The interruption cost for one hour of a petrochemical plant is 33 times higher than that of the average interruption cost for industrial plants across all industries. In addition to the high cost of loss of production, interruptions to the operations of petrochemical and gas-toliquid plants pose safety and environmental hazards. Thus it is necessary to better understand the reliability requirements of petrochemical and gas-to-liquid plants. This study investigated the reliability of electrical distribution networks used in petrochemical and gas-to-liquid plants compared to those used in other industrial plants. A model was developed that can be used to establish the adequacy of the reliability of a distribution network in terms of the components and network topologies used. This model was validated against data that had been collected by the IEEE and applied to an actual petrochemical plant. Over 19 years’ worth of data regarding the trips that have occurred on the distribution network of an existing petrochemical plant was collected and manipulated in order to calculate the reliability indices associated with the equipment used to make up thisRecommended Practice for the Design of Reliable Industrial and Commercial Power Systems. The cost of loss of production and the capital costs associated with increased reliability were calculated for a section of the existing petrochemical plant. The reliability associated with different network topologies that could possibly be used to supply power to this section of the plant were modelled using an appropriate software package. The resulting total cost of ownership over the life of the plant associated with each topology was then calculated in order to establish which network topology is the most appropriate for petrochemical and gas-to-liquid plants. It was concluded the components that affect the reliability of an industrial distribution network are different to those that affect a utility distribution network. These components were listed and compared. It was found that the reliability indices that were calculated for the components that affect the reliability of a petrochemical plant were similar to those provided by the IEEE. 17 out of 20 of the indices that were calculated were within the required factor of deviation. Generally the failure rates of components used in petrochemical plants were very similar to those given in the IEEE Gold Book, while the MTTR’s for the components used in petrochemical plants were found to be slightly better than those given in the IEEE Gold Book. The effect of network topology was found to be significant, with small changes in the topology of a network resulting in large variations in the reliability of the network. It was also found that the most appropriate type of network topology to use in the design of the electrical distribution network of a petrochemical plant is the dual radial network. This is the most conservative of the commonly used network topologies and is the one that is currently used in the existing plant that was studied. Due to the high cost of loss of production in petrochemical plants it was established that any incremental improvement in the reliability of the dual radial network would be beneficial to the total cost of ownership of such a plant. Such incremental improvement of the reliability of the distribution network could be cost effectively achieved by adopting a conservative maintenance strategy and the establishment of a conservative spares inventory. Before this study was undertaken, there was no literature around the reliability of electrical distribution networks that focused specifically on petrochemical and gas-to-liquid plants. This study produced a set of reliability indices and a model that electrical engineers can use in the reliability analysis of petrochemical and gas-to-liquid plants. Furthermore it shows that, because the cost of loss of production in petrochemical plants is so high, the most conservative distribution network design and maintenance philosophies should always be used. distribution network. These reliability indices were compared to those given by the IEEE / Dissertation (MEng)--University of Pretoria, 2013. / gm2014 / Electrical, Electronic and Computer Engineering / unrestricted

Tillgänglighet är väsentligt för att skapa effekt med tekniska system. Detta leder till ett behov av att aktivt arbeta med uppföljning och nyckeltal för att kunna optimera organisation och design i syfte att uppnå den önskade effekten, utifrån tillgängliga resurser. En grund i detta är att ha en gemensam terminologi, god kommunikation och en förståelse för aktörernas roller.   Studien undersöker tillgänglighetsbegreppen och jämför definitionerna i litteratur med verkligheten. Syftet är att förtydliga och belysa problematiken kring begreppen för tillgänglighet och dess nyckeltal samt arbetet med detta. Detta görs bland annat genom att pröva om befintliga begrepp fortfarande är valida. Målsättningen är att arbetet skall styrka de uttalade behoven rörande en diskussion kring tillgänglighetsbegreppen och kunna vara en inledning till vidare studier.   Resultatet visar på att befintliga tillgänglighetsbegrepp är gångbara. Frågan som uppstår är rörande vilken typ av tillgänglighet som bör vara i fokus. Oavsett, är det utmanande att ur ett tillgänglighetsperspektiv, hantera multifunktionella plattformar med olika driftprofiler. Till detta finns det tolkningsdiskrepanser mellan litteraturen och verkligheten, samt inom och mellan organisationerna. Vidare noteras att ensade rutiner för uppföljning saknas och att detta främst är en chefs- och ledningsfråga. / Availability is essential to create effect with technological systems. This leads to a need to actively work on follow-up and key indicators to be able to optimize organization and design in order to achieve the desired effect, with the resources available. Fundamental to this is to have common terminology, good communication and an understanding of the roles of those involved.   This study examines the concepts of availability and compares the definitions from literature with reality. The aim is to clarify and highlight problems with concepts of availability, key indicators and the work being done on this. This is partly done by testing whether or not existing concepts are still valid. The objective is for this work to support needs expressed regarding a discussion of availability concepts, and to be a prelude for further studies.   The results of the study show that existing concepts of availability are still valid. The question that arises relates instead to which type of availability should be in focus. Nevertheless, it is quite clear that it is a challenging task, from an availability perspective, to manage multifunctional platforms with different operating profiles. Furthermore, there are also discrepancies both between literature and reality, and within and between organizations. It was also noted that there is a lack of uniform follow-up procedures, and that this is primarily an issue for commanders and management.