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Reliability of Transmission and Distribution Equipment, 1995., Second International Conference on the

Date 29-31 Mar 1995

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Displaying Results 1 - 25 of 37
  • Experience with the use of RCM in a transmission maintenance environment

    Publication Year: 1995 , Page(s): 192 - 197
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (368 KB)  

    New power system maintenance concepts and techniques are developed almost daily. There has been a major shift towards participation and teamwork with the ever increasing pressure towards more effective and efficient use of resources, a structured process of addressing the complex key issues regarding maintenance is therefore required. A shift towards reliability-centred maintenance (RCM) was thus almost inevitable. A controlled and structured approach is needed to change from a purely time based maintenance philosophy, to one that also considers usage and condition of equipment. This paper discusses the use of such a structured process, namely RCM, for analysing maintenance tasks, as applied in practice. The experience gained with two of a few projects in a transmission network operating and maintenance environment forms the basis of the discussion View full abstract»

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  • Application of RCM to high voltage substations

    Publication Year: 1995 , Page(s): 186 - 191
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (324 KB)  

    The authors describe how, in order to test and assess the benefits of the application of reliability centered maintenance (RCM) in the field of electrical networks, EDF has committed itself to a two year feasibility study on a 400 kV line bay. The use of reliability techniques has not only thrown light on the cost efficiencies potentially at stake, but has been a rewarding challenge in its own right. RCM maintenance policy is oriented towards the prevention of critical failures, evaluated as such on the basis of the cumulation of the seriousness and frequency of the events in question. This study of HV substations focuses on cost effects as regards equipment and the network. The probabilistic approach adopted, combined with the Bayesian treatment of experience feedback, has enabled criticality to be taken into account. Finally, the analysis and management of basic tasks, by assessing efficiency against the criteria of criticality, cost and operational discomfort, have made it possible to focus more accurately on improvements in terms of reliability View full abstract»

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  • Proceedings Second International Conference on the Reliability of Transmission and Distribution Equipment (Conf. Publ. No.406)

    Publication Year: 1995
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (12 KB)  

    The following topics were dealt with: reliability diagnosis and plant failure statistics; design for reliability; condition monitoring; control and protection for improved reliability; distribution system reliability; replacement policies and worth assessment; risk analysis View full abstract»

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  • Co-ordinated protection and control upgrades substation reliability

    Publication Year: 1995 , Page(s): 121 - 126
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (332 KB)  

    Smart microprocessor based devices are now available for power system control and protection. They are intelligent and surpass the performance of their conventional predecessors by far, and are at the same time highly available due to inherent self-monitoring capabilities. They can communicate with each other and with higher control levels and provide valuable data for more effective and secure system operation. Their co-ordinated use in a total system approach for substation automation will significantly improve substation reliability View full abstract»

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  • The Canadian Electrical Association approach to transmission and distribution equipment reliability assessment

    Publication Year: 1995 , Page(s): 7 - 12
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (380 KB)  

    The Canadian Electrical Association (CEA) is an electric utility based organization for exchanging information on technical, marketing and managerial problems of mutual interest to its members. CEA adopted a proposal in 1975 to create a national facility for centralized collection, processing and reporting of reliability and outage statistics for electrical generation, transmission and distribution equipment. The generation equipment reporting system was inaugurated in 1977. The transmission equipment stage of the information system was implemented in 1978 and since that time eight reports have been issued with each report covering five years of data. The distribution equipment stage of the information system was completed in 1993 and Canadian utilities are now beginning to supply data based on agreed procedures. This paper illustrates the philosophies adopted by Canadian utilities for the collection of transmission and distribution equipment data. The paper concentrates on transmission and distribution equipment data collection and illustrates the definitions and indices used to assess the functional components in these domains View full abstract»

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  • Prioritising supply infrastructure works using statistically based analyses

    Publication Year: 1995 , Page(s): 157 - 161
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (284 KB)  

    Like most other companies, London Underground is endeavouring to minimise its distribution network costs while providing the best possible service to its customers. In order to meet these aims, it is necessary to use the capital available to best effect. In London Underground's case, the problems of prioritising capital expenditure are especially difficult because of the diverse nature of the potential projects, ranging from works which will immediately and directly improve service to large numbers of customers, through renewal of ageing infrastructure to works to improve safety. The techniques described here represent a useful set of tools to use when attempting to prioritise power infrastructure work. However, their application requires great care and the results that come from them need careful interpretation. In some cases the form of the results and the uses to which they are put are controversial, making it especially important that both method and application are checked and auditable View full abstract»

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  • Concepts of data for assessing the reliability of transmission and distribution equipment

    Publication Year: 1995 , Page(s): 1 - 6
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (416 KB)  

    This conference is concerned with reliability of transmission and distribution equipment. This authors argue that the concept of reliability can only be objectively assessed by quantifying the behaviour of the individual items of equipment and thus by monitoring, collecting and collating the associated reliability data. This data can then be used to both assess past performance and to predict likely future performance. As importantly, it can be used to judge the merits and benefits, technical and economic, of alternative planning and operational strategies and decisions, It is easily argued that valid and useful data are expensive to collect, but it should be recognised that, in the long run, it will be even more expensive not to collect them View full abstract»

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  • A tap-changer monitoring system incorporating optical sensors

    Publication Year: 1995 , Page(s): 97 - 102
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (312 KB)  

    The National Grid Company (NGC) owns and operates approximately 600 transformers of various ratings up to 1000 MVA. These transformers are very reliable, and have extremely long lives. They have no moving parts, and the main degradation mechanism is deterioration of the paper insulation, which is a very long-term process. The vast majority of transformers at ratings up to 240 MVA have on-load tap-changers to vary their turns ratio, and in marked contrast to the windings, these are complex mechanical switches with many moving parts. It is not surprising that they are less reliable than the windings, and a significant proportion of the serious transformer faults can be attributed to problems originating in the tap-changers. A monitoring system which could detect incipient failures and act to prevent them would thus be of benefit, providing it could be produced at reasonable cost. In addition, by monitoring the performance of the tap-changer continuously, it may be possible to move away from maintenance done at fixed time intervals, and towards a condition-based programme, which could result in significant savings. The authors describe a chromatic modulation technique monitoring system which uses a fibre optic sensor View full abstract»

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  • Maintenance-free vacuum circuit-breaker

    Publication Year: 1995 , Page(s): 37 - 42
    Cited by:  Patents (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (336 KB)  

    The introduction of vacuum switchgear represented the first step in the direction of a maintenance-free medium-voltage circuit-breaker. Switching in a vacuum was the first quenching principle to assure constant electrical and dielectric properties throughout the device's entire service life of more than 20 years, involving for example more than 100 short-circuit clearances or 10000 to 30000 switchings of the rated normal current. These and other superlative characteristics of the vacuum interrupters mean that this quenching principle is not only one of the most reliable, but also one of the most environmentally compatible. Modern medium-voltage circuit-breakers such as those of the Siemens 3AH1 range described by the authors constitute the second step in the direction of a maintenance-free and therefore more reliable overall system. Not only the primary section with its vacuum technology is maintenance-free, the same goes for the circuit-breaker operating mechanism too. In this context maintenance-free means that throughout the circuit-breaker's service life of more than 20 years and under normal operating conditions: no relubrication is necessary, no readjustment is necessary, and the characteristic data do not deteriorate impermissibly. The only external factor influencing the reliability of such a circuit-breaker is deterioration in the insulating capacity as a result of environmental effects. The third and final step in the direction of a completely maintenance-free overall system is integration of the maintenance-free circuit-breaker in the gas-insulated switchgear View full abstract»

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  • Factors affecting the reliability of low voltage aerial bundle cable systems

    Publication Year: 1995 , Page(s): 48 - 51
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (292 KB)  

    Low voltage aerial bundle cable (ABC) has been used for electrical reticulation in Australia since the mid 1980s. The advantages to be obtained from using this type of cable were primary environmental in that trees adjacent to the cable did not have to be lopped excessively, and the risk of bush fires was reduced as the insulated cable system was seen as being less likely to cause arcing than traditional open wire systems. Whilst ABC systems had been used overseas the authors were not convinced that the systems used in Australia would give acceptable long-term performance. Areas that seemed to require further investigation were: the long-term behaviour of the XLPE insulation under the wide range of system and environmental conditions encountered in Australia, and the long term behaviour of the insulated connectors used to interconnect main and branch cables. This paper describes results from a research project undertaken to examine limits of performance for ABC systems, and to identify areas of possible weakness. The authors discuss mechanical strength, protection requirements, and water penetration View full abstract»

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  • Transformer design for high reliability

    Publication Year: 1995 , Page(s): 66 - 72
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (432 KB)  

    As the population of power transformers in service increases and becomes older, electric utilities are focusing attention on the availability of their plant. Users assess availability in terms of: (1) dependability-whether the transformer will be available in the short term, i.e. over the next 5 years; and (2) reliability-whether the transformer will be available in the longer term, i.e. over the next 5 to 15 years. Here, the author describes how it has become necessary for the transformer designer to accept that a transformer is a high integrity piece of equipment that is not expected to fail on test or in service. With this philosophy in place, the designer can be expected to provide designs that will give improved levels of reliability in service compared with previous generations of power transformers View full abstract»

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  • Risk based design of distribution line structure

    Publication Year: 1995 , Page(s): 168 - 174
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (256 KB)  

    Power overhead line regulations and codes generally apply prescriptive methods to the design of structures using working loads multiplied by factors of safety. In contrast, the probabilistic method is founded on designing to a limit state in which strength is matched to stress, with the risk of failure defined by the overlap of the distributions of the limit state model. This work indicates how a stress limit state using probability concepts can be applied to the design of round pole distribution line structures. It indicates that unlike the transmission line, variations which occur in the layout of distribution lines necessitate the use of some contingency factors. Design studies of new and existing lines show that there are substantial savings to be made View full abstract»

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  • Ranking of design criteria to improve rural network performance

    Publication Year: 1995 , Page(s): 145 - 150
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (280 KB)  

    The evaluation of different design criteria to improve the performance of a rural distribution network requires a broad approach to be taken in comparing technical improvements that could be implemented, with the corresponding benefits obtained. This paper describes the examination of an existing rural 11 kV network in Northern Ireland in need of improvement in performance. The basic improvement aims are to halve (i.e. improve) the reported overall security and availability indices and to ensure that the security and availability on any particular circuit are maintained within a specified upper limit. The approach adopted was to model the performance of selected circuits, compare predicted performance with actual historical performance and provide a quantitative assessment of individual and combined improvement measures View full abstract»

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  • The improvement of customer service by system automation [power distribution]

    Publication Year: 1995 , Page(s): 127 - 132
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (380 KB)  

    Distribution automation is practised to varying degrees around the world and is of interest to all power system engineers. Its importance has increased in the United Kingdom following privatisation of the electric utility industry and the consequently increased focus on customer service. The authors detail how Midlands Electricity has embarked on a re-definition of its power supply reliability standard and its new approach is described View full abstract»

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  • Neural network based techniques for distribution line condition monitoring

    Publication Year: 1995 , Page(s): 115 - 120
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (260 KB)  

    Because a power distribution line is spread over a significant area, it is exposed to a variety of hazards. Causes of line abnormal conditions include lightning, wind, ice, snow, salt spray, birds etc. These make it extremely difficult to design an accurate condition monitoring system for distribution lines by using conventional techniques. In this paper, a neural network technique is proposed to develop a novel condition monitoring scheme for a distribution system. The paper starts with description of the modelling techniques for some common abnormal conditions in distribution systems, followed by a presentation of digital simulation of some typical situations such as high impedance, arcing and solid faults. The spectrum technique is employed to analyze the features associated with different conditions. Then special emphasis is placed on the neural network, including the determination of network input, network size and its training. The validation results demonstrate the feasibility of this approach View full abstract»

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  • Transmission equipment reliability using the Canadian Electrical Association information system

    Publication Year: 1995 , Page(s): 13 - 18
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (316 KB)  

    Canadian electric power utilities have been collecting and processing transmission equipment reliability data as part of the Canadian Electrical Association Equipment Reliability Information System (CEA-ERIS) since 1978. Eight concurrent annual reports have been produced each covering a five year period. These data cover transmission lines, transformer banks, circuit breakers, cables, synchronous and static VAr compensators, shunt reactors, shunt capacitors and series capacitors. Overall statistics of failure rate, average downtime and unavailability are obtained for each major component, subdivided into agreed voltage categories, and published on a national basis. Additional statistics such as line and terminal related transmission outage data, integral and terminal related transformer outage data are also compiled and disseminated. This paper illustrates the transmission equipment reliability data in the CEA-ERIS and presents a summary of relevant reliability parameters for the major components covered by the system View full abstract»

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  • Reliability and maintenance practices for Australian and New Zealand HV transmission lines

    Publication Year: 1995 , Page(s): 198 - 203
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (356 KB)  

    Electricity supply authorities throughout the world are under pressure to perform more efficiently and continue to meet demand yet face increasing environmental pressure not to construct additional transmission lines. This means that existing lines must work harder and last longer than ever before. Traditional maintenance activities based on standard inspection periods will need to be replaced by strategies to identify the lines most in need of work or which constitute the greatest risk to the system. This paper reviews Australian and New Zealand practices for transmission line maintenance. It presents the results of a comprehensive survey of line maintenance practices and reliability for electricity supply authorities throughout this region View full abstract»

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  • Assessment of circuit capability and preparation of rating sheets

    Publication Year: 1995 , Page(s): 91 - 96
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (340 KB)  

    The need to work power systems harder using the best knowledge of its capability is central to the objectives of the National Grid Company (NGC) Technology and Science Division (UK). This objective must be balanced by appropriate work on the impact of loading regimes on the life expectancy and maintenance requirements of the power system. This paper describes the development of a unified circuit rating process allowing for the separate characteristics of every power system item in the circuit and the automation of that process using a Critical Unit Program (CUP) written in LOTUS 123. The program is being used to create circuit rating sheets which were previously manually produced in less consistent formats. An example of the output of the CUP system is given. The intention of this work is to enable NGC to operate its power systems harder within the limits set by normal design temperatures. Operators also require guidance on fault current ratings View full abstract»

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  • Case studies in survival analysis of overhead line components

    Publication Year: 1995 , Page(s): 210 - 215
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (276 KB)  

    This paper demonstrates the application of a statistical procedure to analyse data associated with time-to-failure of power overhead line components. Three studies are discussed: full length preservative treated wood poles; disc insulators; and highway lighting. The common aim in each case was the design of maintenance and replacement programs View full abstract»

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  • MV overhead lines using XLPE covered conductors. Scandinavian experience and NORWEB developments

    Publication Year: 1995 , Page(s): 52 - 60
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (420 KB)  

    After 15 years of experience with MV covered overhead line systems in Scandinavia, components, system and installation practices have reached a state of established technology. The system offers phase clearance of only 50 cm and the ability to allow grounded objects to touch the line and phases to touch each other, without any tripping or customer outage. A substantial improvement in service reliability and a reduction in life cycle costs, compared to bare lines, is achieved. The aluminium alloy conductor is covered with black UV-resistant XLPE and filled with grease, to provide corrosion protection and longitudinal watertightness. Arcing guides are applied at insulator tops, to protect the line from arcing damages. Methods for determining the necessary frequency of arcing guides have been developed, based on probabilistic approaches. NORWEB plc has adapted the Norwegian covered line concept, realising it through test sites and by defining a NORWEB design for their further development in accordance with the UK Electricity Supply Regulations of 1988 View full abstract»

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  • Simulation-aided short circuit risk evaluation for circuit breakers in HV substations

    Publication Year: 1995 , Page(s): 175 - 179
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (288 KB)  

    The application of a probabilistic method of circuit breaker failure evaluation is described. A simulation model based on the Monte Carlo method and a specially built computer program are presented. Conclusions are drawn from the results of risk analysis made for a selected part of the Polish power system View full abstract»

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  • Reliability aspects in operational structuring of large-scale urban distribution systems

    Publication Year: 1995 , Page(s): 151 - 156
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (416 KB)  

    Distribution systems largely determine the service quality profile seen by end-customers and dominate overall reliability indices. The most frequent and most significant outages are those in the medium voltage feeder sections. This paper underlines the importance of the incorporation of service quality requirements into operational planning and structuring of medium voltage urban power networks. The network configuration problem is defined as a constrained multiobjective optimization problem where service interruption costs, load imbalance among feeders and transformers as well as real power losses are minimized subject to security and operational constraints. A fuzzy coordination technique is used to obtain a suitable balance between the conflicting and incomparable objectives. The proposed concept is tested on a slightly modified actual underground distribution system View full abstract»

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  • Practical aspects of reliable switchgear design

    Publication Year: 1995 , Page(s): 43 - 47
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (372 KB)  

    Switchgear designers, as well as satisfying the requirements for short circuit and switching performance must also ensure that the equipment has long term mechanical reliability and insulation integrity. Reliability surveys indicate that failures are generally mechanical in nature rather than electrical. For this reason the paper discusses practical aspects of mechanical reliability along with techniques adopted to ensure improved reliability of switchgear operating mechanisms, interrupters, insulation and auxiliary equipment View full abstract»

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  • Reliability design approach for protection and control equipment for MV distribution networks

    Publication Year: 1995 , Page(s): 133 - 138
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (228 KB)  

    Reliability is a main requirement for MV distribution networks. One of the key components is the protection and control equipment. Both functions have traditionally been implemented separately. However, the latest generation of numerical devices available in the market offers a high degree of integration of protection and control functions. Reliability data of conventional protection relays has been based on historical information and experience. As numerical devices are based on computer technology their design has to take into account system architecture, communication network, structure of the algorithms etc., and their reliability has to be evaluated with rigorous techniques. This paper describes the methodology used by the authors' company to monitor reliability and maintainability during specification, design, validation and useful life of equipment View full abstract»

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  • Determination of data for reliability analysis of a transmission system

    Publication Year: 1995 , Page(s): 19 - 23
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (200 KB)  

    Probabilistic methods for reliability evaluation of power systems are more consistent than deterministic ones. This is due to the stochastic nature of power systems. However the application of such methods to practical systems require the availability of the relevant reliability data. Jordan Electricity Authority (JEA) has started the process of evaluating such data for its generating system. The objective of this paper is to perform statistical analysis on collected data over the period 1989-1993 in order to estimate the outage rate and duration of the components of the 132 kV Jordanian Transmission System which is run by JEA View full abstract»

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