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Generation, Transmission and Distribution, IEE Proceedings C

Issue 5 • Date September 1984

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Displaying Results 1 - 4 of 4
  • Overhead lines¿some aspects of design and construction

    Page(s): 149 - 187
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (6804 KB)  

    Overhead lines embrace so many engineering disciplines, that only some aspects of design and construction can be considered in the paper. The new trends in assessing design loads for the components are briefly outlined, together with their interrelation with the strength of the components. It is argued that ultimate loading conditions should replace ?working loads and factors of safety?. Although conductors have been fairly well standardised, new techniques for assessing their performance have recently been developed. However, with the advent of conductors incorporating optical fibres, some basic investigations are required. While there is a better understanding of wind induced phenomena, there is still no universal technique or device to solve galloping problems. After the conductors, the supports represent the second high-cost component of an overhead line, and much of the routine of design can now be performed by computers. Depending on requirements, loadings, ecological factors, economics etc., the supports can adopt many shapes and sizes, from the single member pole for low, medium or even high voltage lines, to the complex lattice types normally reserved for HV or EHV lines. The availability of fewer rolled sections and a limit on larger sizes tax the ingenuity of designers, who have to use, occasionally, compound sections or solid round members. Testing support designs is still a fairly common requirement. Considerable advances have been made in the knowledge of the electrical performance of air gaps, but the problem of insulation co-ordination still remains. Possibly, the greatest innovation in the field of insulators is the improving confidence in the use of composite insulators. The foundations of an overhead line are subjected to loadings seldom encountered with other civil engineering works, i.e. uplift. A review is made of the various shapes and sizes which can be used, together with up-to-date techniques of design. Site investigation is gaining more im- portance and more acceptance, in view of the need to match designs to actual site conditions with the dual purpose of economy and reliability. The influence of foundation movement is also discussed. Regarding installation, the equipment is adapted to the type of construction. It can be fairly simple for distribution lines and may become very sophisticated for transmission lines, especially when acceleration in the progress of work is desired. In addition, consideration of logistics, transportation and access have become exceedingly important. Work in highly inaccessible terrains, or opposition to access road building for ecological reasons, has focused attention on the application of helicopters for overhead transmission-line construction View full abstract»

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  • Computer modelling of series-compensated EHV transmission systems

    Page(s): 188 - 196
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1109 KB)  

    The use of series-compensated lines in long-distance AC transmission practice is well known. There are, however, problems encountered in the protection of such lines, and these arise primarily as a result of the rapid circuit-parameter changes due to the operation of the various capacitor spark gaps protecting the capacitor banks against overvoltages. Realistic simulation of such systems for both protection evaluation and as an aid to the design and development of protective gear is therefore of obvious importance. In the paper, digital methods are developed for accurately simulating the faulted response of series-compensated systems, and, in particular, details are given of methods for simulating changes in circuit state associated with capacitor-gap flashovers. The methods developed are verified using some recently performed field tests, and the paper concludes by establishing some of the factors which influence capacitor-gap flashover times, and their effect on system waveforms for a typical 500 kV long-line application View full abstract»

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  • Microprocessor-controlled HVDC simulator

    Page(s): 197 - 203
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1016 KB)  

    The power convertor and transducer requirements for direct digital control are first discussed with reference to an existing analogue-controlled scaled-down HVDC simulator. The interface between the HVDC simulator, a multimicroprocessor control system and a VDU interactive terminal is then described. A data acquisition scheme is developed and used as a basis for a dual-purpose system, which provides convertor control as the first priority and various interactive tasks as a second priority View full abstract»

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  • Some aspects of system modelling for the estimation of lightning performance of high voltage substations

    Page(s): 204 - 209
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (647 KB)  

    The computation of lightning overvoltages in a gas-insulated substation is carried out for different overhead line equivalent circuits. Models of the back-flashover characteristics of the line insulation in front of the substation are analysed, and an investigation is made into the influence of the number of overhead line spans represented in the equivalent circuit. The results show that the inclusion of three overhead line spans in the equivalent circuit is sufficient for the estimation of the substation lightning performance. The influence of the instantaneous value of the power frequency voltage at the moment of lightning strike is also analysed. Direct strikes to a phase conductor and to the tower top with back flashover are simulated. For relatively small values of lightning current, the phase voltage at the moment of strike has a significant influence View full abstract»

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