oakdale substation. This project was sponsored by Electric Power Research Institute (EPRI), the Department of Energy (DOE), Empire State Electric Energy Research Corporation (ESEERCO), New York State Energy Office (SEO), New York State Energy Research and Development Authority (NYSERDA) and New York State Electric and Gas Corporation (NYSEG).

Investigation of a unified power flow controller

Power flow in an AC transmission system depends on three basic parameters: transmission line impedance, voltage magnitude and phase angle. Maximum utilisation of the power system can be ensured by the control of these parameters in real-time. It is shown experimentally that a unified power flow controller (UPFC) can control each of the parameters either selectively or simultaneously in appropriate combinations. It is also shown that a UPFC can control independently the real and reactive power flow in a transmission circuit. Results from computer simulations and a hardware laboratory model are presented.

Distributed broad-band frequency translator and its use in a 1-3-GHz coherent reflectometer

We present the first frequency translator based on a nonlinear transmission line (NLTL) phase shifter and demonstrate its application in a coherent reflectometer, giving a performance comparable to a commercial network analyzer. Rather than forming shock waves on the NLTL with large signal excitation, we use its voltage-variable delay together with both amplitude and phase linearization to modulate the phase of a small 0.5-3.0-GHz microwave signal. The resultant single sideband modulator exhibits >45 dBc carrier and spurious suppression. This new approach has significant applications in both instrumentation and sensing, particularly because it offers a clear path toward complete integration of a coherent measurement system.

Dual three phase transformation for comprehensive fault analysis of a six phase system

Recently there has been a growing interest in the concept of six phase transmission as an alternative to the upgradation of a line, to increase the power transfer capability within the existing right of way. In this work the six phase system is treated as two mutually coupled three phase systems and a transformation called dual three phase transformation (DTPT) is proposed for the analysis of a six phase system compared to earlier works on this subject. This method has reduced the number of significant combinations to 13, by choosing appropriate reference phases and renaming of the conductors, compared to 23 groups. The DTPT sequence networks are obtained in terms of the familiar three phase sequence components avoiding the use of complex ratio or phase shifting transformers, mutual inductances and the results completely agree with the results of fault analysis using the phase coordinate method. In a companion paper titled “Transposition of a six phase transmission line” it has been established that in the case of conversion of an existing double circuit three phase transmission line into a six phase line, a three barrel transposition somethat similar to the transposition of a double circuit line is sufficient, in which case there is mutual coupling only between the two zero sequence components of the two mutually coupled three phase systems which constitute the six phase system.

Some Renovations in Transient Analysis of Transmission Lines by State-Space Techniques

A method for transient analysis of single phase transmission lines based on state-space technique is presented. Transmission lines are considered as the interconnection of many lumped parameter sections. By this approach state equations are formulated for the system by choosing the capacitor voltages and inductor currents as the state variables. These equations are solved by state space techniques to compute steady-state and transient responses of transmission lines for various source and load connections. A computer program called LPTLAP (Lumped Parameter Transmission Line Transient Analysis Program) has been prepared for both formulation and solution steps.

GENERAL COMPREHENSIVE MODELS FOR SIMULATION OF EARTH CONTRIBUTED FAULTS IN SYNCHRONOUS GENERATORS USING PHASE COORDINATE THEORY

ABSTRACT This paper presents various novel, general and comprehensive models for simulation of single line to ground fault ( SLG) double line to ground fault ( DLG), and three phase fault (3φ ) in synchronous generator using phase coordinate theory. Simulated synchrounous machine is connected to infinite busbar via short three phase transmission line, and is equipped with automatic voltage regulator ( A.V.R), power system stabilizer (P.S.S), and turbine governor sets. The effects of local load at machine' s terminals, fault impedance, and stator neutral grounding impedance are also considered. In proposed models, the Fourier expansion terms can be utilized in machine's inductance matrix. Simulation program written in C language has shown the usefulness of proposed models.

A real-time transmission line model for a digital TNA

This paper presents a validation of a real-time digital simulation of a transmission line model with frequency dependent parameters, The real-time transmission line model is based on Marti's time domain formulation which is adopted in the EMTP and EMTDC programs. Improvements to speed up the calculation are made in order to realize electromagnetic transient simulation in real-time by parallel processing using two digital signal processors (DSPs) for each line. 41 /spl mu/s and 71 /spl mu/s time steps are readily achieved in real time with the new line model for three phase and double circuit (6 conductors) transmission lines respectively, The new line model is now installed in a real-time digital simulator (RTDS). Field test results are presented in this paper for validating the new line model.

Estimation of errors in the fault analysis of six phase transmission lines using transposed models

Fault analysis of power systems represented by transposed line models result in errors that are less tolerable in high phase order systems than in 3-phase systems. Concepts of vector and matrix norm theory are applied to estimate such errors in 6-phase systems without actually making exhaustive fault studies. Error estimates are compared to actual values in typical 3-phase and 6-phase systems.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

OPTIMAL DESIGN OF HIGH VOLTAGE OVERHEAD TRANSMISSION LINES

ABSTRACT This paper presents a method for the optimal design of overhead high voltage 3-phase transmission lines. The optimization objective is to minimize the line total annual cost. Both fixed and running cost items have been considered. The optimization procedure takes also the line relevant technical constraints into account. The solution yields the main design parameters of the line as well as the optimal values of transmission voltage and the optimal number of bundles. The load factor of the transmitted power is taken as one of the optimization input data. Several case studies are presented to compare the suggested methods to other available design procedures.

The Transmission of Bulk Power Over Long Distances

Circular, plate, radial and coaxial arrangements for phases of double circuit transmission lines are proposed. Power transmission over long distances depends on the mutual effect between each two respective phases. A theoretical analysis for voltage, power and current along such lines is presented. The general constants for each configuration are evaluated, as well as the maximum power limit for long distance double circuit transmission lines. Different voltage levels of 500 and 1000 kV are considered for a length of 1000 km. An external impedance is suggested to be connected at various points of coaxial arrangement with separate phases. The capacitive effect for such an external impedance is studied.

A new and systems oriented method of directional antenna tuning

The AM antenna tuning method presented takes into account and absorbs stray inductances and capacitances, and mutual coupling between components with very high initial adjustment accuracy. Besides an antenna monitor and a field strength meter, the equipment used for tuning consists of a high-precision reflectometer, a spring-loaded and side-handled split toroidal clamp-on ammeter, and a Hewlett-Packard HP-15 programmable calculator programmed with routines used to analyze measured raw data. These programs are written to determine power distribution, transmission line matching conditions and phase shifts. The techniques described inherently minimize the number of different ground points one must refer to. In addition, the few grounds needed with these techniques are much closer to true ground. >

Coupling Between Separate Phases of Coaxial Double Circuit Transmission Lines

The paper studies the so-called coaxial overhead transmission lines. The concentric phases are considered. The mathematical analysis for voltage and current is presented. The telegraphic equations of the double circuit power lines with the mutual effect between circuits are introduced. The condition for single circuit transmission line is checked. The mutual effect between both circuits is studied on the basis of the ratio between the two currents of both circuits. The appeared phase shift between the two vectors of currents is inserted in the investigation. The magnetic field intensity at an external point of a line is mathematically expressed. Its value is approximated for the purpose of zero mutual inductance between phases of the same circuit. The mutual inductance between the two nearest groups of phases due to the linkage flux for the studied line is formulated. Its dependency on the distance from the phases as well as on the ratio of currents of both circuits is analysed. Then, the effect of phase shift on the mutual inductance is investigated. An idea for the control of the ratio between currents of both circuits of a line is presented.