Restrictions on right of way and increasing power demand has boosted development of six phase transmission. It offers a viable alternative for transmitting more power, without major modification in existing structure of three phase double circuit transmission system. Inspite of the advantages, low acceptance of six phase system is attributed to the unavailability of a proper protection scheme. The complexity arising from large number of possible faults in six phase lines makes the protection quite challenging. The proposed work presents a hybrid wavelet transform and modular artificial neural network based fault detector, classifier and locator for six phase lines using single end data only. The standard deviation of the approximate coefficients of voltage and current signals obtained using discrete wavelet transform are applied as input to the modular artificial neural network for fault classification and location. The proposed scheme has been tested for all 120 types of shunt faults with variation in location, fault resistance, fault inception angles. The variation in power system parameters viz. short circuit capacity of the source and its X/R ratio, voltage, frequency and CT saturation has also been investigated. The result confirms the effectiveness and reliability of the proposed protection scheme which makes it ideal for real time implementation.

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An improved fault detection classification and location scheme based on wavelet transform and artificial neural network for six phase transmission line using single end data only

The continuous increasing demand of electricity contradicts with the increasing difficulty to secure corridors to construct new transmission lines. This paper investigates alternatives regarding parallel lines from the point of view of the magnetic flux density level under and around current-carrying conductors of the lines. The first alternative is for existing transmission lines by converting a three-phase double-circuit line to six-phase circuit. The second alternative is for new transmission lines by building compact six-phase circuits. The paper shows that compact-compact combination of parallel lines exhibits optimum patterns and it is highly recommended for new projects. The converted-converted combination of transmission lines exhibits the highest levels of magnetic flux densities patterns, but it is still below the maximum permissible level.

Comparison of magnetic-field distribution of noncompact and compact parallel transmission-line configurations

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.

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

In this paper, a new three-phase-to-four-phase transformer with four-phase four-leg structure is first proposed, its electromagnetism principle is analyzed, and the properties and features of the transformer are also discussed. This transformer may be applicable to either four-phase transmission systems or autotransformer (AT) traction power-supply systems in electric railways.

Three-phase-to-four-phase transformer for four-phase power-transmission systems

The demand of electrical energy is continuously increasing. High phase order transmission system is a viable alternative due to increasing costs of right of way. Six phase transmission lines can carry more power for same phase to phase voltage with the same right of way economically. Protection of six phase transmission lines has been a very challenging task. Earlier simulations of six phase transmission line have been done in PSCAD/EMTDC software. In this paper MATLAB® software and its associated Simulink® and Simpowersystem® toolboxes have been used to simulate the six phase transmission line. Application of Artificial Neural Network for protection of six phase transmission line against ground faults is presented, which the authors believe has not been reported earlier. Fundamental components of six phase voltages and currents have been used as inputs for training of the artificial neural network for detection and classification of faulted phase using neural network toolbox of MATLAB®. A sample 765 kV system of 60 km length has been selected for study. The study takes into account the effect of variation in fault inception angle, fault distance location and fault resistance. The results indicate the suitability of proposed technique and its adaptability to changing system conditions.

Detection and classification of faults on six phase transmission line using ANN

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. >

Selection and application of relay protection for six phase demonstration project

Conversion of an existing double-circuit 115 kV overhead transmission line near Binghamton, New York to six-phase operation will provide a commercial demonstration of feasibility of high phase order power transmission. Analyses of insulation performance, corona and field effects, and a load flow and system stability have been performed as part of the preliminary engineering for this project. It is shown that conversion of the Goudey-Oakdale double-circuit 115 kV line to 93 kV six-phase is possible if insulator strings are lengthened to 8 units/string. This results in a 40% increase in thermal loading capacity and a doubling of surge impedance loading, while meeting all applicable electrical environmental requirements. >

Insulation coordination, environmental and system analysis of existing double circuit line reconfigured to six-phase operation

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. >

Design modification and layout of utility substations for six phase transmission

Conversion of an existing double circuit three-phase 115 kV overhead transmission line near Binghamton, New York to six-phase operation will provide a commercial demonstration of the feasibility of high phase order power transmission. An important part of this demonstration is specification of the phase/voltage conversion transformers and requirements to permit single pole switching of the line in a practical manner at minimum cost. The results of engineering studies which led to selection of two delta-wye three-phase transformers at each end, one of each pair with reversed polarity to obtain the 60 degrees shift between phases, are presented. >

J.R. Stewart

Papers

Selection and application of relay protection for six phase demonstration project

Insulation coordination, environmental and system analysis of existing double circuit line reconfigured to six-phase operation

Design modification and layout of utility substations for six phase transmission

Transformer winding selection associated with reconfiguration of existing double circuit line to six-phase operation