Six-phase Line Research Articles

Analysis of Six-Phase Transmission Lines for Increasing Power

In the India, especially in metropolitan areas, transmission infrastructure is congested due to a combination of increasing load demands, declining investment, and aging facilities. It is anticipated that significant investments will be required for new construction and upgrades in order to serve load demands. This paper explores higher phase order systems, specifically, six-phase, as a means of increasing power transfer capability, and provides a comparison with conventional three-phase double circuit transmission lines. Line parameters calculations performed in this thesis show that line impedances in six-phase lines have a slight difference, compared to three-phase double circuit line. The electric and magnetic fields calculations show that, ground level electric fields of the six-phase lines decline more rapidly as the distance from center of the lines increase. The six-phase lines have a better performance on ground level magnetic field. Based on the electric and magnetic field results, right of way requirements for the six-phase lines and three-phase double circuit line were calculated. The calculation results of right of way show that six-phase lines provide higher power transfer capability with a given right of way.

Анализ и расчет пропускной способности воздушных линий электропередачи

Power transport is the most important component of an electric power system. Modernization and optimization of its operation, increase in capacity, as well as variation in connection circuitry with maintained or improved reliability is a crucial objective for the whole energy industry. The paper is about crea­ting a circuit-technical solution for a dual-circuit three-phase power transmission line whereby we define a new operating mode “with a split backup phase”. We herein describe conventional and non-conventional types of AC transmission such as overhead transmission lines, six-phase power lines, and flexible alternating current transmission systems (FACTS). We further analyze ways to improve the efficiency of overhead power transmission lines using structural and functional redundancy. A circuit-technical solution for a dual-circuit power transmission line with expanded operating modes is considered in detail. Possible operating modes of dual-circuit power lines are described. We also consider ways to increase the natural capacity of such lines. We have calculated the capacity of split backup phase lines and present the results of our calculations herein along with an analysis of such capacity in comparison to that of conventional transmission lines.

Analytical Calculation of the Magnetic Field Produced by Electric Power Lines

The magnetic field produced by electric power lines is usually calculated numerically with the use of a computer. However, the analytical calculation of the magnetic field is preferable because it results in a mathematical expression for showing its dependences on the various parameters of the line arrangement. A method to derive the analytical formula of the magnetic field vector produced by any power line is developed in this paper. The specific formulas for the magnetic field produced by any single circuit line in flat, vertical, or delta arrangement, as well as for hexagonal lines considered as double circuit lines in super bundle or low reactance phase arrangements or as six-phase lines, are given. The derived formulas are valid at any point with practical importance, close to or far from the line. The development of the method is made possible with the use of new kinds of numbers, named double complex numbers, to represent the magnetic field vector in the vicinity of power lines. Double complex numbers remarkably simplify the mathematical expressions for the magnetic field vector. Using these numbers, it is observed that the infinite terms of the magnetic field multipole expansion, for flat single circuit lines and for lines exhibiting polygonal symmetry are contracted, resulting in simple formulas for the magnetic field vector, which is used to derive the formulas for the resultant value of the magnetic field. The general formula of the magnetic field vector produced by an arbitrary power line is a rational function of the distance from it. Through the given expressions for the coefficients of this function numerator and denominator, the formula for the magnetic field vector produced by any power line can be derived.

Electrostatic and environmental analyses of high phase order transmission lines

Abstract This paper presents an electrostatic modeling and environmental effect analysis of the high phase order transmission lines (HPOTL) using the charge simulation method. Both the conversion of the existing EHV and UHV double circuit transmission lines to six-phase lines, and the use of new, compact circular configuration HPOTL are introduced and discussed in the light of electric field computation at both the subconductor/conductor surface and the ground level. A new technique is also presented to decrease drastically the electric field at the ground level with a negligible increase in the conductor surface gradient and the charging current of the bottom phases. In this technique, a very few number of extra ground wires under each circuit are added, where they can also be utilized as optical ground wires for telecommunication purposes. Different phase arrangements, voltage ratings and conductor coating of the above-mentioned two cases are studied to investigate the possibilities of increasing the power handling capabilities without augmenting the environmental effects. It seems that HPOTL give a promising cost-effective means for increasing the power handling capability either for the existing double circuit transmission lines by 73% via increasing the operating voltage, or for the compact HPOTL via using six or more phases.

New multiphase mode domain transmission line model

This article presents a new model to represent transmission lines including the frequency dependence of longitudinal parameters. The model uses exact modes, for ideally transposed lines, and “quasi-modes” for non-transposed lines. The line is represented through a cascade of π-circuits, with one π-circuit for each mode. The transformation matrix used is real and it is modeled with ideal transformers. The model is described for three-phase lines, dc lines, double three-phase lines and six-phase lines. An ATP-EMTP implementation of a 440 kV three-phase transmission line is performed to illustrate the model and a comparison with two frequency dependent ATP line models are made, the Semlyen and JMarti ones.

Relay protection operation for faults on Nyseg's six-phase transmission line

This paper describes the performance of the protection system used for the first commercially operated six-phase transmission line in the world-New York State Electric & Gas's 93 kV (phase to phase and phase to ground) line from Goudey Station to Oakdale substation (USA) during faults in the winter of 1993. The paper briefly describes the basics of the High-Phase Order Transmission Demonstration Project and the integration of available state of the art microprocessor based relays, with a programmable logic relay (designed for the protection of conventional three-phase systems) in a hierarchical six-phase protection system. The operation of the protection system during two faults on the line in January and February 1993 is reported. The modeling of the six-phase line in a conventional three-phase short circuit study program is also considered and a comparison between the measured and calculated fault currents is presented.

Analysis of the faults involving adjacent conductors of a six-phase transmission line together with a modelling of the phase conversion transformer

Abstract In a bulk power transmission system the amount of power transfer can be increased by converting the widely used three-phase double-circuit lines into six-phase single-circuit lines instead of upgrading the transmission voltage. In this conversion process only a phase conversion transformer at each end of the line is required while the existing conductors, towers and corridors of three-phase lines can be used intact. However, this conversion will have an effect on the system fault currents and fault levels. The well-known symmetrical component method is suitable for fault analysis in a three-phase system, but it has been found unsuitable for analysing the practical faults on a six-phase line and for modelling the phase conversion transformer. This paper illustrates the way the phase conversion transformer has been incorporated in the six-phase line fault modelling and also presents a new application of the straightforward loop current method by using it to determine the currents and fault MVA corresponding to the common and practical faults on a 132 kV six-phase line. The same method has also been applied to the fault analysis of a 132 kV and a 230 kV three-phase line and the results are compared with those for the six-phase line.

Six-phase transmission line-propagation characteristics and new three-phase representation

A new component transformation is proposed for six-phase systems, applicable for six-phase transmission lines studies, allowing its representation by two uncoupled three-phase lines. Cyclic transposition allows additional properties of the two three-phase groups that are presented. Transposed and nontransposed six-phase lines are analyzed, and the main characteristics of their natural modes are discussed in the frequency domain. An eigenvector normalization method for nontransposed lines that assures null modal conductance and, as a consequence, positive modal resistance, is proposed. Numeric results are presented in relation to an example line of 500 kV/sub rms/, phase to ground, with characteristic power of 5176 MW. >

Design modification and layout of utility substations for six phase transmission

Evaluations performed on the New York State Electric and Gas Corporation's 115-kV Goudey-Oakdale line and Goudey and Oakdale substations to assess the capability of the existing equipment operate as part of a six-phase demonstration project are described. The design modifications that will be made to meet the goals of the commercial demonstration and to allow integration into the existing three phase operating grid are also described. Reconfiguration of an existing double-circuit line to a single-circuit six-phase line requires installation of phase configuration transformers at the end of the line terminals and the associated switching, metering, and protection equipment. In addition, the phase conductors from the terminals of the transformers must be transposed for connection to the transmission line to achieve the desired 60 degrees vectorial separation angle between adjacent phase conductors. Concepts of substation compaction that have been pursued when attempting substation modifications for six-phase reconfiguration are discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Selection and application of relay protection for six phase demonstration project

The protection and control requirements needed for a 115 kV line after it was reconfigured to operate as a single-circuit six-phase line as part of a high-phase-order demonstration project are discussed. Addressed are the required modification and/or additions needed for the existing protection and control equipment. The criteria selected for the protection of the transmission line are described, including the transformers required for six-phase reconfiguration. The commercially available digital protection systems applicable to the protection of the line and their limitations are reviewed. Requirements for protection and control panels, their location for optimal wiring, and facilities to perform tests and measurements are also covered.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Transient stability analysis for symmetrical and unsymmetrical faults in mixed three-phase and six-phase power systems

The aim of this paper is to analyse the transient stability of a three-phase power system with six-phase lines interconnected by three-phase to six-phase transformers. For these mixed power systems a transient stability analysis is performed under all main types of disturbances (short-circuits, generator and load rejection, line outages), particularly in the case of faults at six-phase buses. A generalized procedure to evaluate transient stability is explained in detail. It is based on the symmetrical components method, which allows one to consider also unsymmetrical faults both at three-phase and six-phase buses. For every possible unsymmetrical short-circuit an equivalent fault admittance is defined and its expression is derived. Furthermore, a program worked out for the calculation is explained and some results of its application to a sample mixed power system are reported.

Mixed three-phase and six-phase power system analysis using symmetrical components method

The problem of analyzing a three-phase power system with six-phase lines interconnected by three-phase to six-phase transformers is studied. The approach used is based on the method of symmetrical components, which allows one to obtain a description of the whole mixed system either in terms of symmetrical components at three-phase sequences or in terms of symmetrical components at six-phase sequences. The research proves that this method can be implemented thoroughly and easily without the need to introduce too simplified hypotheses. The models of the six-phase lines and interconnecting transformers, at three-phase and six-phase sequences, are presented in order to obtain a completely homogeneous representation of the whole mixed system suitable for typical studies performed on power systems (load flow, fault analysis, stability studies).

Prediction Of The Optimum coupling For PLC Propagation On Double Circuit And High Phase Order Transmission Lines

The characteristics and performance of the 'Power Line Carrier' digital program are described. Accurate simulation models and efficient propagation algorithms permit fast computation of the voltage attenuation of coupling connections on single-circuit, double-circuit or high-phase order lines. The lossy transmission systems may have discontinuity points due to phase-transpositions, series or shunt circuits with lumped parameters, terminal impedances or shunt-faults. Voltage attenuation of line-to-line and line-to-ground coupling connections is computed as a function of frequency for horizontal and vertical double-circuit lines and for a six-phase line. A sensitivity analysis of the carrier channel attenuation is performed with respect to variations of the average height of the conductors above the ground plane, of the conductor stranding factor, the earth resistivity and the terminal impedances in the case of the double-circuit vertical line. The comparative analysis of the results obtained proposes the best couplings for each line considered.

Six-phase (multiphase) power systems: Some aspects of modelling and fault analysis

This paper presents a further step in the mathematical modelling and analysis of six-phase (multiphase) systems. In earlier publications, a six-phase line, several three-phase/six-phase transformers, loads and a six-phase generator were modelled. The three-phase equivalent representations of various elements were obtained for analysis of the overall system on a three-phase basis. In this paper the equivalent six-phase representations of various elements of a composite three-phase/six-phase system are derived for investigating the phenomena on the six-phase side of the network. Utilizing the element models discussed in the paper, several alternative schemes for fault analysis of a six-phase system employing transformation as well as phase coordinate methods are developed. The validity and effectiveness of the proposed schemes are demonstrated with the help of a sample system.

A Method of Supressing Fault Currents and Improving the Ground level Electric Field in a Novel Six-Phase Power Transmission system

In this paper, it is shown that the maxnuma electric field under the six-phase line with a modified phase arrangement becomes as low as that under the three-phase double-circuit ( conventional ) line. Then, a method is proposed for limiting line-to-ground fault currents and short-circuit currents without causing the fall in unfaulted phase voltages in the six- phase system with its neutrals solidly grounded. The fault analysis and the experimental result demanstrate that for a single line-to-ground fault at the sending end, the fault current in the proposed system is half that in the conventional system. As for the three-phase short-circuit fault at the sending end, the fault current in the proposed system is about 60% of that in the conventional system. It is concluded that the proposed six-phase system is superior in the system transient stability to the conventional system.

EPPC - A Computer Program for Six-Phase Transmission Line Design

Allegheny Power System (APS) conducted a three-year study during 1976-79 on the feasibility of converting some of their 138-kV three-phase double- circuit lines to 138-kV six-phase lines. The analytical development of this novel study has been documented in the form of a generalized computer program entitled "Electrical Parameters and Performance Characteristics" (EPPC). This software is a valuable tool for the design of a six-phase transmission line.

138-kV, Six-Phase Transmission System: Fault Analysis

In the past decade, transmission planners and researchers have been keenly investigating the feasibility of six-phase concept as a planning alternative. The concept, if proved feasible, would alleviate the problem of acquiring additional rights-of-way to meet the increase in electric power and energy demand. Allegheny Power System (APS) has been investigating the conversion of some of their 138-kV three-phase double- circuit lines to 138-kV six-phase lines. The latter is an alternate option to 230-kV three-phase upgrading of the line.